RU2356881C2 - Method of producing at least one product of partial oxidation and/or ammoxidation of hydrocarbon, chosen from group, containing acrolein, methacrolein, acrylic acid, methacrylic acid, acrylonitrile and methacrylonitrile - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention relates to an improved method of producing at least one product of partial oxidation and/or ammoxidation of a hydrocarbon, chosen from a group containing acrolein, acrylic acid, methacrolen, methacrylic acid, acrylonitrile and methacrylonitrile. At least one saturated hydrocarbon is subjected to heterogeneous catalysed dehydrogenation in a gas phase, obtaining a gas mixture, containing at least one partially dehydrogenated hydrocarbon. Components of the gas mixture except saturated hydrocarbon and partially dehydrogenated hydrocarbon are left in the mixture. Alternatively, the extra gas mixture obtained is partially or completely separated, and the gas mixture and/or extra gas mixture are used for obtaining another gas mixture, containing molecular oxygen and/or molecular oxygen and ammonia. This gas mixture is subjected to at least single heterogeneous catalysed partial oxidation and/or ammoxidation of at least one partially dehydrogenated hydrocarbon contained in the gas mixture and/or extra gas mixture. The gas mixture, extra gas mixture and/or the other gas mixture, before at least one partial heterogeneous catalysed oxidation and/or ammoxidation, are subjected to at least a single mechanical separation, aimed at separating particles of solid substance contained in the above mentioned gas mixtures.

EFFECT: reliable and continuous realisation of the process for relatively long periods of time.

6 cl, 1 ex

Description

Description

The invention relates to a technology for the production of unsaturated hydrocarbons, and more particularly to a method for producing at least one partial oxidation and / or ammoxidation product of a hydrocarbon selected from the group consisting of acrolein, acrylic acid, methacrolein, methacrylic acid, acrylonitrile and methacrylonitrile, in which, at least one saturated hydrocarbon is subjected to heterogeneously catalyzed dehydrogenation in the gas phase to obtain a gas mixture containing at least one partially dehydrogenated hydrocarbon contained in the gas mixture, components other than saturated hydrocarbon and partially dehydrogenated hydrocarbon are left in it or, to obtain an additional gas mixture, partially or completely separated, and the gas mixture and / or additional gas mixture is used to obtain a further gas mixture additionally containing molecular oxygen and / or molecular oxygen and ammonia, wherein the further gas mixture is subjected to at least one heterogeneously catalyzed partial oxidized w and / or ammoxidation contained in the gas mixture and / or additional gas mixture of at least one partially dehydrogenated hydrocarbon.

By heterogeneously catalyzed dehydrogenation in this application is meant dehydrogenation that occurs endothermally and in which hydrogen is formed as the primary by-product. It is carried out on fixed catalysts, which reduce the activation energy necessary for the thermal cleavage of CH - bonds. Heterogeneously catalyzed dehydrogenation differs from heterogeneously catalyzed oxydehydrogenation in that the latter is induced by the oxygen present and water is formed as the primary by-product. In addition, heterogeneously catalyzed oxydehydrogenation occurs exothermically.

By complete oxidation of a hydrocarbon is meant that the carbon contained in this hydrocarbon is generally converted to carbon oxides (CO, CO ₂ ).

Interactions with oxygen that are different from this reaction are partial oxidation and partial amoxidation in the presence of ammonia.

The above method is known (cf., for example, documents DE-A 10219686, DE-A 10246119, DE-A 10245585, DE-A 10219685, EP-A 731077, DE-A 3313573, DE-A 10131297, DE-A 10211275, EP-A 117146, GB-A2118939, US-A4532365, US-A 3161670 and EP-A 193310) and, inter alia, are used to produce acrolein, acrylic acid and / or acrylonitrile from propane, methacrolein, methacrylic acid and / or methacrylonitrile from iso butane. Partial amoxidation differs from partial amoxidation mainly by the presence of ammonia in the reaction mixture. By a suitable choice of the ratio of NH ₃ and O _2, partial oxidation and partial ammoxidation can be carried out in parallel, i.e. at the same time. By the addition of an inert diluent gas, partial oxidation and / or amoxidation is kept outside the explosion region.

Moreover (in particular, as described in DE-A 3313573, EP-A 117146, GB-A 2118939, US-A 4532365 and US-A 3161670) both the gas mixture as such and the additional gas mixture as components of the further gas the mixture can be subjected to at least one heterogeneously catalyzed partial oxidation and / or ammoxidation of the at least one partially dehydrogenated hydrocarbon contained in the gas mixture and / or additional gas mixture.

In the simplest case, the transition from the gas mixture to the additional gas mixture can be carried out due to the fact that the water vapor contained in the gas mixture, if necessary, is partially or completely separated. This can be done in such a way that the gas mixture is cooled and, if necessary, the water vapor contained therein is partially or completely condensed.

It goes without saying that other components contained in the gas mixture can also be separated to produce an additional gas mixture. For example, the gas mixture can be directed through a membrane, usually in the form of a pipe, which passes only the hydrogen contained in the gas mixture, and thus partially or completely separates the hydrogen contained in the gas mixture. The CO ₂ contained in the gas mixture can be separated by passing the gas mixture through an aqueous alkaline solution. An alternative separation method is absorption / desorption (stripping) according to DE-A 10245585.

