CS200530B2 - Method of preparing maleinanhydride by the oxidation of n-butane,n-butenes,1,3-butadiene or mixtures thereof with molecular oxygen - Google Patents

Description

The invention relates to a process for the preparation of maleic anhydride by gas phase oxidation of n-butane, n-butenes, 1,3-butadiene or mixtures thereof with molecular oxygen.

Belgian Patent No. 828074 discloses the use of catalysts containing phosphorus, molybdenum, bismuth, copper, at least one metal selected from the group consisting of iron, nickel, cobalt, potassium and optionally lithium, sodium, rubidium, cesium. beryllium, magnesium, calcium, strontium, or barium in the preparation of maleic anhydride from 1-butene, 2-butene, butadiene, pentene, pentadiene, cyclopentadiene and benzene. Comparative Example 4 on pages 20 and 21 above. The patent discloses that the use of a catalyst consisting of a combination of elements corresponding to the general formula P1.0MO12BiO, S6CU0.54039.6 in the oxidation of 1-butene provides a 27.9% yield of maleic anhydride calculated on the amount of starting 1-butene.

French Patent No. 1 -601 955 describes the use of a catalyst consisting of a combination of elements corresponding to the general formula

AO3 — B2O5 — MzCb — N _X O — HsO, where is

And the atom of chromium, molybdenum, tungsten or uranium,

B a vanadium or niobium atom,

M atom of phosphorus, arsenic, antimony or vismuth,

N an atom of copper, silver, iron, cobalt or nickel,

R is lithium, sodium, potassium, cesium or rubidium.

Preferred compositions are 15 to 55% of atomic component A, 30 to 70% of atomic component B, 0 to 15% of atomic component M, 0.1 to 20% of atomic component N and 0 to 15% of atomic component R.

The invention is the result of research into a more efficient catalyst for the oxidation of n-butane, n-butenes and 1,3-butadiene.

The catalyst used in the process of the invention is unexpectedly more advantageous in the preparation of maleic anhydride from n-butane, n-butenes and 1,3-butadiene. When using the catalyst according to the invention, particularly good yields are obtained from 1,3-butadiene and n-butenes.

Indeed, it has been found that a process for the preparation of maleic anhydride by oxidation of n-butane, n-butenes, 1,3-butadiene or a mixture thereof with molecular oxygen in the gas phase at the reaction temperature

250-600 ° C in the presence of a catalyst ob200530 sáhujícího phosphorus, molybdenum, oxygen, or an inert carrier and a promoter and optionally in the presence of steam is improved if a catalyst is used consisting of the combination of elements corresponding to the formula IX _and M03P _b 0 _x (i) where it means

X at least one of arsenic, rubidium, cesium, palladium, cadmium, thalium and indium, and a positive number greater than zero but less than 10, b a positive number greater than zero but less than 3, x the number of oxygen atoms required to saturate valency of other elements present.

Particularly high yields and selectivities with respect to maleic anhydride are achieved by an efficient, convenient and economical process at a relatively low temperature. The exothermic nature of the reaction is low, which facilitates reaction control. The most important factor in the process according to the invention is the catalyst used.

Preferred catalysts of formula I are those in which a is a positive number less than 7 and those in which b is a positive number less than 2. Very good results are obtained with catalysts in which a is 0.01 to 3 ab number 0.01 to 1.0. Catalysts of formula (I) wherein X is at least one element selected from the group consisting of rubidium, cesium, thallium and indium are considered to be very preferred. Excellent results are obtained when all X-elements are introduced into the catalyst separately.

The catalysts of the formula I can be prepared in a variety of ways. These methods are well known to those skilled in the art. Preparations such as coprecipitation, evaporative drying or mixing of oxides, followed by calcination of the resulting catalyst, have been successfully used.

The catalysts of the formula I are preferably prepared in an aqueous suspension or in an aqueous solution of molybdenum-phosphorus-containing compounds by addition of other components and evaporation of the aqueous mixture, as suitable molybdenum compound for the preparation of the catalysts of the formula I include molybdenum oxide, phosphomolybdic acid, molybdic acid and ammoniumheptamolyhdát. Very good results are obtained by using catalysts of the formula I in which at least a part of the molybdenum used for the preparation of the catalyst is supplied in a catalyst. in the form of molybdenum oxide.

