Transition-Metal Phosphide(Phosphosulfide) Hydrogen Evolution And Hydrotreating Catalysts

This paper mainly includes two parts.The effects of cerium oxide additive on Mo P catalysts structure,hydrodenitrification（HDN）of quinoline,hydrodesulfurization（HDS）of dibenzothiophene（DBT）and electrochemical hydrogen evolution（HER）reactions under acidic conditions were studied.In the preparation of catalysts,the method of preparing transition-metal phosphosulfide with thiourea as solid sulfur source was developed,and the transition-metal phosphide（phosphosulfide）compound were also prepared by pyrolysis ZIF materials.The following conclusions are drawn:（1）Mo P and Ce-Mo P（x）（x is Ce/Mo molar ratio）catalysts were prepared by introducing auxiliaries.The addition of cerium oxide significantly improved the adsorption strength and adsorption capacity of H₂ on Mo P.On Mo P and Ce-Mo P（x）catalysts,the HDS reaction of DBT was positively correlated with HER reaction activity,but the HDN reaction of quinoline was negatively correlated with HER reaction.The HDS and HER reactivity of Mo P catalyst decreased with the increase of Ce/Mo molar ratio.On the contrary,the addition of cerium oxide significantly improved the HDN activity of Mo P,and the best Ce/Mo molar ratio was 0.4.The possible reason is that the strong adsorption of H₂ on the active site inhibits the reaction activity of HER and HDS on Ce-Mo P（x）catalyst.However,the HDN reaction of quinoline is structure-sensitive,so the structure of catalyst is an important factor affecting its HDN activity.（2）A new method what is simple,safe and cheap was developed for the preparation of transition-metal phosphosulfide by temperature-programmed reduction using thiourea as solid sulfur source and transition-metal phosphate as precursor.The reactivity of phosphosulfide HER prepared with thiourea in acidic condition was higher than that of transition-metal phosphide without sulfur.The HER reactivity of group VIB Mo and W phosphide and phosphosulfide was higher than that of Group VIII Ni and Co phosphide and phosphosulfide.WP phosphosulfide prepared by this method has the highest HER activity among the catalysts studied in this paper.（3）Co₂P-ZIF and Ni₂P-ZIF catalysts containing impurities were prepared with ZIF-67and ZIF-Ni materials as precursors and red phosphorus as phosphorus source in Ar atmosphere.The HER activity of Co₂P-ZIF and Ni₂P-ZIF catalysts were significantly higher than that of Co₂P and Ni₂P catalysts prepared by temperature-programmed reduction method.HER activity of Co₂P-ZIF decreased after being sulfuretted with dimethyl disulfide（C₂H₆S₂）and thiourea.However,HER activity of Ni₂P-ZIF increased after sulfur with C₂H₆S₂ as sulfurizing agent.