Production of ammonia in the Haber process is one of the largest industrial users of hydrogen gas, due to the large demand of NH3 by the fertilizer industry. Close to half of the ammonia produced is combusted in the Ostwald process to form HNO3. During that process N2O and NOx are produced as waste gases which are removed by the BASF deNOx process. Nitrous oxide in particular is a potent greenhouse gas, approximately three hundred times more potent in infrared absorption than isoelectronic CO2. Thermochemical calculations of Lewis in the 1920’s showed that production of dilute HNO3 directly from N2, O2, and H2O was thermodynamically favorable at ambient temperatures. Addition of a base yields a stronger driving force (1): N2(g) + 2.5 O2(g) + Na2O(s) à 2 NaNO3 (s) DG300 = -76 kcal/mol (1) N2O(g) + 2 O2(g) + Na2O(s) à 2 NaNO3 (s) DG300 = -109 kcal/mol (2) Development of a catalyst for reaction (1) does not appear to have been extensively studied although it could represent a significant reduction in the consumption of H2 to produce NH3 which will be posteriorly combusted in the wasteful Ostwald process. In the BASF deNOx process NH3 is added to the flue gas stream to reduce N2O to N2 by NH3. Development of a catalyst for reaction (1) presents greater kinetic barriers than does reaction (2). In this presentation studies of binding and activation of O2, N2, RCN, and NxOy to transition metal complexes will be discussed. The work of Professor Elena Rybak Akimova and her research group at Tufts University in advancing mechanistic understanding in reactions relevant to this goal will be emphasized.

Insight into possible mechanisms for for oxidation of N2 or N2O to nitrate

2019 Spring National Meeting

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