Advancing Ammonia Synthesis through Plasma-Assisted Catalysis

Abstract

Plasmas can enhance the selectivity, activity, and product yields for many chemical reactions. In the presence of a catalyst, synergy between the catalyst and the plasma exists to assist in the activation of reactants to promote the chemical transformation. We have been particularly interested in the use of non-thermal plasmas for the catalytic production of ammonia from nitrogen/hydrogen gas mixtures. The industrial Haber-Bosch process for ammonia synthesis from nitrogen and hydrogen is carried out at high pressures (100-200 bar) and temperatures (400-500 °C). N2 dissociation is the fundamental barrier for this reaction, and plasma-catalysis has been suggested as viable way to activate N2 under ambient conditions. We have demonstrated that is possible to produce ammonia at atmospheric pressure and temperatures between 100 - 200 °C by coupling the catalyst with a non-thermal plasma. It is speculated that the plasma assists in activating the source gas by generating reactive species, such as vibrationally or electronically excited N2*, ions, and radicals, which interact on the catalyst surface to produce ammonia. In this presentation, we will discuss our experimental results from varying the gas composition, bulk gas temperature, plasma input power, and reactor space velocity and how these conditions influence the catalyst-plasma interactions using a variety of catalysts (Fe/Al2O3, Ru/Al2O3, Pt/Al2O3, Ni/Al2O3, and Co/Al2O3).