Novel hierarchically porous nanocomposites of diatomite-based ceramic monoliths coated with silicalite-1 nanoparticles for benzene adsorption

Abstract

Novel hierarchically porous nanocomposites of diatomite-based ceramic supports coated with silicalite-1 (Sil-1) nanoparticles for benzene adsorption were prepared via a facile preparation route. In this route, porous ceramic supports with three-dimensional reticulated structures were first prepared using the polymeric sponge method in which diatomite was used as the ceramic framework and polyurethane foam was used as the sacrificial template. This process was followed by facile in situ homogeneous coating of Sil-1 on the surface of the ceramic under mild conditions. The hierarchical porosity of the nanocomposites was due to the inherent micropores of Sil-1, the mesopores resulting from the stacking of Sil-1, and the hierarchical macropores of ceramic supports. The specific area and micropore volume of the nanocomposites were 122.9m2/g and 0.07cm3/g, respectively, with a high zeolite loading of 32.4%. The nanocomposites exhibited a much higher benzene adsorption capacity (133.3mg/g(Sil-1)) compared with that of a commercial micron-sized ZSM-5 product (66.5mg/g) and a synthesized Sil-1 (SilSYN, 94.7mg/g). Moreover, adsorption–desorption rate constants of the nanocomposites were three and five times higher than those of the ZSM-5 and SilSYN, respectively, as evaluated via a gravimetric method using an intelligent gravimetric analyzer. The excellent benzene adsorption performance is ascribed not only to the in situ silicalite-1 coating process that facilitates the stability and dispersity of Sil-1 on the modified surface of the ceramic supports but also to the hierarchically porous monolithic structure of the nanocomposites, which is beneficial to the mass transfer efficiency for benzene adsorption.