JPH0242537B2 - - Google Patents

Description

[Detailed description of the invention]

[Detailed Description of the Invention] The present invention relates to a catalyst for producing an acid anhydride, particularly maleic anhydride, by oxidizing a hydrocarbon, and a method for producing the same. For example, benzene; general formula R'- _CH2 - _CH2-
Hydrocarbons of _CH2 - _CH2R '' (wherein R' and R'' are hydrogen or alkyl groups, and the total number of carbon atoms in R' and R'' is not more than 6, preferably not more than 4); It is known to produce maleic anhydride by oxidizing a hydrocarbon such as a cycloalkane (e.g. cyclohexane) having a -CH- _CH2 - _CH2 -CH- group (preferably cyclic). Although mixtures such as naphtha can be used, n-butane is the preferred feedstock. n-butenes can also be used. Generally, the hydrocarbon feedstock is contacted with a solid catalyst in the gas phase with oxygen. The maleic anhydride is recovered from the reaction product by oxidation.Oxygen can be supplied in the form of air and is generally kept at a concentration below the lower explosive limit (except in the case of fluidized beds). of hydrocarbons and this mixture is contacted with a catalyst under conditions of appropriate temperature and pressure (fuel lean system).
system). In this case, the reaction product gas is usually discharged or combusted after recovering maleic anhydride. Alternatively, as disclosed in German Patent Application No. 2412913, hydrocarbons are mixed with air at a concentration higher than its upper explosive concentration and the mixture is contacted with a catalyst under conditions of appropriate temperature and pressure. let me,
It is also possible to recover maleic anhydride from the reaction product gas (ie, a fuel rich system). It is also possible to carry out the oxidation reaction within explosive limits using a fluidized bed reactor. It is important that the catalyst has a high selectivity, ie that the yield of maleic anhydride is as high as possible based on the hydrocarbons consumed in the reaction. When recycling unreacted hydrocarbons, it is desirable to achieve high yields per pass to avoid recycling an unreasonably high proportion of hydrocarbons; The selectivity with respect to the yield of maleic anhydride based on the hydrocarbons consumed is relatively more important. One object of the present invention is a catalyst for the oxidation of hydrocarbons to maleic anhydride, which in the case of fuel-poor systems is evaluated by the one-pass yield obtained under suitable reaction conditions. Catalysts with good selectivity and, in the case of fuel-poor systems, with acceptable selectivity as measured by selectivity based on the hydrocarbons consumed at acceptable conversions under appropriate reaction conditions. An object of the present invention is to provide a method for manufacturing the same. A catalyst for oxidizing hydrocarbons to maleic anhydride is produced by reacting a vanadium compound and phosphoric acid in an acidic solution, evaporating to dryness to obtain a catalyst precursor consisting of a vanadium/phosphorus mixed oxide, and heating this catalyst. It has been produced by activation through processing.
The reaction solution may be an aqueous solution, for example as disclosed in GB 1409094, or a solution in an organic solvent as disclosed in GB 1416099. . Alternatively, the catalyst precursor may be precipitated by adding water under controlled conditions to a vanadium/phosphoric acid solution, as described in South African Patent Application No. 41/1976. You can also do it. However, the process of this South African patent application is difficult to control and requires an extra step compared to a process consisting simply of evaporating the precursor solution. However, the method of evaporating the precursor solution tends to result in a mixture of compound and phase, and the surface area of the catalyst obtained upon activation tends to be low.
We believe that one harmful substance present at this time is Z.
