The Haber process is currently used to produce ammonia, an essential feedstock for the fertilizer industry that feeds 48% of the world's population. However, high temperatures and pressure are necessary and many recycle steps are needed meaning it is an energy intensive and expensive process that can only feasibly occur on a large scale.
It would be of great benefit if ammonia could be produced under milder conditions. This would create the possibility of smaller scale ammonia production, which would allow fertilizers to be produced at point of use. Lower temperature and pressures mean that it is feasible that the system could be powered by renewable energy, such as wind or solar power. This changes the process from an environmentally unfriendly process to one that is carbon emission free. This movement away from fossil fuels is both economic and environmentally friendly.
One possible method of achieving ammonia production at mild conditions is the use of absorbents. The produced ammonia is absorbed and so removed from the reaction, which forces the equilibrium towards producing more products. This gives higher yields of ammonia despite the less favorable conditions.
There are a number of factors that will be considered when developing the new absorbent. The absorbent must have a high ammonia capacity. As stationary applications are being targeted, capacity by volume is most important although good capacity by weight would be beneficial. The strength of the ammonia absorbent interaction must also be considered. This should be strong enough to ensure equilibrium is shifted but not so strong as to make removing the ammonia difficult. Another consideration is the ability of the ammonia to diffuse through the absorbent. It must be possible for the ammonia to travel through the pores easily to ensure the maximum capacity is achieved.
The main aims of the project are a greater understanding of how ammonia interacts with an absorbent leading to development of a new ammonia absorbent for use in ammonia production.
Many novel research methods will be used in achieving these aims. A variety of syntheses will be used to prepare the absorbents. Varied characterization will be utilized including a number of novel techniques. It is also hoped that synchrotron experiments will give new information about how the ammonia molecules order within the absorbents. NEXAFS will also be used to understand the bonding in the absorbent and the effect this has on the ammonia storage mechanism.
This project falls within the EPSRC Physical Sciences research area and is jointly funded by Siemens.