JPS6158224B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a new and improved catalyst composition for use in a method for producing methalleuric acid by vapor phase catalytic oxidation of methacrolein. Conventionally, many catalysts have been proposed for the method of producing methacrylic acid by gas-phase catalytic oxidation of methacrolein. As one of these systems, Mo
Catalysts mainly composed of -P-As combinations have shown relatively good yields. However, the use of highly toxic arsenic is disadvantageous in terms of safety, and the arsenic compound also has the disadvantage of being easily scattered and having a short catalyst life. Another type of catalyst is a catalyst based mainly on a combination of Mo-P-Cs or Mo-P-Ba, and it is known that the addition of seium or barium increases the yield and improves the catalyst life. However, the yield is still insufficient. In either system, the method of producing methacrylic acid by gas phase catalytic oxidation of methacrolein has not yet been commercialized and is unsatisfactory as a practical catalyst. (2) Summary of the Invention The object of the present invention is to provide a catalyst composition for producing methacrylic acid that is industrially advantageous and has high performance. That is, the present invention proposes a composition comprising a metal such as molybdenum, phosphorus, barium, vanadium, antimony, and copper and oxygen as a catalyst and specified as follows. Mo _a P _b Ba _c V _d Sb _e Cu _f O _gHere , a to g represent the atomic ratio of each element, and a=
When 12, b=0.1~5, c=0.1~5, d=
0.05~5, e=0~5, f=0~5 (however, e≠
0 and f≠0), and g is a value naturally determined from the valence of other metals, and takes a value of 36 to 84. Phosphormolybdic acid, etc. is used as a catalyst for the production of methacrylic acid by oxidation of methacrolein.
It is known that heteropolyacid compounds having a Keggin structure are effective, but Mo-P, Mc-P
-Ba or Cs, Mo-P-Ba-Cu or Sb or V, Mo-P-Cs-Cu or Sb or V, the yield of methacrylic acid is low. However, the present inventors found that Mo-P-Ba-V
The present invention was completed based on the discovery that by combining Sb and Cu into a composite material, a synergistic effect is exhibited and remarkable high performance is achieved. For example, using _{a supported catalyst (support ratio 41.8%) consisting of Mo 12 P 2 Ba 1 V 0.5 Sb 1 Cu 0.2 in terms of atomic ratio , the} reaction temperature was 310°C and the space velocity was 500 h ^-1 ( When methacrolein was oxidized with air in the presence of water vapor (converted to NTP), the conversion rate of methacrolein was 92.4.
%, methacrylic acid selectivity of 82.9%, and methacrylic acid yield of 76.7% (see Example 2 below). However, in the system using Ba, JP-A-149618
The Mo-P-Ba-Sb catalyst described in the publication has a content of 61.2%.
(yield of methacrylic acid) is only 60% (yield of methacrylic acid) for the Mo-P-Ba-Cs-V catalyst described in JP-A-51-6917, whereas the metal component of the present invention It can be seen that the combination of these results in a dramatic improvement in performance. The combined effect of this combination of metal components is particularly great in suppressing side reactions under high conversion conditions. Furthermore, the catalyst of the present invention has a stabilized structure within the range of its catalyst composition, and can be used even in industrial applications that require a long life. (3) Detailed Description of the Invention (a) Preparation of Catalyst The catalyst of the present invention can be produced by a conventional method for preparing general multi-metal oxide catalysts. As raw materials for metal components, for molybdenum, we use ammonium molybdate, molybdic acid, molybdenum oxide, etc. For phosphorus, we use orthophosphoric acid, metaphosphoric acid, phosphorus pentoxide, pyrophosphoric acid, ammonium phosphate, etc. For barium, we use barium nitrate, Barium carbonate, barium sulfate, barium hydroxide, barium oxide, etc. For vanadium, ammonium metavanadate, vanadium oxide, vanadyl oxalate, etc. For antimony, antimony oxide, antimony chloride, etc. For copper, copper nitrate, copper sulfate, etc. Compounds such as cuprous chloride and cupric chloride can be used. Furthermore, heteropolyacids such as phosphomolybdic acid and ammonium phosphomolybdate can also be used as raw materials for molybdenum and phosphorus. These raw materials can be mixed in predetermined amounts by an appropriate method, but preferably each raw material is dissolved in water and mixed to form a solution as uniform as possible. Furthermore, if necessary, silica gel or silica sol is mixed and dispersed as a carrier component. In addition, customary carrier materials such as diatomaceous earth, celite, talc, kaolin, bentonite, crystalline silica, fused silica, etc. can be added to the mixed solution. Next, after concentrating the obtained mixed solution as necessary,
