KR20070029748A - Method for the extended operation of a heterogeneous catalyzed gas phase partial oxidation of at least one organic compound - Google Patents

Abstract

The invention relates to a method for the extended operation of a heterogeneous catalyzed gas phase partial oxidation of at least one organic compound on a catalyst bed during which, in order to prevent the deactivation the catalyst bed, the working pressure in the gas phase is increased during the operating period of the catalyst bed. ® KIPO & WIPO 2007

Description

METHODS FOR THE EXTENDED OPERATION OF A HETEROGENEOUS CATALYZED GAS PHASE PARTIAL OXIDATION OF AT LEAST ONE ORGANIC COMPOUND}

The present invention relates to heterogeneity of one or more organic compounds in one or more oxidation reactors through which the starting reaction gas mixture comprising one or more organic compounds, oxygen molecules, and one or more inert diluent gases is passed through one or more catalyst beds at elevated temperatures. It relates to a long term method of catalyzing gas phase partial oxidation.

Complete oxidation of an organic compound using oxygen molecules herein means that all the carbon present in the organic compound is converted to carbon oxides and all the hydrogen present in the organic compound is converted to hydrogen oxides such that the organic compound is converted under the reactive activity of the oxygen molecule. Means that. All the various conversions of organic compounds under reactive activity of oxygen molecules are summarized herein as partial oxidation of organic compounds.

In particular, partial oxidation herein refers to the conversion of an organic compound under reactive activity of an oxygen molecule containing at least one oxygen atom in chemical bond form rather than before the partial oxidation occurs upon completion of the conversion.

Diluent gases that behave substantially inertly under the conditions of heterogeneous catalyzed gas phase partial oxidation are more than 95 mol%, preferably more than 99 mol%, when the constituents observe each component alone. It refers to a diluent gas that remains unchanged under the conditions of catalyzed gas phase partial oxidation.

It is commonly known that numerous basic compounds can be obtained through partial and heterogeneous catalyzed oxidation of a wide range of organic compounds using oxygen molecules in the gas phase. Examples include the conversion of propylene to acrolein and / or acrylic acid (see, eg, DE-A 23 51 151), tert-butanol, isobutene, isobutene to methacrolein and / or methacrylic acid Conversion of methyl ethers of butane, isobutyraldehyde or tert-butanol (for example, German patent DE-A 25 26 238, European patent EP-A 92097, EP EP-A 58927, German patent See DE-A 41 32 263, DE-A 41 32 684, and DE-A 40 22 212), conversion of acrolein to acrylic acid, conversion of methacrolein to methacrylic acid (eg See, for example, German Patent DE-A 25 26 238), the conversion of o-xylene, p-xylene or naphthalene to phthalic anhydride (see, for example, European Patent EP-A 522 871), or corresponding Conversion from butadiene to acid, and also maleic anhydride (for example, German Patent DE-A 21 06 796 and Copper DE-A 16 2 4 921), conversion of n-butane to maleic anhydride (see, eg, British Patent GB-A 14 64 198 and GB 12 91 354), for example to anthraquinones Conversion of indane (see eg DE-A 20 25 430), conversion of ethylene to ethylene oxide or conversion of propylene to propylene oxide (eg DE-B 12 54 137 DE-A 21 59 346, European Patent EP-A 372 972, International Patent Publication WO 89/0710, German Patent DE-A 43 11 608 and in Beyer, Lehrbuch der organischen See Chemie [Textbook of organic chemistry], 17 edition (1973), Hirzel Verlag, Stuttgart, p.261), conversion of propylene and / or acrolein to acrylonitrile (for example in German patent DE-A 23 51 151), conversion of isobutene and / or methacrolein to methacrylonitrile (ie, in this specification, the term partial oxidation Ammonooxidation, ie also included in partial oxidation in the presence of ammonia, oxidative dehydrogenation of hydrocarbons (see eg DE-A 23 51 151), acrylonitrile or acrolein and / or acrylic acid Conversion of propane to (for example, German patent DE-A 10 13 1297, European patent EP-A 1090 684, EP-A 608 838, German patent DE-A 10 04 6672 , EP-A 529 853, International Patent Publication WO 01/96270 and German Patent 10 02 8582), conversion of isobutane to methacrolein and / or methacrylic acid, and also acetic acid Reaction of ethane to provide ethylene, reaction of ethylene to provide ethylene oxide, reaction of benzene to provide phenol, and reaction of 1-butene or 2-butene to provide corresponding butanediol, and the like.

The catalyst used is usually in the solid state.

Especially often, the catalyst used is an oxide catalyst or a noble metal (eg Ag). In addition to oxygen, the catalytically active oxide composition may comprise only one other element or more than one other element (multielement oxide composition). Particularly often, the catalytically active oxide composition used is a composition comprising more than one metal element, in particular more than one transition metal. In this case, reference is made to the multimetal oxide composition. Typically, multielement oxide compositions are not merely physical mixtures of oxides of elemental components, but rather heterogeneous mixtures of complex multiple compounds of these elements.

In general, the heterogeneous catalyzed gas phase partial oxidation, in particular the abovementioned oxidation, is carried out at elevated temperatures (generally hundreds of degrees Celsius, typically 100 to 600 degrees Celsius).

Since most heterogeneous catalyzed gaseous partial oxidation proceeds highly exothermic, for heat removal reasons, a fluidized bed or isothermal fixed bed reactor (e.g., For example, the partial oxidation is suitably often performed in a catalyst bed of a tube bundle reactor in which the molten salt melt for heat removal is conducted around.

However, heterogeneous catalyzed gas phase partial oxidation can also be carried out in principle in a catalyst bed arranged in an adiabatic reactor.

It is known that the working pressure (absolute pressure) in heterogeneous catalyzed gas phase partial oxidation can be less than 1 bar, 1 bar or more than 1 bar. It is generally 1 to 10 bar, usually 1 to 3 bar.

The target conversion is carried out during the residence time of the reaction gas mixture in the catalyst charge as the reaction gas mixture passes through the catalyst charge.

Due to the generally exothermic nature of the generally heterogeneous catalyzed gaseous partial oxidation of organic compounds and oxygen molecules, the reaction partner is substantially inert under the conditions of catalytic partial oxidation in the gas phase and is released at its heat capacity. It is typically diluted with an absorbable gas.

One of the most frequently used inert diluent gases is nitrogen molecules that are automatically used when the oxygen source used for heterogeneous catalyzed gas phase partial oxidation is air.

Due to its general availability, another inert diluent gas used in many cases is steam. Both nitrogen and steam are additionally incombustible inert diluent gases in an advantageous manner.

In many cases, circulating gases are also used as inert diluent gases (see for example EP-A 1180508). Circulating gas refers to residual gas remaining after one or multiple stages. In multistage heterogeneous catalyzed gas phase partial oxidation of organic compounds, in contrast to one stage heterogeneous catalyzed gas phase partial oxidation, gas phase partial oxidation is not one but two or more in series connected reactors (these reactors are Can be incorporated seamlessly), in which case the oxidant can be replenished between successive reactors; Multistage is used, in particular when partial oxidation proceeds in successive steps; In these cases, it is often appropriate to optimize both the catalyst and other reaction conditions with a particular reaction step, and to carry out the reaction step in a dedicated reactor in a separate reaction step; On the other hand, it can also be used if the conversion is spread over a plurality of reactors connected in series, for reasons of heat removal or for other reasons (see, for example, DE-A 19902562); An example of heterogeneous catalyzed gas phase partial oxidation, often performed in two steps, is partial oxidation of propylene to acrylic acid; In the first reaction step, propylene is oxidized to acrolein, and in the second reaction step, acrolein is oxidized to acrylic acid; Correspondingly, the preparation of methacrylic acid is usually carried out in two steps starting from isobutene; On the other hand, when the appropriate catalyst charge is used, all of the above mentioned partial oxidations are also one step of the at least one organic compound when the target product is somewhat selectively removed from the reaction gas mixture (eg, by being absorbed with a suitable solvent). (Both steps in one reactor) can be carried out in heterogeneous catalyzed gas phase partial oxidation. In general, the circulating gas mainly consists of the inert diluent gas used for partial oxidation, and also the vapors typically produced as a by-product or added as diluent in partial oxidation, and carbon oxides formed by undesired complete oxidation. In some cases, it also contains small amounts of oxygen not consumed in partial oxidation (residual oxygen) and / or unconverted organic starting compounds.

The vapor formed as a by-product ensures that in most cases partial oxidation proceeds without significant change in the volume of the reaction gas mixture.

In accordance with the above, the inert diluent gas used for most heterogeneous catalyzed gas phase partial oxidation of organic compounds has at least 90% by volume, often at least 95% by volume of N ₂ , H ₂ O and / or CO ₂ , It consists essentially of a nonflammable inert diluent gas.

The inert diluent gas used first helps to absorb the heat of reaction and secondly keeps the reaction gas mixture outside the explosive range to ensure safe operation of the heterogeneous catalyzed gas phase partial oxidation of organic compounds. In heterogeneous catalyzed gas phase partial oxidation of unsaturated organic compounds, it is also often possible to use saturated hydrocarbons, ie flammable gases, as inert diluent gases.

In addition, the heterogeneous catalyzed gas phase partial oxidation of one or more organic compounds on a catalyst bed disposed in one or more oxidation reactors can be operated substantially continuously over an extended period of time on the same catalyst bed. In general, the reaction conditions can be kept substantially constant.

However, the catalyst layer loses quality during the run time. In general, in particular, the activity of one or more catalyst layers declines. This is particularly disadvantageous as the reactant conversion is reduced and the possible space-time yield is reduced as the operating time of one or more catalyst beds is increased under otherwise constant operating conditions.

EP-A 990 636 and EP-A 11 060 598 have different substantially constant operating conditions in order to maintain a partial conversion rate in one pass of the reaction gas mixture through at least one catalyst bed. Attempts to take account of the above-mentioned phenomena in the long term operation of heterogeneous catalyzed gas phase partial oxidation of one or more organic compounds on the same catalyst layer by gradually raising the temperature of the catalyst layer during the operation time under

A disadvantage of the procedure recommended in EP-A 990 636 and EP-A 11 060 598 is that as the temperature rise of the catalyst bed increases, their aging process is generally accelerated, which is typical. This is why the catalyst bed changes completely when the maximum value of the catalyst bed temperature is reached.

EP-A 614 872 and DE-A 10 35 0822 sometimes regenerate the catalyst bed (for example sometimes conducting a hot mixture of oxygen molecules and inert gas through the catalyst bed). It is recommended to delay the need to exchange the catalyst completely. However, a disadvantage of this procedure is that it involves interrupting production over an extended period of time.

German patent DE-A 10 23 2748 proposes a compromise, in which a partial replacement of the catalyst bed with a fresh catalyst charge is provided instead of a complete exchange of the catalyst bed.

A disadvantage of this limitation is that partial changes in the catalyst bed are also associated with significant cost increases and inconveniences.

As an approach to the solution, and also when the isothermal reactor itself no longer achieves the highest conversion rate, the adiabatic reactor begins to help and, thus, for the purpose of maximally delaying the exchange of catalyst beds in the isothermal reactor, It has already been proposed in principle to provide a wider range of catalyst layers I equipped in an isothermal reactor in an expensive and inconvenient manner, and a smaller catalyst layer II equipped in an adiabatic reactor in a relatively less expensive and inconvenient manner.

However, a disadvantage of this procedure is that it requires an increased number of reactors and therefore an increased investment.

In view of the prior art described, an object of the present invention is an improved process for the long term operation of heterogeneous catalyzed gas phase partial oxidation of one or more organic compounds on one or more oxidation reactors and one or more (one and the same) catalyst beds. To provide.

Thus, a starting reaction gas mixture comprising at least one organic compound, oxygen molecules, and at least one inert diluent gas is passed through at least one catalyst bed at elevated temperatures and to inhibit inactivation of the at least one catalyst bed, 1 in one or more oxidation reactors, including increasing the working pressure in the gas phase, based on the same time space velocity (l (STP) / l · h) in one or more catalyst beds of the starting reaction gas mixture, during the run time. A long term method of heterogeneous catalyzed gas phase partial oxidation of more than one organic compound has been found.

The increase in pressure caused by the deposition of the components present in the reaction gas mixture in solid form during the run time is excluded.

The time-space velocity on the catalyst bed catalyzing the reaction step of the (starting) reaction gas mixture is measured in standard liters (= l (STP); Ie volume (liter) of (start) reaction gas mixture taken under 25 ° C. and 1 bar). In addition, the temporal space velocity can only be based on one component of the (starting) reaction gas mixture. In such a case, the amount of such components (l (STP) / l · h) is the amount conducted through one liter of catalyst bed per hour.

The realization of an increase in the working pressure in the gas phase in the present invention is, for example, downstream of one or more oxidation reactors (outlets for the reaction gas mixture of the oxidation reactor) containing one or more catalyst beds (ie, of one or more oxidation reactors). It is possible in a simple way to mount a pressure regulator (apparatus for controlling the working pressure in one or more oxidation reactors) connected downstream. This may be for example a vane regulator or a throttle device, for example a throttle valve, in a particularly simple manner. Alternatively, it is also possible, for example, to automatically increase the pressure drop of the reaction gas mixture on the flow path of the reaction gas mixture and thus the working pressure at the same time and space velocity on one or more catalyst beds of the starting reaction gas mixture. It is also possible to insert only partially permeable perforated diaphragms into the flow path of the reaction gas mixture. Such perforated diaphragms can, for example, have a number of passages (holes in the simplest case) and can then be partially or completely closed.

The pressure regulator does not necessarily have to be mounted directly downstream of the associated oxidation reactor. Rather, it is sufficient to realize the procedure of the present invention when a pressure regulating device is introduced into the further flow path of the product gas mixture leaving the oxidation reactor so that the pressure increase diffuses into the oxidation reaction as a result of the back pressure. In other words, if the product gas mixture exiting the oxidation reactor is subsequently conducted to, for example, the bottom zone of the column for absorbing the target product in the absorption liquid introduced in the top zone of the column, the pressure regulator may also It can be placed on top. However, this change will generally be less desirable as the column pressure is typically limited for safety reasons. In addition, the absorption behavior can be performed disadvantageously. This also applies if the product gas mixture on the further path is conducted to the bottom zone of the column for fractional condensation of the target product. In general, the above-mentioned column involves separating the packing which increases the mass transfer surface area.

When connected in series of oxidation reactors, the pressure regulating device can be mounted downstream of each of the individual reactors in connection with the present invention.

The success of the procedure of the present invention may presumably be due to the pressure increase accompanied by an increase in the residence time of the reactants on the catalyst surface. This increased residence time is then presumably sufficient to re-enable the target reaction on the reaction site that has already been inactivated to a certain degree. In addition, the measures of the present invention also involve an increased partial pressure of related reactants.

The degree of increase in working pressure selected in the individual case in the process according to the invention depends on the extent to which the catalyst bed is inactivated at the time of increasing work pressure and on the particular reaction system. In accordance with the present invention typically an increase in the working pressure (in this specification is always based on the reason for standardization of the point of introduction of the reaction gas mixture into the catalyst bed, is calculated in this regard including the inert preliminary bed) It will be at least 25 bar or at least 50 bar before this partially or fully exchange. In general, the aforementioned increase in working pressure in the process according to the invention is between 25 or 50 mbar and 3000 mbar, often between 100 and 2500 mbar, in many cases between 200 and 2000 mbar and often between 300 and 1500 mbar , Sometimes from 400 to 1000 mbar, and will rarely be from 500 to 750 mbar.

Advantageously in accordance with the present invention, the pressure increase of the present invention is continuously a function of the deactivation rate of one or more catalyst beds (the measurement of activity being reacted to the catalyst bed at the same time and space velocity on the catalyst bed and at the same working pressure Temperature required to achieve the same reactant conversion based on a single pass through of the gas mixture. However, this can also be done step by step.

The highest value of the work pressure increase in the present invention is generally achieved when further work pressure increase involves a significant decrease in the selectivity of the target product formation. The latter can occur, for example, if the very long residence time of the reactants on the site on the catalyst surface, which is still fully active, causes an increase in complete combustion, thereby reducing the yield of the target product. However, this reduction in selectivity can also be acceptable if, for example, the required conversion can still be achieved only at temperatures that will damage the catalyst and / or the reactor, for example.

Because of this effect on selectivity, also, heterogeneously catalyzed gas phase partial oxidation of at least one organic compound on the catalyst layer is usually not carried out at the maximum possible working pressure from the start. Ultimately, the increased working pressure also increases the compression cost of the starting reaction gas mixture. Another limitation to the pressure increase of the present invention is that in many partial oxidations the difference between the highest and lowest temperatures produced in the catalyst bed is often at most 100 ° C, preferably at most 80 ° C, or at most 60 ° C, or at most 40 ° C. It may be the difference between the highest temperature and the lowest temperature produced in the catalyst bed since it should be below 20 ° C, or below 10 ° C.

Frequently, the working pressure at the start of the process according to the invention will be 1.2 to 2 bar. When the catalyst bed is exchanged, the working pressure will therefore typically be 3 bar or less according to the invention.

In principle, the process according to the invention is suitable for all heterogeneous catalyzed gas phase partial oxidations listed specifically at the beginning of this specification. These are particularly heterogeneous catalysis of propane with acrylic acid as described in WO 01/96270, DE-A 10316465, DE-A 10245585 and DE-A 10246119. Gas phase partial oxidation. The aforementioned patent documents should be considered as cited herein.

However, the procedure of the present invention is, for example, EP-A 700 893, EP-A 700 714, DE-A 19 91 0508, DE-A 19 91 9596 , DE-A 10351269, DE-A 10350812, DE-A 10350822, EP-A 11 59 247, DE-A 10 31 3208, DE -A 102004021764, copper DE-A 19 94 8248, European patent EP-A 990 636, copper EP-A 11 06 598, German patent DE-A 30 02 8289 and copper DE- Particularly suitable for heterogeneous catalyzed fixed bed gas phase partial oxidation of propene to acrolein and / or acrylic acid, preferably carried out in a tube bundle reactor in one step as described in A 10232482, and in two steps Heterogeneous catalyzed fixed bed gas phase partial oxidation of propene to acrolein carried out in the reactor or heterogeneous catalyzed fixed bed gas phase partial oxidation of acrolein to acrylic acid Particularly suitable for the first and second steps of.

