Effect of in-situ carbon dioxide sorption on methane reforming by nickel-calcium composite catalyst for hydrogen production

Abstract

Hydrogen production plays an important role in hydrogen energy development. The steam reforming reaction is an efficiency way for hydrogen production via thermochemical method. But the hydrogen concentration was limited to be about 70% because of thermodynamic equilibrium. In order to avoid equilibrium limiting, the by-product CO2 removal during reaction was a suitable solution that drives the reaction to the right. In this study, the steam reforming of methane by in-situ CO2 sorption was investigated. The CaO material was used as CO2 acceptor because of its high capacity, fast kinetics and generality. The reforming catalysts were prepared by simple physical mixing of the 20 wt.% Ni/Al2O3 catalyst and CaO sorbents. The steam reforming of methane experiments was carried out by a fixed bed reactor. The experimental results indicate that the steam reforming of methane via in-situ CO2 sorption obviously obtained the H2 purity above 95% higher than conventional reaction without in-situ CO2 removal (~72% H2). The impurities involving CO and CO2 during reaction were suppressed below 0.5% before CO2 sorbent saturation. In this work, the highest H2 purity and CH4 conversion were founded to be 98.4% and 95% at 873K under steam/carbon ratio of four conditions. The methane steam reforming with high conversion strongly depended on the CO2 capture performance. The cause was attributed to the equilibrium limiting of reaction overcoming by in-situ CO2 sorption. It is also found that the product components and methane conversion was insignificantly affected in the range of space velocity from 7200 to 19200 cm3/hr/g.