Temperature-regulated construction of hierarchical titanosilicate zeolites†
Titanosilicate zeolites are an important class of heterogeneous catalysts that are widely used in several catalytic processes. The construction of hierarchical titanosilicate zeolites (e.g., TS-1 with an MFI structure) is of great interest as they can promote the mass transportation and molecular accessibility of reactant molecules. Herein, we presented a temperature-regulated method to construct anatase-free hierarchical TS-1 zeolite catalysts by utilizing a two-step hydrothermal crystallization strategy with tetrabutylammonium hydroxide (TBAOH) as the sole organic structure-directing agent. The two-step crystallization process, i.e., initial crystallization at lower temperature followed by secondary crystallization at higher temperature, afforded the incorporation of more active Ti species into TS-1 and the formation of hierarchical structures resulting from the layer-stacking growth. The prepared hierarchical TS-1 zeolite catalysts showed superior catalytic performance in the oxidative desulfurization of bulky organosulfur compound dibenzothiophene compared with their microporous counterpart, giving a higher turnover number (23.5 vs. 1.7). The temperature-based kinetic regulation approach offers an effective way to construct hierarchical titanosilicate zeolite catalysts with controllable active Ti atoms.