The process according to the invention is particularly useful in that the catalyst used is a multi-element oxide in which the active composition comprises at least one of molybdenum and / or tungsten elements and bismuth, tellurium, antimony, tin and copper elements, or Mo, Bi And a catalyst which is a multimetal oxide containing Fe element, it is suitable for heterogeneous catalyzed fixed bed gas phase partial oxidation of propene to acrolein. Multimetal oxide compositions of the aforementioned type, comprising Mo, Bi and Fe, and particularly suitable according to the invention, are described in particular in DE-A 10 34 4149 and DE-A 10 34 4264. Which is a multimetal oxide composition comprising Mo, Bi and Fe. They are also particularly multimetal oxide active compositions of formula I of DE-A 19 95 5176, multimetal oxide active compositions of formula I of DE-A 19 94 8523, DE-A 10 10 1695 Multimetal oxide active compositions of formulas I, II and III, DE-A 19 94 8248 multimetal oxide active compositions of formula I, II and III, formulas I, II and DE-A 19955168 Multimetal oxide active compositions of III, and also the multimetal oxide active compositions specified in EP-A 700714.

The field of the process according to the invention relates to the use of one or more fixed catalyst layers used in accordance with the invention in the case of partial oxidation of propene to acrolein in German patent DE-A 10046957, DE-A 10063162, Copper DE-C 3338380, Copper DE-A 19902562, European Patent EP-A 15565, German Patent DE-C 2380765, European Patent EP-A 807465, Copper EP-A 279374 , German Patent DE-A 3300044, European Patent EP-A 575897, US Patent US-A 4438217, German Patent DE-A 19855913, International Patent Publication WO 98/24746, German Patent Mo, Bi and Fe disclosed in DE-A 19746210 (Formula II), Japanese Patent JP-A 91/294239, European Patent EP-A 293224 and EP-A 700714 Also suitable in the case of metal oxide catalysts. This is especially true of the exemplary embodiments of the above patent documents, preferably of these in particular European Patent EP-A 15565, EP-A 575897, German Patent DE-A 19746210 and DE-A 19855913. Applies to exemplary embodiments. In this connection the catalyst according to Example 1c of EP-A 15565 and also the active composition is the corresponding method, except that the composition Mo ₁₂ Ni _6.5 Zn ₂ Fe ₂ Bi ₁ P _0.0065 K _{0.06O Ox.10} SiO ₂ . Particular emphasis is given to the catalysts produced. Also, an unsupported hollow cylindrical catalyst having an external dimension of 5 mm × 3 mm × 2 mm or 5 mm × 2 mm × 2 mm (each of outer diameter × height × inner diameter) as serial number 3 of DE-A 19855913 Emphasize the examples (stoichiometric: Mo ₁₂ Co ₇ Fe ₃ Bi _0.6 K _0.08 Si _1.6 Ox), and the unsupported multimetal oxide II catalyst according to example 1 of DE-A 19746210. Mention may also be made of the multimetal oxide catalysts of US Pat. No. 4,438,217. The latter has a particularly dimensions of 5.5 mm × 3 mm × 3.5 mm or 5 mm × 2 mm × 2 mm or 5 mm × 3 mm × 2 mm or 6 mm × 3 mm × 3 mm or 7 mm × 3 mm × 4 mm This is especially true when it has a hollow cylindrical structure of (outer diameter x height x inner diameter). Likewise relevant in the context of the present invention are the multimetal oxide catalysts and external dimensions of DE-A 10101695 or WO 02/062737.

Further, in connection with the present invention German patent DE which is an unsupported hollow cylindrical (ring) catalyst having an external dimension of 5 mm × 3 mm × 2 mm or 5 mm × 2 mm × 2 mm (each of outer diameter × height × inner diameter) -A 10046957 Example 1 (stoichiometry: [Bi ₂ W ₂ O ₉ x 2WO ₃ ] _0.5 · [Mo ₁₂ Co _5.6 Fe _2.94 Si _1.59 K _0.08 Ox] ₁ ), and also the external dimension is 5 mm × 3 The coating of DE-A 10063162, except that it is a coated cyclic catalyst of the appropriate coating thickness and corresponding to a support ring of mm × 1.5 mm or 7 mm × 3 mm × 1.5 mm (outer diameter × height × inner diameter, respectively) Catalysts 1, 2, and 3 (stoichiometric: Mo ₁₂ Bi _1.0 Fe ₃ Co ₇ Si _1.6 K _0.08 ) are very suitable.

Numerous multimetal oxide active compositions which are particularly suitable for the catalyst of propene partial oxidation to acrolein in connection with the present invention can be included in formula (I).

Mo ₁₂ Bi _a Fe _b X ¹ _c X ² _d X ³ _e X ⁴ _f O _n

In the above formula,

X ¹ = nickel and / or cobalt,

X ² = thallium, alkali metal and / or alkaline earth metal,

X ³ = zinc, phosphorus, arsenic, boron, antimony, tin, cerium, lead and / or tungsten,

X ⁴ = silicon, aluminum, titanium and / or zirconium,

a = 0.5 to 5,

b = 0.01 to 5, preferably 2 to 4,

c = 0 to 10, preferably 3 to 10,

d = 0 to 2, preferably 0.02 to 2,

e = 0 to 8, preferably 0 to 5,

f = 0 to 10, and

n is a number determined by the valence and the frequency of the elements in the general formula (I) in addition to oxygen.

They are obtainable in a manner known per se (see eg DE-A 4023239) and are usually molded undiluted to obtain spheres, rings or cylinders, or in the form of coated catalysts. Furnace, ie preformed inert support coated with active composition. It will also be appreciated that they can be used as catalysts in powder form.

In principle, the active compositions of the formula (I) obtain in a simple manner a very intimate, preferably finely divided, dry mixture corresponding to their stoichiometry from a suitable source of these elemental components and at a temperature of 350 to 650 ° C. It can be produced by firing. Firing is carried out, for example, under an inert gas or oxidizing atmosphere, for example air (a mixture of inert gas and oxygen), and also under a reducing atmosphere (eg inert gas, NH ₃ , CO and / or H ₂ ). Can be. The firing time can be from several minutes to several hours and typically shortens with temperature. Useful sources for the elemental component of the multimetal oxide active composition I are compounds which are already oxides and / or compounds which can be converted to oxides by heating in the presence of at least oxygen.

In addition to oxides, such useful starting compounds include, in particular, halides, nitrates, formates, oxalates, citrates, acetates, carbonates, amine complexes, ammonium salts and / or hydroxides (which are in gaseous form upon final firing at a later time). NH ₄ OH, (NH ₄ ) ₂ CO ₃ , NH ₄ NO ₃ , NH ₄ CHO ₂ , CH ₃ COOH, NH ₄ CH ₃ CO ₂ and / or may be decomposed to provide a compound that is released to Compounds such as ammonium oxalate may additionally be incorporated into intimate dry mixtures).

Starting compounds for the preparation of the multimetal oxide active composition I may be intimately mixed in dry or wet form. When they are mixed in dry form, the starting compounds are advantageously used as finely divided powders and are calcined after mixing and optionally compaction. However, preference is given to intimate mixing in wet form. Typically, the starting compounds are mixed with each other in the form of aqueous solutions and / or suspensions. In particular, when the starting material is a source of elemental components in the exclusively dissolved form, an intimate dry mixture is obtained in the mixing process described. The solvent used is preferably water. The aqueous composition obtained is then dried and the drying process is preferably carried out by spray-drying the aqueous mixture at an outlet temperature of 100 to 150 ° C. from the spray tower.

Typically, the multimetal oxide active composition of formula (I) is used in a fixed catalyst layer rather than in powder form, rather in a specific catalyst shape, and the molding can be carried out before or after the final firing. For example, an unsupported catalyst may be compressed from the powder form of the active composition or its unbaked and / or partially calcined precursor composition into the desired catalyst shape (eg, tableting or extrusion), It may optionally be prepared by the addition of an adjuvant such as graphite or stearic acid as a lubricant and / or molding aids and reinforcing agents such as glass fine fibers, asbestos, silicon carbide or potassium titanate. Examples of suitable unsupported catalyst shapes include solid cylinders or hollow cylinders having an outer diameter and a length of 2 to 10 mm. In the case of hollow cylinders, wall thicknesses of 1 to 3 mm are advantageous. It will also be appreciated that the unsupported catalyst can have a spherical shape and the diameter of the sphere can be 2 to 10 mm.

A particularly advantageous hollow cylindrical shape is 5 mm x 3 mm x 2 mm (outer diameter x length x inner diameter) in the case of unsupported catalysts.

It will be appreciated that the powdered active composition or its powder precursor composition that has not yet been calcined and / or not partially calcined can also be shaped by application to a preformed inert catalyst support. Coating of the support body to produce the coated catalyst is generally suitable for rotation, as disclosed, for example, in DE-A 2909671, EP-A 293859 or EP-A 714700. It is carried out in a container where possible. To coat the support body, the powder composition to be applied is advantageously wetted and again dried after application, for example using hot air. The coating thickness of the powder composition applied to the support body is advantageously selected within 10 to 1000 μm, preferably 50 to 500 μm, more preferably 150 to 250 μm. Alternatively, the powder compositions to be applied can also be applied directly to the support body from their suspensions or solutions (eg in water).

Useful support materials are conventional porous or nonporous aluminum oxide, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide, or silicates such as magnesium silicate or aluminum silicate. Generally they behave substantially inactive with respect to the target reaction on which the method of the first reaction step according to the invention is based. Regularly shaped support bodies with pronounced surface roughness, for example spherical or hollow cylinders, are preferred, but the support bodies may have a regular or irregular shape. Spherical supports made of soapstone (e.g., Steatite C220 from Ceramtec) and having a diameter of 1 to 8 mm, preferably 4 to 5 mm and having a substantially nonporous surface roughened It is suitable to use. However, suitable support bodies also include cylinders with a length of 2 to 10 mm (eg 8 mm) and an outer diameter of 4 to 10 mm (eg 6 mm). In the case of rings suitable as support bodies according to the invention, the wall thickness is also typically 1 to 4 mm. According to the invention, the annular support body to be used is preferably 2 to 6 mm in length, 4 to 8 mm in outer diameter and 1 to 2 mm in wall thickness. In particular, rings having a shape of 7 mm × 3 mm × 4 mm or 5 mm × 3 mm × 2 mm (outer diameter × length × inner diameter) are suitable as support bodies according to the invention. It will be appreciated that the fineness of the catalytically active oxide composition to be applied to the surface of the support body will be adapted to the desired coating thickness (see EP-A 714 700).

In addition, in connection with the present invention, multimetal oxide active compositions suitable in particular for the catalyst of the fixed catalyst layer of propene partial oxidation to acrolein are the compositions of the following formula (II) and as a result of their chemical composition different from their periphery Limited from their space periphery, the maximum diameter (longest line passing through the band center to connect two points on the surface (interface)) is from 1 nm to 100 μm, often from 10 nm to 500 nm or from 1 μm to 50 or 25 It includes a three-dimensional zone of the chemical composition Y ¹ _{a '} Y ² _b' O _{x 'which} is μm.

[Y ¹ _{a '} Y ² _b' O _{x '} ] _p [Y ³ _c' Y ⁴ _{d '} Y ⁵ _e' Y ⁶ _{f '} Y ⁷ _g' Y ² _{h '} O _y' ] _q

In the above formula,

Y ¹ = only bismuth, or bismuth and at least one telelium, antimony, tin and copper,

Y ² = molybdenum, or molybdenum and tungsten,

Y ³ = alkali metal, thallium and / or samarium,

Y ⁴ = alkaline earth metal, nickel, cobalt, copper, manganese, zinc, tin, cadmium and / or mercury,

Y ⁵ = iron, or iron and at least one chromium and cerium element,

Y ⁶ = phosphorus, arsenic, boron and / or antimony,

Y ⁷ = rare earth metal, titanium, zirconium, niobium, tantalum, rhenium, ruthenium, rhodium, silver, gold, aluminum, gallium, indium, silicon, germanium, lead, thorium, and / or uranium,

a '= 0.01 to 8,

b '= 0.1 to 30,

c '= 0 to 4,

d '= 0 to 20,

e '= greater than 0 to 20,

f '= 0 to 6,

g '= 0 to 15,

h '= 8 to 16,

x ', y' = number determined by the valence and the frequency of the element in formula (II) besides oxygen, and

p, q = p / q is a number from 0.1 to 10.

Particularly advantageous multimetal oxide compositions II are compositions in which Y ¹ is only bismuth.

Among these, also general compositions of the general formula (III) are preferred.

[Bi _{a "} Z ² _b" O _{x "} ] _p" [Z ² ₁₂ Z ³ _{c "} Z ⁴ _d" Fe _{e "} Z ⁵ _f" Z ⁶ _{g "} Z ⁷ _h" O _{y "} ] _q"

In the above formula,

Z ² = molybdenum, or molybdenum and tungsten,

Z ³ = nickel and / or cobalt,

Z ⁴ = thallium, alkali metal and / or alkaline earth metal,

Z ⁵ = phosphorus, arsenic, boron, antimony, tin, cerium and / or lead,

Z ⁶ = silicon, aluminum, titanium and / or zirconium,

Z ⁷ = copper, silver and / or gold,

a "= 0.1 to 1,

b "= 0.2 to 2,

c "= 3 to 10,

d "= 0.02 to 2,

e "= 0.01 to 5, preferably 0.1 to 3,

f "= 0 to 5,

g "= 0 to 10,

h "= 0 to 1,

x ", y" = number determined by the valence and frequency of the element in formula (III) besides oxygen, and

p ", q" = p "/ q" ratios of 0.1 to 5, preferably 0.5 to 2.

Very particular preference is given to compositions III in which Z ² _{b ″} is (tungsten) _{b ″} and Z ² ₁₂ is (molybdenum) ₁₂ .

Furthermore, among the suitable multimetal oxide compositions II (polymetal oxide compositions III) according to the invention, [Y ¹ _{a '} Y ² _b' O _{x '} of the suitable multimetal oxide compositions II (polymetal oxide compositions III) according to the invention ] _p ([Bi _{a "} Z ² _b" O _{x "} ] _p" ) at least 25 mol% (preferably at least 50 mol%, more preferably at least 100 mol%) of the total proportions differ from their periphery Chemical compositions Y ¹ _{a '} Y ² _b' O _{x '} [Bi _{a "} Z ² _b" O _{x "} defined as a result of their chemical composition and defined from their periphery and having a maximum diameter of 1 nm to 100 μm. ] In the form of a three-dimensional zone.

With regard to shaping, reference to the multimetal oxide I catalyst applies to the multimetal oxide II catalyst.

The preparation of the multimetal oxide active composition II is described, for example, in EP-A 575897 and also DE-A 19855913, DE-A 10344149 and DE-A 10344264. have.

Suitable active compositions for the catalyst of at least one fixed catalyst layer suitable for the partial oxidation of acrolein to acrylic acid in the context of the present invention are multimetal oxides known by the above reaction type comprising Mo and V elements.

The multimetal oxide active compositions comprising Mo and V are described, for example, in US Pat. No. US-A 3775474, US-A 3954855, US-A 3893951, and US-A 4339355. Or EP-A 614872 or EP-A 1041062, or WO 03/055835, or WO 03/057653.

Also particularly suitable are the multimetal oxide active compositions of DE-A 10 32 5487 and also DE-A 10 32 5488.

Also in connection with the present invention, as active compositions for fixed bed catalysts for the partial oxidation of acrolein to acrylic acid, EP-A 427508, DE-A 29 09 671, DE-C 31 51 805, copper DE-B 26 26 887, copper DE-A 43 02 991, European patent EP-A 700 893, copper EP-A 7147 00 and German patent DE-A Particularly suitable are the multimetal oxide compositions of 19 73 6105. In this connection, the exemplary embodiments of EP-A 714 700 and DE-A 19 73 6105 are particularly preferred.

Numerous of these multimetal oxide active compositions comprising Mo and V elements can be included in Formula IV.

Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _n

In the above formula,

X ¹ = W, Nb, Ta, Cr and / or Ce,

X ² = Cu, Ni, Co, Fe, Mn and / or Zn,

X ³ = Sb and / or Bi,

X ⁴ = at least one alkali metal,

X ⁵ = at least one alkaline earth metal,

X ⁶ = Si, Al, Ti and / or Zr,

a = 1 to 6,

b = 0.2 to 4,

c = 0.5 to 18,

d = 0 to 40,

e = 0 to 2,

f = 0 to 4,

g = 0 to 40 and

n is a number determined by the valence and frequency of the elements in the formula (IV) excluding oxygen.

Preferred embodiments among the active polymetal oxides IV in the context of the present invention are embodiments encompassed by the following definitions of the variables of formula IV.

X ¹ = W, Nb and / or Cr,

X ² = Cu, Ni, Co and / or Fe,

X ³ = Sb,

X ⁴ = Na and / or K,

X ⁵ = Ca, Sr and / or Ba,

X ⁶ = Si, Al and / or Ti,

a = 1.5 to 5,

b = 0.5 to 2,

c = 0.5 to 3,

d = 0 to 2,

e = 0 to 0.2,

f = 0 to 1, and

n is a number determined by the valence and frequency of the elements in the formula (IV) excluding oxygen.

In addition, very particularly preferred polymetal oxides IV according to the invention are oxides of the general formula (V).

Mo ₁₂ V _{a '} Y ¹ _b' Y ² _{c '} Y ⁵ _f' Y ⁶ _{g '} O _n'

In the above formula,

Y ¹ = W and / or Nb,

Y ² = Cu and / or Ni,

Y ⁵ = Ca and / or Sr,

Y ⁶ = Si and / or Al,

a '= 2 to 4,

b '= 1 to 1.5,

c '= 1 to 3,

f '= 0 to 0.5

g '= 0 to 8, and

n '= number determined by the valence and the frequency of the elements in the formula (V) excluding oxygen.

The multimetal oxide active composition (IV) can be obtained in a manner known per se, for example as disclosed in DE-A 4335973 or EP-A 714700. In particular, suitable multimetal oxide active compositions comprising Mo and V in connection with the present invention for the partial oxidation of acrolein to acrylic acid are also multimetal oxide active compositions of DE-A 10 261 186.

