Synthesis Gas To Light Olefins Over Iron-based Molecular Sieve-Supported Catalysts

Light olefins mainly refer to ethylene and propylene, which are very important organic chemical materials, and are key intermediates of various chemical materials such as synthetic plastic and chemical fiber material. Preparation of light olefins by catalystic conversion of synthesis gas is an essential way to realize the rational and optimized utilization of coal and natural gas resources in our country. Therefore, the direct conversion of synthesis gas to light olefin is of great academic and economic value.In this paper, supported iron-based catalysts were prepared firstly with silicon aluminium molecular sieve as the carrier, and influences of the catalytic perforance were examined. The catalysts were characterized by TG, BET, XRD, Raman, Pyridine-IR, XPS and the effects of parameters such as soaking orders, calcination temperature, calcination atmosphere, reaction temperature, reaction pressure and space velocity, on the reaction were investigated in a fixed-bed reactor.Secondly, using ZSM-5 as the carrier, the comparable catalytic performance of adding K and Mn promoters were studied. The results showed that Fe/ZSM-5,FeK/ZSM-5,FeMnK/ZSM-5 catalysts could exhibit the conversion of CO were 22.0%, 65.2%, 63.8% and the selectivity of C2=～C3= were 3.0%, 8.5%, 14.1%, respectively, under the conditions of H2/CO=2(V/V), 380℃, 1.0 MPa, 4400 h-1.Finally, preparation of supported iron-based catalysts with all-silicon molecular sieve and the effect of different iron content Fe/Si-1 catalysts catalystic propoerties were investigated. The best result was obtained over the catalyst with 18wt% iron, over which CO conversion and the selectivity of C2=～C3= reached 53.5% and 10.6%, respectively, under the conditions of H2/CO=2(V/V), 340℃, 1.0 MPa and 4400 h-1. The studied on different morphologies Fe/Si-2 catalysts, the results indicated that Fe/Si-2(a) and Fe/Si-2(b) catalysts the coversion of CO were 60.7%, 23.7% and the selectivity of C2=～C3= were 4.0%, 12.4%, respectively, under the conditions of H2/CO=2(V/V), 340℃, 1.0 MPa, 4400 h-1. Using Si-2(a) as the carrier, the comparable catalytic performance of adding K and Mn promoters were studied. The results showed that Fe/Si-2(a),FeK/Si-2(a),FeMnK/Si-2(a) catalysts could exhibit the conversion of CO were 67.1%, 39.0%, 34.0% and the selectivity of C2=～C3= were 3.0%, 11.4%, 10.8%, respectively, under the conditions of H2/CO=2(V/V), 380℃, 1.0 MPa, 4400 h-1.