Steam reforming of ethanol over cerium-promoted Ni-Mg-Al hydrotalcite catalysts

Abstract

Ethanol steam reforming (ESR) was carried out with very high hydrogen yield over a series of Ce-promoted Ni-Mg-Al hydrotalcite type catalysts. The catalysts were prepared by simultaneous co-precipitation followed by wet impregnation and characterized by XRD, FESEM, EDS, BET and TPR techniques. The ESR activity of the prepared catalyst was assessed in terms of ethanol conversion and hydrogen yield. The catalyst activity as well as distribution of products was observed to vary with cerium loading in the catalyst and the reaction conditions. Catalyst containing 10% Ce showed good activity and stability for longer period of time. A complete process developmental study was performed with the best catalyst by varying three important process parameters, namely reaction temperature (500°C–600°C), feed steam to ethanol ratio (3:1–10:1) and space-time (11.02–44.08kg catalyst h per kmol of ethanol fed). The catalyst was found to be active within the range of parameters studied at atmospheric pressure. However, the most favourable reaction conditions were established at 540°C with steam/EtOH molar ratio of 9 and space-time of 22.04kg cat h/kmol of ethanol fed. Under the optimum condition, about 97% conversion of ethanol was obtained with a hydrogen yield of 4.13mol of hydrogen per mole of ethanol reacted. The space-time–conversion data in the temperature range of 450–550°C were fitted into a power-law model and the activation energy of the ESR reaction was determined to be 54.53kJ/mol.