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.