Mesoporous Silica Based Gold Catalysts: Novel Synthesis and Application in Catalytic Oxidation of CO and Volatile Organic Compounds (VOCs)

Hongjing Wu,Leonarda Liotta,Giuseppe Pantaleo,Anna Venezia

doi:10.3390/catal3040774

Hongjing Wu, Leonarda Liotta + Show 2 more

Open Access

https://doi.org/10.3390/catal3040774

Copy DOI

Abstract

Gold nanoparticles, particularly with the particle size of 2–5 nm, have attracted increasing research attention during the past decades due to their surprisingly high activity in CO and volatile organic compounds (VOCs) oxidation at low temperatures. In particular, CO oxidation below room temperature has been extensively studied on gold nanoparticles supported on several oxides (TiO2, Fe2O3, CeO2, etc.). Recently, mesoporous silica materials (such as SBA-15, MCM-41, MCM-48 and HMS) possessing ordered channel structures and suitable pore diameters, large internal surface areas, thermal stabilities and excellent mechanical properties, have been investigated as suitable hosts for gold nanoparticles. In this review we highlight the development of novel mesoporous silica based gold catalysts based on examples, mostly from recently reported results. Several synthesis methods are described herein. In detail we report: the modification of silica with organic functional groups; the one-pot synthesis with the incorporation of both gold and coupling agent containing functionality for the synthesis of mesoporous silica; the use of cationic gold complexes; the synthesis of silica in the presence of gold colloids or the dispersion of gold colloids protected by ligands or polymers onto silica; the modification of silica by other metal oxides; other conventional preparation methods to form mesoporous silica based gold catalysts. The gold based catalysts prepared as such demonstrate good potential for use in oxidation of CO and VOCs at low temperatures. From the wide family of VOCs, the oxidation of methanol and dimethyldisulfide has been addressed in the present review.

Highlights

Gold has been used for coinage, jewelry, and other types of art for thousands of years due to its high stability in wet air
In this review we have provided a survey of the development of highly dispersed mesoporous silica based gold catalysts
It is well known that the conventional methods such as impregnation, deposition-precipitation, colloidal deposition, et al, to prepare highly dispersed Au-NPs confined in the channels of mesoporous silicas are not efficient

Summary

Introduction

Gold has been used for coinage, jewelry, and other types of art for thousands of years due to its high stability in wet air. The large gold nanoparticles aggregate on the surface of amorphous silica with irregular shapes due to poor interaction between gold colloids and silica supports as previously reported in our paper [25] These catalysts exhibit different catalytic activity toward oxidation of CO and VOCs depending on the various particle sizes of gold and the nature of the supports [25,26]. The Dp method is considered as an effective method to prepare supported gold catalysts due to the uniform size and excellent activity of the Au-NPs. the mesoporous materials such as HMS have very poor hydrothermal stability, so it is possible to destroy the intrinsic mesoporous structure under such harsh conditions of the Dp approach, which is confirmed in their papers. The results show that the preparation method influences the porous structure of the support, density and particle size of the Au-NPs, whereas no reaction data on the oxidation of CO or VOCs are reported

Colloidal Synthesis of Au-NPs Incorporated into Mesoporous Silica

Preparation methods

Findings

Concluding Remarks