Hydrogen production by steam reforming of methane over hollow, bulk, and co-precipitated Ni–Ce–Al2O3 catalysts: Optimization via design of experiments

Abstract

In this research, three different structures of Ni–Ce/Al2O3 catalysts are synthesized, characterized, and tested in the steam reforming of methane (SRM) process for the first-time using response surface method (RSM) based on optimal custom for examining the SRM operating conditions. Independent variables listed as Ce content (0, 1.5, 3.0 wt%), Ni content (5, 15, 25 wt%), steam to carbon (S/C) molar ratio (1.5, 2.5, 3.5), SRM temperature (600, 650, 700 °C), and catalyst structure (bulk, hollow, and co-precipitated) are selected for investigation and optimization of CH4 conversion and H2 yield. Among several suggested optimized solutions in the design expert, hollow 17.70Ni-1.93Ce/Al2O3 catalyst is the best choice depicting the highest activity at lower operating conditions. The stability of optimized catalysts in different structures are compared experimentally at their optimized temperature and S/C ratio after being characterized via different techniques. The used samples are also characterized for evaluating the structural change and amount of deposited carbon on their surfaces after 12h time-on-stream. It is observed that hollow 17.70Ni-1.93Ce/Al2O3 has not only the highest CH4 conversion of 92.14% and H2 yield of 94.20% at 676 °C, but also depicts the highest stability which may due to its higher oxygen storage capacity (OSC) that prevents the accumulation of carbon on its surface.