In principle, these multimetal oxide active compositions comprising Mo and V, in particular the compositions of formula IV, are very intimate, preferably in a simple manner, having compositions corresponding to their stoichiometry from suitable sources of their elemental components. Can be prepared by obtaining a finely divided dry mixture and firing at a temperature of 350 to 600 ° C. Firing is carried out in an inert gas or oxidizing atmosphere, for example air (inert gas and oxygen), and also in a reducing atmosphere (e.g., H ₂ , NH ₃ , CO, methane and / or acrolein) and inert gas. Mixture or the reducing gas itself mentioned). The firing time can be several minutes to several minutes and typically shortens with temperature. Useful sources for the elemental component of the multimetal oxide active composition IV include compounds which are already oxides and / or compounds which can be converted to oxides by heating in the presence of at least oxygen.

Starting compounds for preparing the multimetal oxide composition IV can be intimately mixed in dry or wet form. When they are mixed in dry form, the starting compounds are advantageously used as finely divided powders and are calcined after mixing and optionally compaction. However, intimate mixing in wet form is preferred.

Typically this is done by mixing the starting materials in the form of aqueous solutions and / or suspensions. Particularly intimate dry mixtures are obtained in the mixing process described when the starting material is a source of elemental components in the exclusively dissolved form. The solvent used is preferably water. Subsequently, the obtained aqueous composition is dried, and the drying step is preferably performed by spray drying the aqueous mixture at an outlet temperature of 100 to 150 ° C.

Multimetal oxide active compositions comprising Mo and V, in particular the compositions of formula IV, are used in the form of powders, or in particular catalyst forms, for the method of partial oxidation of acrolein to acrylic acid according to the invention, wherein the molding is carried out before the final firing Or afterwards. For example, the unsupported catalyst may be compressed from the powder of the active composition or its unbaked precursor composition into the desired catalyst shape (eg tablet or extrusion), optionally by graphite or as an adjuvant, for example a lubricant. Stearic acid and / or molding aids and reinforcing agents such as glass fine fibers, asbestos, silicon carbide or potassium titanate. Examples of suitable unsupported catalyst shapes include solid cylinders or hollow cylinders having an outer diameter and a length of 2 to 10 mm. In the case of hollow cylinders, wall thicknesses of 1 to 3 mm are advantageous. It will also be appreciated that the unsupported catalyst can have a spherical shape and the diameter of the sphere can be 2 to 10 mm.

It will be appreciated that the powdered active composition or its powder precursor composition, which has not yet been calcined, can also be shaped by application to a preformed catalyst support. Coating of the support body to prepare the coated catalyst is generally carried out in a suitable rotatable vessel as disclosed in DE-A 2909671, EP-A 293859 or EP-A 714700. do.

To coat the support body, the powder composition to be applied is advantageously wetted and dried again, for example using hot air, after application. The coating thickness of the powder composition applied to the support body is advantageously selected within 10 to 1000 μm, preferably 50 to 500 μm, more preferably 150 to 250 μm.

Useful support materials are conventional porous or nonporous aluminum oxide, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide, or silicates such as magnesium silicate or aluminum silicate. Regularly shaped support bodies with pronounced surface roughness, for example spherical or hollow cylinders, are preferred, but the support bodies may have a regular or irregular shape. It is suitable to use spherical supports having a rough surface, which are made of steatite and have a diameter of 1 to 10 mm (eg 8 mm), preferably 4 to 5 mm and are substantially nonporous. However, a suitable support body also includes a cylinder having a length of 2 to 10 mm and an outer diameter of 4 to 10 mm. In the case of rings suitable as support bodies according to the invention, the wall thickness is also typically 1 to 4 mm. According to the invention, the annular support body to be used is preferably 3 to 6 mm in length, 4 to 8 mm in outer diameter and 1 to 2 mm in wall thickness. Furthermore, suitable support bodies according to the invention are in particular rings having a shape of 7 mm × 3 mm × 4 mm (outer diameter × length × inner diameter). It will be appreciated that the fineness of the catalytically active oxide composition to be applied to the surface of the support body will be adapted to the desired coating thickness (see EP-A 714 700).

In addition, advantageous multimetal oxide active compositions comprising Mo and V used for the partial oxidation of acrolein to acrylic acid in connection with the present invention may be prepared in finely divided form (starting composition 1) Preform separately, and then incorporate the preformed solid starting composition 1 into an aqueous solution or an aqueous suspension, or include Mo, V, Z ¹ , Z ² , Z ³ , comprising the above-mentioned elements by stoichiometric formula Incorporate into a finely divided dry mixture (starting composition 2) of a source of elements Z ⁴ , Z ⁵ , Z ⁶ in the desired p: q ratio, dry the resulting aqueous mixture and dry at a temperature of 250 to 600 ° C. A composition of formula (VI) below obtained by firing the dry precursor composition produced before or after to obtain the desired catalyst structure.

[D] _p [E] _q

In the above formula,

D = Mo ₁₂ V _{a "} Z ¹ _b" Z ² _{c "} Z ³ _d" Z ⁴ _{e "} Z ⁵ _f" Z ⁶ _{g "} O _x" ,

E = Z ⁷ ₁₂ Cu _{h "} H _i" O _{y "} ,

Z ¹ = W, Nb, Ta, Cr and / or Ce,

Z ² = Cu, Ni, Co, Fe, Mn and / or Zn,

Z ³ = Sb and / or Bi,

Z ⁴ = Li, Na, K, Rb, Cs and / or H,

Z ⁵ = Mg, Ca, Sr and / or Ba,

Z ⁶ = Si, Al, Ti and / or Zr,

Z ⁷ = Mo, W, V, Nb and / or Ta,

a "= 1 to 8,

b "= 0.2 to 5,

c "= 0 to 23,

d "= 0 to 50,

e "= 0 to 2,

f "= 0 to 5,

g "= 0 to 50,

h "= 4 to 30,

i "= 0 to 20 and

x ", y" = number determined by the valence and frequency of the element in addition to oxygen in formula VI, and

p, q = p / q is a number from 160: 1 to 1: 1.

Z ⁷ ₁₂ Cu _{h "} H _i" O _{y "}

Mo ₁₂ V _{a "} Z ¹ _b" Z ² _{c "} Z ³ _d" Z ⁴ _{e "} Z ⁵ _f" Z ⁶ _{g "}

Preferred is the multimetal oxide active composition VI in which the preformed solid starting composition 1 is incorporated into the aqueous starting composition 2 at a temperature below 70 ° C. EP-A 668104, German Patent DE-A 19736105 and DE-A 19528646 describe in detail the preparation of the multimetal oxide composition III catalyst.

With regard to shaping, the statements made regarding the multimetal oxide IV catalyst apply to the multimetal oxide VI catalyst.

In addition, further multimetal oxide active compositions comprising Mo and V, which are advantageous herein, may be used in three-dimensional zones of the chemical composition Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _x ( Phase) Fraction of Form A [A] _p , three-dimensional zone of composition X ₁ ⁷ Cu _h H _i O _y (Phase) of Fraction [B] _q of Form B and chemical composition X ₁ ⁸ Sb _j H _k O _z Multi-element oxide active composition of formula (VII) comprising fraction [C] _r in three-dimensional zone (phase) C form.

[A] _p [B] _q [C] _r

In the above formula,

A = Mo ₁₂ V _a X ¹ _b X ² _c X ³ _d X ⁴ _e X ⁵ _f X ⁶ _g O _x ,

B = X ₁ ⁷ Cu _h H _i O _y ,

C = X ₁ ⁸ Sb _j H _k O _z ,

X ¹ = W, Nb, Ta, Cr and / or Ce, preferably W, Nb and / or Cr,

X ² = Cu, Ni, Co, Fe, Mn and / or Zn, preferably Cu, Ni, Co and / or Fe,

X ³ = Sb and / or Bi, preferably Sb,

X ⁴ = Li, Na, K, Rb, Cs and / or H, preferably Na and / or K,

X ⁵ = Mg, Ca, Sr and / or Ba, preferably Ca, Sr and / or Ba,

X ⁶ = Si, Al, Ti and / or Zr, preferably Si, Al and / or Ti,

X ⁷ = Mo, W, V, Nb and / or Ta, preferably Mo and / or W,

X ⁸ = Cu, Ni, Zn, Co, Fe, Cd, Mn, Mg, Ca, Sr and / or Ba, preferably Cu and / or Zn, more preferably Cu,

a = 1 to 8, preferably 2 to 6,

b = 0.2 to 5, preferably 0.5 to 2.5,

c = 0 to 23, preferably 0 to 4,

d = 0 to 50, preferably 0 to 3,

e = 0 to 2, preferably 0 to 0.3,

f = 0 to 5, preferably 0 to 2,

g = 0 to 50, preferably 0 to 20,

h = 0.3 to 2.5, preferably 0.5 to 2, more preferably 0.75 to 1.5,

i = 0 to 2, preferably 0 to 1,

j = 0.1 to 50, preferably 0.2 to 20, more preferably 0.2 to 5,

k = 0 to 50, preferably 0 to 20, more preferably 0 to 12,

x, y, z = number determined by the valence and frequency of the element in A, B, C, in addition to oxygen,

p, q = positive

If r = 0 or a positive number, preferably a positive number, and the p / (q + r) ratio = 20: 1 to 1:20, preferably 5: 1 to 1:14, more preferably Q / r ratio = 20: 1 to 1:20, preferably 4: 1 to 1: 4, more preferably 2: 1 to 1: when r is from 2: 1 to 1: 8 and r is a positive number 2, most preferably 1: 1.

Wherein the bands A, B, and, if present, C are distributed relative to each other as in a mixture of finely divided A, finely divided B, and, if present, finely divided C,

Catalytically active multielement oxide compositions VII to V, in which the molar fraction of element Mo is from 20 mol% to 80 mol% in the total amount of all elements in the multielement oxide active composition VII in addition to oxygen, and is present in the catalytically active multielement oxide composition VII The molar ratio (Mo / V) of Mo present at 15: 1 to 1: 1, the corresponding Mo / Cu molar ratio is 30: 1 to 1: 3, and the total amount of corresponding Mo / (W and Nb ) Under the conditions of molar ratio of 80: 1 to 1: 4, all variables are selected within the predefined range.

In the context of the present invention, a preferred multielement oxide active composition VII is a composition in which zone A has a composition within the stoichiometric pattern of formula VIII.

Mo ₁₂ V _a X ¹ _b X ² _c X ⁵ _f X ⁶ _g O _x

In the above formula,

X ¹ = W and / or Nb,

X ² = Cu and / or Ni,

X ⁵ = Ca and / or Sr,

X ⁶ = Si and / or Al,

a = 2 to 6,

b = 1 to 2,

c = 1 to 3,

f = 0 to 0.75,

g = 0 to 10, and

x = number determined by the valence and the frequency of the element in the general formula (VIII) besides oxygen.

The term "phase" as used in connection with the multielement oxide active composition VIII means a three-dimensional zone in which the chemical composition differs from the chemical composition around them. The phase need not be an x-ray-homogeneous phase. Generally, phase A forms a continuous phase in which particles of phase B and, if present, are dispersed.

Advantageously, the finely divided phase B, and, if present, phase C, has the largest diameter, ie the longest line connecting the two points on the particle surface past the center of the particle, is preferably 300 μm or less, preferably from 0.1 to 200 μm, more preferably 0.5 to 50 μm, most preferably 1 to 30 μm. However, particles having a longest diameter of 10 to 80 μm or 75 to 125 μm are also suitable.

In principle, phase A, phase B, and, if present, phase C may be in amorphous and / or crystalline form in the multielement oxide active composition VII.

Intimate dry mixtures on which the multi-element oxide active compositions of the formula (VII) are based and subsequently thermally treated to convert them to the active compositions are described, for example, in WO 02/24327, DE-A 4405514, Copper DE-A 4440891, Copper DE-A 19528646, Copper DE-A 19740493, European Patent EP-A 756894, German Patent DE-A 19815280, Copper DE-A 19815278, It can be obtained as described in EP-A 774297, DE-A 19815281, EP-A 668104 and DE-A 19736105.

The basic principle for preparing an intimate dry mixture in which the multi-element oxide active composition of formula VII results in thermal treatment is one or more multi-element oxide compositions B (X) as starting composition 1, in finely divided form, or separately or combined together. ₁ ⁷ Cu _h H _i O _y ) and, if appropriate, at least one multi-element oxide composition C (X ₁ ⁸ Sb _j H _k O _z ) as starting composition 2, followed by the desired ratio (corresponding to formula VII) Starting composition 1 and, if appropriate, 2 are intimately contacted with a mixture comprising a source of the elemental component of multielement oxide composition A, in a composition corresponding to the stoichiometry of formula A, optionally drying the resulting intimate mixture It is to let.

Mo ₁₂ V _a X _b ¹ X _c ² X _d ³ X _e ⁴ X _f ⁵ X _g ⁶ O _x

The mixture comprising the components of starting composition 1 and, if appropriate, 2 and the source of elemental components of multimetal oxide composition A (starting composition 3) may be in intimate contact with the dry or wet form. In the latter case, care should be taken not to solution only the preformed phase (crystalline) B and, if appropriate, C. In aqueous media, the latter is usually convinced at pH values that are not much deviated from 7 and at very high temperatures. When intimate contact is carried out in wet form, it is usually finally dried (eg by spray drying) to obtain an intimate dry mixture which is thermally treated according to the invention. In the case of dry mixing, this dry material is obtained automatically. In addition, phase B preformed in finely divided form and, if appropriate, phase C, may be plastically reshaped, comprising a source of elemental components of the multimetal oxide composition A recommended in DE-A 10046928. It will be appreciated that it may be incorporated into a mixture. In addition, intimate contact of the components of the starting composition 1 and, if appropriate, the components of the multielement oxide composition A (starting composition 3) with the components of starting component 1 can be performed for granted as described in DE-A 19815281. .

Heat treatment and shaping to obtain the active composition can be carried out as described in the multimetal oxide active compositions IV to VI.

Very generally, multimetal oxide active compositions IV to VII catalysts can be advantageously prepared according to the teachings of DE-A 10 325 487 or DE-A 10 325 488.

The operation of the reaction step from propene to acrolein (and application of the method according to the invention) is, for example, to EP-A 700 714 or DE-A 4 431 949 or to International Patent Publications. The fixed catalyst bed in a tube bundle reactor packed with a fixed bed catalyst, as described in WO 03/057653 or WO 03/055835 or WO 03/059857 or WO 03/076373. Using a catalyst described as suitable for the reaction can be carried out in the simplest manner, as appropriate from the point of view of application.

In other words, in the simplest manner, the fixed catalyst layer is placed in a uniformly filled metal tube of a tube bundle reactor, and a heating medium (one zone method), generally a salt melt, is conducted around the metal tube. The salt melt (heating medium) and the reaction gas mixture can be conducted in a simple forward or reverse direction. However, the heating medium (salt melt) can also be conducted around the tube bundle in a meandering manner seen on the reactor and is present in the forward or reverse direction with respect to the flow direction of the reaction gas mixture which is only visible on the entire reactor. The volume flow rate of the heating medium (heat exchange medium) is typically 0 to 10 ° C., often 2 to 8, due to the temperature rise of the heat exchange medium (due to the exothermicity of the reaction) from the inlet point into the reactor to the outlet point from the reactor. ℃, often 3 to 6 ℃ degree. The inlet temperature of the heat exchange medium into the tube bundle reactor is generally 250-450 ° C., often 300-400 ° C., or 300-380 ° C. The associated reaction temperature then also moves within these temperature ranges. Suitable heat exchange media are especially fluid heating media. In particular, it is suitable to use melts of salts such as potassium nitrate, potassium nitrite, sodium nitrite and / or sodium nitrate, or melts of low melting metals such as alloys of sodium, mercury and also other metals. Ionic liquids can also be used.

Suitably, the starting reaction gas mixture is fed to the charge of the fixed bed catalyst preheated to the desired reaction temperature.

In particular, the desired high time space velocity of the propene on the fixed catalyst bed (eg, at least 130 l (STP) / l · h, or at least 140 l (STP) / l · h, or 150 l (STP) / l · h or more, or 160 l (STP) / l · h or more, but typically 600 l (STP) / l · h or less, frequently 350 l (STP) / l · h or less) The partial oxidation process of can be suitably carried out in a two-zone or multi-zone tube bundle reactor (also likewise possible in a one-zone tube bundle reactor). A preferred variant of a two-zone tube bundle reactor that can be used for this purpose according to the invention is disclosed in DE-C 2830765. However, it is disclosed in German Patent DE-C 2513405, US Patent US-A 3147084, German Patent DE-A 2201528, European Patent EP-A 383224 and German Patent DE-A 2903582. Two-zone tube bundle reactors are also suitable. Another process is described in EP-A 1106598.

In other words, in a simple manner, at least one fixed catalyst layer used in accordance with the invention is then placed in a uniformly filled metal tube of a tube bundle reactor, and the two substantially spatially separated heating media, generally salt melts, Conductive around the metal tube. The tubular region, in which the special dye bath is spread, represents the reaction zone.

For example, salt bath A preferably flows around the tubular region (reaction zone A) where the oxidation conversion (single pass) of propene proceeds until a conversion value of 40 to 80 mol% is achieved, and salt bath B is preferably Preferably, the subsequent oxidation conversion (single pass) of propene flows around the tubular zone (reaction zone B) which generally proceeds until a conversion value of at least 93 mol% is achieved (reaction zones A, B, if necessary, at individual temperatures). May be followed by an additional reaction zone maintained).

Within a particular temperature zone, the salt bath can in principle be conducted as in the one zone method. The inlet temperature of salt bath B is typically at least 5-10 ° C. above the temperature of salt bath A. Alternatively, the inlet temperature may be within the temperature range of the inlet temperature recommended for the one zone method.

On the other hand, the two-zone high load method for propene partial oxidation to acrolein is described, for example, in DE-A 10 30 8836, EP-A 11 06 598, Or as described in WO 01/36364 or DE-A 19 92 7624, or in DE-A 19 94 8523, DE-A 10 31 3210, It may be carried out as described in DE-A 10 31 3213 or DE-A 19 94 8248.

In general, the process according to the invention in the partial oxidation of propene to acrolein is not more than 70 l (STP) / l · h, or at least 70 l (STP) / l · h of propene on a fixed catalyst bed. , 90 l (STP) / l · h or more, 110 l (STP) / l · h or more, 130 l (STP) / l · h or more, 140 l (STP) / l · h or more, 160 l (STP) / l · h or more, 180 l (STP) / l · h or more, 240 l (STP) / l · h or more, 300 l (STP) / l · h or more, but typically 600 l (STP) / l Suitable for h or less. Here, the temporal space velocity is based on the volume of the fixed catalyst bed, excluding any region that is exclusively constructed and used exclusively with inert materials (unless specifically stated, as is the case here).

