Ammonia cracking hollow fibre converter for on-board hydrogen production

Abstract

This work studies the feasibility of a pioneer technology for on-board hydrogen production: the Ammonia Cracking Hollow Fibre Converter. The catalytic activity of a series of ruthenium-based catalysts supported on carbon xerogel, during the ammonia cracking reaction, was studied in a catalytic packed bed reactor. To improve their physical-chemical properties, carbon xerogels were activated in either carbon dioxide or ammonia atmosphere. The most active catalyst (i.e. Ru-NCX) was then deposited inside the micro-structured hollow fibre support by a combination of sol-gel and incipient wetness impregnation methods. At 450 °C and 1 atm the hollow fibre reactor was 4.6 times more efficient than the packed bed reactor (i.e. rNH3 = 6.5 × 104 molNH3/m3·h·gcat and rNH3 = 3.0 × 105 molNH3/m3·h·gcat, respectively), due to its narrower residence time distribution and reduced mass transfer limitations. Furthermore, the use of the hollow fibre converter entailed significantly lower pressure drop (i.e. >99% less), volume (i.e. 80% less) and catalyst loading (i.e. 80% less) compared to the packed bed reactor. Therefore, the potential of this new technology is enormous, as it will push the incorporation of green ammonia in the present-day fuel scenario.