Facile Preparation of Mesoporous MCM-48 Containing Silver Nanoparticles with Fly Ash as Raw Materials for CO Catalytic Oxidation.

Dong Tian,Bin Lin,Xiaoyong Lu,Yihan Ling,Yonghong Chen

doi:10.3390/mi12070841

Abstract

An environmentally friendly method was proposed to prepare mesoporous Mobil Composition of Matter No.48 (MCM-48) using fly ash as the silica source. Silver nanoparticles were infiltrated on MCM-48 facilely by an in situ post-reduction method and evaluated as an effective catalyst for CO oxidation. The as-prepared MCM-48 and Ag/MCM-48 nanoparticles were characterized by XRD, N2 adsorption/desorption, and TEM. Investigations by means of XPS for Ag/MCM-48 were performed in order to illuminate the surface composition of the samples. Studies revealed the strong influence of the loading of Ag nanoparticles on catalysts in the oxidation of CO. CO conversion values for Ag/MCM-48 of 10% and 100% were achieved at temperatures of 220 °C and 270 °C, respectively, indicating that the Ag-decorated MCM-48 catalyst is extremely active for CO oxidation.

Highlights

Fly ash is a waste product from coal combustion in power plants
It can be seen that Ag/Mobil Composition of Matter No.48 (MCM-48) prepared by the post-reduction technique presented weaker diffraction peaks in the high-angle X-Ray Diffraction (XRD) patterns (such as (111) peak of Ag), which shows that MCM-48-supported Ag nanoparticles presented a smaller size
We proposed that the observed Ag nanoparticle size–reaction temperature relation in the CO oxidation catalyzed by Ag/mesoporous silica catalysts might be attributed to the fine and non-aggregated Ag nanoparticles that are more chemically active

Summary

Introduction

The large amount of SiO2 (50–70%) and Al2 O3 (20–30%) in fly ash makes it suitable for preparing many industrial products. Because the content of SiO2 is above 50%, using fly ash as a silica source to prepare mesoporous silica is an environmentally friendly approach to reuse the waste resources and has been regarded as a suitable skeleton to decorate nanostructured metals due to its large pores (2–50 nm) with a narrow distribution (the ease of macroscopic morphological control) and a high surface area. Panek synthesized Mobil Composition of Matter No. (MCM-41) by a hydrothermal method under a long reaction time of 72 h using pristine fly ash [2]. It could be seen that MCM-41 could be successfully prepared from fly ash, but the long reaction time was not environmentally friendly and limited its widespread application

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