Ammonia Synthesis at Reduced Pressure via Reactive Separation

Abstract

Ammonia is normally made at high temperature and pressure using a promoted iron catalyst. High temperatures are needed to get fast kinetics; the high pressure is used to ensure high conversion. Alternatively, ammonia can be made at high temperature but lower pressure if the product ammonia is rapidly separated. Here, we have systematically studied the effect of temperature and pressure on the rates of reaction. We then have qualitatively investigated the absorptive separation of ammonia using calcium chloride in a reaction−separation process. Rapid separation reduces the constraint of reversible reaction and enables us to obtain appropriate reaction rates at relatively lower pressure. The effect of different operating conditionsreaction temperature, pressure, absorption temperature, and gas transporton production rates is carefully measured, and this elucidates the potential and the limits of this type of low-pressure ammonia synthesis.

Modeling and Optimal Design of Absorbent Enhanced Ammonia Synthesis

“…In the considered range of reactor operating conditions, the reactor particle Reynolds number is in the transitional region. The bed void fraction is determined from the experimental setup in [13].…”

“…An alternative approach is absorbent-enhanced ammonia synthesis in which a bed of supported alkali metal salt replaces the conventional condenser [11,12]. This absorbent allows for more complete ammonia separation as compared to condensation, and subsequently, high ammonia production rates can be achieved while operating at lower pressures [13]. Additionally, ammonia absorption can occur around 200 • C, meaning that cooling water can be used, rather than refrigeration, which is required in the Haber-Bosch process.…”

Plasma-driven catalysis: green ammonia synthesis with intermittent electricity

“…Furthermore, operating ammonia synthesis under milder conditions may allow for scale-down and intermittent operation. 6,68 2.2.1. Hydrogen production.…”

“…The first focus is on modifying the Haber-Bosch process by decreasing the operating temperature and pressure, by using more active catalysts and highly efficient separation of ammonia with sorbents, which is coined the absorbent-enhanced Haber-Bosch process. 6,68 The second focus is on novel ammonia synthesis methods, such as electrochemical ammonia synthesis, 78,79 photochemical ammonia synthesis, 80,81 plasma-driven ammonia synthesis, [82][83][84] homogeneous ammonia synthesis, 66,85 and chemical looping approaches. 86,87 Novel ammonia synthesis methods were recently reviewed by various authors.…”

Hydrogenation of 3d‐metal oxide clusters: Effects on the structure and magnetic properties

“…The catalytic properties of 3 d ‐metal oxide nanoparticles strongly depend on the nature of the metal atoms, which stipulates specific applications of the NPs . Only iron oxide catalysts are used in the Haber process of ammonia production, whereas a number of various kinds of TMONPs can be used for the water oxidation. Magnetic TMONPs are especially interesting because they are important in the application of a nanomedicine branch called theranostics .…”