One-Pot Alkaline Earth and Alkali Metal Salts Assisted Conversion of Glucose to 5-Hydroxymethylfurfural Over Bifunctional SAPO_34 Molecular Sieve Using γ-Valerolactone/Water Solvent System

Abstract

5-Hydroxymethylfurfural known as a biomass-derived pivotal platform chemical is an important alternative for petroleum-based chemicals. However, its large-scale production faces serious barriers and limitation in terms of 5-Hydroxymethylfurfural yield and production cost. In the present work, dual structure directing agent SAPO_34 molecular sieve was prepared by hydrothermal method and XRD, SEM, XRF, BET and pyridine FTIR spectroscopy techniques were employed to characterize the synthesized catalyst. The Lewis/Bronsted SAPO_34 molecular sieve performance was evaluated in the conversion of glucose into 5-Hydroxymethylfurfural in γ-Valerolactone/water solvent system. The effects of alkaline earth and alkali metal salts were also studied. Promising results were obtained which could optimize the 5-Hydroxymethylfurfural yield up to 92%. The ascending overall 5-Hydroxymethylfurfural selectivity trend suggests that the formation of 5-hydroxymethylfurfural is in dominant position at the expense of glucose until 5-HMF yield peak values are obtained. The introduction of metal salts to the reaction medium was beneficial to the reaction efficiency and it was shown that the cations rather than the anions play the main role in the promotion of the conversion. Furthermore, salts containing cations of smaller ionic radius and higher charge density demonstrating superior performance. The analysis of reaction kinetic revealed that glucose conversion activation energy decreased by 5.8 kJ/mole with the addition of MgCl₂ to the reaction medium. Finally, the tests to evaluate the catalyst’s recyclability were conducted both with and without the addition of salt.

Graphical Abstract