JPH09299803A - Oxidation catalyst, manufacture thereof and preparation of methacrylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heteropoly acid based catalyst having high reaction reactivity and selectivity and long catalytic life by producing an oxidation catalyst from an oxide containing phosphorus and molybdenum and a polyelemental oxide containing antimony together with one or more element selected from cerium, zirconium, etc. SOLUTION: This oxidation catalyst is a heteropoly acid type catalyst used for methacrylic acid production by gas-phase oxidation of methacrolein, t- butanol, etc., by bringing them into contact with molecular oxygen and the oxidation catalyst is produced from an oxide containing phosphorus, molybdenum, etc., and a polyelemental oxide containing antimony together with one or more element selected form cerium, etc. That is, solid substances obtained by drying a solution or a suspension produced by dissolving or suspending the catalyst raw materials in water are calcined at 150-300 deg.C and then the resultant calcined substances are kneaded with 0.2-0.8 times by wt. ammonia water containing 0.2-0.8 times by wt. water or 0.015-0.1 times by wt. ammonium hydroxide and after that, the polyelemental oxide is added.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an oxidation catalyst, a method for producing the same, and a method for producing methacrylic acid by the catalyst. More specifically, the present invention relates to a heteropolyacid catalyst used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein, t-butanol, isobutane, isobutene, etc. with molecular oxygen, a method for producing the same, and the catalyst. The present invention relates to a method for producing methacrylic acid.

[0002]

2. Description of the Related Art It has been conventionally known that a heteropolyacid compound having a Keggin structure such as phosphomolybdic acid is effective as a catalyst for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein. However, Mo-
Vapor-phase catalytic oxidation of acrolein to acrylic acid with V-based catalysts has an industrial conversion rate of 99% or higher and 97%.
Compared with achieving stable operation results for more than three years with the above selectivity, the production of methacrylic acid is still at a significantly low level. Therefore, the reaction composition, the selectivity of methacrylic acid, the improvement of the catalyst life or the stability of the catalyst production are required, and the catalyst composition, the preparation method, the drying method,
Energetic research and development has been conducted on the calcination method, catalyst shape, etc., and various proposals have been made so far.

For example, regarding the composition of the catalyst, JP-A-55-
V is essentially essential as a catalyst constituent element of many patent publications including 39236 publication, and many elements such as alkali metal, alkaline earth metal, transition metal, and rare earth metal are effective for improving catalyst performance. Is described. JP-A-61-5043 and JP-A-61-72
33 and JP-A-3-21346 show that a specific Ce compound is effective, and JP-A-3-21346.
No. 238051 discloses that specific Bi raw materials are effective.

Japanese Unexamined Patent Publication (Kokai) No. 6-91172 describes that high catalytic performance can be obtained by pre-calcining Sb and Mo, Cu or V among the catalyst components to use as a complex oxide. . Also, a method for preparing the catalyst, for example,
A step of dissolving and mixing and heating the catalyst raw material, specifying the catalyst raw material, controlling the amount of ammonium and nitric acid, etc. (JP-A-61-283352)
JP, JP-A-3-238050, JP, 6-8
Many proposals have been made also in Japanese Patent No. 6932 and Japanese Patent Laid-Open No. 6-86933.

Japanese Unexamined Patent Publication No. 4-7037 and Japanese Unexamined Patent Publication No. 4-1
No. 6242 discloses p of a solution prepared by dissolving and mixing catalyst raw materials.
A Keggin-type heteropolyacid is prepared by keeping H acidic and heating the solution to 85 ° C. or higher.
After cooling to 0 ° C or lower, alkali ions and ammonium ions or a base such as pyridine is added to give an oxygen concentration of 5
A method of firing with a gas of not less than 100% has been proposed.

In JP-A-6-86932, NH is disclosed._Four/
Mo = (6-18) / 12 and NO _Three/Mo=(0.1
~ 5) / 1 ammonia and nitrate in the solution so that
The amount is controlled, and further 110-200 ℃ in the autoclave
Under these special conditions, the Dawson-type heteropoly acid was added to the solution.
Described to produce and bake in an inert gas atmosphere
ing. Japanese Patent Application Laid-Open No. 6-86933 discloses that a sulfate group
Is effective for the production of Dawson-type heteropolyacid.
It is stated that autoclave heating is not always necessary.
ing.

