Facile Synthesis of Yolk/Core-Shell Structured TS-1@Mesosilica Composites for Enhanced Hydroxylation of Phenol

Houbing Zou,Dongyu Fan,Weiwei Fu,Lijia Liu,Runwei Wang,Qingli Sun

doi:10.3390/catal5042134

Abstract

In the current work, we developed a facile synthesis of yolk/core-shell structured TS-1@mesosilica composites and studied their catalytic performances in the hydroxylation of phenol with H2O2 as the oxidant. The core-shell TS-1@mesosilica composites were prepared via a uniform coating process, while the yolk-shell TS-1@mesosilica composite was prepared using a resorcinol-formaldehyde resin (RF) middle-layer as the sacrificial template. The obtained materials were characterized by X-ray diffraction (XRD), N2 sorption, Fourier transform infrared spectoscopy (FT-IR) UV-Visible spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results showed that these samples possessed highly uniform yolk/core-shell structures, high surface area (560–700 m2 g−1) and hierarchical pore structures from oriented mesochannels to zeolite micropores. Importantly, owing to their unique structural properties, these composites exhibited enhanced activity, and also selectivity in the phenol hydroxylation reaction.

Highlights

Hydroxylation of phenol with hydrogen peroxide (H2O2) as oxidant has been widely applied for the production of two useful compounds, viz. catechol and hydroquinone [1,2]
The scanning electron microscopy (SEM) image (Figure 1a) and transmission electron microscopy (TEM) image (Figure 2a,b) indicate that the TS-1 sample consist of uniform monodisperse nanocrystals with a particle size of 290–350 nm
The SEM micrograph (Figure 1b) shows that the particles are oval in shape with a large diameter (350–400 nm), suggesting that an mSiO2 layer of approximately 30 nm was formed on the surface of the TS-1 crystals

Summary

Introduction

Hydroxylation of phenol with hydrogen peroxide (H2O2) as oxidant has been widely applied for the production of two useful compounds, viz. catechol and hydroquinone [1,2]. While significant achievements have been realized in this approach, the methods employed usually involved either cost-intensive mesostructured templates [15,19,20,21] or complex synthetic procedures [17,18] In this regard, synthesis of TS-1 zeolite-based composites is an alternative approach. We devoted our efforts to study the catalytic properties of TS-1 zeolite-based yolk/core-shell composites in the hydroxylation of phenol and determine the relationship between the mircostructure of the material and its catalytic performance. Sorption, FT-IR, UV-Visible spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

Results and Discussion

Chemicals

Synthesis of Pristine TS-1 Zeolite

Catalytic Tests

Materials Characterization

Conclusions