Dynamic ammonia adsorption by FAU zeolites to below 0.1 ppm for hydrogen energy applications

Hydrogen can be released from ammonia (NH3) by cracking, but the residual ammonia is harmful to polymer exchange membrane fuel cells and should be less than 0.1 ppm (mu mol/mol). In this paper, the adsorption of NH3 by commercial faujasite (FAU) zeolites to below 0.1 ppm have been investigated. The results show that the Si/Al ratio of zeolite is inversely proportional to the adsorption capacity, and the strength of ammonia adsorption by cation Li+ is more than that of Na+ , thus the ammonia adsorption capacity of LiLSX zeolite is greater than that of 13X-HP zeolite. However, the small granule size of crystalline microspheres and the rough surface of 13X-HP zeolite were the factors that lead to the dynamic NH3 adsorption capacity of 13X-HP zeolite close to LiLSX zeolite. In the dynamic 1700 ppm NH3 adsorption, with a breakthrough point of 0.1 ppm, the adsorption capacity is 9.27 wt% for LiLSX zeolite and 8.73 wt% for 13X-HP zeolite. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the adsorption of ammonia by commercial faujasite zeolites, finding that LiLSX zeolite has a greater ammonia adsorption capacity than 13X-HP zeolite, although the latter has a dynamic NH3 adsorption capacity close to LiLSX zeolite.