Supercritical Reaction Process Study For The Synthesis Of Benzylideneacetone

Benzylidene acetone is an important chemical raw material, widely used in electroplating, food industry and other chemical industries. The traditional preparation method is that benzaldehyde and acetone react directly to produce benzylidene acetone through Claisen condensation with basic catalysts. Although this method is relatively mature, it still has several problems in serious waste, the reuse of catalyst and separation.In this article, we studied a new preparation method of benzylidene acetone under supercritical conditions to eliminate the defects in traditional process. The main advantages of this method locate in the simple after-treatment and the reduction of waste water and salts, which benefit from not adding water and base catalysts. By this way, this method solves the waste problem in traditional process to a large extent.In this article, we conducted a systematic study of the synthesis of benzylidene acetone in batch reactor and tubular reactor, and discussed the influences of temperature, pressure, reaction time and the ratio of benzaldehyde to acetone in this paper. In batch reactor, the conversion of benzaldehyde reaches53%and the benzylidene acetone selectivity reaches69%with molar ratio of benzaldehyde to acetone fixed at0.1after2hours of reaction at220℃. In tubular reactor, the conversion of benzaldehyde reaches30%and the benzylidene acetone selectivity reaches85%with molar ratio of benzaldehyde to acetone fixed at0.05after2hours of reaction at330℃and27MPa.Any more, the reaction mechanism was studied in this article. Under supercritical conditions, the reaction can be occurred without any other catalysts. Because a small amount of water was used as catalyst, the reactants could not be dried. Otherwise, the reaction could not be occurred.