A disadvantage of the known methods is that neither the gas mixture, nor the additional gas mixture, nor the further gas mixture undergoes mechanical separation by at least one heterogeneously catalyzed partial oxidation and / or ammoxidation, by which solid particles contained in these gas mixtures can separated from these gas mixtures. If an absorption separation method is used, then the absorption agent is saturated with particles of a solid over time. For example, upon steaming and / or stripping, they can then be carried away.

This is a disadvantage, as in the long trials the applicant unexpectedly found that in the above methods, the smallest particles from the solid catalyst used for heterogeneously catalyzed dehydrogenation can be transferred to the next stage of the heterogeneously catalyzed partial oxidation and / or amoxidation, where they settle on the fixed layer used there catalyst.

The latter has a drawback in the sense that a heterogeneously catalyzed partial oxidation and / or amoxidation is carried out with respect to the stoichiometry of the reaction, usually in the presence of an excess of oxygen.

In the presence of oxygen, catalysts suitable for heterogeneously catalyzed dehydrogenation typically also catalyze the complete combustion of hydrocarbons to produce CO ₂ and H ₂ O (cf., for example, US-A 4788371) and the hydrogen-oxygen reaction of H ₂ with O ₂ to produce H ₂ O This is a disadvantage, as it leads either in an undesirable way to an undesirable consumption of reagents during heterogeneously catalyzed partial oxidation and / or ammoxidation (which at the same time undesirably means additional heat) or is difficult tsenivaemym risk.

An object of the present invention is to provide a process that is particularly suitable for reliable continuous operation over a relatively long period of time (the service life of the catalysts for heterogeneously catalyzed partial oxidation and / or amoxidation is usually several years).

The problem is solved by the proposed method for producing at least one product of partial oxidation and / or amoxidation of a hydrocarbon selected from the group consisting of acrolein, acrylic acid, methacrolein, methacrylic acid, acrylonitrile and methacrylonitrile, in which at least one saturated hydrocarbon subjected to heterogeneously catalyzed dehydrogenation in the gas phase to obtain a gas mixture containing at least one partially dehydrogenated hydrocarbon contained in the gas mixture components other than saturated hydrocarbon and partially dehydrogenated hydrocarbon are left in it, or partially or completely separated, to obtain an additional gas mixture, and the gas mixture and / or additional gas mixture is used to obtain a further gas mixture additionally containing molecular oxygen and / or molecular oxygen and ammonia, wherein the further gas mixture is subjected to at least one heterogeneously catalyzed partial oxidation and / or ammoxidation of the gas mixture and / or an additional gas mixture of at least one partially dehydrogenated hydrocarbon, wherein the gas mixture, the additional gas mixture and / or the further gas mixture are subjected to at least one partially heterogeneously catalyzed oxidation and / or ammoxidation, at least one mechanical separation aimed at separating solids contained in said gas mixtures.

The method according to the invention has an advantage, first of all, when a gas mixture as such and / or an additional gas mixture is used in the method of heterogeneously catalyzed partial oxidation and / or amoxidation, which is obtained from the gas mixture in such a way that, as a rule, contained therein water vapor partially or completely condenses.

Suitable according to the invention, applying the mechanical operation of the separation of gas cleaning apparatuses are, for example, chamber, fenders and centrifugal separators that use dynamic forces. Acoustic separators can also be used in the method according to the invention. Aero cyclones are preferred. According to the invention, in a simple manner, filtration can act as a mechanical separation operation. Suitable filter layers are filter cloths, porous filter media, paper materials or oil-soaked metal filters. Electric separators are also applicable according to the invention. In the simplest case, the gas mixture can pass through an inert fixed bed in which the finest solids contained in the gas mixture are deposited before the gas mixture reaches the catalyst for heterogeneously catalyzed partial oxidation and / or ammoxidation. The concept of a mechanical separation operation also includes spray devices in which direct-flow or counter-current gas is exposed to liquid droplets (e.g., high boiling organic liquids or water) that absorb solid particles contained in the gas. The sprayed liquid is replaced after several recirculation cycles to prevent particles from becoming saturated with the solid.

It goes without saying that according to the invention, various sequentially separated separation steps can also be used.

In general, the heterogeneously catalyzed dehydrogenation of a saturated hydrocarbon according to the invention can be carried out (especially in the case of propane and / or iso-butane), as described in DE-A 3313973, WO 01/96270, DE-A 10131297 or DE-A 10211275.

