Transition-Metal Catalyzed Reduction of Nitrogen to Ammonia

Grant # 08F-02
Principal Investigator: Andreja Bakac
Organization: Iowa State University
Technical Area: Renewable Energy

Public Abstract

Worldwide ammonia production is estimated at over 120 million tons per year, 7% of which is consumed in the United States. Currently, ammonia is manufactured from hydrogen and nitrogen in the so-called Haber-Bosch process at high temperatures and pressures. This process is, unfortunately, highly energy-inefficient and consumes about 2% of global energy production. The steep rise in the demand for biofuels as future energy sources will cause an ever greater increase in the need for nitrogen-based fertilizers, primarily ammonia. It is therefore critical to develop a new, energy-efficient process for ammonia production.

Here we propose to develop such a process by synthesizing novel transition-metal based catalysts for efficient production of ammonia from nitrogen and hydrogen under mild conditions. The benefit of such an approach is two-fold. In addition to the lowering of the energy requirement, the process will increase the yields of ammonia owing to the improved thermodynamics for the overall reaction at temperatures and pressures that are significantly below those currently used in the Haber-Bosch process.

We will synthesize low coordinate mid-transition metal complexes of bulky, multidentate, nitrogen- and phosphorus-based ligands that will facilitate the reduction of the metal (iron, ruthenium, cobalt) by hydrogen, fixation of nitrogen, and finally reduction of nitrogen by the low-valent metal. In the next stage of the project, we will develop and optimize conditions for efficient catalytic dinitrogen hydrogenation. Some of the work will utilize aqueous solvents, an aspect that makes the process environmentally responsible.