Microwave-assisted ammonia decomposition reaction over iron incorporated mesoporous carbon catalysts

Abstract

Microwave-assisted ammonia decomposition reaction was investigated to produce COx free hydrogen, for fuel cell applications. Iron incorporated mesoporous carbon catalysts were prepared at different metal loadings, following an impregnation procedure. Mesoporous carbon acted as the catalyst support, as well as the microwave receptor. Complete conversion of ammonia was achieved at 450°C over the catalyst having 7.7wt% Fe, when the reaction was carried out in the microwave reactor system, using pure ammonia (GHSV of 36000ml/hgcat). However, in the case of using the conventionally heated reactor, complete conversion of ammonia was achieved only at 600°C. Iron oxides, namely maghemite (γ-Fe2O3), magnetite (Fe3O4) and hematite (α-Fe2O3) simultaneously appeared in the structure of the synthesized catalysts, after their calcination at 450°C, under pure N2 flow. Iron oxides present in the calcined catalytic materials then were reduced to metallic iron at 500°C. Formation of iron carbide crystals was observed in the structure of spent catalysts that were used in microwave reactor system, while metallic iron crystals were still present in the catalysts that were tested in conventionally heated system.