An experimental study on mixed reforming performance of Co-based catalysts

Abstract

The major purpose of this research study is to investigate the mixed reforming, both CDRM + SR and CDRM + POX, activity over Co-Ce/ZrO2 bimetallic catalyst, and to experimentally determine the optimal mixture of oxygen sources for the improved catalytic performance. 10 wt.%Co-2 wt.%Ce/ZrO2 catalyst was prepared and tested for its mixed reforming performance. Temperature, CH4/CO2 feed ratio and additional oxygen concentration levels in the feed during mixed reforming tests were used as experimental parameters. The results have shown that, mixed reforming, CDRM + SR and CDRM + POX, activity increase with an increase in temperature. The overall performance and stability in mixed reforming compared to those in individual CDRM has improved with the addition of steam and oxygen. It is observed that the lower CH4/CO2 feed ratios have resulted in higher CO2 conversion and better selectivity. It is concluded that stable activity can be achieved and H2/CO product ratio can be controlled by changing additional oxygen source concentration in the feed. Coke deposition in reactor is decreased with increasing O2 concentration levels in the feed. It is also shown that the additional oxygen source, steam or oxygen, doesn’t significantly affect activity, but the H2/CO product selectivity is closer to unity in CDRM + POX mixed reforming. XPS analysis of freshly reduced and spent catalysts have shown that CO2 conversion is positively affected by surface Co2+/Co3+ ratio. In CDRM+POX mixed reforming, Ce3+/Ce4+ ratio decreases at higher conversion values, due to high utilization of oxygen on active sites. The optimal mixed reforming condition is found as high temperature, low CH4/CO2 feed ratio and addition of O2 with concentration level enough to prevent coke deposition.