Cinnamyl Alcohol Oxidation Using Supported Bimetallic Au\u2013Pd Nanoparticles: An Optimization of Metal Ratio and Investigation of the Deactivation Mechanism Under Autoxidation Conditions

Emilia Rucinska,Samuel Pattisson,Meenakshisundaram Sankar,Graham J Hutchings,David J Morgan,Gemma L Brett,Peter J Miedziak

doi:10.1007/s11244-020-01231-0

Abstract

The aerobic oxidation of cinnamyl alcohol in toluene under autoxidation conditions has been studied using a range of 1 wt% Au–Pd/TiO2 catalysts. The catalysts have been studied to determine the effect of preparation method (impregnation and sol immobilisation) and metal ratio on the conversion of cinnamyl alcohol and the selectivity to cinnamaldehyde. The catalysts prepared by sol-immobilisation demonstrate higher selectivity to the desired aldehyde than the analogous impregnation materials. The most active catalyst was found to be 0.75 wt% Au–0.25 wt% Pd/TiO2 prepared by sol-immobilisation and this demonstrates the importance of metal ratio optimisation in this catalytic process. Furthermore, this metal ratio was found to be most stable under the reactions conditions with little change observed over multiple uses.

Highlights

One of the major challenges facing the chemical industry is to introduce efficient and benign methods for the production of fine chemicals
In the previous paper we studied the phenomenon of autoxidation of cinnamyl alcohol, the effect of reaction conditions and the impact of Au–Pd catalysts, obtained by two different preparation methods, on the reaction
In this work we investigate the influence of metal ratio in bimetallic catalysts prepared by wet impregnation and sol immobilisation (SIm) for the oxidation of cinnamyl alcohol under autoxidation conditions

Summary

Introduction

One of the major challenges facing the chemical industry is to introduce efficient and benign methods for the production of fine chemicals. There is currently a large demand for carbonyl compounds that are obtained through the oxidation of alcohols. Harmful and expensive oxidants such as chromates and permanganates are currently used for these purposes [1]. Heterogeneous catalysts have received great interest as an excellent green alternative for these processes largely due to their ability to utilise O 2 as the oxidant. Au–Pd supported nanoparticles have proven to be extremely active and selective for various alcohol oxidation reactions [2,3,4,5]. Cinnamyl alcohol oxidation is a model reaction to underpin work on renewable and sustainable feedstocks such as lignocellulosic biomass [6,7,8,9]. The desired product of this reaction, cinnamaldehyde, finds many

Objectives

Methods

Results

Conclusion