General formula VO
It was found that it was identified as a hydrogen phosphate having (H ₂ PO ₄ ) ₂ (does not have strong hydrogen bonds). Such hydrogen phosphates are referred to herein as "Phase E." In the present invention, a vanadium compound and phosphoric acid are reacted to produce a catalyst precursor consisting of a solid vanadium/phosphorus mixed oxide, and the solid catalyst precursor is converted into H ₃ PO ₇ by determining the first-order resolving power constant in water. stronger than
contacting a preferably non-oxidizing acid at a concentration of at least 3N (normal), preferably at least 5N, preferably in an aqueous solution, and recovering the precursor;
It is extracted with water or a phase E solvent such as dimethyl sulfoxide until substantially only water or the material insoluble in said solvent remains, the precursor is separated, and the precursor is phased by heating. tungsten, nickel, cadmium, zinc, bismuth, lithium, copper, uranium, zirconium, hafnium, chromium, iron, manganese, molybdenum, cobalt and/or rare earths. The present invention relates to a method for producing an acid anhydride, in particular a catalyst for producing maleic anhydride, containing a promoter selected from metals. It can also be recovered by dissolving the precursor in a strong acid and then distilling the strong acid. It is not necessary to carry out such a phase transition prior to use as a catalyst, since the phase transition occurs at temperatures conventional in the production of acid anhydrides. However, if desired, the phase transition can be carried out at e.g. 340-500 °C before use.
This can be done by heating to a temperature of . The reaction for the preparation of the catalyst is preferably carried out by reacting the vanadium compound and phosphoric acid in an acidic solution (suitably an acidic aqueous solution) and removing the solvent by preferably at least 90%, more preferably at least 95%, preferably by drying. Preferably, a solid or nearly dry solid is left behind to precipitate the vanadium/phosphorus mixed oxide catalyst precursor. The type of catalyst that exhibits catalytic activity usually consists of the beta type (phase B). Properties of the beta type are described in US Pat. No. 3,864,280. The beta form is easily produced from the B′ form. This B′ form may also exist and is considered to be the oxidized equivalent of the beta form. The catalyst thus produced was found to contain a vanadium/phosphorous mixed oxide of the type designated "Phase X". Literature “Canadian Journal of Chemistry” 51・2621
-5 (1973), in the report of Gijordan and Calbo, virtually amorphous aggregates (mass)
There is a description of the isolation of individual crystals of phase X from and the identification of the X-ray diffraction properties of phase X. The present invention has a large surface area, unlike in the Dijordan and Calbo paper mentioned above. The inventors have discovered that the presence of phase X in high surface area catalysts provides catalytic attraction and selectivity in the oxidation reaction of hydrocarbons to maleic anhydride, thereby increasing catalyst efficiency. The proportion of Phase It increases due to Therefore, if, for example, the vanadium/phosphorous mixed oxide catalyst precursor is a volatile acid as mentioned above, for example an acid boiling in the above temperature range at atmospheric pressure, for example an aqueous HBr solution,
If it is precipitated to dryness, preferably by an aqueous EC solution, it tends to produce a catalyst with a high content of phase X in the final type of catalyst. Furthermore, the content of catalytically active phase X can be increased by complete separation and removal of phase E or other phases simultaneously removed from the catalyst precursor. Extraction of the precursor by removing undesired phases in water or the aforementioned solvents also increases the surface area of the catalytically active form. The present invention comprises at least 5 wt%, preferably at least 15 wt% of phase X, and at least 7 m ² /
g Provide a catalyst for the oxidation of hydrocarbons to acid anhydrides, preferably having a surface area of at least 10 m ² /g. The catalyst may be present in even larger amounts, such as at least
