JPH11228487A - Production of methacrylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing methacrylic acid in a good yield by subjecting methacrolein to vapor phase catalytic oxidation. SOLUTION: In this method for producing methacrylic acid by subjecting methacrolein to vapor phase catalytic oxidation, a catalyst represented by the general formula Moa Pb Vc Cud Sbe Nbf Xg Yh Zi Oj [Mo, P, V, Cu, Sb, Nb and O each represent its element; X is at least one kind of element selected from a group comprising Fe, Co, Ni and Zn; Y is at least one kind of element selected from a group comprising Mg, Ca, Sr, Ba, Ti, Cr, W, Mn, Ag, B, Si, Sn, Pb, As, Bi, In, S, Se, Te, La and Ce; Z is at least one kind of element selected from a group comprising Na, K, Rb, Cs and Tl, with the proviso that (a), (b), (c), (d), (e), (f), (g), (h) and (i) represent atom ratio of specific each element] is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing methacrylic acid by gas phase catalytic oxidation of methacrolein with molecular oxygen.

[0002]

2. Description of the Related Art Many proposals have been made on a method and a catalyst for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation. In particular, since the discovery of a heteropolyacid catalyst as a methacrolein oxidation catalyst, many proposals for improvement have been made. For example, JP
The following general formula in JP _{2-161739 P a Mo b V c Fe} d Cu e Sb f X g Y h O i ( wherein, X represents potassium, rubidium, cesium and / or thallium, Y is tellurium, Lanthanum, boron,
Represents silver, magnesium and / or barium. a,
b, c, d, e, f, g and i represent the atomic ratio of each element, and when b = 12, a = 0.3-4 and c = 0.01-
3, d = 0.01-4, e = 0.01-3, f = 0.0
1 to 3, g = 0.01 to 3, h = 0.001 to 5, and i is a value determined by the valence of each component. ) Is disclosed. However, the production of methacrylic acid using the catalyst obtained by these methods is still insufficient in terms of the yield of methacrylic acid,
Further improvements are desired from an industrial point of view.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing methacrylic acid in good yield by gas phase catalytic oxidation of methacrolein with molecular oxygen.

[0004]

SUMMARY OF THE INVENTION The present invention, in producing the gas phase catalytic oxidation to methacrylic acid of methacrolein with molecular oxygen, the following general formula _{Mo a P b V c Cu d} Sb e Nb f X g Y _h Z _i O _j (wherein, Mo, P, V, Cu , Sb, Nb and O represent molybdenum, phosphorus, vanadium, copper, antimony,
X represents at least one element selected from the group consisting of iron, cobalt, nickel and zinc;
Y is magnesium, calcium, strontium, barium, titanium, chromium, tungsten, manganese, silver,
At least one element selected from the group consisting of boron, silicon, tin, lead, arsenic, bismuth, indium, sulfur, selenium, tellurium, lanthanum and cerium, and Z is a group consisting of sodium, potassium, rubidium, cesium and thallium Represents at least one element selected from the group consisting of:
Here, a, b, c, d, e, f, g, h and i represent the atomic ratio of each element, and when a = 12, 0.1 ≦ b ≦ 3,
0.01 ≦ c ≦ 3, 0.01 ≦ d ≦ 2, 0.01 ≦ e ≦
3, 0.01 ≦ f ≦ 3, 0.01 ≦ g ≦ 3, 0 ≦ h ≦
3, 0.01 ≦ i ≦ 3, and j is the atomic ratio of oxygen required to satisfy the atomic ratio of each component. A method for producing methacrylic acid characterized by using a catalyst represented by the formula (1):

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for preparing the catalyst represented by the above general formula used in the present invention does not need to be limited to a special method, and is well known in the art unless a significant uneven distribution of components is involved. Co-precipitation method, evaporation to dryness method,
Various methods such as an oxide mixing method can be used.

The raw materials used for preparing the catalyst are not particularly limited, and nitrates, carbonates, acetates, ammonium salts, oxides, halides and the like of each element can be used in combination. For example, as a molybdenum raw material, ammonium paramolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride and the like can be used. The method for preparing the catalyst is not particularly limited, and a known method for preparing a catalyst for producing methacrylic acid containing at least phosphorus, molybdenum, and vanadium can be used.

[0007] The catalyst used in the present invention may be free of a carrier, but may be supported on an inert carrier such as silica, alumina, silica-alumina, silicone carbide, or diluted with these.

In carrying out the present invention, the concentration of methacrolein in the raw material gas can be changed in a wide range.
The range of from 20 to 20% by volume is appropriate, and the range of from 3 to 10% by volume is particularly preferable. The raw material methacrolein may contain a small amount of impurities such as water and lower saturated aldehyde which do not substantially affect the present reaction.

Although it is economically advantageous to use air as the oxygen source, air enriched with pure oxygen may be used if necessary. The oxygen concentration in the source gas is defined by the molar ratio with methacrolein, and the value is preferably in the range of 0.3 to 4, particularly preferably 0.4 to 2.5. Source gas is nitrogen, steam,
It may be diluted by adding an inert gas such as carbon dioxide.

The reaction can be carried out at a pressure ranging from normal pressure to several atmospheres. The reaction temperature can be selected in the range of 230 to 450 ° C, particularly preferably in the range of 250 to 400 ° C. The reaction can be carried out in a fixed bed or a fluidized bed.

