Highly active and stable cobalt catalysts with a tungsten carbide-activated carbon support for dry reforming of methane: effect of the different promoters

Abstract

Greenhouse effect has become one of the serious issues in the human development. Greenhouse gases are mainly composed of methane and carbon dioxide. Dry methane reforming (DMR) is an excellent technology owing to the direct utilization of greenhouse gases. However, there are severe catalyst sintering and coke deposits in the process of DMR. Therefore, it is necessary to synthesize catalysts with fantastic properties. Here, a series of cobalt catalysts modified by different transition metals (Y, Gd, and Mn) were synthesized applying the impregnation method. The Y-modified catalyst shows excellent catalytic activity and anti-coking ability. Under the reaction condition of 800 °C, the catalyst exhibits not only the highest CH₄ conversion (83%) but also stable CO₂ conversion (94%) after 10 h of reaction. N₂ physisorption, TG, H₂-TPR, XPS, XRD and TEM were applied to research the crystal phase, microstructure and texture characteristics of the catalysts. The results show that the Mn-modified catalyst exhibited a negative influence for the DMR reaction although the catalyst shows a large specific surface area. Gd- and Y-modified catalysts exhibited superior interaction between the metal and carrier, which improves the stability of active metal Co during DMR. Simultaneously, the introduction of Y maintains more number of oxygen vacancies and improves the dispersion of the active metal. The study found that both the activity and coke resistance of the catalyst can be concurrently enhanced due to the addition of Y through promoting the dispersion of the metal and the activation of CO₂. Most noteworthily, after a 50 h stability test, the CH₄ and CO₂ conversion on the Y-modified catalyst dropped from 91% and 95% to 83% and 94%, respectively.