Steam reforming of ethanol over mesoporous Rh/CeZrO2: Mechanistic evaluation using in situ DRIFT spectroscopy

Abstract

AbstractMesoporous CeZrO2 support was prepared by a homogeneous urea coprecipitation route and loaded with 0.05 g/g (5 wt%) Rh2O3 to prepare supported Rh/CeZrO2 catalyst. The mesoporous nature of the catalyst was confirmed by N2 adsorption‐desorption studies, which revealed a type IV isotherm with a characteristic H2 hysteresis. Rh impregnation led to a decrease in the BET surface area and an increase in the CO uptake, as established by pulse chemisorption studies. Temperature‐programmed reduction (TPR) studies revealed significant alteration in the reducibility of the support due to introduction of the active metal. Catalytic ethanol steam reforming (ESR) over the supported catalyst was performed in a tubular microreactor under varying temperatures and space velocities at a constant ethanol‐to‐water ratio of 1:6. Increasing the temperature was found to positively influence both the conversion and hydrogen selectivity. Mesoporous Rh/CeZrO2 catalyst exhibited almost complete ethanol conversion and 62.9 % H2 selectivity at 600 °C and 0.3 mL · min−1 flow rate. The nature of intermediate species and products formed during ethanol steam reforming was established using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), which brought out the significant role of Rh toward aiding ethanol decomposition. Based on these studies, a plausible mechanism for catalytic ethanol steam reforming over Rh/CeZrO2 was proposed. Time‐on‐stream studies revealed the excellent stability of the catalyst over extended periods. Detailed investigations of the spent catalyst revealed the amorphous nature of coke formed on the surface of the catalyst post‐reforming.