Hydrogen is a clean, abundant and highly efficient form of energy, especially when used in fuel cells to generate electricity. Unfortunately, transporting and storing hydrogen gas has its own set of problems. Therefore, as explained in our sister-publication, Trends, the key to unleashing the so-called “hydrogen economy” seems to lie in optimized storage of Hydrogen fuel in the form of Ammonia.
In 1918, German chemist Fritz Haber won the Nobel Prize in Chemistry for synthesis of ammonia from its elements, paving the way for ammonia’s significant role in industrial fertilizers. However, use of ammonia in renewable energy applications has been limited by the processes available to synthesize it. The Haber-Bosch process, used in industrial production of ammonia, requires high temperature and pressure, conditions not typically available in renewable energy storage and transport infrastructure.
Over the past several years, techniques for producing Ammonia and using it on ships, planes and automobiles has been rapidly improving. Now a recent study, published in the Journal of Physical Chemistry C, explains a new ammonia synthesis process using lithium oxide as a molecular scaffold to synthesize ammonia under ambient pressure at temperatures below 400°C. These conditions are easy to mimic in nonindustrial settings.
The researchers combined the lithium hydride with lithium oxide and found that the lithium hydride prevented clumping, leaving small particles with lots of surface area exposed for chemical reactions. Combining the non-agglomerated reactants and adding gaseous hydrogen in the final step of ammonia synthesis, they were able to produce ammonia more quickly than in the traditional process. If ammonia can be produced quickly with relatively simple equipment under modest temperature and pressure conditions, it paves the way for much smaller-scale ammonia production.
The small-scale ammonia synthesis process, based on chemical looping, can be operated under lower pressure and temperature with higher conversion yield than the conventional catalytic process. The new process also obviates the need for expensive metal catalysts — such as ruthenium — used in industrial synthesis of ammonia. This process, pioneered by Japanese researchers, can produce ammonia efficiently under near-ambient conditions. Therefore, this approach is especially relevant to storing energy from renewable energy generation sites, which tend to be smaller and more numerous than industrial production facilities.
Schematic image of small-scale and distributed NH3 synthesis processes. As a next step, the researchers want to optimize the reaction mechanics from a chemical engineering point of view.