Hydrogen generation from ethanol by steam reforming using a Rh catalyst supported over low acidic Al2O3

Abstract

In this paper, we have studied the effect of the synthesis method on the acidity of alumina (Al2O3) support using NH3 chemisorption and impregnated Rh on the Al2O3 support having lower acidity to yield Rh/Al2O3 catalyst. These materials were characterized using different physico-chemical techniques such as BET, XRD, SEM–EDS, TPR, CO pulse chemisorption, and TPO reactions. The performance of the Rh/Al2O3 catalyst was evaluated in catalytic ESR reaction at varying temperatures and space velocities. Our studies revealed that the Rh/Al2O3 catalyst is capable of breaking the C–C bond with a complete elimination of C2 compounds, particularly ethylene in the exit product stream with high H2 yield under the reaction conditions applied. Furthermore, the nature of intermediate species and products formed during catalytic ESR conditions was identified using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), which revealed that both the acetate driven and formate driven mechanism of ESR prevail over the surface of the prepared catalyst. In view of the absence of ethylene in the product stream as well as in the DRIFT study, it was concluded that due to the inherent lower acidity of the alumina support, ethanol molecules prefer the dehydrogenation route over dehydration. DRIFT studies also brought out the significant role of Rh towards aiding ethanol decomposition. Based on these studies, a plausible mechanism for catalytic ESR reaction over Rh/Al2O3 has been proposed. Time-on-stream studies revealed the good stability of the catalyst over extended periods (~20 h).