As part of the MariNH3 programme, the University of Birmingham team, in collaboration with Johnson Matthey, Hyundai Motor Company and other industry partners, has delivered vital findings that have informed the design of new catalyst materials and systems for:

  • the reduction of nitrogen-based emissions – including nitrous oxide (N₂O), nitrogen oxides (NOₓ), and ammonia (NH3) slip, and
  • hydrogen production with heat recovery, improving fuel economy and lowering emissions in ammonia-fuelled engines.

Building on these insights, the team has helped to secure a new Innovate UK-funded project, REducing Greenhouse Gases from Ammonia Engines (REGGAE), under the Clean Maritime Demonstration Competition 6.

REGGAE will develop innovative, cost-effective catalytic technologies to simultaneously reduce N2O greenhouse gases, toxic ammonia and NOₓ emissions from ammonia and hydrogen-fuelled engines. This will be achieved through innovative de-N2O catalysts, ammonia slip catalyst (ASC) formulations, and an integrated aftertreatment system design.

Challenges and solutions

The combustion of ammonia in internal combustion (IC) engines presents a significant challenge due to the increased emissions of N2O, a potent greenhouse gas, and ammonia slip, which is toxic if released into the atmosphere.

The Birmingham research focuses on controlling N2O, ammonia slip and NOx emissions from ammonia engines through catalytic aftertreatment systems, and cracking ammonia into hydrogen while recovering exhaust heat in a prototype catalytic thermochemical reactor.

These innovations are crucial to enabling the practical deployment of ammonia as a zero-carbon fuel, and making the transition towards ammonia engines a feasible, zero-carbon option.

In diesel-ammonia dual-fuel systems, including configurations using partially cracked ammonia to hydrogen using heat recovery, the exhaust gas conditions typical of marine engines pose additional challenges for the de-N2O and ammonia slip catalyst systems. Lower temperatures and potentially increased ammonia slip can significantly impact catalyst performance.

As part of the follow-on REGGAE project these challenges are being addressed through the design of new catalytic formulations and aftertreatment systems in collaboration with Johnson Matthey and Fundacion Valenciaport.

Bespoke engines and catalytic systems research and development facility at University of Birmingham Engine Test Laboratory.

Bespoke engines and catalytic systems research and development facility at University of Birmingham Engine Test Laboratory.

Impact

As part of the MariNH3 programme, catalytic formulations and innovative integrated systems including three-way catalytic converters (TWC), ammonia slip catalysts (ASC), selective catalytic reduction (SCR) catalysts, and ammonia cracker with heat recovery to reduce nitrogen-based emissions such as NOx, ammonia and N2O have been designed and evaluated.

A particular focus has been the development of new catalyst designs to mitigate N2O exhaust gas emissions in spark-ignition (SI) engines fuelled with ammonia. In these systems, improved ammonia combustion reduces ammonia slip, while the higher exhaust gas temperatures (400-650°C) provide favourable conditions for these new de-N2O catalysts to perform effectively – an outcome that has been successfully demonstrated through research.

These advances position the University of Birmingham as a leading authority in catalytic emissions control for ammonia-fuelled engines.