Investigation Of Hydrodeslufurization Of The 4,6-DMDBT Over Mesoporous Zeolite Supported Ni₂P Or CoMo Catalysts

With the increasingly stringent environmental regulations,the high quality fuel is growingly demanded.In order to meet the ultra-low sulfur diesel production,the4,6-DMDBT in oil has to be removed.Currently,the sulfur in these fuels is removed by the hydrodesulfurization?HDS?of sulfur-containing compounds over conventional alumina-supported metal sulfide catalysts?Co?Ni?MoS/?-Al₂O₃?,However,it is difficult to remove 4,6-DMDBT over these catalysts under mild operating conditions,because of their insufficient hydrogenating ability.Therefore,it is crucial to developing HDS catalyst with high hydrogenation activity to remove 4,6-DMDBT under mild condition.In this thesis,we prepared supported Ni₂P and MoS₂ catalysts by use of the porous structure and surface properties of the mesoporous zeolite,which are examined by the HDS of the 4,6-DMDBT.The catalysts were characterized by using series of analysis techniques,such as BET,SEM,and so on,to investigate the effect of the porous structure and surface properties of the mesoporous zeolite on the morphology and dispersion of the Ni₂P and MoS₂ active phase.In chapter 2,mordenite nanosheet assemblies?NS-HMOR?with large external surface area and micro-mesoporous structure was prepared by hydrothermal synthesis method.The rich acidic surface hydroxyl groups and opening micropore structure of the NS-HMOR facilitate the formation of highly dispersed,active Ni₂P clusters?Ni₂P/NS-HMOR?.Compared with a silica-supported Ni₂P catalyst,the Ni₂P/NS-HMOR exhibit higher catalytic activity and better stability in the HDS of the4,6-DMDBT.In chapter 3,Ni₂P catalyst on mesoporous ZSM-5 zeolite?Ni₂P/MZSM-5-CA?was prepared by adding the citric acid into the impregnation solution containing nickel and phosphorus species.During the catalyst calcination,the CA-Ni?II?structure was destroyed and the released Ni²⁺species could interact strongly with MZSM-5 through surface acidic hydroxyl groups,leading to the formation of small Ni₂P particles with good dispersion under the reduction atmosphere.Compared with the Ni₂P catalyst prepared without CA,CA-assisted Ni₂P catalysts show high activity in the 4,6-DMDBT HDS and phenanthrene hydrogenation reactions.In chapter 4,the synthesized mesoporous TS-1 zeolite with high surface was used to prepare supported CoMo catalyst?CoMo/M-TS-1?.The suitable interaction between M-TS-1 and Mo species facilitate the formation of small octahedrally molybdenum oxide particles.And these Mo species are easily transformed into multi-stacked Type II MoS₂ active phases during sulfidation.Therefore,the CoMo/M-TS-1 shows much higher HDS activity for 4,6-DMDBT conversion than that conventional CoMo/?-Al₂O₃ catalyst.Based on the above research results,the effect of Ti species on the active phase morphology was further investigated by using mesoporous Silicalite-1 and SiO₂-TiO₂as support to prepare CoMo catalyst.Compared with CoMo/M-Silicalite-1 and CoMo/SiO₂-TiO₂ catalysts,the MoS₂ active phase with smaller stackings and shorter slab length were formed on the CoMo/M-TS-1 catalyst.According to the“Brim-Edge”model,the CoMo/M-TS-1 should expose more brim sites with hydrogenation activity than those of CoMo/M-Silicalite-1 and CoMo/SiO₂-TiO₂ catalysts,leading to the higher catalytic activity in the HDS of the 4,6-DMDBT.