Effect of Potassium Doping on the Structural and Catalytic Properties of Co/MnO x Catalyst in the Steam Reforming of Ethanol.

The promotional effect of potassium (~1.25 wt%) on a Co/MnO x catalyst was studied for samples prepared by the impregnation method in the steam reforming of ethanol (SRE) process at 420 °C for a H 2 O/EtOH molar ratio of 12/1. The catalysts were characterized using physicochemical methods to study their textural, structural, and redox properties. The XRD studies revealed that, during the treatment of both cobalt-based catalysts under a hydrogen atmosphere at 500 °C, Co 0 and MnO phases were formed by the reduction in Co 3 O 4 and Mn 2 O 3 /Mn 3 O 4 phases, respectively. Potassium doping significantly improved stability and ability for the C-C bond cleavage of the Co/MnO x catalyst. The enhancement of activity (at ~25%) and selectivity to hydrogen (at ca. 10%) and the C1 product, mainly carbon dioxide (at ~20%), of the Co/MnO x catalyst upon potassium doping was clarified by the alkali promoter's impact on the reducibility of the cobalt and manganese oxides. The microscopic observations revealed that fibrous carbon deposits are present on the surface of Co/MnOx and KCo/MnOx catalysts after the SRE reaction and their formation is the main reason these catalysts deactivate under SRE conditions. However, carbon accumulation on the surface of the potassium-promoted catalyst was ca. 12% lower after 18 h of SRE reaction compared to the unpromoted sample.