Low-Cost Synthesis of Titanium Silicalite-1 (TS-1) with Highly Catalytic Oxidation Performance through a Controlled Hydrolysis Process

Abstract

Titanium silicalite-1 (TS-1) has been successfully synthesized in ultralow molar ratio of TPAOH/SiO2 by two-step and multistep hydrolysis process, where the molar ratio of tetrapropylammonium hydroxide/silica (TPAOH/SiO2) could be reduced to 0.08 and 0.065, respectively. Combined characterization of X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microcopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV–vis spectroscopy, and thermal gravimetric (TG) analysis shows that currently synthesized TS-1 samples have the typical “blackberry” morphology, and the particle size is around 300–400 nm, similar to that of the conventional TS-1 synthesized at a high molar ratio of TPAOH/SiO2 (>0.18). Additionally, currently synthesized TS-1 exhibits excellent catalytic oxidation performance in epoxidation of alkene and ammoximation of ketone, even better than that of conventional TS-1. Obviously, fast hydrolysis of a small part of TEOS at a high concentration of TPA+ in the first step induces more nuclei, which in turn accelerates crystallization in the subsequent step. Therefore, effective utilization of TPAOH to build the TS-1 framework is significantly increased. This strategy can greatly reduce the synthesis cost of TS-1, which is suitable for synthesis of TS-1 on an industrial scale.

Photocatalytic Performance and Degradation Pathway of Rhodamine B with TS-1/C3N4 Composite under Visible Light

“…Several bands located at about 550, 800, 1105 and 1228 cm −1 are attributed to the MFI zeolitic structure of TS-1 zeolite [19,42]. The peak at 960 cm −1 is assigned as characteristic of Ti framework [19], indicating the presence of Ti in tetrahedral coordination within the silicalite framework [43]. All the FTIR spectra of TC-A, TC-B and TC-C contain the bands of TS-1 and C 3 N 4 .…”

Insights into the key to highly selective synthesis of oxime via ammoximation over titanosilicates

“…The product was recovered by filtration, drying, and calcination (823 K) to TS-1 samples, which have an average crystalline size of around 300 nm, denoted as conventional TS-1 (CTS-1). By regulating TPAOH/SiO 2 molar ratios from 0.08 to 0.30 in the starting gel, a series of TS-1 zeolites with different particle sizes were prepared in a similar way [30]. Hollow TS-1 (HTS-1) (Si/Ti = 37) material was obtained by modifying the conventional TS-1 (CTS-1) with 0.06 mol/L tetrapropylammonium hydroxide at 443 K for 72 h, based on the previous study [31].…”

“…7). Although acetaldehyde would be consecutively oxidized by active Ti-OOH species to form acetic acid [3], this side reaction would be cut off in actual ammoximation because the excessive NH 3 would compete with acetaldehyde for Ti-OOH species to form NH 2 On the other hand, the probe reaction of alkene epoxidation is a widely accepted way to evaluate the intrinsic catalytic activity of titanosilicates [8,30,48]. So it could reflect the relative catalytic oxidative abilities in activating free H 2 O 2 into Ti-OOH species possessed by titanosilicates with various Lewis acidic strengths.…”

The effect of acid treatment on the active sites and reaction intermediates of the low-cost TS-1 in propylene epoxidation

“…Some attempts have been made to reduce the amount of the template TPAOH required. Deng 6 carried out hydrothermal synthesis of TS-1 with a lower ratio of TPAOH/SiO 2 in two-step and multistep hydrolysis processes by ne tuning the nucleation and growth step during crystallization, which showed good activity in the oxidation of alkene and ammoximation of ketone. To further reduce the cost of the catalyst, tetrapropyl ammonium bromide (TPABr) was used as a template for the synthesis of TS-1.…”