Japanese Patent Laid-Open No. 63-130143 describes that the catalyst performance is improved by redispersing a dry solid matter in water in an amount of 1 to 10 times the solid matter. The calcination of the catalyst also has a great influence on the catalyst performance, and the control of the oxygen concentration and the calcination temperature (JP-A-56-161841, JP-A-3-238050) and the control of ammonia / steam (JP-A-58-58). 67643), firing in an inert gas (JP-A-57-165040), and the like.

On the other hand, for the purpose of controlling the surface area and pores, for example, the addition of pyridine / quinoline (JP-A-57-1714).
44, JP-A-60-209258), addition of activated carbon (JP-A-6-374), addition of alcohol / aldehyde / organic acid (JP-A-6-15178), and the like. There is.

[0009]

However, none of the catalysts proposed hitherto has sufficient reaction results, low productivity, large deterioration with time of the catalyst, high reaction temperature, or catalyst preparation methods. It has problems such as lack of reproducibility and cannot be said to have sufficient performance as an industrial catalyst, and further improvement is desired. An object of the present invention is to use a heteropolyacid catalyst having a higher reaction activity and selectivity and a longer catalyst life, which is used for the production of methacrylic acid by gas phase oxidation of methacrolein, a method for producing the same, and the production of methacrylic acid by the catalyst. To provide a method.

[0010]

In order to solve the above-mentioned problems, the present inventors use the phosphorus which is used for producing an unsaturated carboxylic acid by catalytically oxidizing an aliphatic hydrocarbon with molecular oxygen in the gas phase. As a result of intensive studies on a catalyst containing molybdenum, molybdenum and an alkali metal or thallium, high reaction activity and selectivity and longevity can be obtained by using a multi-component oxide composed of antimony and one or more elements selected from cerium, zirconium and bismuth. It was found that an oxidation catalyst having a catalyst life can be obtained, and in particular, a solution prepared by dissolving or suspending a catalyst raw material in water is dried, and then precalcined at 150 to 300 ° C. ~ 0.8 weight times of water or ammonia water is added in the step of kneading, multi-component oxides are added, and further firing with an inert gas whose oxygen concentration is controlled It found that catalyst is obtained with a high reaction activity and selectivity and long catalyst life Ri, and have completed the present invention.

That is, the present invention provides: An oxidation catalyst comprising an oxide containing phosphorus, molybdenum and an alkali metal or thallium, and a multi-component oxide comprising antimony and one or more elements selected from cerium, zirconium and bismuth. 2. In producing the catalyst, a solution of an oxide raw material containing phosphorus, molybdenum and an alkali metal or thallium dissolved or suspended in water is dried, and then the obtained solid is preliminarily stored at 150 to 300 ° C. Calcination, and 0.2 to 0.8 times by weight of water or 0.015 to
0.2 to 0.1 containing 0.1 times by weight ammonium hydroxide.
In the presence of the oxidation catalyst according to item 3.1 or 2, the method for producing the catalyst according to item 1 above, which comprises kneading with 8 times by weight aqueous ammonia and adding the multicomponent oxide of the formula (II), and methacrolein A method for producing methacrylic acid, which is characterized by performing gas phase oxidation. Hereinafter, the present invention will be described in detail.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Oxidation catalyst The oxidation catalyst of the present invention comprises an oxide containing phosphorus, molybdenum and an alkali metal or thallium, and a multi-element oxide containing antimony and one or more elements selected from cerium, zirconium and bismuth. And preferably of the general formula (I)

[0013]

Embedded image P _a Mo _b V _C B a _d Sb _e Cu _f X _g Y _h O _i (I)

(Wherein X represents one or more elements selected from the group consisting of K, Rb, Cs and Tl, and Y represents
Represents one or more elements selected from the group consisting of Bi, Mn, Cr, Zr, Co, Ce, Zn, Fe and Ni,
The subscripts a, c, d, e, f, g, h and i represent the atomic ratio of each element when b = 12, and a = 0.1-5, c
= 0-5, d = 0-5, e = 0-5, f = 0-2, g =
0.1 to 3, h = 0 to 2, i is a value determined by the valence and atomic ratio of other elements) and an oxide represented by the general formula (II)

