(292a) Effect of CNT on the Catalytic Activity of Cs-Ru/CeO2 catalyst in Microwave-Assisted Ammonia Synthesis

Ammonia is a highly produced and consumed chemical in the world. It is widely used as a raw material for nitrogen containing chemicals, fertilizers, and intermediates for pharmaceutical. Ammonia is also emerging as an energy source of choice for fueling the shipping industry to transition away from conventional fuels and reduce GHG emission. Industrially, ammonia is produced by Haber-Bosch process under high temperature (400–500 °C) and high pressure (150–300 bar) over Iron-based catalyst. This process requires high energy and is capital intensive as it operates at high temperature and pressure. Microwave is a promising technology to produce ammonia at low temperature and pressure with the use of an electromagnetic sensitive catalyst. Microwave irradiation selectively heats active sites on the surface of heterogeneous catalyst, facilitating the transfer of electrons between catalyst and reaction intermediates. A catalyst with high activity under microwave condition is much desired to further improve the energy efficiency and ammonia production.

Based on our previous studies Cs-Ru/CeO₂ catalyst exhibited high microwave sensitivity towards ammonia synthesis at mild conditions. The addition of CNT’s can improve the dielectric loss factor, facilitating heating rate and other mechanical properties. Carbon materials (CNT) can also enhance microwave heating and electrical conductivity. In this study, CNT, and Cs-Ru/CeO₂ catalysts were prepared by three different methods, mechanically mixed, co-precipitation method, and hydrothermal method. Their activity for ammonia under microwave condition were evaluated at ambient pressure and temperature from 260-360^oC. Mechanical mixing of CNT with Cs-Ru/CeO₂ catalyst exhibited the highest activity towards ammonia synthesis as compared to co-precipitation and hydrothermal method. By adding CNT, the activity of baseline catalyst has been tripled. The synergistic effect of combining CNT with Cs-Ru/CeO₂ is caused by the increased dielectric property and electrical conductivity leading to enhance the ammonia production even when mixed mechanically.