Effect of calcination temperature on catalytic performance of alkaline earth phosphates in hydrolysis/dehydration of glucose and cellulose

Abstract

The hydrolysis/dehydration of glucose and cellulose to 5-hydroxymethylfurfural (HMF) catalyzed by alkaline earth phosphates was investigated under hot compressed water condition. The catalysts were synthesized by reactions of CaCO3 or SrCO3 with ortho-H3PO4 via conventional precipitation method in acetone–water media system. The experimental results revealed that the calcination temperature greatly influenced the crystalline phases of the catalysts and the catalytic activity. The calcium and strontium phosphate catalysts without calcination are Ca(H2PO4)·H2O and Sr(H2PO4)2, respectively. The calcium phosphate catalysts calcined at 600 and 900°C are β-CaP2O6 while the strontium phosphate catalysts display Sr2(PO3)4, and α-Sr(PO3)2, respectively. The incorporation of Ca and Sr into phosphate network of calcined samples can further improve catalytic performance. Among all synthesized catalysts, the α-Sr(PO3)2 calcined at 900°C showed the best catalytic activity, providing the HMF yield of 21.0% from glucose dehydration and total yield of glucose and HMF of 34.8% from hydrolysis coupling dehydration of cellulose.