Selective CO Methanation Over Ru Supported on Carbon Spheres: The Effect of Carbon Functionalization on the Reverse Water Gas Shift Reaction

Abstract

Mesoporous carbon spheres (CSs-H) were hydrothermally synthesised using sugar as carbon source. The as-synthesized CSs-H was microporous but after thermal treatment at 900 °C for 4 h it became mesoporous (surface area of 463 m2 g−1). Further treatment of the annealed CSs-H with HNO3 gave a functionalized CSs-H with a high defect content in the carbon matrix which resulted in an increase in surface area (509 m2 g−1). The functionalized and un-functionalized CSs-H were used to support nano Ru particles for CO, CO2 and selective CO methanation reactions. The Ru supported catalysts were prepared using both impregnation and microwave polyol synthesis methods. It was evident from the reduction studies that the functional groups on the surface of the CSs-H influenced the reduction of the RuO2 to Ru. The catalyst with smaller and well dispersed RuO2 particles (d = 2.7 nm) (prepared by the microwave polyol technique) gave a high activity in both CO and selective CO methanation studies. The larger Ru particles observed on the un-functionalized CSs-H showed poor activity for CO and selective CO methanation reactions and also did not promote the reverse water gas shift reaction.