Low Temperature Activation of Carbon Dioxide by Ammonia in Methane Dry Reforming—A Thermodynamic Study

Methane dry reforming (MDR) is an attractive alternative to methane steam reforming for hydrogen production with low harmful environmental emissions on account of utilizing carbon dioxide in the feed. However, carbon formation in the product stream has been the most challenging aspect of MDR, as it leads to catalyst deactivation by coking, prevalent in hydrocarbon reforming reactions. Common strategies to limit coking have mainly targeted catalyst modifications, such as by doping with rare earth metals, supporting on refractory oxides, adding oxygen/steam in the feed, or operating at reaction conditions (e.g., higher temperature), where carbon formation is thermodynamically restrained. These methods do help in suppressing carbon formation; nonetheless, to a large extent, catalyst activity and product selectivity are also adversely affected. In this study, the effect of ammonia addition in MDR feed on carbon suppression is presented. Based on a thermodynamic equilibrium analysis, the most significant observation of ammonia addition is towards low temperature carbon dioxide activation to methane, along with carbon removal. Results indicate that ammonia not only helps in removing carbon formation, but also greatly enriches hydrogen production.