The Research Of Ethylene Oligomerization Performance On Supported Molecular Sieve Catalysts

The industrial synthesis of a-olefins is generally performed via oligomerization of ethylene. A broad variety of α-olefins find key uses as intermediates in the synthesis of co-monomers for the production LDPE, surface-active compounds, PAO, lubricants oils, plasticizers and so on. Ethylene oligomerization processes can tentatively be subdivided into selective and statistical ones which almost use homogenous catalysis system. Compared to homogenous catalysts, the molecular sieve catalysts has the advantages that the operating pressure is in a low level, the catalyst is easy to regenerate and depart from products and so on. Thus heterogenous catalyst is becoming a central issue in ethylene oligomerization.MCM-36molecular sieve with MWW characteristic is made by swelling and subsequent pillaring of MCM-22(P) in hydrothermal environment with non-nitrogen and characterized by XRD,BET,FTIR,TEM, NMR,Py-FTIR, ICP and so on. The prepared samples derived from the high Si/Al ratio layered MCM-22(P) zeolite show good characteristic of MCM-36which has a dual system of pores with mesopores in the interlayer space and micropores inside layers, by using tetramethylammonium silicate as the pillaring agent, swelling24h at80℃and pillaring24h at100℃, and m(CTMAB)/m(MCM-22(P)) at the ratio of2. The resulting pillared materials show good preservation of the layer and pore structure of MWW and have improved BET specific surface area(472m2g-1), pore volume(0.72cm3g-1) and pore radius(2.0nm), compared to the MCM-22zeolite. The aluminum of MCM-36is due to the framework aluminum.Besides, the strong Lewis acid increases significantly after Ni2+and Cr3+supported.MCM-36molecular sieve supported active meatal iron is tested in the ethylene oligomeriza-tion reaction performed in fixed-bed micro-reactor. Results indicate that the Ni supported catalysts show most excellent activity(668g-(kgCat·h)-1) and a-olefins selectivity(33.37%) compared to CrMCM-36and HMCM-36, at the conditions of0.3wt%Ni loading,250℃of temperature,3MPa of pressure and2h-1of WHSV after4h reaction. And the oligomers are the C4～C16olefins most. And NiMCM-36is active and has optimum a-olefins selectivity among Ni-ZSM-5, Ni-AlMCM-41and Ni-MCM-22.