Preparation Of Polymer Carrier Palladium Nanocomposite And Its Application In The Catalytic Oxidation Of Benzyl Alcohol

Benzaldehyde is an important fine chemical intermediate,widely used in medicine,spices,food,dyes and other fields.Currently,benzaldehyde is mainly produced by chlorination hydrolysis of toluene in industry,it has disadvantages such as low conversion rate,poor selectivity of benzaldehyde,many by-products and environmental pollution.More importantly,the product contains chlorine,which limits its application.Therefore,it is urgent to develop efficient,green,chlorine-free benzaldehyde production technology.The preparation of benzaldehyde by oxidation of benzyl alcohol with hydrogen peroxide catalyzed by palladium metal nanoparticles is a green and environment-friendly preparation technology,but the aggregation of palladium nanoparticles will occur due to the high surface energy of palladium nanoparticles in the process of use,thus reducing the catalytic activity.Therefore,it is particularly important to select appropriate carriers and loading methods to fix palladium nanoparticles.In this paper,three different polymer carrier/palladium nanoparticle complexes were prepared by loading palladium nanoparticles onto three polymer carriers by in situ reduction method.1.Polyalpha-methacrylate(PMAA)microspheres were prepared by distillation precipitation polymerization.Pd/PMAA microspheres containing a large number of palladium nanoparticles were prepared by in-situ reduction method after chelating palladium ions with abundant carboxylic acid on the surface.2.The prepared PMAA microspheres,polyvinylidene fluoride(PVDF)powder and pore-forming agent Poloxamer407(F127)were blended in solvent N,N-dimethyl formamide(DMF),and then heated and stirred to produce the dispersion.The PMAA-PVDF microcapsules were prepared by extruding and dropping the dispersion into coagulation bath with a syringe.The Pd/PMAA-PVDF microcapsule catalyst was prepared by in situ reduction method supported by palladium metal nanoparticles.3.The prepared PMAA microspheres,polyvinylidene fluoride(PVDF)powder and pore-forming agent F127 were blended in solvent N,N-dimethyl formamide(DMF),and then heated and stirred to produce the casting solution.PMAA-PVDF membrane was prepared by scraping the film with a film scraper and immersed in coagulation bath.The Pd/PMAA-PVDF membrane catalyst was prepared by in situ reduction method supported by palladium metal nanoparticles.The structures of the three catalysts were studied and applied to the catalytic oxidation of benzyl alcohol with water as solvent and hydrogen peroxide as oxidant to produce benzaldehyde.The experimental results show that the three catalysts have high catalytic activity and selectivity to benzaldehyde.After the reaction,the catalyst and the product are easy to be separated,and the byproducts are few.The reaction process is green,environmental friendly and pollution-free.