The Role of Mg(OH)2 in the So-Called "Base-Free" Oxidation of Glycerol with AuPd Catalysts.

Jile Fu,Qian He,Gemma L Brett,Samuel Pattisson,Graham J Hutchings,Peter J Miedziak,Xiaoyang Huang,Mark Douthwaite

doi:10.1002/chem.201704151

Abstract

Mg(OH)2‐ and Mg(OH)2‐containing materials can provide excellent performance as supports for AuPd nanoparticles for the oxidation of glycerol in the absence of base, which is considered to be a result of additional basic sites on the surface of the support. However, its influence on the reaction solution is not generally discussed. In this paper, we examine the relationship between the basic Mg(OH)2 support and AuPd nanoparticles in detail using four types of catalyst. For these reactions, the physical interaction between Mg(OH)2 and AuPd was adjusted. It was found that the activity of the AuPd nanoparticles increased with the amount of Mg(OH)2 added under base‐free conditions, regardless of its interaction with the noble metals. In order to investigate how Mg(OH)2 affected the glycerol oxidation, detailed information about the performance of AuPd/Mg(OH)2, physically mixed (AuPd/C+Mg(OH)2) and (AuPd/C+NaHCO3) was obtained and compared. Furthermore, NaOH and Mg(OH)2 were added during the reaction using AuPd/C. All these results indicate that the distinctive and outstanding performance of Mg(OH)2 supported catalysts in base‐free condition is in fact directly related to its ability to affect the pH during the reaction and as such, assists with the initial activation of the primary alcohol, which is considered to be the rate determining step in the reaction.

Highlights

Biomass conversion has drawn worldwide attention in recent years because of its potential to be an alternative resource to fossil fuel
AuPdÀMg(OH)2/C catalysts with varying quantities of Mg(OH)2 were prepared by the sol-immobilization method using the pre-synthesized support Mg(OH)2/C. These catalysts were observed to be effective for glycerol oxidation under “base-free” conditions (Supporting Information Figure S1) when high amounts of Mg(OH)2 were loaded onto the carbon support
It has been previously reported that a mixed carbon/Mg(OH)2 support shows much better activity than carbon alone in 5-hydroxymethylfurfural (HMF) oxidation with Pt nanoparticles under base-free reaction conditions, which has been ascribed to the basic sites provided by Mg2+.[13]

Summary

Introduction

Biomass conversion has drawn worldwide attention in recent years because of its potential to be an alternative resource to fossil fuel. The gradually increasing production of biodiesel has generated a huge amount of by-products, the major part of which is glycerol.[1] It is reported that glycerol is comprised of approximately 10 wt % of the total product yield for biodiesel production[2] and as such, it is projected that the demand for the consumption of glycerol will increase from 2000 kt in 2011 to 3070 kt by 2018.[3] transforming glycerol into valuable derivatives could be an effective method to increase the economic efficiency of biodiesel production. Fu+ Department of Chemical and Biochemical Engineering College of Chemistry and Chemical Engineering National Engineering Laboratory for Green Chemical Productions of Alcohols-Ethers-Esters Xiamen University Xiamen 361005

Objectives

Results

Conclusion