Chemical Looping Tar reforming with Fe,Sr-doped La2Zr2O7 pyrochlore supported on ZrO2

Chemical Looping Reforming (CLR) has been proposed as a new technology for tar removal from hot raw gas derived from biomass gasification. In this two-reactor fluidized bed process at atmospheric pressure, the bed material is circulating between a reformer, in which the bed material is in contact with the raw synthesis gas, and a regenerator, in which the bed material is regenerated by oxidizing coke deposits and sulfides with air. In this study Fe,Sr-doped La2Zr2O7 pyrochlores supported on ZrO2 with different Fe and Sr loadings were investigated for their use as a catalyst in CLR. By decreasing the Fe loading to Fe/La = 0.25 the benzene-to-syngas conversion could be improved by about 50% at T = 800 degrees C in comparison with the reference material with Fe/La = 1.25. With this material, benzene and ethylene conversion could be further improved by co-feeding O-2 with the gasification gas, achieving a benzene conversion of up to 80% and an ethylene conversion of about 95% at a temperature of 850 degrees C and a Gas Hourly Space Velocity of 6800 h(-1). The performance of the bed material was found stable over at least 3 redox cycles. Considering the expected lower costs and non-toxicity of this material compared to precious metal- and Nickel-containing catalysts, normally used in fixed-bed systems, it is a promising material for a fluidized CLR system for tar removal.