Catalytic hydrodechlorination reaction of chlorophenols by Pd nanoparticles supported on graphene

Chlorophenols are widely used as industrial chemicals such as herbicides, insecticides, wood preservatives, and disinfectants. However, chlorophenols are very toxic materials and they have become the cause of current environmental issues. Hydrodechlorination (HDC) reaction is a more environmentally friendly removal method of chlorophenols than other methods. In this paper, Pd–modified graphene was prepared and applied to HDC reaction. Pd supported on graphene (refer to Pd/G) was prepared using the recently reported microwave irradiation method. The Pd(II)/GO was made by impregnation methods of palladium precursors in solution phase and was subsequently reduced to Pd/G by microwave irradiation. The morphological and chemical structure of the Pd/G was characterized by XRD, SEM, ICP-MS, EDS, and TEM. It was found that the graphene-based Pd catalyst showed the highest catalytic performance among Pd/Y, Pd/MCM-41, and Pd/G catalysts. This is attributed to the smaller particle size and higher dispersions of Pd nanoparticles on the graphene surface. The catalytic HDC of chlorophenols was investigated. For HDC reaction, 100 ppm solution of chlorophenols such as 4-chlorophenol, six isomers of dichlorophenol, and 2,3,5-trichlorophenol in isopropanol was treated with catalyst and base, such as Na2CO3 and K2CO3, under a hydrogen gas at ambient pressure. The progress of the chlorophenol decomposition was analyzed with GC. All chlorophenols were completely decomposed within 2 h in the 3 % Pd/G catalyst. The reaction pathway of chlorophenols was elucidated from the conversion of chlorophenols and selectivities of products. The reuse of the catalyst was also studied. The performance of the recycled catalyst in HDC reaction up to six successive runs was observed.