In order to produce a fixed catalyst layer for the partial oxidation of the propene of the invention to acrolein, in the process according to the invention, a suitable shaped catalyst body with a multimetal oxide active composition, or with a multimetal oxide active composition Molded body without molded metal body (consisting of inert material) and a multimetal oxide active composition that is substantially inert with respect to heterogeneous catalyzed partial gas phase oxidation of propene to acrolein (molded dilution) It is possible to use only a substantially uniform mixture of the body). Useful materials for such inert shaped bodies are in principle all materials which are also suitable as support materials for the "catalyzed propene to acrolein" coated catalyst. Such useful materials are, for example, silicates such as porous or nonporous aluminum oxides, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide, magnesium or aluminum silicates or the already mentioned copperite (e.g., steatite from Ceramtech). C-220).

The shape of this inert shaped dilution body may in principle be the desired one. In other words, they can be, for example, spheres, polygons, solid cylinders or rings. According to the invention, the selected inertly shaped dilution body is preferably of a shape corresponding to the first stage shaped catalyst body to be diluted by them.

In general, it is preferred if the chemical composition of the active composition used for the partial oxidation of propene to the acrolein described does not change on the fixed catalyst bed. In other words, the active composition used for the individually molded catalyst body may be, for example, a mixture of elements Mo and / or W, and also other multimetal oxides comprising one or more Bi, Fe, Sb, Sn and Cu elements. Although the same mixture can be used advantageously for all shaped catalyst bodies of the fixed catalyst bed.

In the partial oxidation of propene to acrolein, the volume-specific (ie normalized in units of volume) activity is typically continuous, abrupt or stepwise in the fixed catalyst bed in the flow direction of the starting reaction gas mixture. To increase.

Volume-specific activity can be reduced in a simple manner, for example by uniformly diluting the base amount of the shaped catalyst body made in a uniform manner with the molded dilution body. The higher the fraction of the selected shaped dilution body, the lower the specific composition of the active volume or catalytic activity of the fixed bed.

Thus, the volume-specific activity of increasing at least once in the flow direction of the reactant gas mixture on the fixed catalyst bed allows the bed to be formed in a simple manner, e. Starting and then successively or at least once or more than once, suddenly (eg stepwise), the fraction of the formed dilution body in the flow direction can be obtained by decreasing. However, an increase in volume-specific activity may, for example, increase the thickness of the active composition layer applied to the support, or, in certain shapes of the shaped coating catalyst body and active composition type, or have the same shape but the weight ratio of the active composition In this other coating catalyst mixture, it is also possible by increasing the fraction of the shaped catalyst body in which the weight ratio of the active composition is high. Alternatively, the active composition itself may also be diluted during the preparation of the active composition, for example by incorporating an inert diluent material, such as hard calcined silicon dioxide, into a dry mixture of starting compounds to be calcined. Various amounts of added dilution material automatically trigger various activities. As more and more diluent is added, the product activity becomes lower and lower. Similar effects can also be achieved, for example, by suitably changing the mixing ratio of the mixture of unsupported catalyst and coating catalyst (with the same active composition). It will be appreciated that the described variables can also be used in combination.

Naturally, catalyst mixtures having chemically different active compositions and various activities as a result of the various compositions can also be used in the fixed catalyst layer of propene partial oxidation to acrolein of the present invention. These mixtures can then be diluted with an inert dilution body.

With the active composition, a layer exclusively composed of an inert material (eg, only a molded dilution body) can be arranged upstream and / or downstream of the region of the fixed catalyst layer of propene partial oxidation to acrolein of the invention. have. Likewise, they can be at the temperature of the fixed catalyst bed. The shaped dilution body used in the inert layer may have the same shape as the shaped catalyst body used in the region of the fixed catalyst layer with the active composition. In addition, the shape of the molded dilution body used in the inert layer may differ from the shape of the molded catalyst body mentioned above (eg, spherical instead of annular).

Frequently, the molded body used for this inactive layer has a spherical shape with an annular shape of 7 mm × 7 mm × 4 mm (outer diameter × length × inner diameter) or a diameter d of 4-5 mm.

In many cases, the area of the fixed catalyst layer with the active composition is constructed as follows for the partial oxidation of propene to acrolein in the flow direction of the reaction gas mixture in the process according to the invention.

Firstly, 10 to 60% of the length, preferably 10 to 50%, more preferably 20 to 40%, most preferably 25 to 35% (ie, 0.70 to 1.50 m of length, Preferably from 0.90 to 1.20 m), each of the total lengths of the fixed bed catalyst charge zones is one uniform of the active composition, the shaped catalyst body and the molded dilution body, both preferably having substantially the same shape. Mixture or two consecutive homogeneous mixtures (dilution is reduced), where the weight ratio of the molded dilution body (the material density of the molded catalyst body and the material density of the molded dilution body is generally only slightly different) is typical 5 to 40% by weight, preferably 10 to 40% by weight or 20 to 40% by weight, more preferably 25 to 35% by weight. Subsequently, up to the end of the length of the region of the fixed catalyst layer having the active composition frequently downstream of the first zone (ie, up to 2.00-3.00 m, preferably 2.50-3.00 m in length), (first zone A layer of the shaped catalyst body diluted to a lesser amount, or most preferably a single layer of the same shaped catalyst body also used in the first zone, is advantageously arranged.

The abovementioned is especially true when the shaped catalyst body used in the fixed catalyst bed is an unsupported catalyst ring or a coated catalyst ring (especially those listed as preferred herein). For the purposes of the above-mentioned constructions, both the catalyst body or its support ring, and the molded dilution body, molded in the process according to the invention advantageously have an annular shape of 5 mm × 3 mm × 2 mm (outer diameter × length × inner diameter). Substantially.

Also mentioned above is when a molded coating catalyst body is used, in place of the inert molded dilution body, where the content of the active composition is 2-15% by weight lower than the active composition content of the formed coating catalyst body at the end of the fixed catalyst layer. Yes.

In general, a pure inert material layer, suitably 1 or 5 to 20% in length, based on the total length of the fixed catalyst bed, starts the fixed catalyst bed in the flow direction of the reaction gas mixture. Typically used as a heating zone for the reaction gas mixture.

Typically, the catalyst tubes in the tube bundle reactor for the step of propene partial oxidation to acrolein are made of ferritic steel and typically have a wall thickness of 1 to 3 mm. Their inner diameter is generally (uniformly) 20 to 30 mm, often 21 to 26 mm. Appropriately from the viewpoint of application, the number of catalyst tubes installed in the tube bundle container is 5000 or more, preferably 10000 or more. Frequently, the number of catalyst tubes installed in the reaction vessel is 15000 to 30000. Tube bundle reactors with a catalyst tube number exceeding 40000 are typically exceptional in this reaction step. Within the vessel, the catalyst tubes are usually arranged in a uniform distribution, and the distribution is suitably selected such that the spacing (known as catalyst tube pitch) of the central internal axis of the immediately adjacent catalyst tube is 35 to 45 mm (eg See, for example, European Patent EP-B 468290).

The reaction step operation from acrolein to acetic acid (and application of the process according to the invention) is for example described in EP-A 700 893 or DE-A 4 431 949 or in International Patent Publication WO 03. As described in / 057653, WO 03/055835, or WO 03/059857, or WO 03/076373, an anchoring layer is suitably in view of application in the simplest manner. It can be carried out using a catalyst described as suitable for the fixed catalyst bed of the reaction in a tube bundle reactor filled with a catalyst.

In other words, in the simplest manner, the fixed catalyst layer to be used is placed in a uniformly filled metal tube of the tube bundle reactor and the heating medium (one zone method), generally the salt melt, is conducted around the metal tube. The salt melt (heating medium) and the reaction gas mixture can be conducted in a simple forward or reverse direction. However, the heating medium (salt melt) can be conducted around the tube bundle in a way that is bent from the reactor point of view, only on the entire reactor being present in the forward or reverse direction with respect to the flow direction of the reaction gas mixture present. The volume flow rate of the heating medium (heat exchange medium) is typically 0 to 10 ° C., often 2 to 8, due to the temperature rise of the heat exchange medium from the inlet point into the reactor to the outlet point from the reactor (due to the exothermic nature of the reaction). ℃, often 3 to 6 ℃ degree. The inlet temperature of the heat exchange medium in the tube bundle reactor (which here corresponds to the temperature of the fixed catalyst bed) is generally 220 to 350 ° C., often 245 to 285 ° C., or 245 to 265 ° C. Suitable heat exchange media are especially fluid heating media. In particular, it is suitable to use melts of salts such as potassium nitrate, potassium nitrite, sodium nitrite and / or sodium nitrate or melts of low melting metals such as, for example, sodium, mercury and also various metal alloys. Ionic liquids can also be used.

Suitably, the starting reaction gas mixture is fed to the charge of the fixed bed catalyst preheated to the desired reaction temperature.

In particular, the desired high temporal space velocity of the acrolein on the fixed catalyst bed (eg, at least 130 l (STP) / l · h, or at least 140 l (STP) / l · h, but generally is 350 l (STP) in the case of up to / l · h, or up to 600 l (STP) / l · h), the process according to the invention for the partial oxidation of acrolein to acrylic acid is suitably carried out in a two-zone or multi-zone tube bundle reactor. (It is also possible to likewise carry out in a one-zone tube bundle reactor). A preferred variant of a two zone tube bundle reactor which can be used for this purpose according to the invention is disclosed in DE-C 2830765. However, it is disclosed in German Patent DE-C 2513405, US Patent US-A 3147084, German Patent DE-A 2201528, European Patent EP-A 383224 and German Patent DE-A 2903582. Two-zone tube bundle reactors are also suitable.

In other words, in the simplest manner, at least one fixed catalyst layer used in accordance with the invention is disposed in a uniformly filled metal tube of a tube bundle reactor, and the two substantially spatially separated heating media, generally salt melt Conductive around the metal tube. The tube region in which the particular salt bath is spread represents the temperature or reaction zone.

For example, salt bath C flows around the tubular region (reaction zone C) where the oxidation conversion (single pass) of acrolein proceeds until a conversion value of 55 to 85 mol% is achieved, and salt bath D is generally 90 mol% The subsequent zone of oxidation (single pass) of the subsequent acrolein flows around the tube zone (reaction zone D), where necessary, until further conversion values are achieved (if necessary, reaction zones C, D are additional reaction zones maintained at separate temperatures). This can lead to).

Within a particular temperature zone, the salt bath can in principle be conducted as in the one zone method. The inlet temperature of salt bath D is typically at least 5 ° C. to 10 ° C. above the temperature of salt bath C. Alternatively, the inlet temperature may be within a temperature range for the inlet temperature recommended for the one zone method.

On the other hand, a two-zone high load method of acrolein partial oxidation to acrylic acid is described, for example, in German Patent DE-A 19 94 8523, European Patent EP-A 11 06 598, or German Patent DE-A It may be performed as described in 19 94 8248.

Thus, the process according to the invention is not more than 70 l (STP) / l · h, or at least 70 l (STP) / l · h, at least 90 l (STP) / l · h of the acrolein on the fixed catalyst bed , 110 l (STP) / l · h or more, 130 l (STP) / l · h or more, 180 l (STP) / l · h or more, 240 l (STP) / l · h or more, 300 l (STP) / l · h or more, but typically 600 l (STP) / l · h or less. The temporal space velocity is based on the volume of the fixed catalyst bed, excluding any area used, exclusively made of inert material.

For the partial oxidation of acrolein to acrylic acid of the present invention, to prepare one or more fixed catalyst layers, a suitable shaped catalyst body having a multimetal oxide active composition, or a molded catalyst body having a multimetal oxide active composition and ( Using only a substantially homogeneous mixture of shaped bodies (molded dilution bodies) consisting of inert materials and having no multimetal oxide active composition that behaves substantially inert to heterogeneous catalyzed partial gas phase oxidation It is possible. Useful materials for such inactive shaped bodies are in principle all materials which are also suitable as support materials for coating catalysts "acrolein to acrylic acid" suitable according to the invention. Such useful materials include, for example, silicates such as porous or nonporous aluminum oxides, silicon dioxide, thorium dioxide, zirconium dioxide, silicon carbide, magnesium or aluminum silicates, or the previously mentioned copperstones (e.g. from Ceramtech). Steatite C-220).

The shape of this inert shaped dilution body may in principle be the desired one. In other words, it can be, for example, spherical, polygonal, solid cylindrical or annular. According to the invention, the selected inert shaped dilution body will preferably correspond to the shape of the shaped catalyst body to be diluted by them.

In general, the chemical composition of the active composition used in connection with the partial oxidation of acrolein to acrylic acid of the invention is preferred if it does not change on the fixed catalyst bed. In other words, the active composition used for the individual molded catalyst body may be a mixture of various multimetal oxides comprising Mo and V elements, but the same mixture should be used advantageously for all shaped catalyst bodies of the fixed catalyst bed. do.

For the partial oxidation of acrolein to acrylic acid of the invention, the volume-specific (ie normalized in units of volume) activity is preferably continuously, suddenly or stepwise in the fixed catalyst bed in the flow direction of the reaction gas mixture. Usually increases.

Volume-specific activity can be reduced in a simple manner, for example by diluting a base amount of the shaped catalyst body made in a uniform manner with the molded dilution body. The higher the fraction of the selected shaped dilution body, the lower the amount of active composition, i.e., catalytic activity, in the particular volume of the fixed bed.

Thus, the volume-specific activity of increasing at least once in the flow direction of the reaction gas mixture on the fixed catalyst bed is in a simple manner, for example for the process of partial oxidation of acrolein to acrylic acid according to the invention, for example By starting the layer with a high fraction of the inert shaped dilution body based on one type and then reducing said fraction of the dilution body formed continuously or at least once or more than once, suddenly (eg stepwise) in the flow direction. Can be achieved. However, an increase in volume-specific activity may, for example, increase the thickness of the active composition layer applied to the support, or, in certain shapes of the shaped coating catalyst body and active composition type, or of higher active compositions having the same shape but higher In mixtures of coating catalysts with different weight ratios, it is also possible by increasing the fraction of the shaped catalyst body in which the weight ratio of the active composition is high. Alternatively, the active composition itself can also be diluted during the preparation of the active composition, for example by incorporating an inert diluent such as hard calcined silicon dioxide into a dry mixture of starting materials to be calcined. Various amounts of added dilution material automatically induce various activities. As more and more diluent material is added, the resulting activity will be less and less. Similar effects can also be achieved, for example, by varying the mixing ratio appropriately in a mixture of unsupported catalyst and coating catalyst (with the same active composition). It will be appreciated that the described variables can also be used in combination.

Of course, catalyst mixtures having chemically different active compositions, and various activities as a result of the various compositions, can also be used for the fixed catalyst layer of the acrolein partial oxidation to acrylic acid of the present invention. These mixtures can then be diluted with an inert dilution body.

Upstream and / or downstream of the region of the fixed catalyst layer with the active composition, a layer exclusively composed of an inert material (eg only a molded dilution body) can be arranged. These can likewise be brought to the temperature of the fixed catalyst bed. The shaped dilution body used in the inert layer may have the same shape as the shaped catalyst body used in the region of the fixed catalyst layer with the active composition. In addition, the shape of the molded dilution body used in the inert layer may also differ from the shape of the molded catalyst body mentioned above (eg spherical instead of annular).

Frequently, the molded body used in this inactive layer has an annular shape of 7 mm x 7 mm x 4 mm (inner diameter x length x outer diameter), or a spherical shape with a diameter d of 4-5 mm.

In many cases, in the process of the invention for the partial oxidation of acrolein to acrylic acid, the area of the fixed catalyst layer with the active composition is established as follows in the flow direction of the reaction gas mixture.

Firstly, 10 to 60% of the length, preferably 10 to 50%, more preferably 20 to 40%, most preferably 25 to 35% (ie, 0.70 to 1.50 m of length, Preferably from 0.90 to 1.20 m), each of the entire length of the fixed bed catalyst charge zone is one uniform of the active composition, the shaped catalyst body and the molded dilution body, both preferably having substantially the same shape. With one mixture or two consecutive homogeneous mixtures (dilution is reduced), where the weight ratio of the molded dilution body (the material density of the molded catalyst body and the material density of the molded dilution body is generally only slightly different) It is usually 10 to 50% by weight, preferably 20 to 45% by weight, more preferably 25 to 35% by weight. Subsequently, up to the end of the length of the region of the fixed catalyst layer having the active composition frequently downstream of the first zone (ie, up to 2.00-3.00 m, preferably 2.50-3.00 m of length), (first A layer of molded catalyst body diluted in a smaller amount than in the zone or in the first zones, or most preferably the sole layer of the same molded catalyst body also used in the first zone (or in the first two zones) This is advantageously arranged.

The abovementioned is particularly true when the shaped catalyst body used in the fixed catalyst bed is an unsupported catalyst ring or coating catalyst sphere (especially those listed here as preferred for the partial oxidation of acrolein to acrylic acid herein). do. For the purposes of the above-mentioned constructions, both the molded catalyst body or their support rings, and the molded dilution body in the acrolein partial oxidation process to acrylic acid according to the invention are advantageously annular 7 mm × 3 mm × 4 mm (Outer diameter x length x inner diameter) substantially.

Also mentioned above is when, instead of an inert molded dilution body, a molded coating catalyst body in which the content of the active composition is 2 to 15% by weight lower than the active composition content of the formed coating catalyst body at the end of the fixed catalyst bed is used. Yes.

Generally, a pure inert material layer, suitably 5 to 20% in length, based on the total length of the fixed catalyst bed, starts the fixed catalyst bed in the flow direction of the reaction gas mixture. Typically used as a heating zone for the reaction gas mixture.

Typically, the catalyst tubes in the tube bundle reactor for the acrolein partial oxidation of the present invention are made of ferritic steel and typically have a wall thickness of 1 to 3 mm. Their inner diameter is generally (uniformly) 20 to 30 mm, often 21 to 26 mm. Appropriately from the viewpoint of application, the number of catalyst tubes installed in the tube bundle container is 5000 or more, preferably 10000 or more. Frequently, the number of catalyst tubes installed in the reaction vessel is 15000 to 30000. Tube bundle reactors with a catalyst tube number exceeding 40000 are typically exceptional in acrolein partial oxidation. Within the vessel, the catalyst tubes are usually arranged in a uniform distribution and the distribution is suitably selected such that the spacing (known as catalyst tube pitch) of the central internal axis of the immediately adjacent catalyst tube is between 35 and 45 mm (eg, European Patent EP-B 468290).

