CS200531B2 - Method of preparing maleinanhydride by the oxidation of n-butane,n-butenes,1,3-butadiene or mixtures thereof with molecular oxygen - Google Patents

Description

(54) A process for the preparation of maleic anhydride by oxidation of n-butane, n-butenes,

1,3-butadiene or mixtures thereof with molecular oxygen

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 of iron, nickel, cobalt, potassium and optionally lithium, sodium, rubidium, cesium, beryllium, magnesium, calcium, strontium or barium the preparation of maleic anhydride from 1-butene, 2-butene, butadiene, pentene, pentadiene, cyclopentadiene and benzene. Comparative Example 4 on pages 20 and 21 of the aforementioned patent demonstrates that the use of a catalyst consisting of a combination of elements corresponding to the general formula

Pi, ₀ Mqi2Bí _Bi36 Cuo _{i5 i6} 9 40 ₃ in the oxidation of 1-butene gives 27.9% yield of maleic anhydride, calculated on the starting amount of 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

AO 3 - Ό 2-5 - M ₂ O 5 - N _X O - R 20, 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 compounds 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.

It has been found that the 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 a reaction temperature of 250 to 600 ° C in the presence of a catalyst containing phosphorus, molybdenum, inert carrier and promoter, and optionally in the presence of steam is improved when using a catalyst consisting of a combination of elements corresponding to formula I

X _and Mo 12 P _b R b _c O _x (I), where is

X at least one element selected from the group consisting of tin, a rare earth element, nickel, zirconium, barium, iron, rhodium, manganese, rhenium, ruthenium, cobalt and copper, and a positive number greater than zero but less than 20, b and a number of 0.001 to 10; x the number of atoms required to saturate the valences of the other elements present.

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

Preferred are catalysts of formula I wherein a is a positive number less than 12, furthermore formula I wherein b is 0.01 to 5 and formula I where c is 0.01 to 5. Particularly preferred are catalysts of of formula I ,. wherein b is 0.5 to 1.5 and c is 0.1 to 1.0. Particularly preferred are furthermore catalysts of the formula I in which X represents at least one element from the group comprising nickel, copper, tin and a rare earth element.

The catalysts of the invention can be prepared in a variety of ways. These ways are. is 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 and phosphorus-containing compounds, by adding the other components and evaporating the aqueous mixture. Suitable molybdenum compounds for the preparation of the catalysts (I) include molybdic oxide, phosphomolybdic acid, molybdic acid and ammonium heptamolybdate. 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 the form of molybdenum oxide.

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

Very good catalysts of the formula I are obtained by refluxing phosphoric acid and oxide. molybdenum in water for 1.5 to 3 hours, but more effectively, phosphomolybdic acid can be used directly, by adding the remaining ingredients to the aqueous suspension and welding to a thick paste to which at least one of the ingredients is added in the form of halides or oxyhalides and air dried at 110-120 ° 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, with 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 it may also be a preferred molecular oxygen-containing synthetic 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 20 moles of oxygen per mole of hydrocarbon is preferred.

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 μτη. 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 by using a coated catalyst consisting essentially of an inert support material having a diameter of at least 20 μΐΆ on the 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 μτη is preferred. Particularly preferred according to the invention for the reactors are carriers which are spherical and have a diameter of about 0.2 cm to 2 cm. Suitable examples of such inert carriers include alundum, silica, alumina, alumina, silicon carbide, titanium dioxide, and zirconia. Of these carriers, alundum, silica, alumina and alumina are particularly preferred.

The catalysts may contain substantially any proportion of support 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. The partially wetted carriers are then contacted with the powder of the catalytically active material ^- 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.

Example 1

A catalyst of formula is prepared

Ni ₀ , ₂ Cuo, 25Moi2Pi, 3 ₂ Rb20 _x this way:

a suspension containing 86.4 g (0.6 mol) of molybdenum trioxide and 7.7 g (0.067 mol) of 85% phosphoric acid in 800 ml of distilled water is boiled under stirring for two hours. The color is greenish yellow. 0.74 grams (0.01 mole) of nickel oxide is added to this suspension, there is no color change. 2.49 g (0.0125 mol) of copper (II) acetate hydrate is added and again no color change is observed. Continue boiling for a further 1.5 hours, stop boiling, add distilled water to the volume to 800 ml and stir the suspension overnight. The next day, 14.4 g (0.1 mole) of rubidium acetate is added and a pale yellow precipitate is formed immediately. This mixture boils off to a thick paste then dried in an oven at 110-120 ° ^C overnight. The catalyst is milled and sieved to a 20/30 mesh size.

A reactor with a stainless steel tube having an internal diameter of 1.02 cm is constructed. A portion of the catalyst was charged to a 20 ml reaction zone of the reactor.

The reactor is warmed to the reaction temperature and a mixture of air and 2-butene of the composition shown in Table 1 is passed through the catalyst at an apparent contact time of 1.0 to 1.5 seconds and the efficiency of the catalyst is evaluated by collecting and analyzing the products.

The results of the tests are given in Table 1. The following equations are used to assess the balance of carbon atoms in the feedstock and in the product:

moles obtained

And the yield in one = '- _- --- 3 χ passage 100 y ^moles of hydrocarbon introduced overall conversion selectivity moles of hydrocarbon reacted moles of hydrocarbon introduced yield in a single-pass conversion of the total

X100

Table 1

Characteristics of Ni ₀ , ₂ CuO, 25Moi2Pi, 32Rb20 _x catalyst for the production of maleic anhydride from 2-butene

Example Clock Air / bath / hydrocarbon operation ratio

Temperature ° C Temperature ° C exoth. all maleic anhydride

2 0.7 92 375 3 3.3 96 340 4 5.0 96 299 5 24.0 91 315 6 26.5 91 308 7 28.0 120 304 8 46.0 106 317 9 46.0 93 302 Example 10 Preparation of maleic anhydride from 1,3-butadiene The same way, as described above,

and reacting the catalyst of the formula

418 39.3 35.8 386 43.8 39.5 322 44.5 32.5 343 50.3 34.2 337 48.9 32.6 331 45.2 35.1 366 49.1 37.3 319 48.1 43.6 > CU ₀ , ₂₅ MO12P _Li32 Rb2O _x

with air and 1,3-butadiene. The air / 1,3-butadiene 84/1 mixture was passed through the catalyst at a reaction temperature of 285 ° C and an apparent contact time of 1.5 seconds. The results of this test show a 17.8% yield of all acid in one pass.

Claims (3)

SUBJECT 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 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 Mot2P _b R b _c O _x (I), where is X at least one of tin, rare earth element, nickel, zirconium, barium, iron, rhodium, manganese, rhenium, ruthenium, cobalt and copper, And a positive number greater than zero but less than 20, b, c number 0.001 to 10, x the number of oxygen atoms required to saturate the valences of the other elements present. 2. Process according to claim 1, characterized in that a catalyst comprising a combination of elements corresponding to the formula I is used, wherein a is a positive number greater than zero but less than 12, b a number of 0.01 to 5, in particular 0.5 to 5. 1,5, c is from 0,01 to 5, in particular from 0,1 to 1 and X and x have the meaning given in 1. 3. A process according to claim 1, wherein the catalyst is a combination of elements corresponding to formula I, wherein X is nickel, copper, tin or a rare earth element, and a, b, c, x are as defined in