Study On Preparation And Properties Of Catalysts For Synthesis Of Ethylene Oligomerization To α-Olefins

In this paper,the key technical problems was the preparation of catalysts for synthesis of ethylene oligomerization to a-olefins.The mesoporous ZSM-5 molecular sieve which was prepared by hydro-thermal synthesis method,which is used as the carrier,and then synthesizing Ni-HZSM-5,Cr-HZSM-5 and Ni/Cr-HZSM-5 catalysts to analyze differernt reactive metal which affects the performance of ethylene oligomerization.The physicochemical properties of catalysts were characterized by XRD,FT-IR,SEM-EDX,TEM,BET and UV-vis methods.The reaction temperature,metal content and space velocity were discussed to obtain the best catalytic activity.The reaults ware as follows:(1)The mesoporous ZSM-5 molecular sieve was prepared by hydrothermal synthesis method and the Ni-HZSM-5 catalyst was synthesized by ion exchange to modify ZSM-5.The results of XRD,FT-IR,SEM-EDX,TEM,BET and UV-vis indicated that Ni-HZSM-5 possessed the typical structure of mesoporous molecular sieve,large specific surface area and pore diameter.That the Ni species were present in the molecular sieve in both four ligands and eight ligands.Then the catalytic performance for ethylene oligimerization was investigated under optimal reaction conditions:reaction temperature(275 ℃),0.06Ni-HZSM-5 catalyst,GHSV(1.2 L/h).The ethylene conversion was up to 87.82%,and the selectivity of C3,C4,C5 and C6 was up to 3.38%,57.25%,8.63%and 30.74%,respectively.(2)The Cr-HZSM-5 catalyst was synthesized by ion exchange to modify ZSM-5.The results of XRD,FT-IR,SEM-EDX,TEM,BET and UV-vis indicated that Cr-HZSM-5 possessed the typical structure of mesoporous molecular sieve,large specific surface area and pore diameter.That the Cr species exist in the molecular sieve at four ligands.The catalytic performances for ethylene oligimerization was investigated under optimal reaction conditions:reaction temperature(275 ℃),0.06Cr-HZSM-5 catalyst,GHSV(1.2 L/h).The ethylene conversion was up to 83.22%,and the selectivity of C3,C4,C5 and C6 was up to 2.88%,48.68%,9.23%,39.21%,respectively.(3)The bi-metal Ni/Cr-HZSM-5 catalyst was synthesized by ion exchange to modify ZSM-5.The results of XRD,FT-IR,SEM-EDX,TEM and BET indicated that bi-metal catalyst possessed the typical structure of mesoporous molecular sieve.The catalytic performance for ethylene oligimerization was investigated under optimal reaction conditions:reaction temperature(275 ℃),0.05Ni/0.03Cr-HZSM-5 catalyst,GHSV(1.2 L/h).The ethylene conversion was up to 84.53%,and the selectivity of C3,C4,C5 and C6 was up to 3.51%,54.69%,7.93%,33.87%,respectively.