As already described, both partial oxidation of propene and acrolein in the process according to the invention can be carried out in a one-zone or two-zone tube bundle reactor. If the two reaction stages are connected in series, it is also possible that only the first reaction stage is carried out in a one zone tube bundle reactor and the second reaction stage is carried out in the two zone tube bundle reactor (or vice versa). In this case, the reactant gas mixture of the first reaction stage may be added directly to the second reaction stage, if appropriate, after replenishing the inert gas, or oxygen molecules, or inert gas and oxygen atoms, and, if appropriate, upon completion of the direct and / or indirect intermediate cooling. Supplied.

An intermediate cooler may be disposed between the tube bundle reactors of the first and second reaction stages, which may optionally contain an inert layer.

The fixed catalyst layer of propene partial oxidation and the fixed catalyst layer of acrolein partial oxidation for the process of the invention for the two-step partial oxidation of propene to acrylic acid are also described, for example, in WO 03/059857, As described in EP-A 911313 and EP-A 990636, for example, a single multiple catalyst tube tube bundle reactor likewise having two temperature zones can also be installed spatially and continuously. I can understand that. This case is called a single reactor two stage process. In this case, one temperature zone generally extends on one fixed catalyst bed. An additional inert layer can be arranged between the two fixed catalyst layers, and if appropriate, the inert layer is placed in a third temperature zone and heated separately. The catalyst tube can be continuous or disconnected by an inert bed.

The inert gas to be used in the fill gas mixture (starting reaction gas mixture 1) of the "propene reaction stage to acrolein" is, for example, 20 volume percent or more, or 30, regardless of the propene time space velocity selected for the fixed catalyst bed. At least 40% by volume, or at least 40% by volume, or at least 50% by volume, or at least 60% by volume, or 70% by volume, or 80% by volume, or 90% by volume, or at least 95% by volume of nitrogen molecules.

The inert diluent gas may also consist, for example, of H ₂ O 2 to 35 or 20% by weight, and N ₂ 65 to 98% by volume.

Inert diluent gases such as propane, ethane, methane also at a propene time space velocity on the fixed catalyst bed of "propene reaction to acrolein" of greater than 250 l (STP) /l.h. It is recommended to use butanes, pentanes, CO ₂ , CO, steam and / or noble gases in the process according to the invention. However, it will be appreciated that these gases can be used at lower propene time space velocities.

The working pressure (particularly at the start of the operating time of the fixed catalyst bed) in the gas phase partial oxidation of propene to acrolein can be below atmospheric pressure (eg below 0.5 bar) or above atmospheric pressure. Typically, the working pressure in the gas phase partial oxidation of propene will be a value of 1 to 5 bar, often 1 to 3 bar.

Typically, the reaction pressure in the partial propene oxidation to acrolein of the present invention will not exceed 100 bar. However, based on the same time-space velocity of starting reaction gas mixture 1 of l (STP) / l · h, the working pressure during the operating time of at least one fixed catalyst bed for the partial oxidation of propene to acrolein is at least one fixed It is essential to the present invention to increase in order to inhibit deactivation of the catalyst bed. The pressure will be increased to the extent described in the general area of this specification. The procedure of the invention is described in EP-A 990 636, EP-A 11 06 598, EP-A 614 872, DE-A 10 35 0822, DE-A It will be appreciated that in combination with the procedure for extending the on-stream time of the catalyst bed recommended in 10 23 2748 and DE-A 10351269, it will be understood that it can be used very generally. Thus, several years of catalyst bed uptime can be achieved.

The O ₂ : propene molar ratio of the starting reaction gas mixture 1 for oxidation of propene to acrolein, which is conducted through a suitable fixed catalyst bed in the process according to the invention, will typically be at least 1 (downstream acrolein to acrylic acid). Substantially regardless of whether there is an oxidation step). Typically, the ratio will be a value of 3 or less. Often, the O ₂ : propene molar ratio in the mentioned fill gas mixture will advantageously be between 1: 2 and 1: 1.5. In many cases, the propene partial oxidation process to acrolein has a propene: oxygen: inert gas (including steam) volume ratio (l (STP) / l · h) in the starting reaction gas mixture 1 of 1: (1 to 3). : (3 to 30), preferably 1: (1.5 to 2.3): (10 to 15).

The propene fraction in the starting reaction gas mixture 1 can be, for example, 4-20% by volume, often 5 or 7-15% by volume, or 6 or 8-12% by volume, or 5-8% by volume (in each case, the total volume). Can be set to the value of.

Typical compositions of starting gas mixture 1 (regardless of the time-space velocity selected and whether or not followed by acrolein partial oxidation to acrylic acid)

Propene 6 to 6.5 vol%,

H ₂ O 3-3.5 volume percent,

CO 0.3-0.5% by volume,

0.8 to 1.2 vol.% CO ₂ ,

0.025 to 0.04% by volume of acrolein,

0 ₂ 10.4-10.7 volume percent, and

Nitrogen molecule as a residue to reach 100%, or

Propene 5.4% by volume,

Oxygen 10.5% by volume,

CO _x 1.2% _by volume,

N ₂ 80.5% by volume, and

H ₂ O 2.4% by volume

It may include a component of.

However, the starting reaction gas mixture 1 for the partial oxidation of propene to acrolein can have the following composition according to the invention.

Propene 6-15% by volume,

4-30% by volume of water (often 6-15% by volume),

0 to 10% by volume (preferably 0 to 5% by volume) other than propene, water, oxygen and nitrogen,

Sufficient oxygen molecules with a molar ratio of oxygen molecules present to propene molecules present between 1.5 and 2.5, and

Nitrogen molecule as a residue to bring the total amount to 100% by volume.

According to the invention, another starting reaction gas mixture 1 for the partial oxidation of propene to acrolein is

Propene 6.0% by volume,

Air 60% by volume, and

H ₂ O 34 vol%

It may include.

Alternatively, Example 1 of EP-A 990 636, or Example 2 of EP-A 990 636, or Example 3 of EP-A 1 106 598, or EP EP The starting reaction gas mixture 1 of the composition according to Example 2 of -A 1 106 598 or Example 53 of EP-A 1 106 598 can be used for the "propene reaction step to acrolein".

A further starting reaction gas mixture 1 for the propene reaction step to acrolein, suitable according to the invention, can be within the following composition ranges.

Propene 7-11% by volume,

H ₂ O 6-12% by volume

0 to 5% by volume of components other than propene, water, oxygen and nitrogen,

Sufficient oxygen with a molar ratio of oxygen present to propene present, between 1.4 and 2.2, and

Nitrogen molecule as a residue to bring the total amount to 100% by volume.

Propenes used in the starting reaction gas mixture 1 are in particular polymer grade propenes and chemical grade propenes as described, for example, in DE-A 10232748.

It may also be mentioned at this point that a part of the fill gas mixture of the "propene reaction to acrolein step" may be known as the circulating gas, regardless of whether the "acrolein reaction step to acrylic acid" is followed. Can be. As already described, this is the gas remaining from the product gas mixture of the reaction stage after removal of the product, usually in the finishing operation after the final reaction stage (acrolein and acrylic acid removal), and in part as a substantially inert diluent gas. Recycle to the propene reaction stage and / or any subsequent acrolein reaction stage.

The oxygen source used is usually air.

In the process according to the invention the temporal space velocity on the fixed catalyst layer (excluding the pure inert zone) of the starting reaction gas mixture 1 is typically 1000 to 10000 l (regardless of whether the "acrolein reaction step to acrylic acid" is followed). (STP) / l · h, typically 1000 to 5000 l (STP) / l · h, often 1500 to 4000 l (STP) / l · h.

When propene partial oxidation to acrolein followed by acrolein partial oxidation, the product gas mixture of the propene reaction stage is fed to the acrolein reaction stage, if appropriate, after intermediate cooling. The oxygen required in the acrolein reaction stage may be added to the propene reaction stage in excess of the starting reaction gas mixture 1 and thus may be a component of the product gas mixture of the propene reaction stage. In this case, the product gas mixture of the propene reaction stage, if appropriate cooled immediately, may be the charge gas mixture of the direct acrolein reaction stage. However, from acrolein to acrylic acid, some or all of the oxygen required for the second oxidation step may not be added to the product gas mixture of the propene reaction step until they enter the acrolein reaction step, for example in the form of air. . This addition may be associated with the direct cooling of the product gas mixture of the acrolein reaction step.

The inert gas present in the fill gas mixture for the acrolein reaction stage (starting reaction gas mixture 2) (whether or not there is a previous propene reaction stage), resulting from the abovementioned linkage, is for example at least 20% by volume. Or at least 30 vol%, or at least 40 vol%, or at least 50 vol%, or at least 60 vol%, or at least 70 vol%, or at least 80 vol%, or at least 90 vol%, or at least 95 vol% nitrogen molecules. It may be made of.

However, the inert diluent gas in the fill gas for the acrolein reaction step is H ₂ O 5 to 25 or 20% by weight (eg can be formed in the preceding propene reaction step and / or added if appropriate) and N ₂ 70 Often from 90% by volume.

However, at an acrolein time space rate on the fixed catalyst layer for partial oxidation of acrolein to acrylic acid, in excess of 250 l (STP) / l · h, inert diluent gases, for example propane, ethane, methane, butane The use of, pentane, CO ₂ , steam and / or noble gases is recommended in the process according to the invention. It will be appreciated that these gases can also be used at relatively low acrolein time space velocities.

The working pressure (particularly at the start of the operating time of the fixed catalyst bed) in the gas phase partial oxidation of acrolein to acrylic acid can be below atmospheric pressure (eg below 0.5 bar) or above atmospheric pressure. Typically, the working pressure in the gas phase partial oxidation of acrolein can be a value of 1 to 5 bar, often 1 to 3 bar.

Typically, the reaction pressure of the acrolein partial oxidation of the present invention will not exceed 100 bar. However, based on the same time-space velocity of starting reaction gas mixture 2 of l (STP) / l·l, the working pressure during the operating time of at least one fixed catalyst bed for the partial oxidation of acrylic acid to acrylic acid is It is essential to the present invention to be increased to inhibit inactivation of one or more fixed catalyst beds. The pressure can be increased to the extent described in the general area of this specification. The procedure of the invention is described in EP-A 990 636, EP-A 11 06 598, EP-A 614 872, DE-A 10 35 0822, DE-A It will be appreciated that it can be used very commonly in combination with procedures for prolonging the run time of catalyst beds recommended in 10 23 2748 and DE-A 10351269. Thus, several years of catalyst bed uptime can be achieved.

The O ₂ : crolein molar ratio of the fill gas mixture to the acrolein reaction stage conducted through the appropriate fixed catalyst bed in the process according to the invention will typically be at least 1 (regardless of the presence of the preceding propene reaction stage). Typically, the ratio will be a value of 3 or less. According to the invention, the O ₂ : crolein molar ratio of the abovementioned fill gas mixture will often be 1 to 2 or 1 to 1.5. In many cases, the process according to the invention results in acrolein: oxygen: vapor: inert gas volume ratio (l (STP)) in starting reaction gas mixture 2 (fill gas mixture for the acrolein reaction stage) of 1: (1 to 3). : (0.5 to 10) :( 3 to 30), preferably 1: (1 to 3) :( 0.5 to 10) :( 7 to 20).

The acrolein fraction in the fill gas mixture for the acrolein reaction stage (whether or not there is a previous propene reaction stage) is, for example, 3 or 6 to 15 volume percent, often 4 or 6 to 10 volume percent, or 5 To 8% by volume (in each case based on total volume). In the "acrolein process to acrylic acid process" of the present invention, the temporal space velocity on the fixed catalyst layer (here, except for the pure inert region) of the fill gas mixture (starting reaction gas mixture 2) is typically referred to as "propene process to acrolein". As in, 1000 to 10000 l (STP) / l · h, typically 1000 to 5000 l (STP) / l · h, often 1500 to 4000 l (STP) / l · h.

When the process according to the invention is carried out, after the adjustment operation a new fixed catalyst layer for partial oxidation of propene to acrolein is usually started (ie irrespective of whether partial oxidation of acrolein formed with acrylic acid is followed) After determining the composition of reaction gas mixture 1 and determining the time-space volume on the fixed catalyst bed for propene partial oxidation of starting reaction gas mixture 1, the temperature of the fixed catalyst bed (or heating medium into the heating zone of the tube bundle reactor) Inlet temperature) will be controlled in such a way that the C ^pro conversion of propene in one pass of reaction gas mixture 1 through the fixed catalyst bed is at least 93 mol%. When preferred catalysts are used, at least 94 mol%, or at least 95 mol%, or at least 96 mol%, or at least 97 mol% C ^pro values and often even higher C ^pro values are also possible.

If the heterogeneous catalyzed partial oxidation of propene to acrylate is carried out continuously, the composition of the starting reaction gas mixture 1 and the time-space velocity on the fixed catalyst bed of the starting reaction gas mixture 1 will remain substantially constant ( If desired, the space time velocity is adapted to fluctuating market demand). Propene conversion (ie, at least 93 mol%, or at least 94 mol%, or at least 95 mol%, or at least 96 mol%, or at least 97 mol%) in one pass of the reaction gas mixture in the desired target passage In order to maintain C ^pro ), the deterioration of the activity of the fixed catalyst bed over time is often (as well as by raising the temperature of the fixed catalyst bed (inlet temperature of the heating medium into the temperature zone of the tube bundle reactor) under these production conditions The flow rate of the heating medium will typically be kept substantially constant). However, this above procedure is associated with the disadvantages described earlier in this specification.

Thus, as described in DE-A 10351269, a gas mixture G consisting of oxygen molecules, inert gas, and, if appropriate, steam, is conducted through the fixed catalyst bed at a temperature of the fixed catalyst bed of 250 to 550 ° C. In order to achieve this, the procedure sometimes advantageously interferes with gas phase partial oxidation. Subsequently, partial oxidation of the propene is sustained while substantially maintaining the reaction conditions (propene time space velocity on the fixed catalyst bed is preferably recovered slowly) and the temperature of the fixed catalyst bed is adjusted to the desired target value of the propene conversion. Are adjusted in a way that is reached. In general, for the same conversion, these temperature values will be somewhat lower than the temperature of the fixed catalyst bed before the partial oxidation and the treatment of the invention with the gas mixture G. Starting from this temperature value of the fixed catalyst bed, partial oxidation will continue while maintaining substantially remaining conditions, and over time the deactivation of the fixed catalyst bed will be appropriately suppressed by occasionally raising the temperature of the fixed catalyst bed. . For example, within the following year, the partial oxidation according to the invention is interrupted at least once, in order to conduct the gas mixture G through the fixed catalyst bed in the manner of the invention. Subsequently, the partial oxidation according to the invention commences again as described and the like. However, measures of the present invention that increase the working pressure will make it possible to adequately exert its influence with the rise of the temperature of the catalyst bed during the operating time of the catalyst bed. This can be done step by step or uniformly.

In a corresponding manner, when carrying out the process according to the invention, a new fixed catalyst bed for the partial oxidation of acrolein to acrylic acid, after being controlled, determines the composition of the starting and starting reaction gas mixture 2 of the reaction step and After determining the temporal space velocity on the appropriate fixed catalyst bed of starting reaction gas mixture 2, the temperature of the fixed catalyst bed (or the inlet temperature of the heating medium to the heating zone of the tube bundle reactor) is determined by the starting reaction gas mixture 2 through the fixed catalyst bed. It will usually be operated in such a way that the conversion rate of the acrolein C ^acr in one pass of is controlled in a manner of at least 90 mol%. When preferred catalysts are used, at least 92 mol%, or at least 94 mol%, or at least 96 mol%, or at least 98 mol%, and often even at least 99 mol% and higher C ^acr values are also possible.

If the heterogeneous catalyzed partial oxidation of acrolein to acrylic acid is carried out continuously, the composition of starting reaction gas mixture 2 and the time and space velocity on the fixed catalyst bed of starting reaction gas mixture 2 will remain substantially constant (if appropriate However, the time-space velocity is adapted to changing market demands). Acrolein conversion for one pass of the fill gas mixture in the desired target passage (ie, at least 90 mol%, or at least 92 mol%, or at least 94 mol%, or at least 96 mol%, or at least 98 mol%, Or to maintain a value of 99 mol% or more), the deterioration in activity of the fixed catalyst bed over time is typically achieved by raising the temperature of the fixed catalyst bed (inlet temperature of the heating medium into the temperature zone of the tube bundle reactor) under these production conditions. Sometimes (as well as the flow rate of the heating medium is typically kept substantially constant). However, this procedure alone is associated with the disadvantages described earlier in this specification.

Thus, in order to conduct the gas mixture G through the fixed catalyst layer of partial oxidation of acrolein to acrylic acid at a temperature of the fixed catalyst layer of 200 to 450 ° C. (in a two-step partial oxidation of propene to acrylic acid, propene of acrolein Conducting through the fixed catalyst bed of oxidation), the procedure results in gas phase partial oxidation at least once, for example, the temperature rise taken of the fixed catalyst bed is permanently at least 10 ° C. or at least 8 ° C. On the basis of temperature). Subsequent partial oxidation is then continued while substantially maintaining the reaction conditions (the temporal space velocity of the acrolein on the appropriate fixed catalyst bed is preferably recovered slowly, for example as described in DE-A 10337788). The temperature of the fixed catalyst bed is adjusted in such a way that the acrolein conversion reaches the desired target value. In general, for the same conversion, these temperature values will be somewhat lower than the temperature of the fixed catalyst bed before the partial oxidation and the treatment of the invention with the gas mixture G. Starting from this temperature value of the fixed catalyst bed, partial oxidation of acrolein lasts while maintaining substantially remaining conditions, and then over time the deterioration of the activity of the fixed catalyst bed is appropriately achieved by occasionally raising the temperature of the fixed catalyst bed. Suppressed. For example, before the temperature rise of the fixed catalyst bed to be carried out is permanently at least 10 ° C. or at least 8 ° C., the partial oxidation according to the invention is carried out through the gas mixture G through the fixed catalyst bed of acrolein partial oxidation of acrolein to acrylic acid. In order to conduct (when appropriate, through the fixed catalyst bed of the propene reaction stage), it is interrupted at least once. Subsequently, the partial oxidation according to the invention commences again as described and the like. In addition, the measures of the present invention that increase the working pressure will allow to properly exert its influence with the temperature rise of the catalyst bed during the operating time of the catalyst bed. This can be done step by step or uniformly. In the case of the two-step partial oxidation of the present invention of propene to acrylic acid, for example, it is possible for a pressure regulating device to be mounted downstream of each of the two reaction stages and further to conduct them to the condensed phase in the bottom region. It is possible to mount on top of a downstream absorption column or a fractional condensation column, for the purpose of transferring acrylic acid from the gaseous product gas mixture of partial oxidation.