[0015]

Embedded image Sb _j Z _k O _m (II)

(Wherein Z represents one or more elements selected from Ce, Zr and Bi, and the subscripts j, k and m are
Representing the atomic ratio of each element when j = 1, k = 0.
1 to 0.5, m is a value determined by the valence and atomic ratio of other elements), and is a heteropolyacid catalyst composed of 3 to 80% by weight (based on the total catalyst weight) of a multicomponent oxide.

(2) Method for Producing Oxidation Catalyst As a preferred method for producing the oxidation catalyst of the present invention, the formula (II)
The solution obtained by dissolving or suspending all the catalyst raw materials other than the multi-component oxide in
After pre-baking at .about.350.degree.
2 to 0.8 times by weight of water or ammonia water is added to perform a kneading treatment, and preferably in this treatment step, the formula (II) is used.
Sb-Z multi-component oxide (Z = Ce, Zr, Bi) is added in an amount of 3 to 80% by weight, preferably 5 to 50% by weight based on the total weight of the catalyst, and the kneaded solid is dried. Examples include a method of firing at 350 to 450 ° C. under a flow of an inert gas containing oxygen by volume.

The Sb-Z multi-component oxide is Sb raw material and C
Water is added to a raw material of one or more metals selected from e, Zr, and Bi, and the mixture is kneaded, followed by drying by a conventional method and then heat treatment. There are no particular restrictions on the raw materials used. Examples of the Sb raw material include antimony oxide and antimony chloride, and antimony oxide is particularly preferable. Z
Examples of the raw material include carbonates, hydroxides and oxides, and carbonates are particularly preferable. Processing is 400-1200 ℃
Is suitable, and 600 to 1000 ° C. is particularly preferable. If the treatment temperature is too low, the combined effect is not clear, and if it is too high, the dispersibility as a catalyst component may be deteriorated due to the aggregation of oxides. The Z / Sb ratio is in the range of 0.1 to 1.0, preferably 0.2 to 0.6. If the proportion of Z is low, the combined effect of the mixed oxides is not clear, and if it is too high, Z
A single oxide of is formed. It is not necessary to adopt a specific crystal structure like ZSb ₂ O ₄ after heat treatment. Although the catalytic performance is remarkably improved by adding the Sb-Z multi-component oxide, the reason is not always clear. S
It is considered that the addition of the bZ multi-component oxide to the oxide promotes the reoxidation process of the catalyst and stabilizes the crystal structure, and as a result, suppresses the aggregation of the heteropolyacid.

As metal component raw materials for catalyst components other than Sb-Z multi-component oxides, ammonium paraparamolybdate, molybdic acid, molybdenum oxide, etc. for molybdenum, ammonium metavanadate, vanadium oxide, vanadyl oxalate, etc. for vanadium, phosphorus For orthophosphoric acid, metaphosphoric acid, phosphorus pentoxide, pyrophosphate, ammonium phosphate, etc., for copper, copper nitrate, copper sulfate, cuprous chloride, cupric chloride, etc., for antimony, antimony oxide, antimony chloride, etc. Compounds of can be used. Regarding other metals, oxides, hydroxides that can be converted into oxides by firing, nitrates, acetates, oxalates, carbonates,
Compounds such as chlorides can be used, but among them, nitrates are preferable. Further, a heteropolyacid such as phosphomolybdic acid or ammonium phosphomolybdate can be used as a raw material for molybdenum and phosphorus.

A solution prepared by dissolving or suspending all catalyst raw materials in water is heated at 40 to 100 ° C. for 0.5 to 24 hours, preferably at 50 to 90 ° C. for 1 to 6 hours while stirring. From this range, high selectivity may not be obtained at low temperature or short time, and activity may decrease at high temperature and long time. A carrier component such as silica, diatomaceous earth, or celite may be added to this mixed solution. The mixed solution that has undergone the heating treatment is dried by a usual method. Generally 100
Evaporate to dryness in a hot air dryer maintained at ~ 250 ° C.