It is further preferred to contain 40wt% of phase X, preferably at least 50wt%. The content of phase X can be estimated from the integrated intensity of its characteristic line in the X-ray diffraction pattern. Internal standards can be used in such estimations if desired. Preferably, the catalyst contains less than 15%, more preferably less than 10%, of amorphous vanadium/phosphorus mixed oxide. If the catalyst contains vanadium/phosphorus mixed oxides other than phase X, these mixed oxides are preferably present at least partially as phase B or phase B'. The accelerators formulated according to the invention consist of tungsten, nickel, cadmium, zinc, bismuth, lithium, copper, uranium, zirconium, hafnium, chromium, iron, manganese, molybdenum, and/or preferably cobalt and/or rare earth metals. selected from the group. Examples of rare earth promoters include cerium or more preferably lanthanum. The atomic ratio of accelerator and vanadium is
A range of 0.0015:1 to 1:1 is preferred. The promoter can be introduced into the catalyst by including the appropriate compound in the solution in which the vanadium/phosphorus mixed oxide is precipitated; It can also be introduced by mixing or by impregnating the solid catalyst with a solution of the appropriate promoter compound and drying the impregnated solid. 10 m ² /g or more promoted with rare earth metal promoters, especially lanthanum and/or cerium,
More preferably, vanadium/phosphorus mixed oxide catalysts having a surface area of 15 m ² /g or more are novel. The atomic ratio of vanadium and phosphorus is 0.5 to 2:1,
Preferably it is in the range of 1:0.8 to 1:1.7. The surface area of the catalyst is at least 10 m ² /g after phase transition
more preferably at least 15 m ² /
For example, it is preferably 10 or 15 to 50 m ² /g. Its surface area preferably does not exceed 150 m ² /g, more preferably does not exceed 70 m ² /g. The vanadium compound can be used in a solvent such as vanadium pentoxide, vanadium sesquioxide, vanadyl chloride such as VOC ₂ , vanadium oxytrihalide,
By dissolving vanadium oxydihalide, vanadyl sulfate or vanadium phosphate (),
Can be introduced into solution. In this case, an acid stronger than phosphoric acid,
For example, hydrochloric acid, hydrobromic acid, sulfuric acid or nitric acid are present. Such acids may be formed in situ during the reaction from the anions present in the vanadium compound;
Alternatively, it may be formed in situ, for example by hydrolysis of phosphorus oxytrihalide. The phosphoric acid may be supplied in the form of orthophosphoric acid; metal salts of orthophosphoric acid such as sodium dihydrogen phosphate; monofluorophosphoric acid; phosphorus pentoxide; oxytrihalogenated phosphorus or condensed phosphorus (e.g. pyrophosphoric acid, tripolyphosphoric acid). . Such phosphoric acids, for example, convert to phosphoric acid if water is present. If desired, vanadium() can be converted to vanadium() by adding a reducing agent such as oxalic acid, formic acid, citric acid or other reducing carboxylic acids.
Return to. Suitably, the catalyst can be treated with a suspension of an inert support, such as, for example, alumina, silicon carbide, diatomaceous earth, pumice or, preferably, silica. Suitable colloidal silica sols are, for example, EI
"LUDOX" sold by DuPont
(trademark). Such supports can be incorporated into the catalyst or into the precursor, or the precursor may be formed from a solution incorporating the support. To measure the surface area of a catalyst excluding the reinforcing agent or carrier, the catalyst is first prepared and then measured directly, after which the reinforcing agent or carrier is added. If the catalyst is formed on a reinforcing agent or support, the surface area of the catalyst according to the invention is defined as the surface area that the catalyst prepared in the same way but in the absence of the reinforcing agent or support would have. The solution for obtaining the precursor is preferably an aqueous solution, but may also contain organic solvents, such as isobutanol or tetrahydrofuran, if desired. Preferably at least 1 gram molecule of water is present per gram atom of vanadium. Preferably, the solvent is water only. If necessary, the catalyst of the invention can be prepared by reacting a vanadium compound with phosphoric acid, preferably in the presence of a suitable solvent such as water and/or a lower alcohol (e.g. methanol) to form the alpha form VOPO ₄ , which is then reacted with the aforementioned It is produced by tempering at high temperature in the presence of a strong acid such as hydrochloric acid.
