KR880000922B1 - Process for the preparation of maleic anhydride use vanadium phosphorus catalysts - Google Patents

Abstract

Maleic anhydride is prepared by oxidation of n-butane, nbutene or 1,3-butadiene in gas phase with oxygen molecule or oxygen-containing gas at 250≰-600≰C in the presence of a catalyst composed of complex oxide of vanadium and phosphorous. The catalyst was prepared by drying and calcining of the catalyst precursor, which was obtained by reducing vanadium (+5)-containing compound to +3.5-4.6, average valence state, in liquid medium composed of olefinic-halogenide organic liquid, and adding phosphorous-containing compound in the above medium before the reduction step or after that.

Description

Method for preparing maleic anhydride using vanadium phosphorus catalyst

The present invention relates to a process for preparing dicarboxylic anhydrides using vanadium phosphorus catalysts. In particular, it relates to a process for preparing maleic anhydride from C ₄ -hydrocarbons such as n-butane, n-butene, 1, 3-butadiene or mixtures thereof using the catalyst.

Catalysts containing vanadium and phosphorus oxides may be prepared using n-butane, n-butene or oxygen-containing gases with molecular oxygen or oxygen-containing gases and n-butane, n-butene, 1,3-butadiene or mixtures thereof. The same C ₄ -hydrocarbons were oxidized and used to prepare maleic anhydride. Conventional methods for preparing these catalysts mix vanadium compounds, phosphorus compounds and optionally promoter element compounds in a reducing medium under conditions that provide vanadium in valence below +5 to form catalyst precursors that can be converted to oxides. It is. The catalyst oxide precursor is then recovered and then calcined to obtain the active catalyst material.

The use of hydrogen chloride gas as a reducing agent to reduce vanadium is described in US Pat. No. 4,002,650, wherein the vanadium and phosphorus components are present in aqueous solution. Hydrogen chloride gas as a reducing agent of vanadium is also described in US Pat. Nos. 3,864,280, 4,017,521 and 4,043,943, in which the vanadium and phosphorus components are reacted in a saturated organic liquid medium. In particular, organic media described in US Pat. No. 4,043,943 include saturated halogenated organics containing oxygen and inert diluents comprising halogenated aromatics and hydrocarbon materials.

A similar manufacturing technique is described in EP 3431, which describes an additional step of grinding the vanadium-phosphorus precursor to make the particle size 500 to 700 μ (0.5 to 0.7 mm).

Such reducing agents described in this document require special care in their use in preparing these catalysts due to the corrosiveness of the materials used.

US Pat. No. 4,016,105 discloses vanadium using organic acids (e.g., oxalic acid, citric acid, formic acid, ascorbic acid and malic acid) or aldehydes (e.g. formaldehyde and acetaldehyde) together with a co-reducing secondary alcohol as a reducing agent. A process for preparing a phosphorus oxide-containing catalyst is described. These reducing agents are added to an aqueous solution containing vanadium and phosphorus components.

Processes for preparing catalysts containing vanadium and phosphorus oxides are described in US Pat. Nos. 4,132,670 and 4,187,235, which contain vanadium-containing compounds in organic liquid media such as alcohols, aldehydes, ketones, ethers or mixtures thereof. The dispersion is formed to form a dispersion, which is then heated to reduce vanadium, followed by addition of phosphoric acid in an organic solvent. The organic medium may contain an inert diluent comprising a chlorinated hydrocarbon. These patents teach that organic compounds suitable for use in the preparation of the oxides should not contain olefinic double bonds.

US Pat. Nos. 4,149,992 and 4,116,868 describe methods for preparing vanadium and phosphorus-containing catalysts from pentavalent phosphorus-containing compounds in a liquid reaction medium. Liquid reaction media may include aromatic compounds such as benzyl chloride.

In the prior art, it is difficult to separate and recover the catalyst precursor from the reaction solution. When hydrogen chloride gas is used as the reducing agent for vanadium compounds, the reception and treatment of the excess corrosive gas required is a problem for the production of catalysts on a commercial scale. Typically, the solution containing the precursor should be evaporated to a normal catalyst precursor-containing paste, which must be dried and then ground. This is too difficult to use in commercial scale processes, especially when the catalyst precursor-containing solution contains flammable organic liquids.

Accordingly, it is an object of the present invention to provide a process for preparing vanadium and phosphorus-containing oxidation catalysts.

Another object of the present invention is a catalyst useful for preparing maleic anhydride by oxidizing C ₄ -hydrocarbons, in particular a process for preparing vanadium and phosphorus-containing catalysts which exhibit high yield and high selectivity to maleic anhydride. To provide.

