Synthesis of Acid Free Benzaldehyde by Highly Selective Oxidation of Benzyl Alcohol Over Recyclable Supported Palladium Catalyst

Abstract

Aim and Objectives: This research work deals with the highly selective oxidation of benzyl alcohol to benzaldehyde by palladium doped graphene oxide catalyst which was synthesized by a modified Hummer’s method. The effect of reaction parameters like temperature, time and catalyst loading were studied. It was found that fine tuning of reaction temperature and presence of small amount of benzyl alcohol in product prevents undesirable formation of benzoic acid crystals which forms on auto oxidation of benzaldehyde. Benzoic acid or substituted benzoic acid formation was hindered by the presence of < 2% benzyl alcohol at a reaction temperature of 50˚C which was further supported by palladium doped graphene oxide catalyst. Materials and Methods: Modified Hummer’s method was used for the synthesis of graphene oxide and palladium doped graphene oxide was synthesized by insitu method in which graphene oxide dispersed in 20mL of distilled water was ultrasonicated for 2h. Palladium solution was added and it was further ultrasonicated for 30min for homogeneous deposition of palladium on graphene oxide support. To this, 2 mL of sodium borohydride solution was added and stirred at room temperature for 4h. The resulting solution was centrifuged and the residue was dried at 60°C for 12 h. Results: The morphological characteristics and the functional groups of supported catalyst were characterized by X-ray diffraction, Field emission scanning spectroscopy, Fourier transform infrared spectroscopy and the produced benzaldehyde was characterized by gas chromatography. Conclusion: PdGO catalyst was prepared using sodium borohydride as a reducing agent by modified Hummer’s method and utilized for the oxidation of benzyl alcohol to benzaldehyde. A maximum conversion of 89% and selectivity of 99% was obtained and the catalyst could be reused upto five times without any compromise on conversion and selectivity.