High Temperature and Pressure Pure-Silica Zeolite Ammonia Adsorbents and Their Use in Adsorption-Enhanced Catalytic Reactors

Improving the efficiency of ammonia synthesis processes by integrating reaction with separation is a topic of long-standing interest. One approach is the use of sorption-enhanced catalytic reactors, where in situ ammonia sorption removes it from the vapor phase and allows reaction to proceed with ammonia yields beyond those dictated by thermodynamic equilibrium in the absence of sorption. While many sorbents have been used for this purpose, challenges remain with full regeneration at practical ammonia pressures limiting the potential benefits of sorption-enhanced reactors. Here, we introduce pure-silica zeolites for this application. First, we determine high-pressure high-temperature adsorption data using a specially designed adsorption equipment. Our findings indicate that pure-silica zeolites exhibit high ammonia working adsorption capacity compared to previously reported commercial adsorbents. Molecular simulations provide information on adsorbate distribution and explain observed trends in adsorbed amounts and enthalpies. A proof of concept is demonstrated using a batch sorption-enhanced catalytic reactor.