Catalytic Oxidation Of Benzyl Alcohol By PVDF Composite Catalytic Membrane

As an important chemical intermediate,benzaldehyde is widely used in medicine,pesticide and other fields.Traditional industrial benzaldehyde production is mainly based on chlorination hydrolysis method.It has low selectivity of products and removes chlorine difficultly.The reaction process of benzaldehyde by catalytic oxidation of benzyl alcohol is simple,mild and chlorine-free.It is a widely used method for the preparation of benzaldehyde.However,the traditional oxidant is heavy metal oxide and produces a large number of high valence state metal oxides,which pollute the environment.Alcohol is easy to be deeply oxidized into carboxylic acid,reducing the selectivity of benzaldehyde.The catalyst is easy to deactivate after the reaction and is difficult to separate from the reactants.This paper designed a kind of composite catalytic membrane not only being used as a catalyst carrier,but also being reaction interface and separation"barrier"to achieve green efficient catalytic oxidation of benzyl alcohol to benzaldehyde.It offers a new idea for the green production of chlorine-free benzaldehyde.(1)Sandwich composite catalytic membrane:The palladium(Pd)nanoparticles were prepared by sodium borohydride reduction method,and the Pd nanoparticles were deposited on the membrane in the form of vacuum filtration deposition.The second layer were coated on the surface to prepare sandwich composite catalytic membrane.The composite membranes were characterized by transmission electron microscopy(TEM),scanning electron microscopy(SEM),physical and chemical adsorption(BET),X ray photoelectron spectrometer(XPS),contact angle tester and so on.And It's studied the composite catalytic membrane under different reaction conditions on the liquid phase catalytic oxidation of benzyl alcohol to benzaldehyde.It was found that the temperature of 80?,benzyl alcohol of 5mmol,flow rate of82.5m L/min,reaction time of 4 h,volume ratio of H₂O₂ to H₂O of 1:4 and the load content catalyst of 19.45mg/g were the optimal reaction conditions,resulting the yield of benzaldehyde was 2.01mmol and selectivity was 93.17%.(2)Double layer composite catalytic membrane:The PVDF@Pd catalytic membrane was prepared by sodium borohydride reduction and phase transformation.Thereinto,Pd nanoparticles were directly reducted and dispersed in the casting solution.Then the second layer was coated in the membrane surface to prepare double layer catalytic composite membrane.The composite membranes were characterized by TEM,SEM,BET,XPS,contact angle tester.The different reaction conditions on the effect of catalytic performance in the catalytic oxidation of benzyl alcohol were studied.It was found that the flow rate of 82.5m L/min,benzenyl alcohol of 5mmol,volume ratio of H₂O₂ to H₂O of 1:4,catalyst load of 1.16mg/g,temperature of 100?,reaction time of 4h were optimal reaction conditions,resulting the yield of benzaldehyde was 1.67mmol and the selectivity was 84.27%.