Synthesis Of Supported Transition-metal Phosphides And Hydrodesulfurization Network Of DBT On Bulk CoP

With continuous declining in quality of petroleum feedstocks and the stringent environmental legislation, people pay more and more attentions to develop novel catalysts for hydroprosessing. Transition metal phosphides have recently been the focus of research due to their high activity and stability. The temperature programmed reduction can be used to prepare the transition metal phosphides. Nevertheless, there are some obvious deficiencies. For example, the reaction has to reach a very high temperature, a big H2flow velocity and excess phosphorous is needed. The hydrogen plasma was used to sovle this problem and substitute the temperature programmed reduction.Bulk transition metal phosphides show a low HDS activities but supported transition-metal phosphides show a relatively high HDS actibities. So how to prepare the supported transition-metal phosphides more easily is the topices of recent researches. MCM-41were chosen for the carrier. The oxidic precursors, which were prepared in different ways, were reduced by hydrogen plasma. Two kinds of Supported transition-metal phosphides (Ni2P/MCM and CoP/MCM) were prepared in this way and then characterized by XRD and ICP. Hydrodesulfurization activities were studied at the fixed reactor. Because of the interaction during P and the carrier, we must add more P to prepare the supported transition-metal phosphides(MP/MCM-C) by co-impregnation method. Sequential-impregnation method can prevent the interaction and prepared the supported transition-metal phosphides(MP/MCM-S) stoichiometric. It was shown that the HDS activity of MP/MCM-S were higher than MP/MCM-C because of the excess P, which can affect HDS activity of supported transition-metal phosphides.A bulk CoP catalyst was prepared by co-precipitation of cobalt phosphate followed by hydrogen plasma(PR) with H2. The hydrodesulfurization(HDS) of dibenzothiophene(DBT) and its hydrogenated intermediates1,2,3,4-tetrahydro-dibenzothiophene(TH-DBT) and1,2,3,4,4a,9b-hexahydro-dibenzothiophene(HH-DBT) was studied at340℃and4MPa both in the presence and absence of piperidine(Pi). Bulk CoP exhibited a relatively high hydrogenation/dehydrogenation activity and high desulfurization activity. Pi retarded the hydrogenation of DBT to a greater extent than the desulfurization. A minor amount of dibenzothiophene(DBT) observed in the HDS of TH-DBT and HH-DBT is due to dehydrogenation of TH-DBT. We postulate a reaction network of the HDS of DBT over CoP catalysis.