Another object of the present invention is a process for preparing vanadium and phosphorus-containing catalysts useful for oxidizing C ₄ -hydrocarbons to produce maleic anhydride, wherein the average valence state of vanadium present in the catalyst using a mild buffering agent. Is to provide a method to make about +3.5 to +4.6.

Another object of the present invention is a method for preparing vanadium and phosphorus-containing catalysts useful for oxidizing C ₄ -hydrocarbons to produce maleic anhydride, which is simple, economical, free from corrosion and / or flammability, and commercial scale. It is to provide a method that can be used.

It is still another object of the present invention to provide a method for preparing a vanadium and phosphorus-containing catalyst useful for preparing maleic anhydride by oxidizing C ₄ -hydrocarbons, and providing a method for improving the recovery of the catalyst precursor from the reaction medium. .

The above and other objects and the advantages of the method according to the invention over the known methods are clearly described in the following specification, which is realized according to the invention described and claimed hereinafter.

a) The pentavalent vanadium-containing compound is introduced into an olefinic halogenated organic liquid-containing liquid medium. ;

b) reducing some or all of the vanadium to a valence of +4;

c) phosphorus-containing compounds are added to the medium to form catalyst precursor precipitates;

d) recover the catalyst precursor precipitate;

e) drying the catalyst precursor precipitate;

f) The catalyst precursor precipitate is calcined.

Another aspect of the invention consists of the following steps a) to e);

a) a pentavalent vanadium compound and a phosphorus compound are introduced into an olefinic halogenated organic liquid-containing liquid medium;

b) reducing some or all of the vanadium to a valence state of about +4 in the presence of the phosphorus compound to form a vanadium-phosphorus mixed oxide precursor;

c) recovering the vanadium-phosphorus mixed oxide catalyst precursor;

d) drying the catalyst precursor;

e) calcining the catalyst precursor.

The catalyst prepared by the above method oxidizes maleic acid by oxidizing C ₄ -hydrocarbons (e.g., n-butane, n-butene, 1,3-butadiene or mixtures thereof) in the vapor phase using molecular oxygen or an oxygen-containing gas. It is particularly effective for preparing anhydrides in high yield and selectivity. Almost all products produced by this oxidation method are maleic anhydride, with only a small amount of lower acid detected.

In a method for producing an oxidation catalyst containing a mixed oxide of vanadium and phosphorus, a vanadium compound (particularly a pentavalent vanadium compound) is introduced into an olefinic halogenated organic liquid medium. Suitable vanadium compounds containing pentavalent vanadium include vanadium pentaoxide or vanadium salts such as ammonium metavanadate and vanadium oxytrihalide. Vanadium pentoxide is preferred.

In contrast to what is taught in the prior art, the inventors have found that an olefinic halogenated organic liquid can reduce pentavalent vanadium to an average valence of +3.5 to +4.6, i.e., to remove some or all of the pentavalent vanadium introduced into the liquid. It has been found that it is a suitable and mild vanadium reducing agent capable of reducing to a valence state of +4, i.e., reducing some or all of the pentavalent vanadium introduced into the acte to the valence state of +4. This partial rhythm of vanadium makes it possible to use it in the preparation of catalysts useful for preparing maleic anhydride from c4-hydrocarbons. Stronger reducing agents reduce the vanadium to a much lower valence state, or base metal, in both cases substantially inactive catalysis.

As used herein, the term "olefinic halogenated organic liquid" is essentially a compound containing carbon, hydrogen and halogen (preferably salt and / or bromine) and containing one or more non-aromatic carbon-carbon double bonds. Which may include compounds having other functional groups that do not adversely affect the formation of recoverable vanadium and any mixed oxides. In the above, vanadium has an average valence of about +3.5 to +4.6. These compounds should be liquid at temperatures of about 20 ° C to about 150 ° C. These compounds preferably have a high boiling point, preferably about 150 ° C. or higher, and most preferably about 200 ° C. or higher. The olefinic halogenated compound preferably contains one or more halide atoms bonded to allyl carbon atoms. In a preferred embodiment of the present invention, the olefinic halogenated organic liquid used does not contain oxygen functionality.

The olefinic pinned halogenated organic liquids used act as solvents for phosphoric acid and are relatively unreactive with phosphoric acid. However, these liquids do not act as solvents for mixed oxides of vanadium and phosphorus.

Olefinic halogenated organic liquids suitable for use in the present invention include compounds such as perchloropropene, hexachlorobutadiene, hexachlorocyclopentadiene and tetrabromoethylene. Perchloropropene and hexachlorobutadiene are preferred.

The liquid medium used in the process of the present invention may consist of almost any olefinic halogenated organic liquid, or other organic reducing liquids for vanadium (e.g. isobutanol) or non-reducing liquids for vanadium (e.g. tertiary butyl alcohol) It may further contain. The liquid medium used in the process of the invention is preferably almost anhydrous.

