Enhanced Catalytic Activity on Post‐Synthesized Hollow Titanium Silicalite‐1 with High Titanium Content on the External Surface

Abstract A titanium silicalite‐1 (TS‐1) extrudate with high content of titanium on the external surface was post‐synthesized by using the mixed solution of tetrapropylammonium hydroxide and the hydrolysate of tetrabutyl titanate. The influence of Ti concentration in the post‐synthesis solution on the physicochemical properties and catalytic performance of TS‐1 was also studied. The amorphous silica support covering on the external surface of TS‐1 was crystallized, and some hollows appeared in the samples that were post‐synthesized. Most titanium introduced by this method are located at the external surface of the new generated TS‐1 particles. The molar ratio of Si/Ti on the external surface decreases with the increase of the Ti concentration in the post‐synthesis solution. The catalytic activity for phenol hydroxylation over the TS‐1 samples is enhanced after the post‐synthesis due to the new generated framework Ti on the external surface, providing the reactants more easily adsorbable active centers. A proper Ti concentration (10 vol%) in the post‐synthesis solution leads to the highest catalytic activity by obtaining a proper ratio of tetrahedral and octahedral Ti to anatase TiO 2 .