JPS62153243A - Production of methacrylic acid - Google Patents

Abstract

PURPOSE:To keep high catalyst activity for a long period and industrially and advantageously obtain the aimed compound in high yield and selectivity, by using a catalyst having specific components and composition in catalytically oxidizing methacrolein in the vapor phase to produce methacrylic acid. CONSTITUTION:Methacrolein is catalytically oxidized in the vapor phase with molecular oxygen in the presence of a catalyst expressed by the formula (X is one or more elements selected from K, Rb, Ce and Tl; Y is one or more elements selected from Mn, Ti, Al, Mg, Zn and Ba; a>= indicate the atomic ratio of each element; a is 0.3-3; c is 0.01-3; d is 0.01-3; e is 0.01-3; f is 0.01-2; g is 0.01-3; h is 0.01-3 when b is 12; i is the number of oxygen atoms required for satisfying the valence of the respective above-mentioned components) to advantageously obtain methacrylic acid using the above- mentioned catalyst having high practicality in activity, selectivity and life.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein.

[Conventional technology]

Conventionally, many methods have been proposed for producing acrylic acid or methacrylic acid by vapor phase catalytic oxidation of acrolein or methacrolein. However, these methods mainly focus on producing acrylic acid from acrolein, and when the catalysts proposed there are used for producing methacrylic acid, the selectivity is low due to large side reactions, and the service life is short. was too short and impractical. On the other hand, many catalysts have been proposed for the production of methacrylic acid from methacrolein, but all of them have drawbacks such as unsatisfactory reaction results, a large decrease in catalyst activity over time, and too high reaction temperatures. , further improvements are desired.

[Problem that the invention seeks to solve]

As a result of research into a method for advantageously producing methacrylic acid from methacrolein, the present inventors have found a catalyst that improves the above-mentioned drawbacks and is highly practical in terms of activity, selectivity, and service life, thereby completing the present invention.

[Means for solving problems]

The present invention is based on the general formula % (wherein or an element selected from the group consisting of potassium, rubidium, cesium and thallium, Y is an element selected from the group consisting of manganese, titanium, aluminum, magnesium, zinc and barium). , a to l indicate the atomic ratio of each element, and when b = 12 & = 0. S ~ 5
, c=0.01-6, d=0.01-3, e=0.
01~5, f=0.01~2, g-=o, ot~6, h
= [], 01 to 3, where 1 is the number of oxygen atoms necessary to satisfy the valence of each component), using methacrolein with molecular oxygen. This is a method for producing methacrylic acid, which is characterized by gas phase catalytic oxidation.

X and Y in the formula may each be two or more types of elements.

According to the method of the present invention, it is possible to obtain methacrylic acid from methacrolein in high yield and high selectivity, and in particular, high catalytic activity is maintained over a long period of time, so the industrial value is extremely large.

The method for producing the catalyst used in the present invention does not need to be limited to a special method, and conventionally known methods such as evaporation to dryness, precipitation, etc. can be used as long as the components are not significantly unevenly distributed. The raw materials for catalyst preparation include nitrates of each element,
Carbonates, ammonium salts, halides, oxides, etc. can be used in combination.

Although the catalyst used in the present invention is effective even without a carrier,
It can also be supported on an inert carrier such as silica, alumina, silica-alumina, silicon carbide, or diluted with an inert carrier.

When carrying out the present invention, in the presence of the above catalyst,
Gas phase catalytic oxidation of methacrolein with molecular oxygen. The concentration of methacrolein in the feed gas can vary within a wide range, but is preferably between 1 and 20% by volume, particularly between 6 and 10% by volume. The raw material methacrolein may contain small amounts of impurities such as water and lower saturated aldehydes, but these impurities do not substantially affect the reaction.

Although it is economical to use air as the oxygen source, air enriched with pure oxygen can also be used if necessary. The oxygen concentration in the raw material gas is defined by the molar ratio to methacrolein, and this value is preferably 0.3 to 4, particularly 0.4 to 2.5. The raw material gas may be diluted by adding an inert gas such as nitrogen, water vapor, or carbon dioxide gas. The reaction pressure is preferably from normal pressure to several atmospheres. Although the reaction temperature can be selected within the range of 260 to 450°C, 250 to 400°C is particularly preferred. The reaction can be carried out in a fluidized or fixed bed.

In the Examples and Comparative Examples below, parts mean parts by weight, and the analysis was performed by gas chromatography.

Further, the reaction rate of methacrolein, the selectivity and single flow yield of the produced methacrylic acid are defined as follows.

Reaction rate of methacrolein (%) Selectivity of methacrylic acid (%) Number of moles of reacted methacrolein Single flow yield of methacrylic acid (%) Number of moles of methacrolein supplied Example 1 100 parts of ammonium paramolybdate, 3.9 parts of ammonium metavanadate and 92 parts of cesium nitrate were dissolved in 300 parts of pure water. A solution of 8.2 parts of 85% phosphoric acid dissolved in 10 parts of pure water and a solution of 1.1 parts of telluric acid dissolved in 10 parts of pure water were added thereto, and the temperature was raised to 95° C. with stirring.

Next, a solution of 3.4 parts of copper nitrate, 16 parts of ferric nitrate, and 1.8 parts of magnesium nitrate dissolved in 80 parts of pure water was added.
The mixture was heated to 100° C. and evaporated to dryness while stirring. The obtained solid material was dried at 130° C. for 16 hours, then pressure-molded, and heat-treated at 680° C. for 5 hours under air circulation. The composition of the obtained catalyst (elements other than oxygen, the same applies below) is PH
, 5Mo12Vo, 7 Fe, ), 4 cuoj Te
64 CslMgo, ts.

This catalyst was packed into a reactor, and 5% methacrolein and 1% oxygen were added.
A mixed gas of 0% water vapor, 30% water vapor, and 55% nitrogen (volume %) was passed through the reactor at a reaction temperature of 290° C. and a contact time of 3.6 seconds. When the product was collected and analyzed by gas chromatography, the reaction rate of methacrolein was 87.5%, the selectivity of methacrylic acid was 86.2%, and the single flow yield was 75.4%.

When the reaction was continued for about 1000 hours under the same conditions, the reaction IL for methacrolein was 87.2% and the selectivity for methacrylic acid was 86.0%.

Examples 2-6 Each catalyst in the table below was prepared according to Example 1.

The reaction was carried out under the same conditions as in Example 1. The results are shown in the table. The single flow yield was 75. It was o~75.4%.

Comparative Example In the same manner as in Example 1, PL5Mo12V (1,7Cuo
, 3Csl was prepared and reacted under the same conditions as in Example 1, the reaction rate of methacrolein was 83.
．． 1%, methacrylic acid selectivity 81.0%, single flow yield 6
It was 7.6%.

Claims (1)

[Claims] General formula P_aMo_bV_cFe_dCu_eTe_fX_g
Y_hO_i (wherein X represents an element selected from the group consisting of potassium, rubidium, cesium and thallium; Y represents an element selected from the group consisting of manganese, titanium, aluminum, magnesium, zinc and barium; a to i Indicates the atomic ratio of each element, when b = 12, a = 0.3
~3, c=0.01~3, d=0.01~3, e=0.
01-3, f=0.01-2, g=0.01-3, h=
0.01 to 3, and i is the number of oxygen atoms necessary to satisfy the valence of each component. A method for producing methacrylic acid, characterized by catalytic oxidation.