After the pentavalent vanadium compound is introduced into the liquid medium, the vanadium is reduced before or after the phosphorus-containing compound is added to the liquid medium. The reduction reaction is preferably carried out by heating the resulting reaction medium with stirring. Preferred vanadium and phosphorus oxide catalysts for oxidizing C ₄ -hydrocarbons to obtain maleic anhydride contain vanadium in an average valence of about +3.5 to about +4.6. This average valence state is obtained by reducing at least a portion of the pentavalent vanadium introduced into the reaction mixture to the +4 state. It is preferred that the average valence of vanadium reduce the state to about +4.1.

Suitable phosphorus compounds containing pentavalent phosphorus include phosphoric acid, phosphorus pentoxide or phosphorus highly halogenated (eg phosphorus pentachloride). Preference is given to phosphoric acid and phosphorus pentoxide. The pentavalent phosphorus-containing compound is a reaction medium in the form of a solution of a phosphorus-containing compound dissolved in a liquid reaction medium component (e.g., a halogenated olefinic organic liquid or isobutanol) or a liquid capable of producing a phosphorus-containing compound in the liquid reaction medium. It is preferable to add to. After the phosphorus-containing compound is added to the liquid reaction medium, it is preferable to heat the liquid reaction medium, optionally with stirring. The phosphorus-containing compound described above is added to the liquid medium (containing the olefinic halogenated organic liquid) before or after the reduction of pentavalent vanadium actually takes place.

The total H 2 O content in the liquid medium is preferably about 5% or less. According to the method of the present invention, the vanadium phosphorus mixed oxide catalyst precursor forms fine granular particles, which are recovered from the liquid reaction medium by conventional methods such as filtration, centrifugation and decantation.

The catalyst precursor or catalyst precursor precipitate is dried and then calcined at temperatures between 250 ° C. and 600 ° C., preferably in the presence of an oxygen-containing gas.

It is within the scope of the present invention to add the promoter element-containing compound to the reaction mixture at a suitable time before or after the reduction of vanadium to reduce the vanadium to contain the promoter element in the catalyst precursor or catalyst precursor precipitate. Suitable promoters include, but are not limited to, U, Co, Mo, Fe, Zn, Hf and Zr. U and Co are preferred.

The catalyst prepared by the above method may have a ratio of phosphorus to vanadium of about 0.5: 1 to about 2: 1. Preferably about 0.9: 1 to about 1.3: 1. The ratio of any promoter element to vanadium may be from 0: 1 to about 1: 1. When it contains an accelerator, it is preferable to contain so that the ratio with respect to vanadium may be 0.05: 1-0.5: 1. The catalyst is activated by calcination for at least 5 hours in air or oxygen-containing gas at temperatures between 250 ° C. and 600 ° C. Activation of the catalyst is carried out by passing a mixture of steam and air or only air over the catalyst for about 1 to 5 hours at a temperature of 300 ° C to 500 ° C.

Hydrocarbons that react to form maleic anhydride include n-butane, n-butene, 1, 3-butadiene or mixtures thereof. Preference is given to using mixtures of hydrocarbons produced in n-butane or refineries. Molecular oxygen required for the reaction to prepare maleic anhydride is most conveniently added as air, but synthetics containing molecular oxygen are also suitable. In addition to hydrocarbons and molecular oxygen, other gases may be added to the reaction feed. For example, steam or nitrogen can be added to the reactants.

The proportion of reactants can vary widely and is not very important. The ratio of molecular oxygen to hydrocarbon may be about 2 to about 30 mole of oxygen per mole of hydrocarbon. Preferred oxygen / hydrocarbon ratios are from about 4 to about 20 moles of oxygen per mole of hydrocarbon.

The reaction temperature can vary widely and depends on the specific hydrocarbon and catalyst used. Generally a temperature of about 250 ° C. to about 600 ° C., preferably 350 ° C. to 500 ° C., is used.

The catalyst may be used in a single step or may be used by adding a support. Suitable supports include silica, alumina, silica-alumina allardum, silicon carbide, titania, boron phosphate, zirconia and the like. The catalyst can be used in a fixed bed reactor using purification, pellets, etc., or in a fluidized bed reactor using a catalyst having a particle size of less than about 300 microns. The contact time can be as short as 1 second of moisture or as long as 50 seconds. The reaction can be carried out at atmospheric pressure, above atmospheric pressure or below atmospheric pressure.