This tempered precipitate is then extracted with water or other solvent for extracting phase E and converted to the catalytically active form by heating until a phase transition occurs as described above. Maleic anhydride is produced by contacting the catalyst of the present invention with a hydrocarbon raw material in the presence of oxygen to oxidize the hydrocarbon. In this oxidation method, it is preferable to supply n-butane as the hydrocarbon to a fixed catalyst bed or a fluidized bed at an air concentration of 0.5 to 1.5 vol%. This oxidation reaction is preferably carried out at a temperature of 250-600°C, more preferably 300-450°C. The reaction pressure can range from 0.5 to 20 atm absolute;
Preferably it is 1 to 3 absolute atmospheres. The catalyst of the present invention can also be used in the reaction of oxidizing ortho-xylene or naphthalene with oxygen. The following examples show that the performance of catalysts containing phase X can be greatly improved by the presence of trace amounts of promoters. Example 1 Vanadium pentoxide (60.6 g) and concentrated aqueous hydrochloric acid (790 ml) were heated with stirring for about 2 hours to obtain a dark blue solution. Orthophosphoric acid (88%,
89.1 g) was added, and the resulting solution was further refluxed for about 2 hours. This solution was then distilled to about 200ml.
200 ml of concentrated aqueous hydrochloric acid were added and the resulting solution was refluxed for a further 1 hour and then evaporated to dryness. The resulting solid was dried in an air oven at 110°C. The P:V ratio of this catalyst pre-drive was 1.2:1. The resulting solid was boiled with water (200 ml/g solid) for about 1 hour and the resulting blue suspension was filtered in a hot oven, washed with a small amount of warm water and dried at 150°C.
A portion of this dry solid was mixed with a commercially available pelletizing agent "Sterotex" (2 wt%) and pelletized under a pressure of 17 tons. The pellets were crushed and sieved into particles of size 500-710 microns. particles
Drying at 150° C. for 16 hours and then impregnating with an aqueous solution containing 8 g of cobalt chloride (as CoCl ₂ .6H ₂ O) per 100 ml gave a catalyst with a Co:V atomic ratio of 0.04:1. After drying, a 5 ml portion was charged into a tubular fixed bed reactor and the catalyst was heated at a heating rate of 3°C/min.
It was heated to 385°C and fired on the spot. After firing,
Reactor temperature of 430℃, atmospheric pressure and 1.5vo1 in air
At a GHSV of 1000/hr of % n-butane gas, this catalyst gave a one-pass yield of 60 mole % with a butane conversion of 88%. The surface area of the final catalyst is 13
m ² /g, and was found to contain 44% phase X by X-ray powder diffraction analysis. Example 2 A catalyst precursor was made as in Example 1, but
In this example, a solution of cobalt chloride (4-5 g, _CoCl2.6H2O ) in isobutanol ( ₂₅ ml) was used to impregnate the catalyst particles. The Co:V ratio of the catalyst is 0.034:1
It was hot. After drying, a 5 ml portion was loaded into a tubular fixed bed reactor and the catalyst was calcined in situ as in Example 1. After calcination, reactor temperature of 420℃, atmospheric pressure, 1000/hour GHSV of 1.5% n-butane in air
In , this catalyst gave a one-pass yield of 56 mol% with a butane conversion of 87%. The surface area of the final catalyst was 10 m ² /g, and X-ray powder diffraction analysis showed that the catalyst contained 46% of phase X. Example 3 A catalyst pre-driver was prepared as in Example 1, extracted with water, dried, pelletized, sieved and sized.
The particles were 500-710 microns. Next, Example 1
A series of cobalt promoter-containing catalysts were prepared using the method of 2007 and varying the Co:V ratio using various concentrations of cobalt chloride aqueous solutions. A 5 ml portion of each catalyst was charged to the reactor and calcined in situ according to the method of Example 1. Each catalyst was then used to oxidize maleic anhydride to maleic anhydride in 1.5%-butane contained in air. The results are shown in Table 1.

Table: Example 4 This example demonstrates the use of lanthanum as an accelerator. A catalyst precursor was prepared as in Example 1, extracted with boiling water, pelletized, and sieved to a size of 500~
The particles were 710 microns. The particles are then airborne.