Due to the fact that the heterogeneously catalyzed dehydrogenation reaction occurs with an increase in volume, the conversion can be increased by reducing the partial pressure of the products. This can be achieved in a simple manner, for example, by dehydrogenation under reduced pressure and / or by mixing mainly inert diluent gases, for example water vapor, which for hydrogenation is normally an inert gas. Dilution with water vapor leads to another advantage, as a rule, reduced coking of the catalyst used, since water vapor reacts with the coke formed on the principle of coal gasification. In addition, water vapor can be used as a diluent gas in the subsequent at least one zone of oxidation and / or amoxidation. Water vapor can be easily completely or partially separated from the dehydrogenation gas mixture (for example, by condensation), which makes it possible to increase the proportion of diluent gas N ₂ with further use of the resulting additional gas mixture in at least one partial oxidation and / or ammoxidation. Other diluents suitable for heterogeneously catalyzed dehydrogenation are, for example, CO, methane, ethane, CO ₂ , nitrogen, and noble gases such as He, Ne and Ar. All of these diluents can be used either as such or in the form of various mixtures. It is also advantageous that said diluents are generally also suitable diluents for at least one partial oxidation and / or ammoxidation. Inert diluents are, in particular, behaving inert under the reaction conditions (i.e., chemically changing by less than 5 mol%, preferably less than 3 mol%, and particularly preferably less than 1 mol%). In principle, all dehydrogenation catalysts known in the art are suitable for heterogeneously catalyzed dehydrogenation. They can be roughly divided into two parts. Namely, those that have an oxide nature (for example, chromium oxide and / or aluminum oxide), and those consisting of a relatively noble metal (for example, platinum, palladium, tin, gold, silver), which are deposited on, as a rule , an oxide carrier.

This means that according to the invention all dehydrogenation catalysts that are recommended in WO 01/96270, EP-A 731077, DE-A 10211275, DE-A 10131297, WO 99/46039, US-A 4788371, EP-A- can be used 0 705 136, WO 99/29420, US-A 4220091, US-A 5430220, US-A 5877369, EP-A-0117146, DE-A 19937196, DE-A 19937105, as well as DE-A 19937107. In particular, they can used catalysts according to example 1, example 2, example 3 and example 4 of DE-A 19937107.

This is about dehydrogenation catalysts that contain from 10 to 99.9 wt.% Zirconia, from 0 to 60 wt.% Alumina, silicon dioxide and / or titanium dioxide and from 0.1 to 10 wt.%, at least one element of the first or second main group, element of the third side group, element of the eighth side group of the Periodic system, lanthanum and / or tin, with the proviso that the sum of weight percent is 100%.

For carrying out a heterogeneously catalyzed dehydrogenation according to the invention, in principle, all types of reactors and process variants known from the prior art are suitable. Descriptions of such process variants contain, for example, all prior art documents cited in relation to dehydrogenation catalysts.

A comparatively detailed description of the dehydrogenation methods suitable according to the invention is also contained in the publication "Catalytica® Studies Division, Oxidative Dehydrogenation and Alternative Dehydrogenation Processes, Study Number 4192 OD, 1993, 430 Ferguson Drive, Mountain View, California, 94043-5272 U.S.A.

A characteristic feature of partial heterogeneously catalyzed dehydrogenation of saturated hydrocarbons is that it passes endothermally. This means that the heat (energy) necessary to set the desired reaction temperature must either be supplied to the initial reaction gas mixture before and / or during the heterogeneously catalyzed dehydrogenation.

Further, for heterogeneously catalyzed dehydrogenation of saturated hydrocarbons, such as propane and isobutane, due to the high temperatures required for the reaction, it is typical that low-boiling, high molecular weight organic compounds are formed in small quantities up to carbon, which precipitate on the surface of the catalyst and, as a result, deactivate it . To reduce these negative accompanying phenomena, the reaction mixture to be passed over the surface of the catalyst for heterogeneously catalyzed dehydrogenation at high temperature, containing the saturated hydrocarbon to be dehydrogenated, can be diluted with water vapor. The precipitated carbon under such conditions is partially or completely destroyed by the principle of coal gasification.

Another way to eliminate precipitated hydrocarbons is to pass oxygen-containing gas from time to time through the dehydrogenation catalyst at high temperatures and thereby burn the deposited carbon. Successful suppression of the formation of carbon deposits is also possible due to the fact that molecular hydrogen is added to the saturated hydrocarbon (for example, propane or isobutane) to be heterogeneously catalyzed by dehydrogenation and molecular hydrogen is added before it is passed through the dehydrogenation catalyst at high temperature.

It goes without saying that it is also possible to add water vapor and molecular hydrogen in the mixture to the saturated hydrocarbon to be heterogeneously catalyzed by dehydrogenation. The addition of molecular hydrogen to the heterogeneously catalyzed dehydrogenation of propane also reduces the undesired formation of allen (propadiene), propine and acetylene as by-products.

A suitable reactor form for the heterogeneously catalyzed dehydrogenation according to the invention is a fixed-bed tubular reactor or a shell-and-tube reactor. This means that the dehydrogenation catalyst is in the same reaction tube or in the reaction tube assembly as a fixed bed. The reaction tubes are heated due to the fact that in the space surrounding the reaction tubes, gas is burned, for example, a hydrocarbon such as methane. Favorable is such an embodiment in which such a direct form of heating of the contact tubes is used for approximately the first 20 to 30% of the filling of the fixed catalyst and the remaining length of the filling is heated to the desired reaction temperature released during the combustion of radiant heat. In this way, approximately isothermal reaction is achieved. Suitable inner diameters of the reactor tubes are from about 10 to 15 cm. A typical shell-and-tube dehydrogenation reactor includes from 300 to 1000 reaction tubes. The internal temperature of the reaction tube lies in the range from 300 to 700 ° C., preferably from 400 to 700 ° C. The initial reaction gas mixture is fed into the tubular reactor preheated. It is possible that the gas mixture leaves the reactor with a temperature reduced by 50 to 100 ° C. This outlet temperature may also be higher or at the same level. In the framework of the above method, it is advisable to use oxide dehydrogenation catalysts based on chromium oxide and / or aluminum. Often, diluent gas is not used, but rather as the starting reaction gas from substantially one saturated hydrocarbon K (e.g., propane or crude propane) as the starting reaction gas. Also, the dehydrogenation catalyst can be used undiluted in most cases.