[Examples 1 and 2]

A catalyst of Empirical Formula V _1.0 P _1.2 U _0.2 O _x is prepared as follows. 45 g of vanadium pentoxide and 42.2 g of uranil acetate dihydrolate are added to 500 ml of hexachlorobutadiene and then refluxed for 16 hours. Acetic acid is distilled off from the uranium-containing compound and then refluxed for about 16 hours. 58.8 g of 0-phosphoric acid is added to the mixture while refluxing for about 16 hours during which 9 ml of water is collected from the Dean-Stark trap. The resulting mixture is filtered to give a dark green catalyst precursor solid which is then washed in methylene chloride and then dried at 100 ° C. The granular precursor is ground to less than 50 mesh (0.297 mm), then mixed with 3% by weight of graphite and then compacted into 3/16 inch (0.48 cm) pellets. The pellets are calcined at 400 ° C. and then ground and then screened to 10 to 13 mesh (0.595 to 2.00 mm).

[Examples 3 to 4]

According to the method described in Examples 1 to 2 above, a catalyst of Formula V _1.0 P _1.2 U _0.02 O _x is prepared using cobalt chloride hexahydrate as the promoter metal-containing compound.

Examples 1 to 20 were used to prepare maleic anhydride from butane using a 20 cc fixed bed reactor consisting of a stainless steel tube of 38 cm length having an outer diameter of about 1.3 cm and an axial thermowell of 0.31 cm in total length. 4 catalyst is used. The reactor is heated with a Split Stainless steel block furnace. A flask for collecting the resulting maleic anhydride is placed in ice water and then sent to Carle Analytical Gas Chromatography III for analysis. The reaction conditions and test results are shown in Table 1 below.

The results are described in the following terms.

×100Single pass yield =

× 100

×100Total conversion rate =

× 100

Selectivity =

The method for producing a mixed oxide-containing catalyst of vanadium and phosphorus according to the present invention eliminates the risk of using corrosive substances (eg, hydrogen chloride gas). In addition, vanadium and phosphorus-containing catalyst precursors can simply be separated from the reaction medium by filtration or similar methods without the risk of evaporating large amounts of flammable liquids. The liquid reaction medium prepared by the process of the present invention can be recycled for separation in the catalyst precursor and for use in the reaction. As can be seen from the results in Table 1, the catalyst prepared according to the process of the present invention in an olefinic halogenated organic liquid as a liquid medium or in a liquid medium for the partial reduction of vanadium is a C ₄ -hydrocarbon (e.g. Butane) exhibits high yield and selectivity for maleic anhydride.

Thus, it will be apparent to those skilled in the art that the present invention may accomplish the above-mentioned object. The invention is not limited to the embodiments described above. These are merely illustrative of the feasibility and include vanadium and phosphorus-containing compounds, olefinic halogenated organic liquid-containing liquid media, accelerator element-containing compounds, Accordingly, the sources and conditions of hydrocarbons are defined herein without departing from the spirit of the invention as described herein and the scope of the invention, including the changes and modifications included in the appended claims. Determined from the overall description of the

TABLE 1

Preparation of Maleic Anhydride from m-butane

X = the number of oxygen needed to satisfy the valence needed for other elements

Claims (9)

The pentavalent vanadium-containing compound is introduced into an olefinic halogenated organic liquid-containing liquid medium, and then the vanadium is reduced to an average valence state of about +3.5 to about +4.6 and phosphorus- before or after the reduction reaction is carried out. The containing compound was added to the medium to form a catalyst precursor, and then vaporized under a reaction temperature of 250 ° C. to 600 ° C. in the presence of a catalyst containing a mixed oxide of vanadium and phosphorus, prepared by recovering, drying and calcining the catalyst precursor. A process for preparing maleic anhydride by oxidizing n-butane, n-butene, 1, 3-butadiene or mixtures thereof with molecular oxygen or an oxygen-containing gas. The process according to claim 1, wherein the reaction of vanadium is carried out in the presence of a phosphorus-containing compound. The process of claim 1 wherein the organic liquid medium is essentially anhydrous. The process of claim 1 wherein the reduction of vanadium is carried out by heating the vanadium-containing liquid medium. The method of claim 1 wherein the organic nucleus contains a chlorinated olefinic organic liquid. The method of claim 1, wherein the organic liquid contains a brominated olefinic organic liquid. The process of claim 1 wherein the oxidation catalyst is selected from hexachlorobutadiene, perchloropropene, hexachlorocyclopentadiene, tetrabromoethylene and mixtures thereof. The method according to claim 1, wherein the oxidation catalyst is represented by the following empirical formula. V ₁ P _a M _b O _x Wherein M is selected from U, Co, Mo Fe, Zn, Hf, Zr and mixtures thereof, a is from 0.5 to 2.0, b is from 0 to 1.0, and x is the valence required for other elements The number of oxygen needed to The method of claim 1, wherein the boiling point of the organic liquid is about 150 ° C. or more.