Effect of Ni-Co addition on Pd promoted Al2O3 catalysts for dry reforming of methane

Abstract

This study investigates the effectiveness of x Ni – (5 – x) Co / 5 Pd – Al2O3 (where x=0, 1.25, 2.5, 3.75, and 5) bimetallic catalysts and the influence of the Pd on their activity in the dry reforming of methane. Comprehensive characterization techniques including XRD, TPR, TPD, SEM, TGA, and Raman analysis are employed to examine the catalysts. XRD analysis of the calcined catalysts reveals the presence of multiple oxides such as NiO, CoO, Co3O4, and PdO. The metal-support interaction and the particle sintering of the catalysts depend on the amount of Co loading, for higher Co loadings (> 2.5 wt%) resulted in weakened metal-support interaction as indicated by TPR analysis. Also, the particle sintering was observed with an increase in Co loading observed from SEM and TEM analysis. The activity analysis demonstrates that the 5 Ni / 5 Pd – Al2O3 catalysts exhibit superior performance in terms of both CH4 (59%) and CO2 (64%) conversions, as well as stability, compared to the Ni-Co bimetallic catalyst. The addition of Co leads to decreased activity, Furthermore, TGA analysis indicates minimal carbon deposition on the 5 Ni / 5 Pd – Al2O3 catalyst during the 7-hour activity study. Notably, Raman analysis reveals a lower presence of graphitic carbon on the catalyst, which contributes to its stable catalytic activity. The presence of Pd in the 5 Ni catalyst reduces carbon deposition and enhances its activity. However, in the case of the Ni-Co bimetallic catalyst, the promotional effect of Pd appears to be negligible. Overall, these findings emphasize the promising potential of the 5 Ni / 5 Pd – Al2O3 catalyst for efficient and stable dry reforming of methane.