On a large technical scale, several (for example, three) such shell-and-tube reactors can be operated in parallel. Moreover, if necessary, two such reactors can according to the invention be in dehydrogenation mode, while the catalyst loading is regenerated in the third reactor, without the operation being interrupted in at least one partial zone.

Such management of the method is advisable, for example, with the Linde dehydrogenation method known from the literature. It is also important according to the invention that the use of such a shell-and-tube reactor is sufficient.

This method is also applicable to the so-called "steam active reforming (STAR) process", which was developed by Phillips Petroleum Co. (cp., For example, US-A 4902849, US-A 4996387 and US-A 5389342). As a dehydrogenation catalyst in the STAR process, platinum promoters containing zinc-magnesium spinel containing promoters are used as carriers (cf., for example, US-A 5,073,662). Unlike the BASF-Linde propane dehydrogenation process, the propane to be dehydrogenated in the STAR process is diluted with water vapor. Typical is the molar ratio of water vapor to propane in the range from 4 to 6. The outlet pressure of the reactor is often from 3 to 8 atm, and the temperature of the reactor is suitably selected in the range from 480 to 620 ° C. A typical catalyst load for the reaction mixture is from 0.5 to 10 h ⁻¹ (LHSV).

The heterogeneously catalyzed dehydrogenation according to the invention can also be carried out in the moving bed. For example, a movable catalyst bed may be placed in a radial flow reactor. In it, the catalyst slowly moves from top to bottom, while the reaction gas mixture flows radially. Such process management is used, for example, in the so-called UOP-Oleflex dehydrogenation process. Due to the fact that the reactors in this method are operated adiabatically, it is advisable to operate several reactors (typically up to four reactors) included in the cascade. As a result of this, a too high difference between the temperatures of the reaction gas mixture at the inlet and at the outlet of the reactor can be prevented (in adiabatic mode, the inlet reaction gas mixture acts as a heat carrier, the decrease in the reaction temperature depends on the heat content of it), and despite this, a sufficient overall conversion can be achieved .

If the catalyst bed leaves the mobile bed reactor, it is fed to the regeneration step and then reused. As a dehydrogenation catalyst for the present process, for example, a spherical catalyst, which consists mainly of platinum on a spherical alumina support, can be used. In the UOP embodiment, hydrogen to be fed to the saturated hydrocarbon K (e.g., propane) to be dehydrogenated is to prevent premature aging of the catalyst. Working pressure is usually from 2 to 5 atm. In the case of propane, the ratio (molar) of hydrogen to propane is expediently from 0.1 to 1, the reaction temperature is preferably from 550 to 650 ° C., and the contact time of the catalyst with the reaction mixture is selected from about 2 to 6 h ⁻¹ .

In the described method with a fixed bed, the geometry of the catalyst can also be spherical, but it is also possible cylindrical (hollow or solid) or other geometric shape.

As another embodiment of heterogeneously catalyzed dehydrogenation of saturated hydrocarbons, Proceedings De Witt, Petrochem. Review, Houston, Texas, 1992 a, N1 describes the possibility of a heterogeneously catalyzed dehydrogenation in a fluidized bed in which the hydrocarbon is not diluted.

According to the invention, in this case, for example, two fluidized beds can be operated in parallel to each other, one of which, without adversely affecting the process, can be in a regenerated state from time to time. In this case, chromium oxide on alumina is used as an active mass. The operating pressure is usually from 1 to 2 atm and the dehydrogenation temperature is usually from 550 to 600 ° C. The heat required for dehydrogenation is introduced into the reaction system so that the dehydrogenation catalyst is preheated to the reaction temperature. Such a dehydrogenation method is known from literature as the Snamprogetti-Yarsintez method.

Alternative to the above methods, heterogeneously catalyzed dehydrogenation can be carried out with a significant exclusion of oxygen according to the method developed by ABB Lummus Crest (cf. Proceedings De Witt, Petrochem. Review, Houston, Texas, 1992, P1).

A common feature of the heterogeneously catalyzed methods for the dehydrogenation of saturated hydrocarbons described so far with a significant exclusion of oxygen is that they are carried out at conversions of ≥ 30 mol% (as a rule, this is 60 mol%) (in terms of a one-time pass of the reaction zone) of saturated hydrocarbon (e.g. propane). According to the invention, the advantage is that it is sufficient for a saturated hydrocarbon (for example, propane) to obtain a conversion of from 5 mol.% To 30 mol.% Or 25 mol.%. This means that heterogeneously catalyzed dehydrogenation can also be carried out at a conversion of from 10 to 20 mol% (in terms of a one-time passage of the reaction zone). The reason for this, among other things, is that the remaining amount of unreacted saturated hydrocarbon (e.g. propane) in the subsequent at least one partial oxidation and / or partial amoxidation mainly acts as an inert diluent gas and, later, to a considerable extent without losses again return to the dehydrogenation zone and / or at least one zone.

