Nippon Shokubai Kagaku Kogyo Co., Ltd.

Syoichi Matsumoto

Hiroshi Yoshida

Masatoshi Ueoka

Masao Baba

Yosuke Ogata

In the production of methacrylic acid by the vapor phase catalytic oxidation of isobutylene, t-butanol, methacrolein isobutyl aldehyde or isobutyric acid, or mixture thereof, the reaction product gas is condensed by contact with an aqueous phase containing methacrylic acid and acetic acid thereby forming an aqueous solution of methacrylic acid and a gas phase containing methacrolein and methacrylic acid. The aqueous solution of methacrylic acid is extracted with a saturated hydrocarbon solvent containing from 6-9 carbon atoms. The methacrylic acid is extracted into the solvent phase and an aqueous phase containing acetic acid is also formed. Methacrolein is recovered from the gas containing methacrolein and methacrylic acid by contacting the gas with an aqueous phase containing methacrylic acid and acetic acid. An aqueous phase containing methacrylic acid, acetic acid and methacrolein is formed in the methacrolein recovery step. This aqueous phase is contacted with a molecular oxygen containing gas to desorb methacrolein into a gas containing methacrylic acid and methacrolein and also forming an aqueous phase containing methacrylic acid and acetic acid. This aqueous phase is recycled to either or both of the methacrylic acid condensation step and the methacrolein recovery step. Methacrylic acid is recovered from the gas containing methacrylic acid and methacrolein produced in the methacrolein desorption step by mixing this gas with an aqueous phase containing acetic acid recovered from the methacrylic acid extraction step (C). This results in a gas-containing methacrolein which is recycled to the vapor phase reaction.

Process for recovering methacrolein

A process for producing a methacrylic ester which comprises catalytically oxidizing isobutylene, tert-butanol, methacrolein or isobutyl aldehyde in a vapor phase; removing light-boiling substances form the resulting reaction product by distillation or stripping; extracting methacrylic acid from the resulting methacrylic acid aqueous solution using a saturated chain aliphatic hydrocarbon having 6 to 9 carbon atoms as a solvent; recovering the solvent from the obtained solvent solution of methacrylic acid; esterifying the resulting methacrylic acid by the reaction of it with a lower aliphatic alcohol or a lower alicyclic alcohol having 1 to 12 carbon atoms using a porous strongly acidic cation exchange resin as a catalyst for esterfication; and then subjecting the thus obtained esterification reaction product to a purification step.

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Himeji, Japan

Syoichi Matsumoto