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Understanding Nitrogen Fixation [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy, 2012.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description
2.6 MB : digital, PDF file
Additional Creators
Cornell University, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
The purpose of our program is to explore fundamental chemistry relevant to the discovery of energy efficient methods for the conversion of atmospheric nitrogen (N₂) into more value-added nitrogen-containing organic molecules. Such transformations are key for domestic energy security and the reduction of fossil fuel dependencies. With DOE support, we have synthesized families of zirconium and hafnium dinitrogen complexes with elongated and activated N-N bonds that exhibit rich N₂ functionalization chemistry. Having elucidated new methods for N-H bond formation from dihydrogen, C-H bonds and Broensted acids, we have since turned our attention to N-C bond construction. These reactions are particularly important for the synthesis of amines, heterocycles and hydrazines with a range of applications in the fine and commodity chemicals industries and as fuels. One recent highlight was the discovery of a new N₂ cleavage reaction upon addition of carbon monoxide which resulted in the synthesis of an important fertilizer, oxamide, from the diatomics with the two strongest bonds in chemistry. Nitrogen-carbon bonds form the backbone of many important organic molecules, especially those used in the fertilizer and pharamaceutical industries. During the past year, we have continued our work in the synthesis of hydrazines of various substitution patterns, many of which are important precursors for heterocycles. In most instances, the direct functionalization of N₂ offers a more efficient synthetic route than traditional organic methods. In addition, we have also discovered a unique CO-induced N₂ bond cleavage reaction that simultaneously cleaves the N-N bond of the metal dinitrogen compound and assembles new C-C bond and two new N-C bonds. Treatment of the CO-functionalized core with weak Broensted acids liberated oxamide, H₂NC(O)C(O)NH₂, an important slow release fertilizer that is of interest to replace urea in many applications. The synthesis of ammonia, NH₃, from its elements, H₂ and N₂, via the venerable Haber-Bosch process is one of the most significant technological achievements of the past century. Our research program seeks to discover new transition metal reagents and catalysts to disrupt the strong N {triple_bond} N bond in N₂ and create new, fundamental chemical linkages for the construction of molecules with application as fuels, fertilizers and fine chemicals. With DOE support, our group has discovered a mild method for ammonia synthesis in solution as well as new methods for the construction of nitrogen-carbon bonds directly from N₂. Ideally these achievements will evolve into more efficient nitrogen fixation schemes that circumvent the high energy demands of industrial ammonia synthesis. Industrially, atmospheric nitrogen enters the synthetic cycle by the well-established Haber-Bosch process whereby N₂ is hydrogenated to ammonia at high temperature and pressure. The commercialization of this reaction represents one of the greatest technological achievements of the 20th century as Haber-Bosch ammonia is responsible for supporting approximately 50% of the world's population and serves as the source of half of the nitrogen in the human body. The extreme reaction conditions required for an economical process have significant energy consequences, consuming 1% of the world's energy supply mostly in the form of pollution-intensive coal. Moreover, industrial H₂ synthesis via the water gas shift reaction and the steam reforming of methane is fossil fuel intensive and produces CO₂ as a byproduct. New synthetic methods that promote this thermodynamically favored transformation (ΔG{sup o} = -4.1 kcal/mol) under milder conditions or completely obviate it are therefore desirable. Most nitrogen-containing organic molecules are derived from ammonia (and hence rely on the Haber-Bosch and H₂ synthesis processes) and direct synthesis from atmospheric nitrogen could, in principle, be more energy-efficient. This is particularly attractive given ...
Report Numbers
E 1.99:doe/cornell/15659
doe/cornell/15659
Subject(s)
Other Subject(s)
Note
Published through SciTech Connect.
05/25/2012.
"doe/cornell/15659"
Paul J. Chirik.
Type of Report and Period Covered Note
Final; 05/01/2007 - 04/30/2010
Funding Information
FG02-05ER15659
View MARC record | catkey: 14065981