In the case of this two-stage reaction, however, a pressure regulator is often sufficient downstream of the second reaction stage (preferably directly at the outlet of the product gas mixture) in which the acrolein is partially oxidized to acrylic acid.

Surprisingly, in the case of a fixed catalyst layer which has been partially deactivated over an extended operating time, an increase in the working pressure results in reactivation of the catalyst bed. Surprisingly, furthermore, when the pressure increase is carried out discreetly, no significant decrease in the selectivity of the target product formation of the catalyst bed, in particular the fixed catalyst bed, occurs.

The process according to the invention thus enables, on the one hand, the uptime of a longer catalyst bed, in particular a fixed catalyst bed, in the reactor system before they are partially or fully exchanged. On the other hand, the achieved reactant conversion, integrated over time, is likewise increased.

The process according to the invention is for the partial oxidation of propene to acrolein (for partial oxidation of acrolein to acrylic acid), the temporal space velocity 110 l (STP) / l · h on the fixed catalyst layer of propene (acrolein) At least 120 l (STP) / l · h, or at least 130 l (STP) / l · h (under higher reactant time-space velocities, the catalyst generally deactivates faster) It is advantageous. For two-stage partial oxidation of propene to series-linked acrylic acid, the temporal space velocity on the fixed catalyst layer for acrolein partial oxidation of acrolein is in each case below the propene time space velocity on the fixed catalyst layer for propene partial oxidation. And 20 l (STP) / l · h or less.

When combining the process according to the invention with the procedure for intermediate regeneration of the catalyst bed, it is possible to operate the catalyst bed at a predetermined conversion rate, always below the set maximum temperature, for long term operation.

Circulating gas formation associated with the removal of acrylic acid from the product gas mixture can be carried out as described in WO 97/48669.

In general, a freshly charged fixed catalyst layer for propene partial oxidation and acrolein partial oxidation to acrolein and acrylic acid, respectively, is described in EP-A 990 636 and EP-A 11 06 598. Likewise, both hotspot formation and their temperature selectivity will be configured in a very low manner.

Finally, in all gas phase partial oxidations mentioned and discussed herein, the increase in the working pressure of the present invention is after 2000 hours, or after 4000 hours, or after 7000 hours, or after 9000 hours, or 12000 hours of at least one catalyst bed. It should be emphasized that after, or after 15000 hours, or after 18000 hours, or after 21000 hours, or after 24000 hours, or after 27000 hours, or after 30000 hours, or after more operating hours. Intermediate regeneration is included therein. In the two-step propene partial oxidation of propene to acrylic acid, in the case of a new catalyst layer, the reaction operation is started to a propene reaction stage of 1.4 to 1.9 bar at the inlet pressure and the inlet pressure is increased to 2.5 to over the operating time. It has been found advantageous to raise to 3.0 bar.

In addition, the operation of the process according to the present invention may also be carried out by one or more air compressors (for example DE-A 10259023, German patent) which compress the air typically used as an oxygen source, in order to bring the starting reaction gas mixture to the required working pressure. It should be emphasized that the need for a conventional and radial compressor according to DE-A 10353014). Typically, air compressors used for heterogeneous catalyzed partial gas phase oxidation are designed to allow a pressure of at most 0.5 bar to pass at a predetermined time and space velocity on the catalyst bed of the starting reaction gas mixture for economic reasons. do. Thus, in order to realize the procedure of the present invention, advantageous air compressors (e.g., the radial compressors mentioned) for the reaction gas mixtures may be used at predetermined time and space velocities where they are greater than 0.5 to 4 bar, often 0.6 to 3.5 bar, In such a way that they can pass between 0.7 and 3 bar, and often between 0.8 and 2.5 bar or between 1 and 2 bar (ie the maximum possible working pressure by the compressor can be up to 4 bar above the minimum working pressure). In particular, this means that the time space velocity on the catalyst bed of the starting reaction gas mixture is at least 1500 l (STP) / l · h, or at least 2000 l (STP) / l · h, or at least 2500 l (STP) / l · h, Or 3000 l (STP) / l · h or more, or 4000 l (STP) / l · h or more. In general, the aforementioned time space velocity in the process according to the invention is a value of 5000 l (STP) / l · h or less. Optionally, other components of the starting gas mixture (eg circulating gas) can be brought to working pressure in an air compressor, if necessary. However, reactants such as propene and propane are usually stored as liquids and can generally be evaporated directly from them to working pressure. In some cases, the circulating gas is compressed separately.

Examples and Comparative Examples

A) Preparation of Catalyst C _p Used in Partial Oxidation of Propene to Acrolein

Preparation of Cyclic Supported Catalysts Having Stoichiometric Active Multimetal Oxides

[Bi ₂ W ₂ O ₉ · 2WO ₃ ] _0.5 [Mo ₁₂ Co _5.5 Fe _2.94 Si _1.59 K _0.06 O _x ] ₁ .

1. Preparation of Starting Composition 1

209.3 kg (W 72.94 wt.%) Of tungstic acid were stirred in portions at 775 kg at 25 ° C. in aqueous bismuth nitrate solution (Bi 11.2 wt.%; Free nitric acid 3 to 5 wt .; material density: 1.22 to 1.27 g / ml). . The resulting aqueous mixture was then stirred at 25 ° C. for a further 2 hours and then spray dried.

Spray drying was performed in a reverse direction at a gas inlet temperature of 300 ± 10 ° C. and a gas outlet temperature of 100 ± 10 ° C. in a rotating disk spray tower. The resulting spray powder (30 μm of particle size is substantially uniform) of 12% by weight of ignition loss (ignition at 600 ° C. for 3 hours in air) followed by paste in a kneader with 16.8% by weight of water (based on powder) And extruded into a 6 mm diameter extrudate using an extruder (rotation moment: 50 Nm or less). They were cut into 6 cm sections and dried in air on a 3-zone belt dryer at temperatures 90-95 ° C. (zone 1) and 125 ° C. (zone 2) and 125 ° C. (zone 3) for 120 minutes of residence time, followed by 780 Thermally treated (fired; air-flowing rotary tube oven (volume 1.54 m ³ , 200 m ³ (STP) air / hour). The composition was essential: the desired phases were WO ₃ (monocrystalline) and Bi ₂ W ₂ O _9, and the presence of γ-Bi ₂ WO ₆ (Russellite) was not intended, therefore, the compound γ-Bi ₂ WO ₆ had to repeat the manufacture until reflection disappeared, if still measured by reflection in X-ray powder diffractometer at reflection angle 2θ = 28.4 ° (CuKα irradiation) after firing, raising firing temperature within specific temperature range Or at constant firing temperature Increased the time. X ₅₀ value of the preformed calcined mixed oxide obtained in this way, the resulting particle size (as described in [Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition (1998) Electronic Release, Chapter 3.1.4 or DIN 66141 ] Is then 5 mm.The milled material is then subdivided into 1% by weight (based on milled material) of Sipernat® type from Degussa. It was mixed with SiO ₂ (bulk density 150 g / l; X ₅₀ value of SiO ₂ particles was 10 μm and BET surface area was 100 m ² / g).

2. Preparation of Starting Composition 2

Solution A was prepared by dissolving 213 kg of ammonium heptamolybdate tetrahydrate (MoO ₃ 81.5 wt.%) At 60 ° C. in 600 l water with stirring, and the resulting solution was maintained at 60 ° C. in an aqueous solution of potassium hydroxide 0.97 It stirred and mixed at 20 degreeC with kg (KOH 46.8 weight%).

Solution B was prepared by introducing 116.25 kg of iron (III) nitrate solution (14.2 wt.% Fe) into 262.9 kg (12.4 wt.% Co) aqueous solution of cobalt nitrate at 60 ° C. The solution B was then continuously fed over 30 minutes into the initially charged solution A while maintaining 60 ° C. The mixture was then stirred at 60 ° C. for 15 minutes. Subsequently, 19.16 kg of Ludox silica gel (SiO ₂ 46.80 wt%, density: 1.36-1.42 g / ml, pH 8.5-9.5, maximum alkali content 0.5 wt%) from Dupont was produced 19.16 kg Was added and the mixture was then stirred at 60 ° C. for an additional 15 minutes.

The mixture was then spray dried in reverse at a rotating disk spray tower (gas inlet temperature 400 ± 10 ° C., gas outlet temperature 140 ± 5 ° C.). The resulting spray powder had a ignition loss (ignite in air at 600 ° C. for 3 hours) at approximately 30% by weight and a substantially uniform particle size of 30 μm.

Preparation of Multimetal Oxide Active Compositions

Starting composition 1 is uniformly mixed with starting composition 2

[Bi ₂ W ₂ O ₉ · 2WO ₃ ] _0.5 [Mo ₁₂ Co _5.5 Fe _2.94 Si _1.59 K _0.08 O _x ] ₁

Mix in a mixer with a blade head in the amount required for the phosphorus multimetal oxide active composition. Based on the overall composition mentioned above, Timlex AG (TIMREX) P44 type (Constitution analysis: at least 50% by weight less than 24 μm, at least 10% by weight at least 24 μm and 48 from Timcal AG, San Antonio, USA) An additional 1% by weight of finely divided graphite, up to 48 μm, up to 5% by weight, up to 48 μm, BET surface area: 6-13 m ² / g) was homogeneously mixed. The resulting mixture was then subjected to a K200 / 100 compressor type with grooved slippery grooves (gap width: 2.8 mm, sieve width: 1.0 mm, lower particle size sieve width: 400 μm, target compression force: 60 kN, screw Rotational speed: 65 to 70 revolutions per minute) was transferred to a compressor (Hosokawa Bepex GmbH, Reingarten, D-74211, Germany). The resulting compact had a hardness of 10 N and had a substantially uniform particle size of 400 μm to 1 mm.

The compact is then mixed with an additional 2% by weight of the same graphite, based on its weight, followed by a rotary tableting press of type Rx73 from Kilian, D-50735 Cologne, Germany. Under an atmosphere of nitrogen to obtain an annular shaped unsupported catalyst precursor body of 5 mm × 3 mm × 2 mm (outer diameter × length × inner diameter) shape with a side breaking strength of 19 N ± 3N.

As used herein, lateral fracture strength refers to fracture strength when compressing an annular shaped unsupported catalyst precursor body to a cylindrical surface (ie, parallel to the surface of the ring orifice) at the right angle.

All lateral fracture strengths herein were determined using a Z 2.5 / TS1S type material tester from Zwick GmbH (D-89079 Ulm, Germany). The material tester was designed for similar static stresses with a single-impetus, static, dynamic, or varying profile. It is suitable for tensile, compression and bending experiments. The installed force transducer of the KAF-TC type from AST company (Manufacturer D 01307 Dresden, Germany) with manufacturer number 03-2038 has been calibrated according to DIN EN ISO 7500-1 and can be used in the 1-500 N measuring range. (Relative measurement uncertainty: ± 0.2%).

Initial force: 0.5 N,

Initial force speed: 10 mm / min,

Experimental Speed: 1.6 mm / min

The measurement was carried out with a parameter of.

The upper die was slowly lowered just above the cylindrical surface of the initially annular unsupported catalyst precursor body. The upper die was then stopped to continue lowering at apparently slower experimental speeds with the minimum initial force needed to lower further.

The initial force at which the shaped unsupported catalyst precursor body shows crack formation is the side fracture strength (SCS).

During the final heat treatment, in each case, 1000 g of the shaped unsupported catalyst precursor body was initially placed in an airflow muffle furnace (capacity 60 l, 1 l / h air per gram of the shaped unsupported catalyst precursor body). Heated to 190 ° C. at room temperature (25 ° C.) at a heating rate of 180 ° C./hour. The temperature was maintained for 1 hour and then raised to 210 ° C. at a heating rate of 60 ° C./hour. The temperature was then maintained at 210 ° C. for 1 hour and then raised to 230 ° C. at a heating rate of 60 ° C./hour. After holding at this temperature for 1 hour, the temperature was likewise raised to 265 ° C at a heating rate of 60 ° C / hour. The temperature of 265 ° C. was then maintained for 1 hour as well. The furnace was then initially cooled to room temperature to substantially complete the decomposition phase. The furnace was then heated to 465 ° C. at a heating rate of 180 ° C./hour and the firing temperature was maintained for 4 hours.

The cyclic unsupported catalyst C _p was obtained from the cyclic shaped unsupported catalyst precursor body.

Specific surface area S for the resulting cyclic unsupported catalyst C _p , the total pore volume V, the pore diameter d ^max which contributes the largest contribution to the total pore volume, and those pore diameters with a diameter greater than 0.1 and less than 1 μm in the total pore volume. The percentages were as follows.

S = 7.6 cm ² / g.

V = 0.27 cm ³ / g.

d ^max [μm] = 0.6.

V ^0.1 _1-% = 79.

In addition, the ratio R of the apparent material density to the actual material density ρ (as defined in EP-A 1340538) was 0.66.

On an industrial scale, the same cyclic catalyst was used with a belt firing device (the bed height at decomposition (chambers 1 to 4) was advantageously 44 mm at a residence time of 1.46 hours per chamber, advantageously at firing (chambers 5 to 8). It was prepared by heat treatment as described in Example 1 of DE-A 10046957, except that it was 130 mm at a residence time of 4.67 hours. The surface area of the chamber (at a uniform chamber length of 1.40 m) was 1.29 m ² (decomposition) and 1.40 m ² (firing) and a coarse-mesh belt with 75 m ³ (STP) / hour of feed air sucked by the rotary ventilator It flowed from below through a coarse-mesh belt. In the chamber, the temporary and local deviation of temperature from the target value was always below 2 ° C. In addition, the procedure was as described in Example 1 of DE-A 10046957.

B) Preparation of Catalyst C _A (Coating Catalyst) Used for Partial Oxidation of Acrolein to Acrylic Acid and with a Stoichiometric Formula of Mo ₁₂ V ₃ W _1.2 Cu _2.4 O _x

1. General description of the rotary tube furnace used for firing

A schematic drawing of a rotary tube furnace is shown in FIG. 1 attached hereto. The following reference numerals relate to FIG. 1.

The central member of the rotary tube furnace is the rotary tube 1. The length was 4000 mm and the inner diameter was 700 mm. Made of 1.4893 stainless steel, the wall thickness was 10 mm.

The inner wall of the rotary tube furnace was equipped with a lifting lance 5 cm high and 23.5 cm long. They were mainly used to lift and mix thermally treated materials in rotary tube furnaces.

At the same height of the rotary tube furnace, four lifting windows (quadrant) in each case were mounted equidistant around the circumference (in each case separated by 90 °). Eight quadrants (23.5 cm apart) were placed along the rotary tube furnace. Two adjoining quadruple hoisting windows are oriented to one side with respect to each other on the circumference. At the start and end of the rotary tube furnace (first and last 23.5 cm) there was no lift window.

The rotatable tube was freely rotated in a cube (2) each having four electrically heated (resistance heating) heating zones of continuous and equal length of the rotatable tube and each surrounding the circumference of the rotatable tube furnace. Each of the heating zones could heat the appropriate rotating tube zone to a temperature between room temperature and 850 ° C. The maximum heating power of each heating zone was 30 kW. The distance between the electrical heating zone and the rotary tube outer surface was about 10 cm. At the start and end points, the rotatable tube protruded approximately 30 cm beyond the cube.

The rotation speed could be variably adjusted between 0 and 3 revolutions per minute. The carousel could be rotated left or right. When rotated to the right, the material remained in the rotary tube. When rotated to the left, the material was transferred from inlet 3 to outlet 4. The angle of inclination of the rotary tube with respect to the horizontal plane could be adjusted between 0 ° and 2 °. During batch operation it was virtually 0 °. In continuous operation, the lowest point of the rotary tube was the material outlet. The rotary tube could be cooled quickly by turning off the electrical heating zone and turning on the ventilator (5). It sucked ambient air through the holes 6 at the bottom of the cube and transported through three flaps 7 with variablely adjustable openings in the lid.

The material inlet was controlled via a rotary star feeder (mass control). Material discharge was controlled through the direction of rotation of the rotary tube, as already mentioned.

In the case of a batch operation of the rotary tube, an amount of material of 250 to 500 kg could be thermally treated. Amounts were typically placed exclusively in the heating zone of the rotary tube.

From the window 8 lying on the central axis of the rotary tube, a total of three thermoelectric elements 9 were directed vertically into the material at 800 mm intervals. In this specification, the temperature of a material refers to the arithmetic mean of three thermoelectric temperatures. According to the invention, the maximum deviation of the temperature measured twice in the material in the rotary tube was less than approximately 30 ° C., preferably less than 20 ° C., more preferably less than 10 ° C., and most preferably less than 5 or 3 ° C. .

The gas stream could be conducted through a rotary tube, thereby adjusting the firing atmosphere or generally the atmosphere of the heat treatment of the material.

Heater 10 made it possible to heat the gas stream conducted to the rotary tube to the desired temperature (eg, from the rotary tube to the desired temperature for the material) before entering the rotary tube. The maximum power of the heater was 1 x 50 kW + 1 x 30 kW. In principle, the heater 10 could for example be an indirect heat exchanger. Such heaters could in principle also be used as coolers. In general, however, the gas stream was an electric heater conducted on a heated metal line using electricity (97D / 80 CSN flow from C. Schniewindt KG, suitably 58805 Neuerade, Germany). Type burner).

In principle, the rotary tube device made it possible to partially or completely recycle the conducted gas stream through the rotary tube. The recirculation line required for this goal was connected to the rotary tube in a fluid manner at the rotary tube inlet and rotary tube outlet using a ball bearing or graphite pressure seal. These leads were washed off with inert gas (eg nitrogen) (blocking gas). Two flush streams 11 fed a gas stream conducting through the rotary tube at the inlet to the rotary tube and at the outlet from the rotary tube. Suitably, the rotary tubes were narrowed at the start and at the end, each of which was fed into the tubes of the recirculation line which was guided and dropped.

