Study On Spinel Composite Oxide Catalysts For Ethane Oxychlorination

Polyvinyl chloride(PVC)is a general-purpose material with great demand in construction,agriculture,automobile manufacturing industry and national defense etc.worldwide every year.PVC is usually polymerized from vinyl chloride monomer(VCM).Generally,there are three processes for producing VCM:acetylene hydrochlorination,ethylene oxychlorination and ethane oxychlorination.Among them,the ethane oxychlorination is a novel,environmentally friendly and cheap method to produce VCM for PVC industry dues to the ethane is cheap and could easy to get from coal chemistry industry.One of the key factors to realize ethane oxychlorination is the lack of efficient and stable catalysts.Therefore,the development of catalysts for ethane oxychlorination has great research value.In this paper,the catalytic performance of spinel oxide catalyst for ethane oxychlorination to vinyl chloride was studied.Three main research works have been carried out around catalysts.(1)The research for the catalytic performance of CuB2O4(B = Fe,Al,Cr and Mn)catalysts with different B-site cation composition for ethane oxychlorination was conducted.The results showed that CuCr204 exhibits the best selectivity of C2H3C1(42.91%)with a conversion of C2H6(84.85%),which can be attributed to the tetragonal crystal structure and good crystallinity of CuCr2O4.(2)The study for the catalytic properties of Cu1-xMgxCr2O4 catalyst modified by Mg2+ at the tetrahedral site and CuCr2-xFexo4(x = 0,0.2,0.4,0.6,0.8,and 1.0)catalyst modified by Fe3+ at the octahedral site were investigated,respectively.The results showed that Mg2+ doped Cu1-xMgxCr2O4 catalysts were more effective and active for ethane oxychlorination than CuCr2-xFexO4 catalysts.The C2H3C1 selectivity and C2H6 conversion of Cu0.6Mg0.4Cr2O4 catalyst are 50.21%and 95.63%,respectively.It could be attributed to the diffraction plane change from the original CuCr2O4(020)plane to the Cu0.6Mg0.4Cr2O4(121)due to the addition of Mg2+.The theoretical simulation results of the adsorption configuration of C2H6,C2H3Cl and C2H4 on(020)and(121)crystal planes showed that Co0.6Mg0.4Cr2O4 catalyst would enhance the adsorption ability of the crystal(121)plane to C2H6,C2H3C1 and C2H4.C2H3C1 is preferentially desorbed in the conversion of reactant C2H6 on the(121)plane.It is evidence the difference of electron density between C2H3Cl and C2H4 on the planes contributes to the improvement of the C2H3Cl selectivity of Cu0.6Mg0.4Cr2O4 catalyst.(3)The research for the catalytic behavior of 5wt%assistant/Cu0.6Mg0.4Cr2O4(assistant = ZrO2,CeO2 and Mn2O3)modified by oxide additives for ethane oxychlorination was carried out.The results showed that 5wt%CeO2/Cu0.6Mg0.4Cr2O4 exhibited the best catalytic activity,the selectivity of C2H3Cl is 70.49%and the conversion of C2H6 is 99.98%,respectively.It is obviously that the addition of Ce02 additives improved the selectivity of C2H3C1,compared with Cu0.6Mg0.4Cr2O4.It could be attributed that the addition of CeO2 promoter not only makes the reduction peak of Cu(?)? Cu(?)move to the low temperature zone,but also makes the 5wt%CeO2/Cu0.6Mg0.4CrO4 catalyst have the best oxygen species migration characteristics.In addition the increases of the Cu2+ in the low binding energy orbit(Cu 2p3/2)and the lattice oxygen O? content were also occurred in the 5wt%CeO2/Cu0.6Mg0.4CrO4 catalyst due to the supported CeO2 promoter.