Ammonia Production at Milder Conditions for Distributed Manufacturing

Ammonia produced via the well-known Haber-Bosch (HB) process is one of the most important innovations of the 20^th century. In the conventional process, reactants are produced through steam reforming of natural gas. Once produced, hydrogen and nitrogen react at high temperatures (400–500 °C) and high pressures (150–300 bar) in the HB reactor to produce ammonia. High temperature is needed to accelerate reaction kinetics while high pressure is required to increase the single-pass conversion. The HB process is critical to sustain the food production, as it is an indispensable ingredient of nitrogen fertilizers. Not only a fertilizer, ammonia is recently proposed as an indirect form of hydrogen storage because of its high hydrogen density (17.8 wt.%) and the viability of long-term storage and delivery.

Distributed “green” ammonia produced with hydrogen from water electrolysis and nitrogen from air has been considered as an alternative to the fossil fuel-based ammonia production. To realize the idea of distributed ammonia manufacturing, designing optimized small-scale HB process that operates at milder conditions is on demand. In this presentation, I will discuss two strategies to reduce the pressure and temperature requirements. First, the idea of replacing the phase-changing condensation with high-temperature absorption will be discussed that can lead to reducing the operating pressure by a factor of ten (10-20 bar). I will then discuss the design of better catalyst materials that can reduced the reaction temperature to 300 °C.