Catalyst Screening and Kinetic Modeling for CO Production by High Pressure and Temperature Reverse Water Gas Shift for Fischer-Tropsch Applications

In this work, catalyst screening and reaction kinetic modeling are performed for two Ni-based and one Rh-based commercial catalysts for a reverse water gas shift (rWGS) reaction under atmospheric and 30 bar_a pressure. Ni-based catalysts displayed higher activity compared to Rh-based catalysts despite the severe initial deactivation Ni-based catalysts suffered, which increases catalyst selectivity toward CO formation. Ni/Al₂O₃ catalyst with lower Ni content (2 w-%) exhibited higher selectivity toward CO formation compared to the Ni/Al₂O₃ catalyst with higher Ni content (15 wt %). The Ni/Al₂O₃ (2 wt % of Ni) catalyst was further tested for kinetic modeling. Three kinetic models were developed based on reaction mechanisms and kinetic models obtained from other publications for rWGS/WGS, methanation, and methane steam reforming reactions based on different mechanistic approaches. The model based on mechanistic assumptions originally proposed by Xu and Froment was concluded to be the most suitable to describe the high temperature reaction system of the rWGS and methanation over supported nickel catalyst. On the basis of statistical analysis, the model proposed by Xu and Froment was also concluded to be the best for the catalyst and reaction system studied in this work.