[0011]

The present invention will be described below by way of examples. The analysis was performed by gas chromatography. In the description, "parts" indicates parts by weight, and the conversion of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid are defined as follows. Conversion of methacrolein (%) = moles of reacted methacrolein / moles of supplied methacrolein × 100 Selectivity of methacrylic acid (%) = moles of produced methacrylic acid / moles of reacted methacrolein × 100 Yield (%) of methacrylic acid = moles of methacrylic acid formed / moles of supplied methacrolein × 100

Example 1 150 parts of ammonium paramolybdate was dissolved in 150 parts of pure water. A solution obtained by dissolving 4.12 parts of cobalt nitrate in 20 parts of pure water and a solution obtained by diluting 16.33 parts of 85% by weight phosphoric acid with 30 parts of pure water were added thereto and heated to 95 ° C. with stirring. Next, copper nitrate 5.1
3 parts dissolved in 20 parts of pure water, barium nitrate 1.8
A solution of 5 parts in 10 parts of pure water, antimony trioxide 1
0.32 parts, 3.76 parts of niobium pentoxide and 6.63 parts of ammonium metavanadate were sequentially added and stirred. Subsequently, a solution obtained by dissolving 7.16 parts of potassium nitrate in 50 parts of pure water was added, and the obtained slurry was heated to 101 ° C. and evaporated to dryness with stirring. 13
After drying at 0 ° C. for 16 hours, pressure molding was carried out, and 39
Heat treatment was performed at 0 ° C. for 6 hours, and this was used as a catalyst.

The elemental composition of the resulting catalyst other than oxygen (the same applies hereinafter) was as follows. Mo ₁₂ P ₂ V _0.8 Cu _0.3 Sb ₁ Nb _0.4 Co _0.2 Ba
_0.1 K ₁ This catalyst was charged into a reaction tube and methacrolein 5% by volume,
A mixed gas containing 10% by volume of oxygen, 20% by volume of steam and 65% by volume of nitrogen was passed at a reaction temperature of 280 ° C. for a contact time of 3.6 seconds. When the product was collected and analyzed by gas chromatography, the conversion of methacrolein was 89.5%, the selectivity of methacrylic acid was 89.2%, and the yield of methacrylic acid was 79.8.
%Met.

Comparative Example 1 According to Example 1, Mo ₁₂ P ₂ V _0.8 Cu _0.3 Nb _0.4 Co _0.2 Ba _0.1 K
_When a catalyst having a composition of ₁ was prepared and reacted under the same conditions as in Example 1, the conversion of methacrolein was 85.0%, the selectivity of methacrylic acid was 86.1%, and the yield of methacrylic acid was 73.2.
%Met.

Comparative Example 2 A catalyst having a composition of Mo ₁₂ P ₂ V _0.8 Cu _0.3 Sb ₁ Co _0.2 Ba _0.1 K ₁ was prepared according to Example 1, and reacted under the same conditions as in Example 1. Rein conversion of rhein 86.8%, selectivity of methacrylic acid 86.7%, yield of methacrylic acid 75.3
%Met.

Comparative Example 3 A catalyst having a composition of Mo ₁₂ P ₂ V _0.8 Cu _0.3 Sb ₁ Nb _0.4 Ba _0.1 K ₁ was prepared according to Example 1, and reacted under the same conditions as in Example 1. Rein conversion of rhein 86.6%, selectivity of methacrylic acid 86.5%, yield of methacrylic acid 74.9
%Met.

[Examples 2 to 12] Table 1 in accordance with Example 1
Were prepared and reacted under the same conditions as in Example 1. Table 1 summarizes the conversion of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid in each case.

[0018]

[Table 1]

Comparative Example 4 According to Example 1, Mo ₁₂ P ₂ V _0.6 Cu _0.2 Sb _0.5 Fe _0.1 Co _0.2 W
_When a catalyst having a composition of _0.2 Te _0.04 K _0.8 Tl _0.2 was prepared and reacted under the same conditions as in Example 1, the conversion of methacrolein was 87.0%, the selectivity of methacrylic acid was 86.7%, and the yield of methacrylic acid was Rate 75.4
%Met.

[0020]

According to the present invention, methacrylic acid can be produced in good yield by gas phase catalytic oxidation of methacrolein with molecular oxygen.

Claims (1)

[Claims] The method according to claim 1 methacrolein in producing the gas phase catalytic oxidation to methacrylic acid with molecular oxygen, the following general formula _{Mo a P b V c Cu d} Sb e Nb f X g Y h Z i O j ( wherein , Mo, P, V, Cu, Sb, Nb and O are molybdenum, phosphorus, vanadium, copper, antimony,
X represents at least one element selected from the group consisting of iron, cobalt, nickel and zinc;
Y is magnesium, calcium, strontium, barium, titanium, chromium, tungsten, manganese, silver,
At least one element selected from the group consisting of boron, silicon, tin, lead, arsenic, bismuth, indium, sulfur, selenium, tellurium, lanthanum and cerium, and Z is a group consisting of sodium, potassium, rubidium, cesium and thallium Represents at least one element selected from the group consisting of:
Here, a, b, c, d, e, f, g, h and i represent the atomic ratio of each element, and when a = 12, 0.1 ≦ b ≦ 3,
0.01 ≦ c ≦ 3, 0.01 ≦ d ≦ 2, 0.01 ≦ e ≦
3, 0.01 ≦ f ≦ 3, 0.01 ≦ g ≦ 3, 0 ≦ h ≦
3, 0.01 ≦ i ≦ 3, and j is the atomic ratio of oxygen required to satisfy the atomic ratio of each component. A method for producing methacrylic acid, comprising using the catalyst represented by the formula (1).