Copper-supported hydroxyapatite catalysts for bio-isobutanol synthesis from sustainable short-chain alcohols

Abstract

Developing high-performance catalysts for the direct production of isobutanol through the Guerbet reaction is a challenge today, due to the potential of isobutanol as fuel. The present study describes the synthesis and characterization of Cu-supported hydroxyapatite catalysts. The synthesis of isobutanol has been investigated through batch experiments and in a continuous-flow reactor operating in a gas-solid phase. This study used ethanol and methanol as the primary feedstock for the synthesis process. It was found that Cu supported hydroxiapatite catalysts are capable of catalyzing the formation of isobutanol from CH3OH and C2H5OH at temperatures (300 to 500 ºC) and 1atm in a continuous flow reactor. Notably, the highest selectivity to isobutanol was observed at 400 ºC. The use of Cu10/HAP 1.65 catalyst in a batch reactor greatly enhances the selectivity of iBuOH in the liquid phase, increasing it from 18% (vapor-phase) to 65%. The data showed that the reaction of ethanol/methanol was limited by the 1-propanol-to-isobutanol reaction, which is a secondary reaction of the key intermediate. A reaction scheme has been proposed.