Influence of synthesis conditions of Co/SiC and TiC-SiC catalyst on H2 production from NH3

Abstract

Developments in suitable catalytic design (including novel and low-cost supports and active metal) gain the perspective of ammonia as ‘hydrogen carrier’ for the decarbonization of the energy sector. Herein, this study provides valuable insight into the utilization of different cobalt loadings (1.5–10 wt%) and cobalt precursors (nitrate, citrate, acetate and chloride) on SiC and TiC-SiC-based supports for hydrogen production from ammonia decomposition. The reduction degree, particle size and surface area were found to determine the catalytic activity. Hence, 2.5 wt% and 5 wt% of Co led to an optimal particle size and amount of active sites on TiC-SiC and SiC supports, respectively. The choice of a suitable cobalt precursor had a clear effect on the reduction of cobalt species. A higher reduction degree with an enhanced ammonia conversion resulted from the nitrate precursor, whereas a lower catalytic performance was obtained when cobalt chloride was used in both supports. On the other hand, the in-situ ammonia pre-treatment was found to be an efficient alternative for activating the cobalt catalysts in both supports. Among the different investigated catalyst formulations, the highest activity was achieved when a nitrate precursor and both in-situ H2/Ar or NH3/Ar pre-treatments were used to prepare the TiC-SiC-based catalyst. The 2.5Co-N/TiC-SiC catalyst reached a specific activity of 0.11 molH2 molCo-1 s-1 with an ammonia conversion higher than 80 % at 450 ºC.