Polyvinyl alcohol templated synthese of hierarchical SAPO-11

This work reports that the polyvinyl alcohol successfully templates the intracrystal mesoporous structure of hierarchical SAPO-11 molecular sieves. The structures of prepared hierarchical SAPO-11 materials and a conventional SAPO-11 simultaneously synthesized are characterized by X-ray diffraction, N₂ adsorption/desorption, scanning electron microscopy and high resolution transmission electron microscopy. The characterizations demonstrate that this synthesized hierarchical SAPO-11 possesses a mesopore structure with a much regular pore size distribution. Importantly, these mesopores are intracrystal but not intercrystal. The bifuntional isomerization catalyst with this hierarchical SAPO-11 as support shows a high selectivity in hydroisomerization reaction of hexane, evidencing that the catalytic selectivity is improved by introduction of mesopore structure into the SAPO-11 crystal. The templating mechanism of polyvinyl alcohol in formation of mesopores is well discussed at the ending. This work provides a potential template to prepare hierarchical catalyst materials. (paper)