The role of various preparation techniques and nickel loadings in ethanol steam reforming over mesoporous nanostructured Ni–Al2O3 catalysts

Abstract

This study involved the preparation of Al2O3 support and Ni/Al2O3 catalysts through different methods such as mechanochemical, impregnation, and co-precipitation. These prepared samples were then assessed for their performance in the ethanol steam reforming (ESR) process. The results indicated that the 10Ni/Al2O3 catalyst, which was created using the impregnation method and exhibited a high BET surface area of 200.8 m2/g along with well-dispersed nickel, displayed exceptional performance in the ethanol steam reforming reaction. When compared to other catalysts, it exhibited greater activity and stability. A series of Ni/Al2O3 catalysts were prepared with nickel contents ranging from 2.5 to 20 wt%. The study showed that increasing the amount of nickel from 2.5 to 12.5 wt% led to a boost in the catalysts' ability to be reduced, which in turn resulted in improved catalytic performance. However, increasing the nickel content beyond 12.5 wt% led to a decline in catalytic performance. This decrease could be attributed to weaker Ni–Al2O3 interactions, an increase in particle size from 2.7 to 7.8 nm, and a significant reduction in the BET surface area from 198.3 m2/g to 166.4 m2/g. Temperature-programmed oxidation (TPO) profiles revealed that the carbon deposits on the catalyst's surface exhibited a whisker-like structure, and higher nickel contents correlated with increased oxidation peak temperatures and intensities. Moreover, the 12.5Ni/Al2O3 catalyst demonstrated remarkable stability over a 550-min reaction period. The study's findings indicated that as the Tcal. rose from 500 to 700 °C, the catalytic activity gradually lessened. The 12.5Ni/Al2O3 catalyst calcined at 500 °C, characterized by a small particle size and moderate Ni–Al2O3 interaction, exhibited the most favorable catalytic activity.