苯甲酸气相加氢制苯甲醛的反应机理研究

通过改变苯甲酸和苯甲醛催化加氢的氢气流量、预还原时间、反应温度来研究苯甲酸催化加氢的反应机理,为取代苯甲酸催化加氢的理论研究提供参考模型,同时也为加氢催化剂的设计和工艺条件的选择提供实验理论依据.副产物甲苯主要是来自于主产物苯甲醛的进一步加氢反应,而少部分来自于苯甲酸双氧空位吸附.研究表明,苯甲酸单氧空位催化加氢符合M.v.K机理,而苯甲醛的深度加氢和苯甲酸的双氧空位加氢并不完全符合M.v.K机理.根据催化剂层三段反应的分析,可将反应器设计成漏斗状或在上、中、下三层中采用不同粒径的催化剂,达到同时提高苯甲酸转化率和苯甲醛选择性的目的.

The Mechanism for Vapor-phase Hydrogenation of Benzoic Acid to Benzaldehyde

By optimizing reaction conditions,such as GHSV,pre-reduction time and reaction temperature,the reaction mechanism of catalytic hydrogenation of benzoic acid to benzaldehyde was investigated,the results not only provided reference for theoretical model of hydrogenation of substituted benzion acids,but also set up theoretical basis for catalyst design and choice of process conditions. Moreover,the present work showed that toluene as by-product was mainly from further hydrogenation of benzaldehyde,while a small part of toluene was from hydrogenation of benzoic acid adsorbed at double oxygen vacancy sites.The results indicated that the catalytic hydrogenation of benzoic acid adsorbed at single oxygen vacancy site was consistent with M.v.K mechanism,but the catalytic hydrogenation of benzaldehyde and benzoic acid at double oxygen vacancy sites were not fully consistent with the M.v.K mechanism.Analysis of three stage reactions in catalyst bed suggested that,to improve both the conversion of benzoic acid and the selectivity of benzaldehyde at the same time,the reactor can be designed as funnel-shaped ,and/or be filled with different size of catalyst in the upper,middle and lower layer,respectively.