Gold/Substituted Hydroxyapatites for Oxidative Esterification: Control of Thin Apatite Layer on Gold Based on Strong Metal-Support Interaction (SMSI) Results in High Activity.

Gold nanoparticles (Au NPs) deposited on various cation- and anion-substituted hydroxyapatites (Au/sHAPs) show oxidative strong metal-support interaction (SMSI), wherein a thin layer of the sHAP covered the surface of the Au NPs by heat treatment in an oxidative atmosphere. Calcination of Au/sHAPs at 300 °C caused a partial SMSI and that at 500 °C gave fully encapsulated Au NPs. We investigated the influence of the substituted ions in sHAP and the degree of the oxidative SMSI on the catalytic performance of Au/sHAPs for oxidative esterification of octanal or 1-octanol with ethanol to obtain ethyl octanoate.