The High-Performance Hollow Silicalite-1@Titanium Silicalite-1 Core-Shell Catalyst for Propene Epoxidation

Abstract

Hollow silicalite‐1@titanium silicalite‐1 (H−S‐1@TS‐1) core‐shell catalyst was synthesized in hydrothermal system with hollow silicalite‐1 serving as core. In this novel method, tetrapropylammonium hydroxide (TPAOH) served as the single template in the whole synthesis process so as to avoid secondary structure directing agents (SDAs) that traditional methods applied to give core‐shell TS‐1. Since inner hollow structure was given by S‐1, H−S‐1@TS‐1 avoided framework Ti leaching in coventional dissolution‐recrystallization process that gave hollow TS‐1 and thus it was in absence of extra‐framework Ti. H−S‐1@TS‐1 showed better propene epoxidation activity (TOF=13.61 mol (mol h)−1) than microporous TS‐1 (TOF=8.08 mol (mol h)−1) and micro‐TS‐1 post‐treated with TPAOH solution (TOF=9.75 mol (mol h)−1) due to the synergy function of pure framework Ti species, higher surface Ti content and enhanced diffusion property.

Hollow core–shell structured TS-1@S-1 as an efficient catalyst for alkene epoxidation

“…In the first step, H-TS-1 was obtained by post-treatment of the TS-1 in alkaline system following the procedure reported in literature. 26 Typically, 4 g TS-1 was suspended in 14.642 g TPAOH (25 wt%) solution, the molar compositions of final mixture was 1.0 Si : 0.27 TPAOH : 9.1 H 2 O, after stirring for 1 h, the mixture was crystallized in a 100 mL Teflon-lined autoclave under 443 K for 72 h under static conditions. The product was recovered by filtration, drying, and calcinations as mentioned above, denoted as H-TS-1-x (x stands for Si/Ti).…”

Coordination States and Catalytic Performance of Ti in Titanium Silicalite-1

“…However, this method leads to the transformation of tetrahedrally coordinated Ti to extraframework Ti, which is harmful for the catalytic performance. Therefore, we provided a method for synthesizing a hollow core-shell material to prevent the generation of extra-framework Ti [36]. The hollow silicalite-1@titanium silicalite-1 (H-S-1@TS-1) core-shell material was synthesized in a TPAOH hydrothermal system with hollow silicalite-1 serving as the core (see Figure 8).…”

Nano-Cavities within Nano-Zeolites: The Influencing Factors of the Fabricating Process on Their Catalytic Activities

“…Post-treatment recrystallization was the key process [ 22 ]. In addition to increasing the catalytic activity, this strategy could stabilize production and reduce the risk of failure, which had become a widely-accepted essential process for the production of the TS-1 zeolite catalyst [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. The post-treatment to enhance catalytic activity was explained from the aspects of reducing microporous channels based on a hollow structure and/or improving the content of active titanium [ 11 , 23 , 31 , 32 ].…”