Utilization of greenhouse gases through carbon dioxide reforming of methane over Ni–Co/MgO–ZrO2: Preparation, characterization and activity studies

Abstract

MgO–ZrO2 mesoporous support (Zr/Mg molar ratio=9) impregnated with 6wt% Ni, 6wt% Co and 3wt% of both Ni and Co were prepared using a novel surfactant assisted-impregnation method. Carbon dioxide reforming of methane using these catalysts was studied in a quartz tube microreactor at a CH4/CO2 feed ratio of 1, 750°C, 1atm with a gas hourly space velocity of 125,000mL/g/h. Based on reactant's conversion and syngas production, the bimetallic catalyst was the most suitable catalyst for the reaction. The catalyst exhibited high and constant activity during 40h reaction time with methane and carbon dioxide conversions of 80% and 84%, respectively with a syngas ratio close to unity without significant deactivation as compared to the respective monometallic catalysts. For longer time on stream, the catalyst showed constant activity up to 60h after which it gradually decreased. The bimetallic catalyst also exhibited excellent regenerability by restoring its initial catalytic activity after 1h of regeneration in air. The catalysts were also characterized by XRD, XPS, N2-physisorption, H2-chemisorption, TGA-DTA, HRTEM, H2-TPR, TPH and SEM. The high performance of the bimetallic catalyst was due to the stabilization of t-phase in zirconia, better metal dispersion, small metal particle size and synergetic effect between Ni and Co particles. The XPS results showed that bimetallic catalyst had the ability to hinder metal oxidation and exhibited presence of higher surface basicity which were responsible to maintain the stability of the catalyst.