To implement the above conversions, as a rule, it is favorable to carry out a heterogeneously catalyzed dehydrogenation at an operating pressure of 0.3 to 3 atm. Further, it is favorable to dilute the saturated hydrocarbon subjected to the heterogeneously catalyzed dehydrogenation with water vapor. Thus, the heat capacity of water makes it possible, on the one hand, to compensate for part of the action of the dehydrogenation endothermy, and, on the other hand, dilution with water vapor reduces the partial pressure of the initial and final product, which favorably affects the dehydrogenation balance. Further, the use of water vapor, as indicated, favorably affects the life of the noble metal-containing dehydrogenation catalysts. If necessary, molecular hydrogen may be added as a further component. The molar ratio of molecular hydrogen to saturated hydrocarbon (for example, propane) in this case is, as a rule, 5. The molar ratio of water vapor to saturated hydrocarbon can accordingly be from 0 to 30 with a relatively low conversion of the hydrocarbon, it is advisable from 0.1 to 2 and advantageously from 0.5 to 1. It is also advisable for a process with a low dehydrogenation conversion that only a relatively low amount of heat is consumed during a single pass of the reactor with the reaction gas, and for a conversion reactor on single pass is sufficient relatively low reaction temperature.

Therefore, it may be appropriate to carry out dehydrogenation with a relatively low conversion (as it were) adiabatically. This means that the reaction gas feed mixture is usually first heated to a temperature of from 500 to 700 ° C (respectively, from 550 to 650 ° C) (for example, by direct heating of the surrounding wall). In the normal case, a single adiabatic passage through the catalyst bed is sufficient to achieve the desired conversion, with the reaction stock being cooled to about 30 ° C to 200 ° C (depending on conversion and dilution). The presence of water vapor as a coolant favorably affects the process from the point of view of its adiabatic behavior. The low reaction temperature allows to achieve a longer service life of the used catalyst.

In principle, heterogeneously catalyzed dehydrogenation with a relatively low conversion is possible adiabatically or isothermally, both in a fixed-bed reactor and in a moving or fluidized-bed reactor.

It should be noted that in the method according to the invention, for its implementation, in particular in adiabatic mode, a separate shaft furnace type reactor is sufficient as a fixed-bed reactor through which the reaction gas mixture passes axially and / or radially.

In the simplest case, we are talking about one single closed reaction volume, for example, a vessel whose internal diameter is from 0.1 to 10 m, it is also possible from 0.5 to 5 m and in which a fixed catalyst layer is deposited on a supporting device (e.g. grate). Through the catalyst-loaded reaction volume, which is thermally insulated in adiabatic mode, the hot reaction gas containing saturated hydrocarbon K is axially flowing. The geometry of the catalyst can be either spherical or annular or tow-shaped. Due to the fact that in this case the reaction volume can be realized with a very cheap apparatus, all catalyst geometries that have particularly low pressure losses are preferred. First of all, this is the geometry of the catalyst, which leads to large volumes of hollow spaces or is structurally made, such as, for example, monoliths, respectively, cellular elements. To carry out a radial flow of a reaction gas containing saturated hydrocarbon K, the reactor can consist, for example, of two cylindrical grate grids inserted concentrically into one another and the catalyst backfill can be placed in their annular gap. In the case of adiabatic management of the method, the metal shell should be, if necessary, thermally insulated.

Suitable catalyst fillings for heterogeneously catalyzed dehydrogenation with a relatively low conversion in a single pass are suitable, in particular, those described in DE-A 19937107, especially all of the catalysts described in the examples.

After prolonged use, these catalysts can be easily regenerated due to the fact that at the inlet temperature from 300 to 600 ° C, often from 400 to 550 ° C, diluted with nitrogen and / or water vapor is passed through the catalyst first in the first stage of regeneration (preferably ) air. The catalyst load of the regenerating gas in this case is, for example, from 50 to 10,000 h ^-1 and the oxygen content in the regenerating gas is from 0.5 to 20 vol.%.

In the subsequent regeneration step, with otherwise otherwise identical regeneration conditions, air can be used as the regenerating gas. From the point of view of application technology, it is recommended to rinse the catalyst before its regeneration with an inert gas (for example, N ₂ ).

In conclusion, it is generally recommended to regenerate with still pure molecular hydrogen or diluted inert gas (preferably water vapor) with molecular hydrogen (the hydrogen content should be 1 vol.%) Under otherwise identical conditions.

Heterogeneously catalyzed dehydrogenation with a relatively low conversion (30 mol%) can in all cases be carried out under the same catalyst loads (this applies both to the total reaction gas and to the saturated hydrocarbon K contained in it), as well as variants with high conversion (> 30 mol%). This reaction gas load can be, for example, from 100 to 10,000 h ^-1 , often from 300 to 5,000 h ^-1 , i.e. repeatedly from 500 to 3000 h ^-1 .

