Title : Ammonia synthesis activity of nanostructured Ni2 (W,Mo)3 N and Co3 (W,Mo)3 N compounds
Abstract:
The Haber –Bosch process is very successful development, and great achievements in the twentieth century for the production of ammonia. The process involves combining pure H2 and N2 directly over a promoted iron catalysts at temperatures of 450-500 ºC and reaction pressures of over 100 atmospheres. This process produces over 150 million metric tons of ammonia each year and consumes over 1 % of the world’s energy supply. Furthermore, the process is estimated to generate ca. 3 % of global greenhouse gas emissions. Thus, it would be desirable to develop alternative catalytic materials that could operate at lower temperatures and pressures in order to reduce the energy consumption. Metal nitride materials have shown a significant activity for ammonia synthesis under ambient pressure. There is a significant literature of ternary materials including Co3 Mo3 N and Ni2 Mo3 N but few studies exist of varying the electronic structure of these materials by substitution. In this work a series of different compositions in the form of Ni2 (W,Mo)3 N and Co3 (W,Mo)3 N were prepared and investigated for ammonia synthesis activity. Ammonia synthesis from 75% H2 and 25% N2 was carried out at ambient pressure. All of the materials were found to be active at higher temperature.