The solid thus obtained is prebaked by circulating air under the temperature condition of 150 to 350 ° C, preferably 200 to 300 ° C. 0.2 to this pre-baked product
2.0 weight times of water and Sb-Z multi-component oxide are added and kneaded. If the amount of water is less than 0.2 times by weight, the kneading may be insufficient, and if it exceeds 2 times by weight, the catalyst performance may be deteriorated due to unnecessary dissolution of the catalyst component. The water used here is not particularly limited,
Water that does not contain unnecessary metal ions, such as deionized water and distilled water, is preferable.

Further, in place of water, 0.2 to 0.8 weight times ammonia water containing ammonium hydroxide in an amount of 0.015 to 0.1 weight times the amount of ammonium hydroxide is added to the pre-sintered product. The kneading treatment so that the preliminarily calcined product becomes neutral or alkaline makes it possible to obtain a catalyst with higher performance, which is particularly preferable. If the amount of ammonium hydroxide is less than 0.015 times by weight, the effect of adding ammonia is not clear, and if it exceeds 0.1 times by weight, the initial activity may decrease and the stability of the catalyst may be impaired. The catalyst component which has been kneaded is dried by a usual method.

When used as a supported catalyst, water can be added to the obtained kneaded product to adjust the viscosity, if necessary, and it can be used by supporting it on a carrier such as alumina or silicon carbide by an appropriate method. . The dried catalyst component is crushed and then tableted. In addition to this, a general molding method such as extrusion molding in a paste form and drying can be arbitrarily selected. There is no particular limitation on the shape of the catalyst, and the shape of sphere, cylinder, pellet, ring, etc. can be selected in consideration of the reactor type, conditions, etc. The shape of the ring gives favorable results when used in vessels.

Optimum conditions vary depending on the catalyst raw material, catalyst composition and preparation method used, but generally 300 to 500 ° C. for 1 to 24 hours, preferably 350 to 450 ° C. for 2 to 12
The catalyst is activated by firing for a time. Firing
It is carried out under an inert gas flow whose oxygen concentration is controlled to 0.1 to 5% by volume, preferably 0.2 to 2% by volume. If the oxygen concentration is less than 0.1% by volume, in order to sufficiently desorb ammonia, a high temperature at which the catalyst itself becomes unstable is required, or when the treatment is carried out at an appropriate temperature, it is extremely long. There is a problem that it takes time. If it exceeds 5% by volume, some of the ammonia burns on the catalyst, making it difficult to control the calcination, and in some cases, the decomposition of the catalyst components causes a large amount of molybdenum trioxide to be produced, which may significantly reduce the catalytic performance. There is.

(3) Method for producing methacrylic acid The catalyst of the present invention can be used for ordinary catalytic oxidation reaction,
Especially when it is adopted in the method for producing methacrylic acid,
It is preferable to carry out the reaction in the presence of water vapor at a reaction temperature of about 400 ° C. and a reaction pressure of about 0.5 to 10 atm. As the methacrolein of the reaction raw material, for example, a product gas obtained by catalytically oxidizing isobutene or t-butanol for the purpose of producing methacrolein may be used as it is, or the product gas may be purified to produce methacrolein. It may be used after being separated from other gases.

Air is generally used as the oxygen source for the oxidation, but of course oxygen (molecular oxygen), a mixed gas obtained by diluting oxygen with an inert gas such as carbon dioxide or nitrogen may be used. . A mixed gas of water vapor, a reaction raw material, oxygen and the like (hereinafter referred to as a reaction mixed gas) flows through the catalyst,
The appropriate contact time is usually about 1 to 20 seconds. As the composition of the reaction mixed gas, for example, 0.2 to 4 mol of molecular oxygen and 1 to 20 mol of water vapor are used with respect to 1 mol of methacrolein.

In addition, this catalytic oxidation reaction can be carried out with reference to the usual knowledge about methacrolein oxidation unless it goes against the gist of the present invention. The oxidation catalyst obtained in the present invention can also be used for oxidative dehydrogenation of isobutyric acid and production of methacrylic acid by oxidation of isobutyraldehyde. It can also be used when producing methacrylic acid from isobutylene in a single step. In these reactions, the reaction conditions similar to the oxidation of methacrolein can be adopted.