In a particularly elegant manner, heterogeneously catalyzed dehydrogenation can be carried out with a relatively low conversion in a lattice reactor.

It contains sequentially in space more than one catalyst layer catalyzing dehydrogenation. The number of catalyst layers can be from 1 to 20, suitably from 2 to 8, and also from 3 to 6. The catalyst layers are preferably arranged radially or axially sequentially one after another. From the point of view of application technology, it is advisable to use a fixed catalyst in such a lattice reactor.

In the simplest case, the fixed catalyst beds are located axially in the shaft type reactor or in the annular gaps of the concentrically cylindrical grate grating inserted into each other. It is also possible to arrange annular gaps in the segments one above the other and to direct the gas after radial entry into one segment into the next segment lying higher or lower.

Advantageously, the reaction gas mixture on its way from one catalyst bed to another is subjected to intermediate heating in a grate reactor, for example, passing through heat exchanger fins heated by hot gases or passing through pipes heated by hot combustion gases.

If the lattice reactor operates in an adiabatic mode, then for the desired conversion (30 mol%), in particular when using the catalysts described in DE-A 19937107, especially in the exemplary embodiments, it is sufficient to feed the reaction mixture into a preheated dehydrogenation reactor to a temperature of 450 to 550 ° C and inside the lattice reactor to keep at this temperature. This means that the general dehydrogenation should be carried out at an extremely low temperature, which is especially good for the service life of the fixed catalyst layer between the two regeneration processes.

It is even more advantageous to carry out the above intermediate heating directly (autothermal mode). To this end, molecular oxygen is added to the reaction gas mixture either before passing through the first catalyst layer and / or between the next catalyst layers in a limited volume. Depending on the dehydrogenation catalyst used, a limited combustion of the hydrocarbon contained in the reaction gas mixture, if necessary already deposited on the surface of the coal catalyst, respectively carbon-like compounds and / or formed in the process of heterogeneously catalyzed dehydrogenation and / or added to the reaction gas mixture, is thus carried out hydrogen (from the point of view of the application technique, it may be appropriate to introduce catalyst layers into the lattice reactor loaded with a catalyst that specifically (selectively) catalyzes the combustion of hydrogen (and / or hydrocarbon) (as such a catalyst are suitable, for example, described in documents US-A 4788371, US-A 4886928, US-A 5430209, US-A 5530171, US -A 5527979 and US-A 5563314, for example, such catalyst layers can be placed in a grating reactor in an alternating order to the layers containing the dehydrogenation catalyst.) The heat of reaction released in this way allows an almost isothermal mode of heterogeneously catalyzed degene to be carried out in an autothermal manner. rirovaniya.

With increasing selected residence time of the reaction gas in the catalyst bed, dehydrogenation is thus possible at a decreasing or substantially constant temperature, which makes it possible to have a particularly long catalyst life between the two regeneration steps.

As a rule, the above oxygen supply should be carried out in such a way that the oxygen content of the reaction gas mixture, in terms of the amount of saturated hydrocarbon contained in it, is from 0.5 to 30 vol.%. In this case, both pure molecular oxygen or oxygen diluted with an inert gas, for example, CO, CO ₂ , N ₂ , noble gases, and especially air, are suitable as an oxygen source. The resulting combustion gases, as a rule, act additionally with dilution and, as a result, contribute to heterogeneously catalyzed dehydrogenation.

The isotherm of heterogeneously catalyzed dehydrogenation can be improved due to the fact that closed, before being filled with favorable, but not necessarily evacuated, built-in elements (e.g., tubular) are embedded in the lattice reactor in the cavities between the catalyst layers. Such plugs may be placed in the catalyst bed. These plug-ins contain suitable solids or liquids that melt or evaporate when a certain temperature is exceeded and at the same time consume heat and, where the temperature drops below the specified temperature, condense again and release heat.

The possibility of heating the outlet reaction gas mixture for heterogeneously catalyzed dehydrogenation to the desired reaction temperature also consists in burning part of the saturated hydrocarbon K and / or H ₂ contained therein by means of molecular oxygen (for example, on a suitable, specifically acting combustion catalyst, for example, by means of simple bypassing and / or transmission) and in the action of the heat of combustion thus released on the desired reaction temperature. The resulting combustion products, such as CO ₂ , H ₂ O, as well as N ₂ , accompanying, if necessary, the molecular oxygen required for combustion, form preferably inert diluent gases.

It is especially elegant to carry out the above hydrogen combustion, as described in DE-A 10211275, i.e. in a method for continuous heterogeneously catalyzed partial dehydrogenation of a saturated hydrocarbon in the gas phase, in which

- the reaction gas containing the dehydrogenation-saturated hydrocarbon is continuously fed to the reaction zone,

- the reaction gas in the reaction zone is passed through at least one fixed catalyst layer in which molecular hydrogen and at least partially dehydrogenated hydrocarbon are obtained by catalyzed dehydrogenation,

- at least one molecular oxygen-containing gas is added to the reaction gas before and / or after entering the reaction zone,

- molecular oxygen in the reaction zone partially oxidizes the molecular hydrogen contained in the reaction gas to water vapor; and

- a gas product is selected from the reaction zone, which contains molecular hydrogen, water vapor, partially dehydrogenated hydrocarbon and saturated (to be dehydrogenated) hydrocarbon,

which consists in separating the gas product from the reaction zone into two partial streams of identical composition and returning one of the two partial streams as a circulation gas to the dehydrogenation reaction zone and using the other partial stream as a gas mixture according to the invention.

