High-Pressure Electrochemical Promotion of Ammonia Synthesis over an Industrial Iron Catalyst

Abstract

The catalytic reaction of ammonia synthesis is of paramount importance in the chemical industry, mainly for fertilizers production.1,2 The reaction is equilibrium limited and is favored by low temperatures and high operating pressure. Since the pioneering work of Haber and Bosch the industrial ammonia synthesis is carried out over potassium-promoted Fe catalysts at pressures up to 300 bar. Here we show that the catalytic activity of state-of-the-art fully promoted industrial ammonia synthesis catalysts can be enhanced by up to 1300% by interfacing the catalyst with a proton conductor (CaIn0.1Zr0.9O3-α) and electrochemically supplying protons to the catalyst surface. The rate increase is up to 6 times larger than the rate of proton supply to the catalyst. This is the first demonstration of the effect of electrochemical promotion, or non-Faradaic electrochemical modification of catalytic activity (NEMCA)3-9 using a commercial catalyst and under high (50 bar) pressure. It is also the first demonstration of scale-up of an electrochemically promoted catalytic reactor as 24 electrically connected catalyst pellets were used. The results could in principle lead to a substantial decrease in the operating temperature and pressure of ammonia synthesis reactors.