Cyclone 12 was placed downstream of the outlet of the gas stream conducted through the rotary tube to remove solid particles entrained in the gas stream and droplets (the centrifugal separator is solid particles suspended in the gas phase by the interaction of centrifugal force and gravity). The centrifugal force of the rotating gas stream as a spiral accelerates sedimentation of the suspended particles.)

The transfer 24 (gas circulation) of the circulating gas stream was carried out using a circulating gas compressor 13 (ventilator) which sucked in the direction of the cyclone and discharged in the opposite direction. Directly downstream of the circulating gas compressor, the gas pressure was generally at least 1 atmosphere. Downstream of the circulating gas compressor, a circulating gas outlet (circulating gas can be discharged through the control valve 14) is arranged. The diaphragm (reduced cross section by about 3 factors, pressure reducer) 15 disposed downstream of the outlet facilitated release.

The downstream pressure of the rotary tube outlet could be regulated via a control valve. This was done in combination with a pressure sensor 16 mounted downstream of the rotary tube outlet, an offgas compressor 17 (ventilator) which sucked towards the control valve, a circulating gas compressor 13 and a fresh gas supply. For external pressure, the pressure downstream of the rotary tube outlet (immediately) could be set high, for example as low as +1.0 mbar, for example as low as -1.2 mbar. In other words, the pressure of the gas stream flowing through the rotary tube could be below the ambient pressure of the rotary tube when leaving the rotary tube.

If not intended to at least partially recycle the gas stream conducted through the rotary tube, the connection between the cyclone 12 and the circulating gas compressor 13 is controlled by a three-way valve principle 26. Made, and the gas stream was conducted directly to the offgas scrubber (23). The connection to the offgas scrubbing device arranged downstream of the circulating gas compressor was in this case likewise made on the three-way valve principle. If the gas stream consists essentially of air, it is aspirated through the circulating gas compressor 13 in this case (27). The connection to the cyclone was based on the 3-way valve principle. In this case, the gas stream is preferably aspirated through the rotary tube such that the internal rotary tube pressure is lower than the ambient pressure.

In the case of continuous operation of the rotary tube furnace apparatus, the downstream pressure of the rotary tube outlet was advantageously set to -0.2 mbar lower than the external pressure. For the batch operation of the rotary tube device, the downstream pressure of the rotary tube outlet was advantageously set to -0.8 mbar lower than the external pressure. The slightly reduced pressure was used for the purpose of preventing contamination of the ambient air with the gas mixture from the rotary tube furnace.

Between the circulating gas compressor and the cyclone a sensor 18 is arranged which determines, for example, the ammonia content and the oxygen content in the circulating gas. Preferably the ammonia sensor is operated by the optical measurement principle (light absorption of a certain wavelength is proportional to the ammonia content of the gas), and MCS 100 devices from Perkin & Elmer were suitable. Oxygen sensors were based on the paramagnetic properties of oxygen, with an oxymat of the type Oxymat MAT SF 7MB1010-2CA01-1AA1-Z from Siemens.

Between the diaphragm 15 and the heater 10, gases such as air, nitrogen, ammonia or other gases could be metered into the circulating gas fraction 19 which is actually recycled. Frequently, the base amount of nitrogen was metered in (20). The separated nitrogen / air separator 21 was used to react with the measurement of the oxygen sensor.

The released circulating gas fraction 22 (offgas) often contains gases such as NOx, acetic acid, NH _3, and the like, and is not totally safe, so they are usually removed in the offgas washing apparatus 23.

For this purpose, the offgas was generally initially conducted through a wash column (essentially a column free of charge containing individual structural packings upstream of its outlet). Offgas and aqueous spray mist were performed in the reverse and forward directions (two spray nozzles with opposite spray directions).

Upon exiting the wash column, the offgas was conducted to a device containing a fine dust filter (generally a series of bag filters) from which the infiltrating offgas was released. Finally, incineration was carried out in the muffle furnace.

A sensor 455, a 455 Jr model from KURZ Instruments, Inc., Monterey, USA, was fed to a rotary tube and used to measure and regulate the flow rates of the blocking gas and other gas streams (measurement principle: Thermal convection mass flow measurement using an isothermal anemometer).

In the case of continuous operation, the material and gas phases were conducted through a rotary tube furnace in the reverse direction.

In the context of the above example, nitrogen always means nitrogen in which the purity exceeds 99% by volume.

2. Preparation of precursor composition for obtaining multielement oxide composition of stoichiometric Mo ₁₂ V ₃ W _1.2 Cu _2.4 O _x

16.3 kg (content: CuO 40.0 wt.%) Of copper (II) acetate hydrate were dissolved with stirring in 274 l of water at a temperature of 25 ° C. A clear solution 1 was obtained.

Separated therefrom, 614 l of water were heated to 40 ° C. and 73 kg (81.5 wt.% MoO ₃ ) of ammonium heptamolybdate tetrahydrate were stirred while maintaining 40 ° C. The mixture was then heated with stirring to 90 ° C. in 30 minutes, then maintained at this temperature, followed by mentioning 11.3 kg of ammonium metavanadate and 10.7 kg of ammonium paratungstate hepta-hydrate (WO ₃ 88.9 wt%) It was stirred in it in order. A clear solution 2 was obtained.

Solution 2 was cooled to 80 ° C. and solution 1 was then stirred in solution 2. The resulting mixture was mixed with 130 l of 25% by weight aqueous NH ₃ solution having a temperature of 25 ° C. Stirring temporarily formed a clear solution having a temperature of 65 ° C. and a pH of 8.5. Once again 20 l of water was added at a temperature of 25 ° C. The temperature of the resulting solution was then raised back to 80 ° C., and the solution was then S-50-N / R spray dryer (gas inlet temperature: 350 ° C.) from Niro-Atomizer, Copenhagen. Gas outlet temperature: 110 ° C.). The spray powder had a particle diameter of 2-50 μm. 60 kg of the spray powder thus obtained were weighed into a VM 160 kneader (Sigma blades) from AMK (Aachener Misch- und Knetmaschinen Fabrik), and acetic acid 5.5 l (≒ 100 wt.%, Glacial acetic acid) and water 5.2 l was added and kneaded (screw rotation speed: 20 rpm). After kneading time for 4-5 minutes, additional 6.5 l of water was added and the kneading process continued until 30 minutes had elapsed (kneading temperature of approximately 40-50 ° C.). The kneaded material was then emptied into an extruder and extruded (length: 1-10 using an extruder (Bonnot Company, Ohio) Model: G 103-10 / D7A-572K (6 “Extruder W Packer) cm; diameter 6 mm) On a belt drier, the extrudate was dried for 1 hour at a temperature (material temperature) of 120 ° C. The dried extrudate formed a precursor composition to be thermally treated.

3. Preparation of the catalytically active composition by heat treatment of the precursor composition (firing of the precursor composition) in a rotary tube furnace apparatus

"B) 1." according to FIG. Heat treatment was carried out in the rotary tube furnace described below under the following conditions.

Heat treatment was carried out batchwise using 300 kg of material prepared as described in "B) 2."

The angle of inclination of the rotary tube with respect to the horizontal plane was 0 °.

The rotary tube was rotated to the right at 1.5 revolutions per minute.

Throughout the entire heat treatment, a 205 m ³ (STP) / h gas stream is conducted through the rotary tube and has the following composition (after exhaust of the original air) and additional blocking gas nitrogen 25 m ³ (STP) / h Supplied at its outlet from a rotary tube.

Consisting of 80 m ³ (STP) / h basic amount of nitrogen (20) and gases discharged from the rotary tube,

25 m ³ (STP) / h blocking gas nitrogen (11),

30 m ³ (STP) / h air (separator 21), and

70 m ³ (STP) / h recycled circulating gas (19).

Shut off gas nitrogen was supplied at a temperature of 25 ° C. A mixture of different gas streams coming from the heater was in each case conducted to the rotary tube at the temperature the material had in each case in the rotary tube.

Within 10 hours, a material temperature of 25 ° C. was heated to 300 ° C. in a substantially linear manner,

The material temperature was then heated to 360 ° C. in a substantially linear manner within 2 hours,

The material temperature was then reduced to 350 ° C. in a substantially linear manner within 7 hours,

The material temperature was then heated to 420 ° C. in a substantially linear fashion within 2 hours and the material temperature was maintained over 30 minutes.

-30 m ³ (STP) / h of air in the gas stream conducted through the rotary tube was then replaced by the corresponding increase in base nitrogen (after the actual heat treatment procedure), turning off the heating of the rotary tube and surrounding the material Inhalation of the air quickly cooled the rotary tube to a temperature below 100 ° C. and finally to ambient temperature,

Over the entire heat treatment, the pressure directly (directly) downstream of the rotary tube outlet of the gas stream was 0.2 mbar lower than the external pressure.

The oxygen content of the gaseous atmosphere in the rotary tube furnace in all phases of the heat treatment was 2.99% by volume. When arithmetically averaged over the entire period of the reducing heat treatment, the ammonia concentration in the gas atmosphere in the rotary tube furnace was 4% by volume.

2 shows the amount of ammonia released from the precursor composition as a percentage of the total amount of ammonia released from the precursor composition during the entire heat treatment process as a function of the material temperature (° C.).

3 shows the ammonia concentration (vol%) of the atmosphere where the heat treatment is carried out during the heat treatment as a function of the material temperature (° C.).

4 shows the molar amount of oxygen molecules and ammonia that are conducted to the rotary tube per hour over a heat treatment to the gas stream and per kg of precursor composition as a function of material temperature.

4. Molding of Multimetal Oxide Active Compositions

Powder particles by grinding the catalytically active material obtained under "B) 3." by using a BQ500 Biplex crossflow classifying mill (from Hosugawa-Alpine, Augsburg, Germany). 50% of the fine particles passed through a sieve having a mesh width of 1 to 10 μm, and fine particles having a particle ratio of the longest dimension of 50 μm or more were less than 1%.

Molding was then carried out as follows.

70 kg annular support body (outer diameter 7.1 mm, length 3.2 mm, inner diameter 4.0 mm; C220 type soapstone from Ceramtech with surface roughness Rz of 45 μm and total pore volume of 1% by volume or less based on the volume of the support body; Germany Patent DE-A 2135620) was charged to a 200 l coating tank (an inclination of 90 °; Hicoater from Lödige, Germany). The coating tank was then set at 16 rpm rotation speed. 3.8 to 4.2 l of an aqueous solution consisting of 75 wt% water and 25 wt% glycerol was sprayed onto the support body for 25 minutes using a nozzle. At the same time, 18.1 kg of the ground multimetal oxide active composition (specific surface area 13.8 m ² / g) were continuously metered through the stirred channel outside the spray cone of the sprayer nozzle. During the coating, the powder supplied was completely absorbed by the surface of the support. Aggregation of the finely divided oxidative active composition was not observed. After the active composition powder and the addition of water is complete, a rotation speed of 2 rpm for 100 ℃ open at (alternatively from 80 to 120 ℃) (about 400 m ³ / h) for 40 min (alternatively 15 to 60 minutes), coating tank Blown into me Based on the overall composition, a cyclic coating catalyst C _A having a proportion of 20% by weight of the oxidizing active composition was obtained. The coating thickness visible both on the surface of one support body and on the surface of the different support body was 170 ± 50 μm.

5 also shows the pore distribution of the powdered active composition powder before it is molded. The pore diameter (μm, log units) is shown on the abscissa.

On the right ordinate, the logarithm of the differential distribution (ml / g) of the specific pore diameter with respect to the total pore volume is indicated (○ curve). The maximum value represents the pore diameter which contributes the most to the total pore volume. The left ordinate plots the integral value (ml / g) of the individual distribution of pore diameters over the total pore volume (□ curve). The last point is the total pore volume (unless otherwise noted, all data herein for determination of the total pore volume and diameter distribution of these total pore volumes are from Micromeritics GmbH, 4040 Neuss, Germany). Determined by mercury porosimetry using an Auto Pore 9220 instrument (band width 30 mm to 0.3 mm), all data herein for determination of specific surface area or determination of micropore volume are DIN 66131 (Brunauer). -Determination of the specific surface area of solids by Brunauer-Emmet-Teller (BET) gas adsorption (N ₂ )).

FIG. 6 shows the individual distribution of the individual pore diameters (in abscissa, Å, logarithmic units) in the micropore range for the total pore volume for the active composition powder (ordinate, ml / g) before molding.

FIG. 7 shows the same as in FIG. 5 except that it is for a multimetal oxide active composition which has been mechanically shaved and subsequently removed from the cyclic coating catalyst C _A , whose specific surface area is 12.9 m ² / g.

FIG. 8 shows the same as FIG. 6 except that it is for a multimetal oxide active composition that has been mechanically shaved and subsequently removed from the cyclic coating catalyst.

C) Two-Step Partial Oxidation of Propene to Acrylic Acid (Industrial Scale)

I. Description of general process conditions in the propene reaction stage (propene → acrolein)

Thermal medium used: salt melt consisting of 60% potassium nitrate and 40% sodium nitrite.

Material of catalyst tube: ferrite steel.

Dimension of catalyst tube: length 3200 mm,

Inner diameter 25 mm,

Outer diameter 30 mm (wall thickness: 2.5 mm).

Number of catalyst tubes in the tube bundle: 25500.

Reactor: 6800 mm diameter cylindrical vessel, annularly aligned tube bundle with free central space

Diameter of the central free space: 1000 mm. Distance of outermost catalyst tube from vessel wall: 150 mm. Uniform catalyst tube distribution in the tube bundle (6 equidistant neighboring tubes per catalyst tube).

Catalyst tube pitch: 38 mm

The catalyst tube was fixed and sealed by the end of the 125 mm thick catalyst tube plate and opened to each of these orifices with a hood connected to the vessel at the upper or lower end. Between the upper hood and the upper catalyst tube plate, a centrally mounted shock plate was placed, and the reactant gas supplied towards it flowed out and dispensed into the catalyst tube in a distribution manner.

Supply of heat exchange medium to tube bundles:

The tube bundle was divided into three deflection plates (10 mm thick in each case) mounted continuously in the longitudinal direction into four equidistant (each 730 mm) length regions (zones) between the catalyst tube plates.

The top and bottom of the deflection plate had an annular shape, the inner ring diameter was 1000 mm and the outer ring diameter extended with a seal to the vessel wall. The catalyst tube was not fixed and was not sealed to the deflection plate. To some extent, a gap with a gap width of less than 0.5 mm was allowed to have a substantially constant transverse flow rate of salt melt in one zone.

The middle deflection plate was circular and extended to the outermost catalytic tube of the tube bundle.

Recycling of the salt melt took place by two salt pumps, each of which was fed in the middle of the length of the tube bundle.

The pump compressed the salt melt into an annular channel aligned at the bottom around the reactor jacket and split the salt melt on the vessel circumference. The salt melt reached the tube bundle in the bottom length region through the window of the reactor jacket. The salt melt is then transferred by a deflection plate

From outside to inside

-From inside to outside

From outside to inside

-From inside to outside

It flowed in a substantially winding manner from bottom to top, shown on the vessel in the order of. The salt melt collected through a window mounted in the top length region around the vessel circumference in an annular channel mounted at the top around the reactor jacket and cooled to the initial inlet temperature was compressed back into the bottom annular channel by a pump.

The composition of the starting reaction gas mixture 1 (mixture of air, chemical grade propylene and circulating gas) over the operating time is

5-7% by volume chemical grade propene,

10 to 14% by volume of oxygen,

1 to 2% by volume of COx,

1-3 vol% of H ₂ O, and

N ₂ 80% by volume or more

It was a range of.

Reactor Charge: The salt melt and reaction gas mixture were inverted in the reactor direction. The salt melt entered at the bottom and the reaction gas mixture at the top. The inlet temperature of the salt melt at start was 337 ° C. The exit temperature of the salt melt at start was 339 ° C. The output of the pump was 6200 m ³ of salt melt per hour. The starting reaction gas mixture was fed to the reactor at a temperature of 300 ° C.

Propene loading in the fixed catalyst bed for partial oxidation of propene: 100 to 120 l (STP) /l.h

Catalyst tube fill (top to bottom) with fixed catalyst layer for propene partial oxidation:

Zone A: 50 cm

Preliminary layer of soapstone ring of shape 7mm * 7mm * 4mm (outer diameter X length X inner diameter)

Zone B: 100 cm

Catalyst charge of a homogeneous mixture of 35% by weight of soapstone rings of shape 5 mm × 3 mm × 2 mm (outer diameter × length × inner diameter) and unsupported catalyst C _p 65% by weight prepared in A)

Zone C: 170 cm

Catalyst Filling of Annular (5 mm × 3 mm × 2 mm = Outer Diameter × Length × Inner Diameter) Unsupported Catalyst C _p Prepared in A)

A heat tube (these numbers are 10 uniformly distributed in the central region of the tube bundle) was constructed and filled as follows to adjust the inlet temperature of the salt melt (these were the hot spot temperatures (maximum temperature along the heat tube). Used to determine which are the arithmetic mean of independent measurements in 10 heat tubes).

Each of the ten heat tubes had a central heat well with 40 temperature measurement points (ie each heat tube contained 40 thermoelements integrated into heat wells at different lengths, and thus at different heights) Forming multiple thermoelectric elements by temperature which can be determined simultaneously in a heat tube).

In each case 13 to 30 of the 40 temperature measurement points (in the flow direction of the reaction gas mixture) were at the first metrology point of the active region of the fixed catalyst bed.

The inner diameter of the heat tube was 27 mm. Wall thickness and tubing material were the same as in the working tube.

The outer diameter of the heat well was 4 mm.

The heat tube was filled as follows.

The heat tube was filled with the annular unsupported catalyst C _p prepared in A). The heat tube was further filled with a piece of catalyst produced from uncyclically supported catalyst C _p and having the longest dimension of 2 to 3 mm.

The catalyst pieces are produced in such a way that the pressure drop of the reaction gas mixture flowing through the heat tube corresponds to the pressure drop of the reaction gas mixture flowing through the working tube (for this purpose, 5 to 20% by weight of the catalyst pieces It must be stationed in the active region (ie, excluding the inactive region) and filled evenly over the entire active region of the fixed catalyst bed of the particular heat pipe. At the same time, the specific total fill height of the active and inactive regions in the working and heat tubes is the same, and the ratio of the total amount of active composition present in the working tubes to the heat exchange surface area of the tubes in the working and heat tubes is set to substantially the same value. .

