Understanding the kinetics and Re promotion of carbon nanotube supported cobalt catalysts by SSITKA

Abstract

CO hydrogenation is carried out on Co/CNT and CoRe/CNT catalysts at 483K, 1.85bar, H2/CO=10. The study addresses a fundamental understanding of the effects of reaction conditions (syngas pressure, temperature and GHSV) and Re promotion on the Co activity and selectivity by SSITKA. A systematic SSITKA study was performed to gain a better understanding of the surface reactions at different conditions by measuring the surface concentrations of CO and CHx intermediates on Co. The TOFs of CO conversion and methane formation are found to be sensitive to H site coverage, which is affected by the competitive adsorption between H2 and CO. Higher temperature mainly increases the reaction rate constant, which changes more significantly as compared with the site coverage of the H and CO. CO pressure and temperature have more significant effect on the methane selectivity than H2 pressure. Re has little effect on the TOF and selectivity of the Co/CNT catalyst. SSITKA experiment reveals that both NCO and NCHx increase slightly with Re promotion. The surface coverage of CO is about ten percent higher on the Re promoted sample, suggesting that Re might be able to enhance CO adsorption a little bit. However, Re promotion does not change the intrinsic site activity and apparent activation energy. The apparent activation energy for methane formation is found to be about 118kJ/mol for both promoted and unpromoted catalysts.