Preparation and application of coconut shell activated carbon immobilized palladium complexes

Abstract

Coconut shell activated carbon (CSAC) granules were used as carriers to immobilize palladium complexes. Boehm titration showed that the hydroxyl content of the carbon surface reached 0.376 mmol g⁻¹ after 20% HNO₃ treatment. Ethylenediamine, benzyl malononitrile and propyl malononitrile were successfully grafted onto the oxidized CSAC. The bidentate nitrogen ligands complexed Pd²⁺ samples were characterized by FT-IR, XPS, ICP and N₂ adsorption–desorption. In oxidative carbonylation of phenol, three bidentate ligand grafted catalysts were evaluated in a high pressure reaction vessel. The results showed that the ethylenediamine grafted catalyst had a phenol conversion of 12.06% and a diphenyl carbonate (DPC) selectivity of 91.03%. In comparison, the benzyl malononitrile grafted catalyst displayed a phenol conversion of 12.00% and a DPC selectivity of 90.65%. The propyl malononitrile grafted catalyst displayed a phenol conversion of 6.22% and a DPC selectivity of 81.02%. Additionally, the ethylenediamine and the benzyl malononitrile grafted catalysts were also investigated in a continuous packed-bed reactor. The results showed that the phenol conversion and the DPC selectivity were comparative to those obtained in a high pressure reaction vessel.