II. Description of Intermediate Cooling

For intermediate cooling, the product gas mixture leaving the propene reaction stage at a temperature substantially corresponding to the salt melt outlet temperature is cooled with a salt melt consisting of 60% by weight potassium nitrate and 40% by weight sodium nitrite and flanged directly onto the reactor. Conducted through a 1-zone tube bundle heat exchanger made of attached ferritic steel. The distance of the bottom tube plate of the reactor from the top tube plate of the cooler was 10 cm. In the heat exchanger, the salt melt and product gas mixture were conducted in countercurrent. The salt bath itself flowed in a meandering manner around the cooling tube through which the product gas mixture passed, in the same manner as in a one stage one zone multi-catalyst tube fixed bed reactor. The length of the cooling tubes was 1.65 m, their inner diameter was 2.6 cm and their wall thickness was 2.5 mm. The number of cooling tubes was 8000. The diameter of the heat exchanger was 7.2 m.

They were evenly distributed on the cross section with uniform tube pitch.

A spiral of stainless steel was introduced (in the flow direction) into the inlet of the cooling tube, the cross-sectional area corresponding substantially to that of the cooling tube. Their length was from 700 mm to 1000 mm (alternatively, the cooling tube could be filled with a huge ring of inert material). They promoted heat transfer.

The product gas mixture left the intermediate cooler at a temperature of 250 ° C. Compressed air with a temperature of 140 ° C. was then mixed in an amount of about 6700 m ³ (STP) / l · h to obtain the composition described below of the fill gas mixture for the acrolein reaction step.

The resulting fill gas mixture (starting reaction gas mixture 2) was fed to a one zone multi-catalyst tube fixed bed reactor of the acrolein reaction stage at a temperature of 220 ° C.

III. Explanation of General Process Conditions in the Acrolein Reaction Step (Acrolein → Acrylic Acid)

A one zone multi-catalyst tube fixed bed reactor was used with the same design as the reactor of the first stage.

The fill gas mixture (starting reaction gas mixture 2) was of the following composition over the run time.

4-6% by volume of acrolein,

0 ₂ 5-8% by volume,

CO _x 1.2-2.5 vol%,

H ₂ O 6-10 volume percent, and

N ₂ 75 vol% or more.

Reactor Charge: The salt melt and fill gas mixture was challenged in countercurrent when viewed in the reactor. The salt melt came from the bottom and the fill gas mixture came from the top.

The inlet temperature of the salt melt at the start was approximately 263 ° C. (at the completion of the control of the fixed catalyst bed for acrolein partial oxidation). The accompanying outlet temperature of the salt melt was approximately 265 ° C. at the start.

The pump output was 6200 m ³ of salt melt per hour.

The starting reaction gas mixture was fed to the reactor at a temperature of 240 ° C.

Acrolein loading of fixed catalyst bed for acrolein partial oxidation: 90 to 110 l (STP) / l · h

The catalyst tube charge (from top to bottom) of the fixed catalyst bed for acrolein partial oxidation is: Zone A:

20cm spare layer of the soapstone ring of shape 7mm * 7mm * 4mm (outer diameter X length X inner diameter)

Zone B:

30% by weight of the soapstone ring of shape 7mm × 3mm × 4mm (outer diameter × length × inner diameter) and uniformity of annular (approximately 7mm × 3mm × 4mm) coating catalyst C _A 70% by weight 100 cm catalyst charge of one mixture.

Zone C:

200 cm catalyst charge of the annular (approximately 7 mm × 3 mm × 4 mm) coated catalyst C _A prepared in B).

The heat tubes (their number is 10 uniformly distributed in the central region of the tube bundle) were constructed and filled as follows.

(They were used to determine the hot spot temperature (maximum temperature along the heat tube) to control the inlet temperature of the salt melt, which is the arithmetic mean of the independent measurements in the 10 heat tubes.)

Each of the ten heat tubes had a central heat well with 40 temperature measuring points (ie, each heat tube contained 40 thermoelements that were integrated into heat wells at different lengths, so that the temperatures were simultaneously in the heat tubes at different heights). Forms multiple thermoelectric elements that can be determined).

In each case 13 to 30 of the 40 temperature measuring points were in the first metering zone of the active zone of the fixed catalyst bed (in the flow direction of the reaction gas mixture).

The inner diameter of the heat tube was 27 mm. Wall thickness and tubing material were the same as in the working tube.

The outer diameter of the heat well was 4 mm.

The heat tube was filled as follows.

The heat tube was filled with the cyclic coating catalyst C _A prepared in B). In addition, the diameter of the support sphere of the spherical coating catalyst (the same active composition as the cyclic coating catalyst, Dongseok C220 (Seramtec)) was 2-3 mm, the active composition fraction was 20% by weight, except that the binder was an appropriate amount of water. Was prepared as described for the cyclic coating catalyst C _A ) with a heat tube.

The pressure drop of the reaction gas mixture passing through the spherical coating catalyst through the heat tube is the same as the pressure drop when the reaction gas mixture passes through the working tube (for this purpose, 5 to 20% by weight of the spherical coating catalyst The active area of the fixed catalyst bed (ie, excluding the inactive area) must be filled in a uniform distribution over the entire active area of the fixed catalyst bed of the particular heat pipe. At the same time, the specific total fill heights of the active and inactive regions in the working and heat tubes were equal and the ratio of the total amount of active composition present in the tubes to the heat exchange surface area of the tubes in the working or heat tubes was set to the same value.

III. Long term driving (results)

The fixed catalyst bed of the tube bundle reactor for partial propene oxidation to acrolein was freshly charged every 1.5 years before the catalyst bed of the tube bundle reactor for acrolein partial oxidation to acrylic acid.

The target conversion of propene converted in a single pass of starting reaction gas mixture 1 through the fixed catalyst bed of the propene oxidation step was set to 97.5 mol%.

The gradual increase in the inlet temperature of the salt melt into the reactor of the propene reaction stage allowed the conversion value to be maintained over the course of the continuous run of the process.

The target conversion of acrolein converted in a single pass of starting reaction gas mixture 2 through the fixed catalyst bed of the acrolein reaction stage was set to 99.3 mol%.

The gradual increase in the inlet temperature of the salt melt into the reactor of the acrolein reaction stage allowed the conversion value to be maintained over the course of the continuous run of the process.

About once a month in the calendar year, the partial oxidation was stopped (the rise of the inlet temperature of the salt melt into the reactor of the acrolein reaction was always above 0.3 ° C. and below 4 ° C. before the monthly stop, and in the case of the reactor for the propene reaction step, The increased value required per month was above 0.5 ° C.), and the inlet temperature of the salt melt finally used in the particular reaction stage and intermediate cooler was maintained and consisted of a gas mixture G consisting of 6% by volume of O ₂ and 95% by volume of N ₂ 95% by volume. Was conducted through the entire reaction system for a period t _G of 24 to 48 hours at a time space velocity on the fixed catalyst bed of the propene reaction step of 30 l (STP) / l · h. Thereafter, partial oxidation was continued and the inlet temperature of the salt melt to the specific reaction stage was adjusted in such a way that the target conversion of the specific reaction stage was still achieved.

After operation for at least two years of the reaction system (calculated from the new charge of the propene reaction stage) as described, after the gas mixture G has passed through the reaction system and the partial oxidation is subsequently continued, after the 13th operation day The reaction conditions and results were as follows (d = operation days after sustaining partial oxidation, SV = time-space velocity on propene reaction stage of propene (l (STP) / l · h), C ^pro = based on single pass Propene conversion (mol%), C ^acr = acrolein conversion (mol%) based on single pass, Y ^AA = yield of acrylic acid (mol%) based on single pass and converted propene; A ^CO = single pass and converted Undesired secondary yield (mol%) of carbon oxides based on propene, T ¹ = salt bath inlet temperature (° C.) in propene reaction stage, T ² = salt bath inlet temperature (° C.) in acrolein reaction stage, P ¹ = Working pressure at the inlet to the propene reaction stage (mbar), P ² = Working pressure (mbar) at the inlet to the acrolein reaction stage:

d SV Y ^AA C ^acr C ^pro Y ^CO T ¹ T ² P ¹ P ² 13 112.9 89.8 99.3 97.7 5.21 348.1 269.5 2270 1810 14 112.8 89.5 99.2 97.5 5.28 348.1 270.1 2265 1805 15 110.6 89.4 99.4 97.4 5.3 348 270.1 2268 1802 16 113.5 89.7 99.3 97.5 5.17 348 270.1 2267 1809 17 113.3 89.7 99.3 97.5 5.17 348.1 270.1 2268 1809 18 113.4 89.7 99.1 97.5 5.14 348 270.1 2265 1809 19 113 89.6 99.1 97.4 5.18 348 270.1 2270 1807 20 113.2 89.6 99.3 97.4 5.15 348 270.1 2269 1805 Comparative Example

After 20 days of operation, the gas mixture G was again inverted through the reaction system as described above, and then perforated diaphragm downstream of the outlet of the tube bundle reactor for partial oxidation of acrolein to acrylic acid to increase the working pressure. The partial oxidation was continued as described except for the difference with which. The diameter of the perforated diaphragm was 1.23 m. It contained 37 evenly distributed holes of 9 cm in diameter. After 13 days of operation (calculated from the duration of partial oxidation), the operating conditions and results were as follows.

d SV Y ^AA C ^acr C ^pro Y ^CO T ¹ T ² P ¹ P ² 13 112.9 89.1 99.2 97.3 5.52 333.8 268.7 2420 2178 14 113.4 89.5 99.4 97.7 5.56 336.4 268.3 2425 2180 15 112.8 89.7 99.3 97.7 5.45 336.4 268.4 2425 2181 16 113.1 89.5 99.2 97.6 5.48 336.4 268.4 2421 2182 17 113.1 89.7 99.1 98 5.66 339 268.6 2420 2177 18 113.1 89.6 99.5 97.9 5.6 338.5 268.6 2422 2180 19 113 89.6 99.2 97.8 5.52 338.5 268.6 2424 2181 20 113.4 89.6 99.3 97.9 5.62 339 268.8 2424 2181 (= Example)

The comparison of the values of T ^{1 in} the examples under elevated working pressure P ¹ at the same propene conversion yields a significantly reduced salt bath inlet temperature into the reactor of the propene reaction stage that does not involve a significant increase in CO _x byproduct formation. Indicates. In the acrolein reaction step, the effect of enhancing the activity of increasing working pressure is likewise clearly recognizable. However, since the catalyst layer of the acrolein reaction stage continued to operate for 1.5 years after the catalyst filling of the propene reaction stage, the deactivation of the catalyst layer of the acrolein stage did not progress much, which is the effect of the increase in the working pressure. That's why it's not noteworthy yet.

D) 2-Step partial oxidation of propene to acrylic acid (lab scale)

I. Description of Experimental Arrangement for Two Reaction Steps

Propene Reaction Step

Top-to-bottom of the reaction tube (V2A steel; outer diameter 30 mm, wall thickness 2 mm, inner diameter 26 mm, center heat well (to accommodate thermoelectric elements) is 4 mm outer diameter and 320 cm long) Was charged.

Zone 1: 50 cm long

Steatite ring of shape 7mm * 7mm * 4mm (outer diameter X length X inner diameter) as spare layer.

Zone 2: 100 cm long

Catalytic charge of a homogeneous mixture of 70% by weight of a 5mm × 3mm × 2mm (outer diameter × length × inner diameter) soapstone ring and annular unsupported catalyst C _p (A).

Zone 3: 170 cm long

Exclusive cyclic unsupported catalyst C _p as in zone 2.

The reaction tube was temperature controlled with countercurrent using a nitrogen-sprayed salt bath (53 wt% potassium nitrate, 40 wt% sodium nitrite, and 7 wt% sodium nitrate).

Acrolein Reaction Step

From top to bottom, the reaction tube (V2A steel; outer diameter 30 mm, wall thickness 2 mm, inner diameter 26 mm, center heat well (to accommodate thermoelectric elements) is 4 mm outer diameter and 320 cm long) Charged.

Zone 1: 20 cm in length

Preliminary layer of soapstone ring of shape 7mm * 7mm * 4mm (outer diameter X length X inner diameter).

Zone 2: 100 cm long

Catalyst charge of a homogeneous mixture of shape 7 mm × 3 mm × 4 mm (outer diameter × length × inner diameter) of 30% by weight of soapstone rings and prepared as in annular coating catalyst C _A (B).

Zone 3: 200 cm in length

Catalytic charge of the exclusive cyclic coating catalyst C _A as in zone 2.

The reaction tube was temperature controlled by countercurrent using a nitrogen sparged salt bath (53 wt% potassium nitrate, 40 wt% sodium nitrite and 7 wt% sodium nitrate).

Between the two reaction stages, an intermediate coolant is placed which is filled with an inert material, through which the product gas mixture of the first reaction stage is conducted and cooled to a temperature of 250 ° C. by indirect cooling.

The first reaction step (propene → acrolein)

5.5 to 5.7 volume percent polymer-grade propene,

H ₂ O 3-3.2 volume%,

CO _x 1-2 vol%,

0.01-0.02% by volume of acrolein,

0 ₂ 10.4-10.6 volume percent, and

Nitrogen molecule as residue in amounts to 100% by volume

It was continuously charged with a starting reaction gas mixture of.

The temporal space velocity on the catalyst charge of propene was chosen at 130 l (STP) /l.h. The salt bath temperature of the first reaction step was T ¹ (° C.). The salt bath temperature of the second reaction step (acrolein → acrylic acid) was T ² (° C.). Sufficiently compressed air at a temperature of 140 ° C. was added to the product gas mixture leaving the intermediate cooler at a temperature of 250 ° C., and the starting reaction gas mixture was a second in which the ratio of oxygen molecules to acrolein (ratio of volume percentages) was 1.3 Fed to the reaction stage. Downstream of the outlet of the second reaction stage, a throttle device is arranged which makes it possible to adjust the working pressure.

Depending on the working pressure (pressure immediately upstream of the first reaction stage (bar) is specified in each case), T ¹ and T ² have a propene conversion of 97.5 mol% and an acrolein conversion of 99.3 mol% (in each case Based on one pass of the reaction gas mixture through the reaction system.

According to the working pressure, the result of the following table was obtained. The results were based on the reaction operation after the previous undisturbed working time of 100 hours at the working pressure of 1.1 bar and the same conversion rate.

T ^1max and T ^2max temperature is the maximum reaction temperature (℃) in certain reaction steps. ΔP ¹ and ΔP ² are the pressure drops (bar) experienced during a particular reaction step.

Working pressure [bar] T ¹ [° C] T ^1max [° C] T ² [° C] T ^2max [° C] ΔP ¹ [bar] ΔP ² [bar] 1.1 334 382 273 308 0.52 0.30 1.57 328 380 268 311 0.41 0.21 1.93 320 382 260 284 0.33 0.17

US Provisional Application No. 60 / 572,124, filed May 19, 2004, is incorporated herein by reference. With regard to the above-mentioned teachings, numerous modifications and variations are possible from the present invention. Thus, it can be assumed that the invention can be carried out differently from the specific methods described herein within the scope of the appended claims.

Claims (20)

The starting reaction gas mixture comprising at least one organic compound, oxygen molecules, and at least one inert diluent gas passes through at least one catalyst bed at elevated temperature and inhibits deactivation of the at least one catalyst bed, so that the operating time of the catalyst bed At least one organic compound in at least one oxidation reactor comprising increasing the working pressure in the gas phase based on the same time space velocity (l (STP) / lh) on at least one catalyst bed of the starting reaction gas mixture Long-term operation of heterogeneous catalyzed gas phase partial oxidation of. The method of claim 1, wherein the at least one organic compound is propylene, acrolein, 1-butene, 2-butene, ethane, benzene, m-xylene, p-xylene, isobutene, isobutane, tert-butanol, isobutyraldehyde, at least one compound from the group consisting of methyl ether, o-xylene, naphthalene, butadiene, ethylene, propylene, propane or methacrolein of tert-butanol. The process of claim 1 or 2, wherein the at least one oxidation reactor is a tube bundle reactor and the catalyst bed is a fixed catalyst bed. 4. The process according to any one of claims 1 to 3, wherein the heterogeneous catalyzed gas phase partial acidification is a two stage partial oxidation of propene to acrylic acid. The method according to any one of claims 1 to 4, wherein the increase in working pressure is at least 25 mbar. The method according to claim 1, wherein the increase in working pressure is between 50 mbar and 3000 mbar. The process according to claim 1, wherein the increase in working pressure is carried out continuously and according to the rate of inactivation of the at least one catalyst bed. The method according to claim 1, wherein the increase in working pressure is carried out stepwise. 9. The composition of claim 1, wherein the at least one organic compound is propylene and the active composition of the catalyst of the at least one catalyst layer is a molybdenum and / or tungsten element, and also bismuth, tellurium, antimony, tin And a multi-element oxide comprising at least one of copper elements. The process according to claim 1, wherein the at least one organic compound is acrolein and the active composition of the catalyst of the at least one catalyst layer is a multielement oxide comprising Mo and V elements. The process according to claim 1, wherein the pressure regulator is mounted downstream of the outlet of the one or more oxidation reactors. The method of claim 11, wherein the pressure regulator is a throttle valve, or a vane regulator or a perforated diaphragm. At least one oxidation reactor and at least one device disposed downstream of the outlet of the at least one oxidation reactor and for adjusting the working pressure in the at least one oxidation reactor. An apparatus comprising at least one oxidation reactor, at least one column connected downstream of at least one oxidation reactor and having individual charges, and an apparatus connected to downstream of the oxidation reactor and for adjusting the working pressure in at least one oxidation reactor. 15. The process of claim 14, wherein the oxidation reactor comprises a catalyst bed and is designed in such a way that a working pressure of greater than 0.5 to 4 can be passed at a predetermined time space velocity on the catalyst bed disposed in the oxidation reactor of the starting reaction gas mixture. The apparatus further comprises an air compressor. The apparatus of claim 13, wherein the at least one oxidation reactor is a tube bundle reactor. The device according to any one of claims 13 to 16, wherein the device for regulating working pressure is a perforated diaphragm. 13. Air compressor according to any one of the preceding claims, designed in such a way that a working pressure of greater than 0.5 to 4 can be passed at a predetermined time and space velocity on the catalyst bed disposed in the oxidation reactor of the starting reaction gas mixture. Method performed in a device comprising a. The apparatus of claim 15, wherein the predetermined time space velocity of the starting reaction gas mixture is at least 1500 l (STP) /l.h. 19. The method of claim 18, wherein the predetermined time space velocity of the starting reaction gas mixture is at least 1500 l (STP) /l.h.

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