Partial-Oxidation Enhanced Thermocatalytic Ammonia Reforming for Onboard Hydrogen Production

Abstract In pursuit of the 2050 net-zero emission target, ammonia has emerged as a promising carbon-free fuel for maritime applications. Integrating an onboard hydrogen supply system with ammonia-fueled engines can improve combustion while enabling more effective utilization of exhaust waste heat, thereby enhancing the overall system efficiency. Among the available pathways, thermocatalytic ammonia reforming provides a feasible route for flexible hydrogen storage and a stable hydrogen supply. However, despite substantial progress in catalyst development and reactor optimization, its low-temperature performance remains inadequate for practical applications. Introducing oxidation reactions offers a potential solution by releasing heat in situ and reducing the reliance on external heat input. Nevertheless, the role of oxidation in thermocatalytic ammonia reforming has not been systematically clarified. In this work, the promoting effect of partial oxidation on thermocatalytic ammonia reforming for onboard hydrogen production was investigated experimentally. The results show that oxygen addition significantly improves low-temperature reforming by increasing ammonia conversion and hydrogen production rates while reducing the energy consumption per unit hydrogen produced. However, this effect weakens with an increasing initial reaction temperature and may even become detrimental at higher temperatures. Under low-temperature conditions, partial oxidation also alleviates the adverse effect of a shortened residence time at high gas hourly space velocities. Although its overall reforming efficiency is lower than that of pure thermocatalytic reforming because part of the ammonia is consumed by oxidation, partial oxidation shows clear potential for the warm-up of ammonia-reforming systems. These findings provide guidance for the design of onboard hydrogen supply systems for ammonia-fueled engines.