Preparation Of Structure-controlled Copper Based Oxides/SAPO-34 Molecular Sieve And Its Catalytic Activity In Synthesis Of Light Olefins From CO₂ Hydrogenation

CO₂ utilization has recently become attractive due to the increasing concern on the effects of CO₂ accumulation in the atmosphere,and its potential as a source of carbon for synthesizing basic chemicals,polymer materials and green fuels.The catalysis of CO₂ with hydrogenation is of particular interest.Light olefins are particularly important in building blocks for chemicals and polymers,thus the development of efficient catalysts for CO₂hydrogenation to olefins is highly desirable,which could reduce both the CO₂ emission and the dependence of chemical production on the depleting fossil fuels.Therefore,composited catalysts of copper-based oxides and SAPO-34 molecular sieves were applied in conversion of CO₂ hydrogenation to light olefins in this thesis.The main contents were as follows:1.Supported methanol dehydration catalyst of（SAPO-34）-kaolin was prepared by hydrothermal method using kaolin as a low-cost material and triethylamine as template agent.The synthesized（SAPO-34）-kaolin was characterized by XRD,SEM,EDS,BET,H₂-TPR and NH₃-TPD techniques.The results show that the synthesized SAPO-34 molecular sieves were prepared by Si and Al of kaolin growing in situ at the surface of residual kaolin.（SAPO-34）-kaolin has good dispersity and relatively high crystallinity.CuO-ZnO/（SAPO-34）-kaolin was prepared through CuO-Zn O supported to the surface of（SAPO-34）-kaolin,which can be used for synthesis of light olefins from CO₂ hydrogenation.Under the condition of temperature at 673 K,pressure at 3.0 MPa,space velocity at 1800 mL×g^-1_cat×h^-1 and V（CO₂）/V（H₂）=1:3,the one-way conversion of CO₂ could reach up to43.5%,with a light olefins selectivity and yield of 63.8%and 27.8%,respectively.For a continuous performance as long as 8 h,the yield of light olefins is over 18.7%.2.SAPO-34 was prepared by temperature-programmed methods using kaolin as a low-cost material and triethylamine as template agent.The synthesized catalyst was characterized by XRD,SEM,EDS,BET,H₂-TPR,NH₃-TPD and FTIR techniques.The results show that the SAPO-34 molecular sieve has a lamellar structure with a thickness less than 100 nm.Through mixing SAPO-34 molecular sieve with kaolin-supported CuO-ZnO,the composited catalyst was prepared and was applied in direct synthesis of light olefins from CO₂ hydrogenation.Under the condition of temperature at 673 K,pressure at 3.0 MPa,space velocity at 1800 m L×g^-1_cat×h^-1 and V（CO₂）:V（H₂）=1:3,the one-way CO₂ conversion could reach up to 57.6%,with a light olefins selectivity and yield of 63.8%and 36.7%,respectively.3.Core-shell catalyst of（CuO-ZnO-Al₂O₃）@SAPO-34 was prepared by hydrothermal method using methanol synthesis catalyst of CuO-ZnO-Al₂O₃ as core and methanol dehydration catalyst of SAPO-34 molecular sieves as shell.The synthesized catalysts were characterized by XRD,SEM and TEM techniques.（CuO-ZnO-Al₂O₃）@SAPO-34 shows excellent catalytic activity in preparing light olefins from CO₂ hydrogenation.Under the condition of temperature at 673 K,pressure at 3.0 MPa,space velocity at 1800 m L×g^-1_cat×h^-1and V（CO₂）/V（H₂）=1:3,the one-way conversion of CO₂ could reach up to 49.2%,with a light olefins selectivity and yield of 45.7%and 22.5%,respectively.