Conversion of ammonia to hydrogen in the microwave reactor system using Mo@Alumina catalysts with the promotion of rare-earth and alkaline earth elements

Abstract

In this study, microwave assisted ammonia decomposition reaction to produce high purity hydrogen over γ-Al2O3 supported molybdenum based catalysts were investigated and the effects of various promoters, rare-earth (lanthanum, cerium) and alkaline-earth (calcium and barium) elements on the catalytic activity were studied. Ammonia conversions of over 94% were obtained over the unpromoted catalysts above 350oC at a flow rate of 60 ml/min of pure ammonia. The overall hydrogen production rate per gram of catalyst was found to be 72.86 mmol/min.gcat with for 30 wt.% Mo loaded unpromoted catalyst at 350oC. The apparent activation energy (Ea) values for these catalysts were found to be around 85 kJ/mol. Among the promoters, Ba and Ce gave better performance below 350oC than Ca and La and the optimum loading was found to be 4 wt.% for them. Neither molybdenum nitride nor molybdenum carbide were detected in the spent form of the catalysts.