Effect of a titania covering on CNTS as support for the Ru catalysed selective CO methanation

One of the major set-backs in the selective CO methanation process, as the final clean-up step in removing residual CO from reformate gas feed, is the reverse water gas shift (RWGS) reaction. This reaction is an undesired reaction because, it runs parallel with the selective CO methanation reaction. This increases the CO outlet concentration. The catalytic performance of ruthenium supported on carbon nanotubes (CNTs), nitrogen doped carbon nanotubes (NCNTs), titania coated carbon nanotubes (NCNT-TiO2 and CNTs-TiO2) and TiO2 anatase (TiO2-A) for selective CO methanation was investigated. The feed composition relevant to reformate gas was used but in the absence of steam. The experiments were conducted within a temperature range of 100 °C and 360 °C. It was observed that carbon dioxide methanation was suppressed until CO methanation attained a maximum conversion for all the catalysts studied. The Ru/NCNT showed higher activity than Ru/CNT at all temperatures examined due to the nitrogen incorporation in the carbon domains. Both Ru/CNT and Ru/NCNT however promoted the RWGS reaction at temperatures above 250 °C. The Ru/CNT-TiO2 catalyst recorded the highest activity for both the CO and selective CO methanation followed by Ru/TiO2-A. The presence of titania on the carbon nanotubes significantly retarded the RWGS reaction from about −120% CO conversion to about 80% CO conversion, while selectivity towards methane increased in all catalysts with increasing temperature