A suitable phosphorus compound which may be used in the preparation of the catalyst is orthophosphoric acid, metaphosphoric acid, trophosphoric acid, phosphorus halides or phosphorus oxyhalides. The remaining components of the catalyst may be added in the form of oxides, acetates, formates, sulfates, nitrates, carbonates, halides and oxyhalides.

Very good catalysts of formula (I) are obtained by refluxing phosphoric acid and molybdenum trioxide in water for 1.5 to 3 hours, but more effectively phosphomolybdic acid can be used directly, adding the remaining components to the aqueous suspension and welding to a thick paste into which at least one of the components is added in the form of a halide or oxyhalides and air-dried at 110 to 120 ° C. The catalysts of formula (I) may also be prepared by mixing the catalyst components in an aqueous suspension or in an aqueous solution, heating the aqueous mixture to dryness and calcining the resulting catalyst.

The calcination can be carried out by heating the dry catalyst components to a temperature of 300 to 700 ° C, the calcination preferably being carried out at a temperature of 325 to 450 ° C,

The reacting hydrocarbons may be n-butane, n-butenes, 1,3-butadiene or mixtures thereof. Preference is given to using 1,3-butadiene, n-butenes or mixtures of hydrocarbons obtained in the refinery. Molecular oxygen is generally added in the form of air, but may also be a suitable synthetic oxygen-containing gas. In addition to hydrocarbons and molecular oxygen, other gases may also be present in the reaction. For example, steam or nitrogen may be added to the reactants.

The ratio of the reactants may vary within wide limits and is not critical. The ratio of hydrocarbon to molecular oxygen may be from about 2 to 30 moles of oxygen per mole of hydrocarbon. A ratio of about 4 to about 10 is preferred. 20 moles of oxygen per mole of hydrocarbon.

The reaction temperature can vary within wide limits, depending on the hydrocarbon used and the catalyst used. Normally, temperatures of about 250 to 600 ° C are used, with 250 to 450 ° C being preferred. .

The catalyst may be used alone or on a support. Suitable carriers include silica, alumina, alundum (synthetic abrasive, substantially fused alumina), silicon carbide, boron phosphate, zirconia and titanium dioxide. The catalysts are generally used in a solid-bed reactor in the form of tablets, pellets or the like, or in a fluidized bed reactor in the form of particles smaller than about 300 μΐη. The contact time can be a fraction of a second or up to 20 seconds or even longer. The reaction can be carried out at atmospheric pressure, at or above atmospheric pressure.

Excellent results are obtained using a coated catalyst consisting essentially of an inert support material with a diameter of at least 20 µπι, an outer surface and a continuous coating of said active catalyst on an inert support with a strong adhesion on the outer support surface.

When using coated catalysts in the reaction to prepare maleic anhydride, the reaction proceeds as very low exothermic, allowing good reaction control. In one pass, a high yield is achieved and the formation of unwanted by-products is eliminated.

A particular coated catalyst consists of an inner support material with an outer surface and a coating of active catalyst material on the outer surface. These catalysts can be prepared in various ways.

The catalyst support material forms the inner core of the catalyst. It is a substantially inert carrier which may have substantially any particle size, but a shape with a diameter greater than 20 μ, τη is preferred. Particularly preferred according to the invention are for the reactors reactors which are spherical and have a diameter of about 0.2 cm to 2 cm. Examples of such inert carriers include alundum, silica, alumina, alumina, carbide, silicon, titanium dioxide, and zirconia.

Of these carriers, alundum, silica, alumina and alumina-silica are particularly preferred.

The catalysts may comprise substantially any proportion of carrier and catalytically active material. The limit of this ratio is determined only by the mutual adaptability of the catalyst and the support. Preferred catalysts contain 10 to about 100 wt. catalytically active substances, based on the weight of the carrier.

Various methods can be used to prepare these coated catalysts. The basic method of preparing these catalysts is to partially wet the carrier with liquid. The carrier should not be damp on the outer surface of all material. It should appear dry to the touch. When the surface is wet, the active catalyst material is agglomerated to separate aggregates upon coating of the support. Partially wetted

Example Element, X = cesium thalium indium carrier is then contacted with the catalytically active material powder and the mixture. is stirred gently until the catalyst is formed. Typically, gentle mixing is carried out by placing the partially wetted carrier in a rotating drum or vessel and adding the active catalyst material. This is really an economic way.