[0028]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded. The conversion rate, selectivity and yield were determined by the following formulas and displayed on a molar basis.

[0029]

## EQU1 ## Conversion (%) = [(moles of reacted methacrolein) / (moles of supplied methacrolein)] × 1
00

[0030]

## EQU2 ## Selectivity (%) = [(moles of methacrylic acid formed) / (moles of reacted methacrolein)] × 10
0

[0031]

## EQU3 ## Yield (%) = [(moles of methacrylic acid produced) / (moles of methacrolein fed)] × 100

Example 1 (Preparation of Sb-Ce oxide) 120 g of cerium oxide, 237 g of antimony oxide and 300 g of pure water were mixed with a kneader. After being dried in an oven at 130 ° C. for 10 hours, it is first air-baked at 600 ° C. for 3 hours, and then air-baked at 800 ° C. for 2 hours. The obtained oxide was crushed and used.

(Catalyst preparation) 212 g of ammonium paramolybdate and 11.7 g of ammonium metavanadate were added to 580 ml of pure water and heated to 60 ° C. With stirring, 23 g of phosphoric acid, 9.75 g of cesium nitrate, 4.8 of copper nitrate
Add an aqueous solution containing 3 g, then antimony trioxide 1
4.5 g was added, the temperature was raised to 80 ° C., and then 2 hours, 8
It was kept at 0 ° C. The obtained slurry container was dried and prebaked in an oven maintained at 250 ° C. for 10 hours. To the obtained solid 135 g, pure water 60 ml and Sb-Ce
Add 15g of oxide and knead for 20 minutes, then 130
Drying was performed in an oven kept at ° C. The obtained solid was tablet-molded into a cylindrical shape with an outer diameter of 5 mm, and oxygen was added at 0.6% by volume.
It was calcined at 400 ° C. for 6 hours under a nitrogen flow containing nitrogen to obtain a catalyst. The composition of the obtained catalyst is 90% by weight in terms of atomic ratio of each component.
・ Mo ₁₂ P ₂ V ₁ Sb ₁ Cu _0.2 Cs _0.5 / 10% by weight
-Sb ₇ Ce ₃ . (However, O, H, N atoms are excluded)

(Catalytic Oxidation Reaction) 30 ml of this catalyst was filled in a stainless steel reaction tube (inner diameter 18 mm) and heated through a niter bath to carry out catalytic oxidation of methacrolein.
Source gas is methacrolein 5 mol%, oxygen 12 mol%,
A mixed gas of 30 mol% steam and 53 mol% nitrogen,
Under normal pressure, the reaction temperature was 290 ° C. and the space velocity was 1400 /
Reacted at time. As a result, the methacrolein conversion rate was 89.
6%, methacrylic acid selectivity was 79.2%, and methacrylic acid yield was 71.1%.

Comparative Example 1 A catalyst was prepared in the same manner as in Example 1 except that the Sb-Ce oxide was not added, and the reaction was evaluated. As a result, the conversion of methacrolein was 89.2% and the selectivity of methacrylic acid was 78.5.
%, And the yield of methacrylic acid was 69.3%.

Comparative Examples 2-3 Sb-C used in Example 1 instead of Sb-Ce oxide
A catalyst was prepared in the same manner as in Example 1 except that the same amounts of cerium oxide (Comparative Example 2) and antimony oxide (Comparative Example 3) as those contained in the e oxide were added, and the reaction was evaluated. The results are shown in Table 1.

Comparative Example 4 A catalyst was prepared in the same manner as in Example 1 except that Sb-Ce oxide was added at the same time in the step of dissolving and mixing other catalyst raw materials.
The reaction was evaluated. As a result, the conversion of methacrolein was 8
The methacrylic acid selectivity was 4.6%, the methacrylic acid selectivity was 80.8%, and the methacrylic acid yield was 68.3%.

