How to Overcome the Water-Gas-Shift Equilibrium using a Conventional Nickel Reformer Catalyst

Abstract

The catalytic water-gas-shift (WGS) reaction into hydrogen and carbon dioxide was investigated using a commercial nickel reformer catalyst. The effects of temperature, flow rate, and catalyst nature on the course of reaction were evaluated. Hydrogen and carbon dioxide were generated in the temperature range between 125 and 475 degrees C. A reaction scheme was used to explain the formation of methane. The WGS reaction and the methanation reaction (MTN) were used to calculate the equilibrium composition at these conditions. A commercial hydrotalcite-like sorbent arranged in a multilayer pattern of catalyst plus sorbent was used for carbon dioxide capture to enhance the WGS reaction. The performance of the catalyst was assessed by comparing the measured conversions, hydrogen yields, and selectivities at steady-state conditions with equilibrium values and with selected results reported recently, as well as conversions, hydrogen yields, and selectivities during the transient period as the hybrid system consisting of catalyst plus sorbent is arranged in a multilayer pattern system. The multilayer pattern system consisting of catalyst plus sorbent can easily overcome the thermodynamic restrictions of the WGS reaction at an operating temperature of 400 degrees C because of the enhanced sorption effect during the reaction process. In addition, lower flow rate regimes, and higher pressures and steam/carbon ratios increase the initial breakthrough period. This sorption-enhanced technique makes the use of Ni-based catalysts for the WGS reaction attractive, and suitable for the adjustment of the hydrogen ratio in synthesis gas streams.