Influence of water in catalyst deactivation and lifetime of methane Bi-Reforming reaction over Ni-Co-Ru tri-metallic catalyst system

Abstract

Recently, the bi-reforming of methane has been an emerging area of interest against conventional synthesis gas generation processes due to the achievable H2/CO ratio of around 2.0 and the possible utilization of feedstock like Biogas substitute to the limited fossil fuel resources. However, commercial implementation still needs to be improved due to the rapid deactivation of catalysts through metal particle sintering and coke formation on active sites. Consequently, developing promising catalysts that can show prolonged stability, high activity, and selectivity during the reaction is worthwhile. A facile synthesis method has been adopted to develop a ceria, magnesia, and zirconia-modified gamma-alumina support. Furthermore, Ni, Co, & Ru metals with varying weight percentages were deposited over the modified support by using a precipitation-deposition approach. The prepared catalysts were well characterized by XRD, XPS, SEM, HRTEM, Physisorption, and Chemisorption studies to elucidate the structure-activity relationship. Ascribed to small particle size, strong metal support interaction, employment of basic promoter MgO and oxygen storage capacitors like ceria and zirconia, and high dispersion of active species, all the catalysts exhibit a higher methane dissociation and carbon dioxide adsorption rate with extended stability. Further, a study has been made to understand how deactivation and catalyst lifetime can be manipulated through the amount of water in the feed composition. It was observed that using 1.8 moles of H2O in the feed can provide a syngas ratio of around 2. Under optimized reaction conditions of temperature 850 °C and weight hourly space velocity 10 Lg−1h−1, the best-selected catalyst exhibits a stable 92% CH4 and 89% CO2 conversion with a studied catalyst lifetime of up to 50 h. After the reaction, the spent catalyst was exposed to Thermogravimetric analysis, Temperature programmed oxidation, and Raman spectroscopy studies, and it was observed that there was a negligible amount of amorphous coke deposited over the catalyst used for 50 h of reaction couldn't have any substantial impact on catalyst activity.