(517b) Novel Thermochemical Synthesis of Ammonia and Syngas from Natural Gas

Natural gas is connected to ammonia and syngas production via a novel thermochemical approach.  Ammonia is required as a main constituent of fertilizer and is widely recognized as at least partially responsible for the boom in food production known as the “green revolution” of the early twentieth century.  However global food production will need to double due to expected increase in world population to 9.6 billion by 2050 and rising demand for protein among developing nations.  Currently global ammonia production is greater than 140 million metric tons annually and will need to increase to keep up with the expected increase in fertilizer demand for food production.  The conventional Haber-Bosch process for ammonia synthesis operates at temperatures as high as 500°C and pressures reaching 300 atmospheres.  Per ton of ammonia produced, the Haber-Bosch process uses 0.6 tons of natural gas as both a source of hydrogen and combustion energy and emits almost 1.6 tons of carbon dioxide. 

In the present work we report an experimental proof-of-concept of a thermochemical reaction cycle to synthesize ammonia and syngas at near-ambient pressure from nitrogen, water, and methane.  Manganese nitride (Mn₆N_2.58), synthesized from its elements, is reacted with steam to produce ammonia and manganese oxide (MnO).  Results show 43-50% of the lattice nitrogen in the nitride mixture is converted to ammonia while all manganese is converted to the oxide.  MnO was reacted with a dilute methane in nitrogen stream yielding the manganese nitride, synthesis gas, and some solid carbon.  The presence of carbon dioxide is not observed.

Based on these results, employment of a thermochemical cycle appears a promising method to produce ammonia from atmospheric nitrogen, steam, and natural gas at near-ambient pressures.  Significantly reduced carbon dioxide emissions while producing a valuable product in synthesis gas present a key advantage for this novel thermochemical approach going forward as global ammonia production increases to enable food production to double by 2050.