Effect of steam on cobalt–calcium catalyzed coal hydrogasification

Abstract

Catalytic hydrogasification (C + H2 → CH4) is an efficient process for methane production from coal. To reduce reactant hydrogen cost, cheap crude gas from coal gasifier without further treatment is proposed to replace hydrogen for the process. In this study, the effect of steam in crude gas on CoCa bimetal catalyzed coal hydrogasification was investigated using H2 and steam mixtures (H2 + steam) in a fluidized bed reactor, with 5% to 30% steam addition. The result demonstrated that the product distribution in H2 + steam was determined by coupled reactions of hydrogasification and steam gasification. A 95.1% carbon conversion with a 68.8% CH4 selectivity was achieved in H2 + 10% steam at 900 °C and 4 MPa. The reaction heat released by hydrogasification can be in situ absorbed through steam gasification, realizing heat utilization in H2 + steam. CoCa exhibited activity for both the reactions. However, the presence of steam significantly inhibited CoCa activity toward hydrogasification. The inhibition mechanism was that the preferentially adsorbed H2O, OH, and O species on cobalt surface blocked the dissociative adsorption of H2 molecules. The study provides an insight for developing an inexpensive and effective process for coal to clean fuels.