Dry at 150°C for 16 hours and add isobutanol (25ml)
A catalyst with a V:La atomic ratio of 1:0.009 was obtained by impregnating the catalyst with a solution of lanthanum nitrate La(NO ₃ ) _{3.6H 2} O (2.7 g) in water. A catalyst with a V:La atomic ratio of 1:0.027 was also prepared using a different concentration of lanthanum nitrate in isobutanol (4.6 g/25 ml). 5 ml portions of each of these catalysts were charged to separate tubular reactor fixed beds and calcined as in Example 1. These catalysts were used to oxidize 1.5% n-butane in air to maleic anhydride. The results are shown in Table 2.

EXAMPLE 5 A catalyst precursor was prepared as in Example 1, extracted with boiling water, dried, pelletized and sieved to particles of size 500-710 microns. particles in the air
It was dried at 150°C for 16 hours. A series of promoter-containing catalysts were made using a range of promoters by then impregnating the catalyst particles with a solution of the appropriate promoter compound in isobutanol. A 5 ml portion of each catalyst was charged to a fixed bed tubular reactor and calcined in situ according to the method of Example 1. Each promoter-containing catalyst was used to oxidize 1.5% n-butane in air to maleic anhydride. The results are shown in Table 3.

Table: Example 6 This example demonstrates the use of molybdenum as an accelerator. Vanadium pentoxide (60.6 g), molybdenum trioxide (8 g) and concentrated aqueous hydrochloric acid (760 ml) were heated under reflux conditions with stirring for about 2 hours to give a dark blue solution. To this solution, add orthophosphoric acid (88
%, 89.3g), and the resulting solution was further diluted with approx.
Refluxed for an hour. This was then evaporated to dryness and the resulting solid was dried in an air oven at 110°C. The resulting solid was then boiled with water (20 ml/g solid) for about 2 hours, and the resulting suspension was hot filtered, washed with a little hot water and dried at 110°C. The V:Mo atomic ratio of this dry solid was 1:0.043. A portion of this dry solid is processed using the commercially available pelletizing agent “Sterotex”.
(3wt%) and pelletized under 17 tons of pressure. Crush the pellets and sieve them to a size of 500~
The particles were 710 microns. A 5 ml portion of this was charged to a fixed bed tubular reactor and the catalyst was calcined in situ as in Example 1. After calcination, at a reactor temperature of 420°C, atmospheric pressure, and 1000/hr GHSV of 1.5% n-butane gas in air, this catalyst has a butane conversion of 75% and a maleic anhydride one-pass yield of 55 mol%. gave. The final catalyst had a surface area of 9 m ² /g and was found to contain 43% phase X by X-ray powder diffraction analysis.

Claims (1)

[Claims] 1. A vanadium compound and phosphoric acid are reacted to form a solid vanadium/phosphorus mixed oxide catalyst precursor, which is then heated to cause a phase transition and to form a type that exhibits catalytic activity. In a method for producing a catalyst for producing an acid anhydride, the solid catalyst precursor is brought into contact with an acid that is stronger than phosphoric acid and has a concentration of at least 3 normal as determined by the first order resolving power constant in water. recovering the precursor; extracting the precursor with water or other solvent for phase E until substantially only water or material insoluble in said solvent remains; and separating the precursor; and tungsten, nickel, cadmium, zinc, bismuth, lithium, copper, uranium, zirconium,
1. A method for producing a catalyst for acid anhydride production, characterized in that a promoter selected from the group consisting of hafnium, chromium, iron, manganese, molybdenum, cobalt and/or rare earth metals is introduced into the catalyst. 2. The method for producing a catalyst according to claim 1, wherein the vanadium/phosphorus mixed oxide has a surface area greater than 10 m ² /g, and the promoter is a rare earth metal. 3. A catalyst for the oxidation of hydrocarbons to acid anhydrides, characterized in that it consists of a vanadium/phosphorus mixed oxide having a surface area greater than 10 m ² /g and is promoted by lanthanum.