(513fl) Thermal & Microwave-Assisted Synthesis of Ammonia with a Chemical Looping Approach

Conventional ammonia synthesis via the Haber Bosch process is one of the oldest and most optimized processes in chemical industry. Much work has gone into attempting to “overcome” the Haber Bosch process by developing alternatives and by improving the process efficiency via traditional high-pressure catalytic means. In the chemical looping conception of the ammonia synthesis process, dinitrogen gas is first reacted with a fully reduced metal catalyst to form a reactive nitride species. Next, the resulting nitride is reacted with gaseous hydrogen to form ammonia. Essentially, the catalyst surface undergoes nitride formation-hydrogenation-ammonia desorption-regeneration, which is why the process is analogous to chemical looping.

Present work has included screening active nitrogen carriers found in literature with a thermal fixed bed reactor configuration. Several bimetallic catalyst species have been identified and tested. Additional experimental work will be undertaken to further characterize the effectiveness of various types of bimetallic and surface modified metal catalyst particles.

The chemical looping process intends to test various catalyst samples under microwave irradiation to improve ammonia synthesis rate and yield. Bulk heating methods such as traditional furnace heaters can cause ammonia decomposition. The hypothesis to be evaluated is that by careful catalyst selection and design, the bulk temperature of the microwave bed can be lowered due to site specific heating.

In addition to comparing thermal and microwave heating approaches, a hybrid reactor configuration consisting of a combination of conventional thermal heating with plasma generation, and a combination of microwave irradiation with plasma will be tested. Mixtures of nitrogen, argon and hydrogen will be tested to further optimize the reaction mixture. We will evaluate the hypothesis that hydrogen in the plasma can act as an oxygen scavenger to prevent NOx formation.