A Study On The Synthesis Of Cinnamaldehyde By Aldol Condensation

Cinnamaldehyde is an important organic synthesis intermediate,and it is widely used in organic synthesis or as an additive for spices,fragrances,medicine,daily fine chemicals,and fordder.At present,cinnamaldehyde is commonly synthesized through condensation reaction between benzaldehyde and aldehyde in industry,but the product yield is relatively low.Altuogh the current researches,which fouce on the process optimization and development of catalysts,have made some progress,there are some problem,including low product yisld and lopng reaction time,needed to be solved.Previous studies have indicated that this condensation reaction is a liquid-liquid reaction,and the conversion of raw materials and yield of product can be improved by the enhancement of mixing and mass treansfer between liquid and liquid,which ultimately improves the economical efficiency of this process.This work adopted benzaldehyde and aldehyde as raw materials to synthesis cinnamaldehyde in stirred tank reactor and rotating packed bed(RPB)reactor,respectively.A seris of analytical methods,including Gas chromatographic internal standard method,GC-MS and infrared spectrometer,for the analysis of raw materials and products were established.And the effects of various operation conditions on the conversion of benzaldehyde and the yield of cinnamaldehyde were investigated.The main conclusions were list as follows:(1)An orthogonal experiment was designed for the synthesis reaction in the stirred tank,and four factors,including the molar ratio of the feed(A),reaction temperature(B),amount of catalyst(C),stirring speed(D),were selected.The results showed that the order of the influencing factors are:C>A>D>B.(2)The optimum conditions for the synthesis of cinnamaldehyde in the stirred tank reactor were acetaldehyde/benzaldehyde(mol)of 1:1.1,acetaldehyde/NaOH of 1:0.28,reaction temperature of 35?,stirring speed of 600 rpm,and reaction time of 50 min.Under this condition,the product yield of cinnamaldehyde can reach 66%.(3)The optimum reaction conditions the synthesis of cinnamaldehyde in RPB were acetaldehyde/benzaldehyde(mol)of 1:1.05,acetaldehyde/NaOH of 1:0.2,reaction temperature of 35?,rotor speed of 1700 rpm,and the reaction time of 40 min.Under this condition,the product yield of cinnamaldehyde can reach 62%.In view of the results in stirred tank reactor and RPB,the product yield in RPB is litte smaller but close to that in stirred tank.Additionally,compared to stirred tank reactor,the reaction time in the RPB can be reduced by one fifth to one quarter,and the amount of catalyst and benzaldehyde can also be reduced.Those results imply that there still is some possibility for adopting RPB as reactor to synthesis cinnamaldehyde in industry.