Mechanism and kinetic parameters of glucose and fructose dehydration to 5-hydroxymethylfurfural over solid phosphate catalysts in water

Abstract

The reaction of dehydration of glucose and fructose was studied over solid acid catalysts (zirconium hydrogen phosphates, and sulfonated and carboxylated activated carbons) in water at 125, 135 and 145°C. Zirconium hydrogen phosphate enhanced their activity and selectivity toward 5-HMF from glucose or fructose after being calcined at 700°C (ZrPO-700).The activation energy of the first step of the dehydration of fructose (formation of an intermediary) was higher than the one of the second step (formation of 5-HMF from intermediary), 209 and 25kJ/mol, respectively. Additionally, the activation energy of glucose isomerization to fructose was 97kJ/mol. Overall; the formation of intermediary between fructose and 5-HMF was the limiting step in the formation of 5-HMF from glucose or fructose.Fitting simulations of experimental data estimated maximum yield and selectivity toward 5-HMF from glucose using ZrPO-700 at 125, 135 and 145°C. These predictions help investigators to estimate conversions and selectivity when pilot plants need to be simulated.