Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1991-08-02
1994-01-04
Dees, Jose G.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562538, 562546, 562599, C07C 5116, C07C 5100
Patent
active
052761789
DESCRIPTION:
BRIEF SUMMARY
UTILIZATION FIELD IN INDUSTRY
The present invention relates to a process for producing methacrolein and methacrylic acid by using, as a starting material, at least one compound selected from isobutylene, t-butanol (tertiary butanol) and methyl t-butyl ether (methyl tertiary butyl ether) and subjecting the starting material to gas phase catalytic oxidation with molecular oxygen or a molecular oxygen-containing gas.
Prior Art
A number of proposals have been made on the catalyst used in production of methacrolein and methacrylic acid by the high-temperature gas phase catalytic oxidation of isobutylene and/or t-butanol. These proposals relate mainly to the selection of the components constituting the catalyst and their ratio.
The above oxidation reaction is a highly exothermic reaction. Therefore, in the reaction, heat build-up in the catalyst layer is large; particularly in the abnormally hot areas called "hot spots", product yield is low due to an excessive oxidation reaction and, moreover, deterioration of catalyst takes place owing to a high thermal load and catalyst life is influenced greatly. Accordingly, heat build-up in hot spots is a serious problem in the industrial practice of the above oxidation reaction. This heat build-up in hot spots tends to be striking particularly when the concentration of material gas is made higher or the space velocity is made larger (such reaction conditions are hereinafter referred to as "high-load reaction conditions" in some cases) in order to enhance the productivity; as a result, the reaction conditions of the oxidation reaction are considerably restricted currently.
Hence, minimization of heat build-up in hot spots is very important for industrial production of methacrolein and methacrylic acid at high yields as well as for reduction of catalyst deterioration and resultant stable operation over a long period. Prevention of heat build-up in hot spots is particularly important in molybdenum-based catalysts because the molybdenum component causes easy sublimation.
Various proposals have hitherto been made in order to suppress heat build-up in hot spots. For example, Japanese Patent Publication No. 36740/1987 proposes the use of a ring-shaped catalyst. The document describes that the change of catalyst shape from spherical or columnar shape to ring shape in the molded catalyst conventionally used for oxidation of isobutylene or t-butanol can suppress heat build-up in hot spots and accordingly an excessive oxidation reaction, and is very effective for the improvement of product yield. This method certainly has an effect of reducing the thermal load for catalyst, but gives no sufficient results under high-load reaction conditions, in particular.
Also, a method in which catalysts of different activities are filled in a plurality of reaction zones formed by dividing the catalyst layer of reactor and in which an oxidation reaction is carried out in the reaction zones, is known in Japanese Patent Publication No. 38331/1988 for production of, for example, acrolein and acrylic acid from propylene.
Further, Japanese Laid-Open Patent Publication No. 127013/1976 discloses the use of a combination of a supported catalyst and a molded catalyst essentially of the same composition for production of unsaturated aldehydes and acids from propylene and isobutylene. The document shows, in Examples, specific cases of producing acrolein and acrylic acid from propylene, but discloses no specific case of producing methacrolein and methacrylicacid from isobutylene. Therefore, it is difficult to evaluate the effect of the above technique on the production of methacrolein and methacrylic acid from isobutylene.
In the reaction for producing methacrolein and methacrylic acid by subjecting isobutylene, t-butanol or methyl t-butyl ether to gas phase catalytic oxidation, all of these starting materials have a methyl group at the .alpha.-position unlike propylene; accordingly, there occur many side reactions caused by the presence of methyl group, such as parallel reactions, successive reactions an
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Aoki Yukio
Kurimoto Ikuo
Ohno Shigeru
Onodera Hideo
Dees Jos,e G.
Nazario Porfirio
Nippon Shokubai Co. , Ltd.
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