Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1997-10-23
2000-03-21
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
502102, 560238, C07C 6974, B01J 3100
Patent
active
060404728
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a catalyst for use in producing a carboxylic ester from an aldehyde, an alcohol and molecular oxygen, a method for producing the catalyst, and a method for the production of a carboxylic ester by using the catalyst. More particularly, the present invention is concerned with a novel catalyst which comprises a carrier having supported thereon palladium and lead in a specific atomic ratio, and which exhibits a maximum intensity peak at a diffraction angle (2.theta.) in a specific range in a powder X-ray diffraction pattern thereof. The present invention is also concerned with a method for producing the catalyst and a method for the continuous production of a carboxylic ester from an aldehyde, an alcohol and molecular oxygen by using the catalyst. In the production of a carboxylic ester using the catalyst of the present invention, the desired carboxylic ester can be obtained with high selectivity even when the reaction is conducted under high temperature and high aldehyde concentration conditions. Further, the catalyst of the present invention exhibits high mechanical strength and high corrosion resistance. In the continuous method for producing a carboxylic ester using the catalyst of the present invention, the desired carboxylic ester can be produced with high efficiency and in high yield for a prolonged period of time.
2. Prior Art
Methods for producing methyl methacrylate or methyl acrylate, which is commercially useful, have already been practiced on a commercial scale. For example, a method for producing methyl methacrylate has been commercially practiced in which methacrolein is oxidized with molecular oxygen to produce methacrylic acid and then, the methacrylic acid produced is reacted with methanol to produce methyl methacrylate. As a result of various attempts for improving catalysts over many years, the yield of methacrylic acid in the above-mentioned step of oxidizing methacrolein has been improved to some extent, namely to a value in the range of from 80% to 85%, which is, however, still unsatisfactory from the commercial viewpoint. Therefore, with respect to the yield of methacrylic acid in the above step, a further improvement has been desired. Further, heteropolyacid catalysts, which are conventionally used in the above reaction for oxidizing methacrolein to produce methacrylic acid, have problems in that they have poor thermal stability, so that the heteropolyacid catalysts are gradually decomposed at the reaction temperatures. It has been reported that improvements have been made in the thermal stability of heteropolyacids. However, it is generally considered that even such improved catalysts are still unsatisfactory in catalytic life when used in commercial practice for the production of methacrylic acid from methacrolein.
On the other hand, a new process for producing methyl methacrylate or methyl acrylate has been attracting attention, in which methacrolein or acrolein is reacted with methanol and molecular oxygen to there-by produce methyl methacrylate or methyl acrylate by a single-step process {hereinafter, methacrolein and acrolein are frequently collectively referred to as "(meth)acrolein", and methyl methacrylate and methyl acrylate are frequently collectively referred to as "methyl (meth)acrylate"}. In this process of reacting (meth)acrolein with methanol and molecular oxygen, it is essential to use a catalyst containing palladium.
Conventionally, the above-mentioned single-step process has a problem in that an aldehyde decomposition reaction occurs as a side reaction to thereby by-produce a hydrocarbon and carbon dioxide gas, so that the yield of a carboxylic ester as the desired product is low. This method is also disadvantageous in that the alcohol undergoes oxidation as a side reaction to by-produce an aldehyde which is different from the aldehyde used as a starting material, and the by-produced aldehyde causes formation of an undesired carboxylic ester which is different from the desired carboxylic
Yamaguchi Tatsuo
Yamamatsu Setsuo
Yokota Koshiro
Asahi Kasei Kogyo Kabushiki Kaisha
Killos Paul J.
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