Preparation of Highly Active Co-Mo HDS Catalysts by the Addition of Citric Acid as a Chelating Agent

摘要

Co-Mo/Al2O3 and Co-Mo/B2O3/Al2O3 catalysts were prepared by a post-treatment of the calcined states with citric acid (CA) and were tested for the HDS reaction of thiophene. The catalysts were characterized by LRS, UV-visible spectroscopy, Mo K-edge EXAFS, TEM, and NO adsorption capacity. Simultaneous impregnation catalysts with citric acid were also prepared for comparison. Sulfided catalysts were characterized by a chemical vapor deposition (CVD) technique using Co(CO)3NO. The addition of citric acid by a post-treatment more effectively increases the catalytic activity and NO adsorption capacity than by a simultaneous impregnation method. Co-CA and Mo-CA surface complexes are formed at the expense of CoMoO4 and polymolybdates. The maximum potential activity of Co-Mo/B2O3/Al2O3 is obtained by a simple post-treatment of the calcined catalyst with citric acid.