By using the catalysts of the present invention in the preparation of maleic anhydride, excellent yields are obtained in a convenient manner to produce small amounts of by-products.

He did

RBO, 5Mo3Po, S30 _x

An aqueous suspension is prepared by adding 55.3 grams of molybdenum trioxide to one liter of boiling distilled water with stirring; the suspension is boiled for about two hours. 4.9 g of a 85% phosphoric acid solution are added to this aqueous suspension; the suspension turns yellow. About 200 mL of distilled water was added to maintain about 800 mL of solution. To this aqueous mixture was added 7.5 g rubidium carbonate; the suspension turns bright yellow. After about 30 minutes, 25 mL of distilled water was added. The catalyst is heated with stirring; Evaporate to dryness and air dry at about 110 ° C. The catalyst is milled and sieved to a 10-30 mesh fraction.

Examples 2 to 4

Various catalysts according to the invention are prepared. These catalysts have the general formula

Xo '5MosPo, 330 _x

Catalysts were prepared as described in Example 1 except that 86.2 g of molybdenum trioxide and 7.7 g of 85% phosphoric acid were used. Elements marked with X are added after phosphoric acid is added. The following compounds are used in the preparation of the catalyst and in the following amounts:

Compound Amount in g

cesium acetate 19.2 thallium acetate 26.3 indium acetate 29.2

After addition of element X, the catalyst is evaporated to dryness, air dried, milled and sieved.

Examples 5 to 23

Preparation of malannic anhydride from 2-butene

A portion of the catalyst particles prepared as described in Examples 2 to 4 were charged to a 20 ml solid-bed reactor equipped with a 1.02 cm. Stainless steel tube.

% yield per pass

The reactor is heated to reaction temperature with air flow and a mixture of air, 2-butene and water in the ratio shown in Table 1 below is passed through the catalyst at an apparent contact time of 1.0 to 1.5 seconds and the catalyst is evaluated by product collection and analysis. The test results are shown in Table 1 below.

The following equations are used to assess the balance of carbon atoms in feed and product feed:

moles of the obtained malannic anhydride

X 100 moles of hydrocarbon introduced Total conversion selectivity = moles of reacted hydrocarbon moles of hydrocarbon introduced Single pass yield total conversion

X 100

X 100

200S30

Preparation of maleic anhydride from 2-butene

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Examples 24 to 27

Preparation of maleic anhydride from 2-butene using supported catalyst.

Catalysts of the formula C 50, 5MosPo, 330 _x , diluted with 30 wt. carriers with a small specific surface area (equal to or less than 20 m ² / g). These catalysts are. used for the reaction of 2-butene and air as described above. The results of these tests are shown in Table 2.

Table 2

Characteristics of the supported catalyst in the preparation of maleic anhydride from 2-butene

Example Catalyst Clock Ratio Temperature ° C Results% Air / Bath Exoth. all maleinTi 4

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SUBJECT

Claims (3)

SUBJECT A process for the preparation of maleic anhydride by oxidizing n-butane, n-butenes, 1,3-butadiene or mixtures thereof with molecular oxygen in the gas phase at a reaction temperature of 250 to 600 ° C in the presence of a catalyst containing phosphorus, molybdenum, oxygen and optionally an inert carrier 0.2 to 2 cm particles and a promoter characterized in that a catalyst consisting of a combination of elements corresponding to formula I is used X _and M03P _b 0 _x (Γ), where is X at least one element selected from the group consisting of arsenic, rubidium, palladium, cadmium, cesium, thalium and indium, and a positive number greater than zero but less than 10, YNALEZU b a positive number greater than zero but less than 3 x the number of oxygen atoms required to saturate the valences of the other elements contained. 2. A process according to claim 1, characterized in that a catalyst comprising a combination of elements corresponding to formula I is used, wherein a is a positive number greater than zero but less than 7, in particular 0.01 to 3, b a positive number greater than zero but less and X and x are as defined in point 1. 3. A process according to claim 1, wherein the catalyst is a combination of elements corresponding to formula I wherein X is rubidium, cesium, thallium, indium, and a, b, x are as defined in point 1. Severography, n. p., Plant 7, Most