Gold nanoparticles supported on magnesium oxide for CO oxidation

Sónia Ac Carabineiro,Nina Bogdanchikova,Pedro B Tavares,Lisete Sg Fernandes,Alexey Pestryakov,José L Figueiredo

doi:10.1186/1556-276x-6-435

Abstract

Au was loaded (1 wt%) on a commercial MgO support by three different methods: double impregnation, liquid-phase reductive deposition and ultrasonication. Samples were characterised by adsorption of N2 at -96°C, temperature-programmed reduction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Upon loading with Au, MgO changed into Mg(OH)2 (the hydroxide was most likely formed by reaction with water, in which the gold precursor was dissolved). The size range for gold nanoparticles was 2-12 nm for the DIM method and 3-15 nm for LPRD and US. The average size of gold particles was 5.4 nm for DIM and larger than 6.5 for the other methods. CO oxidation was used as a test reaction to compare the catalytic activity. The best results were obtained with the DIM method, followed by LPRD and US. This can be explained in terms of the nanoparticle size, well known to determine the catalytic activity of gold catalysts.

Highlights

It is well known from the literature that for gold to be active as a catalyst, a careful preparation is needed to obtain nanoparticles well dispersed on the support [1,2,3,4]
Margitfalvi et al [9] prepared Au/MgO catalysts with high activity for low temperature CO oxidation
CO oxidation was used as a test reaction to compare the catalytic activity

Summary

Introduction

It is well known from the literature that for gold to be active as a catalyst, a careful preparation is needed to obtain nanoparticles well dispersed on the support [1,2,3,4]. MgO is considered as “inactive” [5,6,7,8] since it is basically an irreducible oxide, such as Al2O3. These materials have low ability to adsorb or store oxygen at low temperatures [5]. Margitfalvi et al [9] prepared Au/MgO catalysts with high activity for low temperature CO oxidation. The activity of these catalysts was further increased by modification with ascorbic acid in a relatively narrow concentration range. Gates and co-workers [10,11] managed to produce a Au/MgO catalyst that was active for CO oxidation at 30°C by bringing Au(CH3)2(acac) (acac is acetylacetonate) in contact with partially dehydroxylated MgO and by treatment in flowing helium at 473 K, during which the original mononuclear Au(III) species decomposed, gold

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