Methanation of Carbon Dioxide over Zeolite-Encapsulated Nickel Nanoparticles

Efficient methanation of CO2 relies on the development of more selective and stable heterogeneous catalysts. Herein, we present a simple and effective method to encapsulate Ni nanoparticles in zeolite silicalite-1. In this method, the zeolite is modified by selective desilication, which creates intraparticle voids and mesopores that facilitate the formation of small and well-dispersed nanoparticles upon impregnation and reduction. Transmission electron microscopy and X-ray photoelectron spectroscopy analyses confirm that a significant part of the Ni nanoparticles are situated inside the zeolite rather than on the outer surface. The encapsulation results in increased metal dispersion and, consequently, high catalytic activity for CO2 methanation. With a gas hourly space velocity of 60000 mLg(catalyst)(-1) h(-1) and H-2/CO2 = 4, the zeolite-encapsulated Ni nanoparticles result in 60% conversion at 450 degrees C, which corresponds to a site-time yield of approximately 304 mol(CH4) mol(Ni)(-1) h(-1). The encapsulated Ni nanoparticles show no change in activity or selectivity after 50h of operation, although postcatalysis characterization reveals some particle migration.