Ronald Michalsky - Thermodynamic rationale for designing metal reactants for reactive synthesis of ammonia from steam, nitrogen and biomass at atmospheric pressure

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      Publication Details (including relevant citation   information):

      Ronald Michalsky, Peter H.   Pfromm: Thermodynamic   rationale for designing metal reactants for reactive synthesis of   ammonia from steam, nitrogen and biomass at atmospheric pressure   (submitted, AIChE Journal).

      Abstract:

      Catalytic ammonia synthesis at approximately 30 MPa and 800 K is   technically demanding and consumes about 5% of the global annual   natural gas production causing significant CO2  emissions. A conceptual solar thermochemical reaction cycle to   produce NH3 at near atmospheric pressure without   natural gas is explored here and compared to solar thermochemical   steam/air reforming to provide H2 utilized in the   Haber-Bosch process for NH3 synthesis. Mapping of   Gibbs free energy planes quantifies the trade-off between the   yield of N2-fixation via metal nitridation and   NH3 liberation via steam hydrolysis vs. the   temperatures required for reactant recovery from undesirably   stable metal oxides. Equilibrium composition simulations suggest   that reactants combining an ionic nitride-forming element with a   transition metal (e.g., MgO*Cr2O3,   MgO*Fe2O3, or MgO*MoO3) may   enable the concept near 0.1 MPa (approximately 64 mol% yield of   Mg3N2 through nitridation of   MgO*Fe2O3 at 1300 K, and 72 mol% of the   nitrogen in Mg3N2 as NH3 during   hydrolysis at 500 K). To stabilize the metal nitride at elevated   temperatures cerium is considered as alternative reactant   constituent.

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