Clean hydrogen production from ammonia decomposition over zeolite 13X-supported Ni catalysts

Unlike most H2 production methods, the decomposition of NH3 does not result in carbon dioxide emission and is therefore classified as clean technology. Thus, NH3 holds great promise for the large-scale transportation and storage of H2, and efficient low-temperature NH3 decomposition catalysts are highly sought after. Herein, we examined the textural properties and NH3 decomposition performances of zeolite 13X-supported Ni catalysts prepared by ion exchange, deposition precipitation, and incipient wetness impregnation. The main surface species were identified as Ni phyllosilicates (ion exchange), NiO + Ni phyllosilicates (deposition precipitation), and NiO (impregnation). Compared to other catalysts, the catalyst produced by deposition precipitation achieved the highest H2 formation rate (22.9 mmol gcat-1 min-1 at 30 000 mL gcat-1 h-1, 600 degrees C) and exhibited a 30-40 degrees C lower nitrogen desorption temperature. Given that nitrogen desorption is assumed to be the rate-determining step of catalytic NH3 decomposition, this decrease in the desorption temperature was attributed to improved low-temperature performance. Specifically, the excellent performance of the catalyst obtained by deposition precipitation was ascribed to its large specific surface area and strong metal-support interactions due to the high dispersion and uniform deposition of the active Ni metal on the surface and in the pores of the zeolite support. Ni/zeolite 13X catalyst synthesized by deposition-precipitation exhibits improved low-temperature performance for NH3 decomposition owing to high dispersion and uniform deposition of active Ni on the surface and in the pores of the zeolite support.