The above-described embodiment of the catalytic dehydrogenation used according to the invention is applicable, especially when the saturated hydrocarbon to be dehydrogenated is propane and / or iso-butane.

The gas mixture and / or to be obtained from it, as described above, the additional gas mixture can be used in a known manner to load the heterogeneously catalyzed partial oxidation and / or amoxidation step with a further gas mixture (cf. the above prior art). It is essential for the invention that the gas mixture, the additional gas mixture and / or the further gas mixture is subjected to mechanical separation before at least one heterogeneously catalyzed partial oxidation and / or ammoxidation by means of which they can be separated from these gas mixtures solid particles.

Partial oxidation of the process according to the invention is suitable, in particular, partial oxidation of propene (obtained by partial dehydrogenation of propane) to acrolein and / or partial oxidation of acrylic acid and partial oxidation of isobutene (obtained by partial dehydrogenation of isobutane) to methacrolein and / or methacrylic acid.

Partial ammoxidation according to the invention is suitable, in particular, partial ammoxidation of propene to acrylonitrile, as well as partial ammoxidation of isobutene to methacrylonitrile.

Example

1. The dehydrogenation catalyst

On the outer and inner surface of the carrier on a mixed oxide of ZrO ₂ · SiO ₂ (bundles with a length ranging from 3 to 8 mm and a diameter of 2 mm, obtained according to example 3 from DE-A 10219879) are applied in the same manner as in DE-A 10219879 Pt / Sn alloy, which has oxide elements in the form of Cs, K, and La as promoters. The stoichiometry of the elements (weight ratio) is: Pt _0.3 Sn _0.6 La _3.0 Cs _0.5 K _0.2 (ZrO ₂ ) _88.3 (SiO ₂ ) _7.1 .

The application of alloys equipped with promoters, as described above, is carried out by impregnating the crushed support with a saline solution of the corresponding metals and subsequent heat treatment (1.5 hours) at 560 ° C in an air stream. As part of the heat treatment, both the active components of Pt and Sn and the promoters are converted to their oxide form. In the dehydrogenation reactor described below, the active components of the pre-catalyst (precontact), as described below, are reduced in a stream of hydrogen at 500 ° C. into metals to produce an active catalyst.

2. Dehydrogenation reactor (C330)

650 ml (762 g) of the preliminary catalyst obtained as described above are loaded into a vertically standing tubular reactor (pipe length: 2049 mm, wall thickness: 7 mm, inner diameter: 41 mm, material: steel pipe coated with aluminum oxide) as follows (loading from bottom to top, mounted on a support):

A layer of 299 mm rings of steatite (outer diameter × length × inner diameter = 7 mm × 3 mm × 4 mm), then a layer of 50 mm balls of steatite with a diameter of 4-5 mm, then 25 mm balls of steatite with a diameter of 1.5- 2.5 mm, then 500 mm of the preliminary catalyst, then 50 mm of steatite balls with a diameter of 4-5 mm, then 1080 mm of steatite rings (outer diameter × length × inner diameter = 7 mm × 3 mm × 4 mm). As steatite, Steatit C-220 steatite from CeramTec is used. The reaction tube is heated (electrically) using an NTM Reetz heating spiral furnace (into which the reaction tube is inserted) in four zones immediately following one after the other, each extending to a length of 2 × 220 cm. Between the pipe surface and heating spirals There is an air gap of approx. 72.5 mm. From below, the top of the reaction tube along the length of 1000 mm on its outer wall is covered with microporous insulating material such as MPS-Super G from Mientherm, DE with a layer thickness of 100 mm (as if the adiabatic part of the reaction). In this zone, heating acts as supporting heating, while in the upper region it serves to directly heat the pipe section.

From top to bottom, a thermowell was introduced centered along the length of 1.50 m from the top of the reaction tube (outer diameter = 6 mm, inner diameter = 4 mm) to accommodate several thermocouples.

From the bottom up, a thermowell 60 cm long was inserted into the reaction tube accordingly.

Activation of the preliminary catalyst in a hydrogen stream is carried out as described in example 1 of document DE-A 10211275.

3. Test facility

Propane or n-butane (hereinafter referred to as liquid petroleum gas = LPG) is used as a hydrocarbon subject to heterogeneously catalyzed dehydrogenation of the hydrocarbon.

The test setup consists of 4 parts:

- dosage unit;

- reaction unit;

- a circulating gas unit and an unloading unit.

In the metering unit, the starting materials of the LPG and water (if necessary, in a stream of nitrogen) are fed through the W100 evaporator and transferred to the gas phase in it. After the evaporator, if necessary, air, molecular oxygen and molecular hydrogen are mixed into the gas mixture obtained in the evaporator to obtain the desired fresh starting mixture.

