Dual-template synthesis of hierarchically layered titanosilicate-1 zeolites for catalytic epoxidation of cyclooctene

Abstract

A one-pot facile route for preparing hierarchically layered titanosilicate-1 (LTS-1) zeolites with stable interlayered mesopores was proposed by integrated using bolaform surfactant (BC ph-12-6-6 ) and tetrapropyl ammonium hydroxide (TPAOH) as dual templates. By tuning the molar ratios of BC ph-12-6-6 /TPAOH from 5/0 to 5/9, the corresponding LTS-1 samples showed continuous transformations in morphology and intensified degrees of intergrowth by TS-1 nanosheets, resulting in an effective interlayer self-pillaring to avoid the excessive collapse after the removal of the occupied templates by calcination. Moreover, the LTS-1 samples by dual-template synthesis manifested enriched contents of mononuclear octahedrally coordinated Ti species (“TiO 6 ”). Benefitted by the highly patulous structure and more accessible Ti active sites predominated with high-performance “TiO 6 ” species, the LTS-1 catalysts by dual-template synthesis exhibited a superior catalytic activity in the epoxidation of cyclooctene compared with the layered TS-1 directed by sole template of BC ph-12-6-6 and the conventional bulk TS-1. It is reasonable to expect that the demonstrated work has important implications for the design and facile synthesis of layered titanosilicate zeolite catalysts with a stably hierarchical structure and tunable catalytic oxidation activities by an optimized distribution of titanium coordination states containing the coordinated “TiO 4 ” and “TiO 6 ” species. • One-pot dual-template synthesis of hierarchically layered titanosilicate-1 (LTS-1). • Effective interlayer self-pillaring by integrated templating of BC ph-12-6-6 and TPAOH. • LTS-1 manifests enriched contents of mononuclear octahedrally coordinated Ti species (“TiO 6 ”). • Improved catalytic epoxidation performances by the highly patulous structure and more accessible Ti active sites.