Ni-CaO-CaZrO3 bi-functional materials for high purity hydrogen production via sorption enhanced steam reforming of ethanol

Abstract

Ethanol is an ideal hydrogen carrier, which can be converted to hydrogen-rich syn-gas via the steam reforming reaction. Sorption-enhanced steam reforming is a promising approach to produce high-purity hydrogen by mixing the sorbent and catalyst particles. The idea of bi-functional materials, loading both sorption and catalytic site in a single particle, could transform the inter-particle heat-mass transfer to intra-particle heat-mass transfer. This work studied the sorption-enhanced steam reforming of ethanol (SESRE) over Ni-CaO-CaZrO3 bi-functional catalysts containing sorption and catalytic sites. Bi-functional Ni-CaO-CaZrO3 catalysts were synthesized using a simple sol-gel technique. The influence of operating conditions including temperature, steam-to-carbon ratio (S/C) and weight hourly space velocity (WHSV) on Ni10-Ca90Zr10 bi-functional materials were discussed. The operating condition with a temperature of 600 °C, weight hourly space velocity of 0.34 h−1 and steam-to-carbon ratio of 3 was the most suitable reaction condition for hydrogen production in this study. Over the optimized operation conditions, the influence of Ni loadings on hydrogen production performance was further studied. The result indicated that 10 wt% is the best Ni loading in this study for Ni-CaO-CaZrO3, which enables >95% hydrogen purity in the gaseous product in the pre-breakthrough stage, with the longest breakthrough time (90 min). Furthermore, under the best operation conditions, the Ni10-Ca90Zr10 displayed excellent stability over 10 cyclic tests. In the 10th cycle, about 90% hydrogen purity was constantly obtained for at least 60 min during the pre-breakthrough stages. This study demonstrated that the Ni10-Ca90Zr10 bi-functional material is effective and stable for producing hydrogen from ethanol and has the potential to establish a method of generating clean energy with minimal carbon emission.