The Influence Of Support On Hydrodesulfurization Of Dibenzothiophene Over Ni₂P

As a new kind of catalyst,transition metal phosphides have showed excellent activity and stability for hydrodesulfurization(HDS).In this paper,SiO2,macromesoporous Al2O3(mAl2O3)and cerium oxide-modified Al2O3(Ce-Al2O3)were used as carriers,and the supported nickel phosphides(Ni2P)were prepared by programmed temperature reduction(TPR)of supported nickel phosphate precurs.Dibenzothiophene(DBT)and its hydrogenated intermediates,including tetrahydro-dibenzothiophene(TH-DBT),hexahydrodibenzothiophene(HH-DBT)were used as the model sulfur-containing compounds in the HDS.Based on the HDS result,reaction mechanisms were studied.And we also used gassline as the reactant to test the desulfurization performance of the three catalysts.The intrinsic HDS activities of the Ni2P/SiO2 was higher than that of Ni2P/m-Al2O3 and Ni2P/Ce-Al2O3.DBT were mainly desulfurization by the direct desulfurization(DDS)path.The Ni2P/SiO2 also had high hydrogenation activity.In the presence of sulfur compounds,benzene(BP)and cyclohexyl benzene(CHB)could be further hydrogenation,to generate CHB and cyclohexane(BCH)respectively.Piperidine inhibited the HDS activity of Ni2P/SiO2 on DBT and its hydrogenated intermediates,and had a stronger inhibitory effect on the hydrogenation(HYD)pathway.The HDS reaction activity of DBT over Ni2P/m-Al2O3 was lower than that of Ni2P/SiO2,but the desulfurization performance of gasoline was the highest.The HDS of DBT over Ni2P/mAl2O3 also occurred predominantly through the DDS pathway.The hydrogenation activity of Ni2P/m-Al2O3 was very low,and neither BP nor CHB could have any further hydrogenation reaction.The degree of inhibition of piperidine in the direct desulfurization of DBT,TH-DBT and HH-DBT was almost similar,and piperidine strongly inhibited the hydrogenation of PCHE and the transformation between TH-DBT and HH-DBT.The HDS reaction activity of DBT over Ni2P/Ce-Al2O3 was higher than that of over Ni2P/m-Al2O3,and it has better hydrogenation/dehydrogenation performance.The reaction path of DBT was mainly DDS.In the presence of sulfur compounds,BP could further hydrogenate to CHB over Ni2P/Ce-Al2O3,but the hydrogenation activity was much lower than that of Ni2P/SiO2.TH-DBT could dehydrogenae to DBT over Ni2P/Ce-Al2O3.And piperidine had a stronger inhibitory effect on the hydrogenation.Three isomers of phenyl cyclohexenes(PCHEs)which are 1-PCHE,3-PCHE and 4-PCHE were detected in the HDS reaction products of TH-DBT and HH-DBT,suggesting that DBT and TH-DBT underwent desulfurization mainly through hydrogenolysis,while the desulfrizaiton of HH-DBT occurred mainly through by a β-elimination mechanism.