In the reaction unit, the fresh feed mixture (if necessary, in a mixture with circulating gas) is heated in a W200 pre-heater (heat exchanger) to a temperature of 400 to 500 ° C and then fed to the above C330 dehydrogenation reactor (from top to bottom). The heating zones in this case have the following temperatures from top to bottom: 500 ° C, 550 ° C, 550 ° C and 550 ° C. The inlet pressure in the dehydrogenation reactor is selected at 2 bar.

The gas mixture leaving the dehydrogenation reactor is passed through an air-cooled heat exchanger and cooled to 300 ° C. After that, it is directed along the guide pipe to the unloading unit and further processed in it. If a partial stream of chilled gas mixture is supplied to the discharge unit, then the remaining partial stream is supplied to the circulating gas unit.

In this unit, the partial flow of the gas mixture fed in the cycle is cooled in an oil-powered W420 heat exchanger, first to 150 ° C, then compressed to 2 bar in the V440 compressor and then after passing through the W460 heat exchanger, where it is heated to 300 ° C , combine before the pre-heater W200 with a fresh source gas mixture (and then fed to the pre-heater).

4. Results

The test setup was operated substantially continuously for 3 months. A total of 26 reaction cycles were performed. After each reaction cycle, the dehydrogenation catalyst was regenerated according to the method described in DE-A 10028582 with the following stages: washing, separation, washing, recovery. Within one reaction cycle (the shortest cycle was 3 hours and the longest 100 hours), the conditions were kept constant. The conditions of all cycles had the following scope:

hydrocarbon ZhPG cycle time 3-100 h amount of zhpg 500-2000 g / h fresh water vapor 500-1000 g / h nitrogen 0-50 nl / h air 0-375 nl / h hydrogen 0-150 nl / h temperature of heating zones 500 ° C, 550 ° C, 550 ° C and 550 ° C inlet pressure 2 bar circulating gas ratio 0 or 5 (ratio of cycle-directed quantity   to released quantity)

Parts of the test setup that were exposed to temperatures up to 300 ° C were made of V2A steel. Parts of the test rig that were exposed to temperatures above 300 ° C were made of 1.4841 steel.

After completing a series of tests in all parts of the test setup through which circulating gas and gas mixture flowed, significant amounts of rust deposits could be detected. The reason for this was the rusting of the guide tube, in which (apparently due to the previous cooling of the gas mixture A), water condensed.

Analysis of rust plaque by atomic absorption spectroscopy showed, along with the expected components of Fe, Ni, and Cr, also the proportions of Zr, Si, and Pt, which could only come from a dehydrogenation catalyst. In general, analysis of rust samples showed the following amounts of elements:

carbon: 1.5 g / 100 g Al 2.2 g / 100 g Cr 2.6 g / 100 g Fe 13.1 g / 100 g Mg 10.6 g / 100 g Ni 1.9 g / 100 g Pt 0.019 g / 100 g Si 20.6 g / 100 g Zr 0.17 g / 100 g

In the analysis of a point sample of gas mixture A, the elements Zr, Si, and Pt could not be detected. Obviously, the amounts obtained are below the detection limit.

Claims (6)

1. A method for producing at least one partial oxidation and / or ammoxidation product of a hydrocarbon selected from the group consisting of acrolein, acrylic acid, methacrolein, methacrylic acid, acrylonitrile and methacrylonitrile, wherein at least one saturated hydrocarbon is subjected heterogeneously catalyzed dehydrogenation in the gas phase to obtain a gas mixture containing at least one partially dehydrogenated hydrocarbon; components contained in the gas mixture other than saturated hydrocarbon and a partially dehydrogenated hydrocarbon is left in it or to obtain an additional gas mixture partially or completely separated, and the gas mixture and / or additional gas mixture is used to obtain a further gas mixture additionally containing molecular oxygen and / or molecular oxygen and ammonia, while the further gas mixture is subjected to at least one heterogeneously catalyzed partial oxidation and / or ammoxidation of the at least one additional gas mixture contained in the gas mixture at least one partially dehydrogenated hydrocarbon, characterized in that the gas mixture, additional gas mixture and / or further gas mixture before at least one partially heterogeneously catalyzed oxidation and / or ammoxidation is subjected to at least one mechanical separation directed the separation contained in these gas mixtures of solid particles. 2. The method according to claim 1, characterized in that the saturated hydrocarbon is propane and the heterogeneously catalyzed partial oxidation of the partially dehydrogenated hydrocarbon is the partial oxidation of propene to acrolein and / or acrylic acid. 3. The method according to claim 1, characterized in that the saturated hydrocarbon is iso-butane and the heterogeneously catalyzed partial oxidation of the partially dehydrogenated hydrocarbon is the partial oxidation of iso-butene to methacrolein and / or methacrylic acid. 4. The method according to claim 1, characterized in that the saturated hydrocarbon is propane and the heterogeneously catalyzed partial oxidation of the partially dehydrogenated hydrocarbon is a partial amoxidation of propene to acrylonitrile. 5. The method according to claim 1, characterized in that the saturated hydrocarbon is isobutane and the heterogeneously catalyzed partial oxidation of the partially dehydrogenated hydrocarbon is a partial amoxidation of isobutene to methacrylonitrile. 6. The method according to one of claims 1 to 5, characterized in that at the stage of dehydrogenation using a catalyst consisting of at least one metal deposited on an oxide carrier.