It is supported on a carrier such as α-alumina or silicon carbide by an appropriate method, or it is evaporated to dryness, crushed, and then formed into tablets. In addition, general molding methods such as extrusion molding in a paste form and then drying can also be selected. The catalyst is then calcined at 300 to 500°C for 1 to 40 hours. Calcination is divided into two steps, for example, the solid material that has been evaporated to dryness is once heated to a temperature of 200 to 500°C, molded by a method such as tablet support extrusion, and then further heated to a temperature of 300 to 550°C for a predetermined period of time. A catalyst can also be obtained by calcination. Although all of these component raw materials are usually mixed at once as described above, a portion thereof can also be introduced stepwise in another process, for example, by heating, decomposing, mixing, molding, and baking. (b) Use of catalyst The catalyst of the present invention can be used by a method for producing methacrylic acid by a normal contact reaction, for example, at a reaction temperature of about 200 to 450°C and a temperature of 0.5°C.
It is preferable to carry out the reaction in the presence of water vapor at a reaction pressure of about 10 atm. As the reaction raw material methacrolein, for example,
For the purpose of producing methacrolein, the product gas obtained by catalytic oxidation of isoptylene or tert-butanol may be used as it is, or
The produced gas may be purified to separate methacrolein from other gases before use. Air is generally used as the oxygen source for oxidation, but oxygen (molecular oxygen) or a mixed gas of oxygen diluted with an inert gas such as carbon dioxide or nitrogen may also be used. A mixed gas (hereinafter referred to as reaction mixed gas) containing water vapor, a reaction raw material, an oxygen source, etc. is passed through the catalyst, and the appropriate contact time is usually about 1 to 20 seconds.
As for the composition of the reaction mixture gas, for example, 0.2 to 4 moles of molecular oxygen and 1 to 20 moles of water vapor are used per mole of methacrolein. In addition, this catalytic oxidation reaction can be carried out with reference to knowledge regarding ordinary methacrolein oxidation, as long as it does not go against the gist of the present invention. (c) Examples Hereinafter, the present invention will be explained in more detail using Examples and Comparative Examples. Note that the conversion rate, selectivity, and yield were expressed on a molar basis. Example 1 (Catalyst Preparation) 106.00 g of ammonium paramolybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O) is dissolved in 500 ml of distilled water. A solution of 11.54 g of 85% orthophosphoric acid (H ₃ PO ₄ ) dissolved in 50 ml of distilled water is added to this solution and mixed thoroughly. In this, 6.54 g of barium nitrate (Ba(NO ₃ ) ₂ ) was dissolved in 23 ml of distilled water, and 2.42 g of copper nitrate (Cu(NO ₃ ) ₂ 3H ₂ O) was dissolved in distilled water.
Solution dissolved in 50 ml, suspension of 7.29 g of antimony oxide (Sb ₂ O ₃ ) in 50 ml of distilled water, 100 ml of distilled water
Ammonium _metavanadate ( _MH4VO3 ) in ml
Add 2.93g of the suspension one by one and mix with sufficient stirring. Furthermore, the obtained mixture was heated to 70-80℃.
A porous α-alumina carrier with a diameter of 5 mm was heated to 120
g and evaporated to dryness while stirring to support the catalyst component. Next, it was dried at 120°C for 16 hours, then calcined at 380°C for 6 hours, and used as a catalyst. The loading rate calculated from the weight increase was 38.8%. In this way, the obtained catalyst has an atomic ratio of each component.
It has _a composition of MO ₁₂ P _{2 Ba 0.5 V 0.5 Sb 1 Cu 0.2 .} (Catalytic oxidation reaction) Transfer 40 ml of this catalyst into a stainless steel reaction tube (inner diameter 18
m/m) and heated through a night bath;
Catalytic oxidation of methacrolein was carried out. Raw material gas is methacrolein 3.2%, air 42%, water vapor 39%,
It is a mixed gas with an additional nitrogen content of 15.8%, which is heated under normal pressure, reaction temperature 320℃, and space velocity 500 (hour) ^-1
(in terms of NTP), the following results were obtained. Methacrolein Conversion rate 92.3 mol% Methacrylic acid Selectivity 80.7 mol% Methacrylic acid Yield 74.4 mol% Examples 2 to 5 and Comparative Examples 1 to 4 Except for changing the composition or not adding one or two components, Examples Table 1 summarizes the results of a reaction using a catalyst having the composition shown in Table 1 prepared in the same manner as in Example 1 under the same conditions as in Example 1 except for the reaction temperature.

[Table] Comparative Example 5 Prepared in the same manner as Example 6 except that ammonium metavanadate was not used.
A catalyst with the composition (atomic ratio) of Mo ₁₂ P ₂ Cs _0.5 Sb ₁ Cu _0.2 (support ratio 39.4%) was used, and the reaction _temperature was 310 _° C.
A catalytic oxidation reaction was carried out under the same conditions as in Example 1 except that the temperature was 0.degree. The results were as follows. Methacrolein Conversion rate 84.9 mol% Methacrylic acid Selectivity 67.6 mol% Methacrylic acid yield 57.4 mol%

Claims (1)

[Scope of Claims] 1. A catalyst composition for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein, characterized by having the following composition. Mo _a P _b Ba _c V _d Sb _e Cu _f O ₉ [In the formula, a to g represent the atomic ratio of each element, and a=
When 12, b=0.1~5, c=0.1~5, d=
0.05~5, e=0~5, f=0~5 (however, e≠
0 and f≠0), and g is a value naturally determined from the valence of other metals, and takes a value of 36 to 84. ]