Examples 2 to 3 Example 1 except that Sb-Zr (Example 2) and Sb-Bi (Example 3) were used in place of the Sb-Ce oxide.
A catalyst was prepared in the same manner as in, and the reaction was evaluated. Table 1 shows the results
Shown in

Example 4 A catalyst was prepared in the same manner as in Example 1 except that the ammonia water shown in Table 1 was used instead of deionized water in the kneading step, and the reaction was evaluated. The results are shown in Table 1.

Examples 5-6 Example 4 except that Sb-Zr (Example 5) and Sb-Bi (Example 6) were used in place of the Sb-Ce oxide.
A catalyst was prepared in the same manner as in, and the reaction was evaluated. Table 1 shows the results
Shown in

Example 7 The amount of Sb-Ce oxide added is 70% by weight of the total catalyst weight.
A catalyst was prepared in the same manner as in Example 1 except that the amount of Sb-Ce-Si oxide added was increased so that the amount of water added to the kneading was increased, and the reaction was evaluated. The results are shown in Table 1.

Comparative Example 5 A catalyst was prepared in the same manner as in Example 7 except that Sb-Cu was used instead of the Sb-Ce oxide, and the reaction was evaluated. The results are shown in Table 1.

[0043]

[Table 1]

[0044]

INDUSTRIAL APPLICABILITY The oxidation catalyst of the present invention has higher reaction activity and selectivity and longer catalyst life than conventionally known catalyst systems in the production of methacrylic acid by vapor phase oxidation of methacrolein.

Claims (6)

[Claims] 1. An oxidation catalyst comprising an oxide containing phosphorus, molybdenum and an alkali metal or thallium and a multi-component oxide comprising antimony and one or more elements selected from cerium, zirconium and bismuth. Wherein in the general formula (I) ## STR1 ## _{P a Mo b V C Ba d} Sb e Cu f X g Y h O i (I) ( wherein, X is, K, Rb, than Cs and Tl Represents one or more elements selected from the group consisting of: Y is Bi, Mn,
Represents one or more elements selected from the group consisting of Cr, Zr, Co, Ce, Zn, Fe and Ni, with subscripts a, c,
d, e, f, g, h and i represent the atomic ratio of each element when b = 12, and a = 0.1-5, c = 0-5, d
= 0 to 5, e = 0 to 5, f = 0 to 2, g = 0.1 to 3,
h = 0 to 2, i is a value determined by the valence and atomic ratio of other elements) and an oxide represented by the general formula (II): Sb _j Z _k O _m (II) (wherein , Z represents one or more elements selected from Ce, Zr and Bi, and the subscripts j, k and m represent the atomic ratio of each element when j = 1, and k = 0.1 to 0. .5,
The catalyst according to claim 1, which comprises 3 to 80% by weight (based on the total catalyst weight) of a multi-component oxide represented by (m is a value determined by the valence and atomic ratio of other elements). 3. In producing the catalyst, an aqueous solution obtained by dissolving or suspending a raw material of an oxide containing phosphorus, molybdenum and an alkali metal or thallium in water is dried, and then the obtained solid matter is added to 150 2. Preliminary calcination at ˜350 ° C., and then 0.2 to 0.8 times its weight of water and the multicomponent oxide of formula (II) are added to the precalcined product, and kneading is performed. 2. The method for producing the catalyst according to 2. 4. In producing the catalyst, a solution obtained by dissolving or suspending a raw material of an oxide containing phosphorus, molybdenum and an alkali metal or thallium in water is dried, and then the obtained solid matter is added to 150 wt. Pre-calcined at ˜300 ° C., and kneading the pre-calcined product with 0.2 to 0.8 weight times ammonia water containing 0.015 to 0.1 weight times ammonium hydroxide and formula (II) The method for producing a catalyst according to any one of claims 1 to 3, wherein the multi-component oxide is added. 5. After the addition of the multi-component oxide of the formula (II) and the kneading treatment with water or ammonia water, the dried kneaded product is heated in an inert gas containing 0.1 to 5% by volume of oxygen in an amount of 350 to
The method for producing the catalyst according to claim 1, wherein the calcination is performed in a temperature range of 450 ° C. 5. 6. A method for producing methacrylic acid, which comprises subjecting methacrolein to gas phase oxidation in the presence of the oxidation catalyst according to claim 1.