CO2 reforming of methane over MCM-41-supported nickel catalysts: altering support acidity by one-pot synthesis at room temperature

Abstract

Highly structured neat MCM-41, Na-form, and Al-incorporated MCM-41 mesoporous materials were synthesized using a simple, one-pot procedure at room temperature. The neat MCM-41 material possessed a surface area comparable with other MCM-41 materials prepared using more conventional higher temperature methods. Incorporating Al into the MCM-41 framework increased support acidity while entrapping Na ions in the MCM-41 pores lowered acidity. The neat MCM-41, Na-form, and Al-incorporated MCM-41 were impregnated with 2.5, 5 and 10% Ni and catalytic performance was assessed for CO2 reforming of methane (CH4). XRD, TEM and H2-TPR indicated at low loadings the Ni was highly dispersed on the support, whereby increasing the Ni loading encouraged the formation of larger Ni crystals on the external MCM-41 surface. 2.5% Ni catalysts supported on neat MCM-41 exhibited excellent catalytic activity invoking up to 98% CH4 conversion at 800°C and 26% at 500°C. Carbon accumulation on the catalyst was greater at higher Ni loadings although this was not to the detriment of activity over the reaction time-frame. This result coupled with variations in the H2/CO product ratio and CH4/CO2 conversion difference suggested increasing the Ni loading promoted the Boudouard, CH4 cracking and reverse water gas shift side reactions. Incorporating the MCM-41 with either Al or Na lowered catalyst performance with the promoters found to enhance or suppress the side reactions to varying degrees.