(337v) Absorbents for Renewable Ammonia Separation and Storage

Research Interests: Include a combination of designing efficient and sustainable chemical processes as well as the development of new materials for application in catalytic reactions, chemical processes, or other technological solutions.

Ammonia is a key component in fertilizer required for global food production as well as a variety of specialty chemicals including electrolytes for batteries, food additives, analytical reagents, and as a fuel for medium-to-long-term energy storage. The conventional method (Haber-Bosch) to produce ammonia is unsustainable considering its large energy utility, greenhouse gas emissions and major contribution to climate change. The availability of renewable resources like wind energy coupled with its co-location in areas with high fertilizer demand, give rise to the possible synthesis of carbon-free ammonia at small scale close to the end user. There is a growing interest in this method of ammonia synthesis as excess renewable energy can be stored as ammonia and converted back into electricity or hydrogen fuel during periods of high-power demand. Through our pilot scale process, we have demonstrated that ammonia can be made using air, water, and wind energy but this product is however more expensive than one based on fossil-fuels. One way of reducing this cost is by replacing the traditional ammonia separation by condensation with reactive absorption using metal halides. Although this method of ammonia separation is more efficient, pure absorbent material is unstable and shows decreasing capacity with prolonged usage. Here, we discuss efforts to synthesize stable absorbent materials with improved mass and heat transfer compared to pure metal halides. In addition, we report optimal conditions for uptake and release of ammonia. The production capacity (ammonia processed per unit absorbent and per unit production time) depends on processing parameters - including uptake and regeneration temperatures, ammonia partial pressures, release time, and sweep gas flow rate. Moreover, attention should be paid to balancing the release time with the full cycle time and bed size to ensure that the uptake breakthrough time makes efficient use of the bed. These parameters are mutually interdependent, so their optimization can be nontrivial, but rewarding. Our findings help inform potential processing challenges that need attention in design de-risking to ensure optimal operation in bench-scale and production-scale units for renewable ammonia production.

My research interests include a combination of designing efficient and sustainable chemical processes as well as the development of new materials for application in catalytic reactions, chemical processes, or other technological solutions.