Study On The Synthesis Of 5-hydroxymethylfurfural From Glucose Over Sn,Al-modified Phosphotungstic Acid Catalysts

As a kind of renewable resource with abundant production,the hydrolysis of cellulose biomass to glucose and further catalytic conversion to high value-added chemicals were the key technology to realize the application of biomass resources in various fields.In addition,As an important platform compound,5-hydroxymethylfurfural?5-HMF?was an important basic material for producing biomass biofuels and fine chemicals.In this paper,glucose converting into 5-HMF was studied.1?SnCl₄ and phosphotungstic acid were mixed by solvothermal method?ethanol was used as solvent?.Trimesic acid?BTC?was added to support phosphotungstic acid and regulate pore structure.Sn-supported phosphotungstic acid catalyst was obtained by calcination of this precursor.Characterization analysis showed that the strong electron absorption of phosphotungstic acid produced positive charges around Sn4+,which could be used as Lewis acid sites.As a result,more L acid sites on the surface of the catalyst were beneficial for the isomerization of glucose.Phosphotungstic acid and Sn-OH could be as Bronsted acid sites which catalyzed the formation of 5-HMF.Furthermore,The addition of BTC could effectively support phosphotungstic acid and regulate the structure and pore size of the catalyst,increasing the specific surface area.Therefore,the catalyst was more conducive to the contact between the reactants and the active sites.This series of catalysts were applied in glucose converting to 5-HMF.Results showed that the activity of 2PW/SnO2-B was the best.The yield and selectivity of the 5-HMF were 46.4%and 51.5%,respectively.Furthermore,the activity could be maintained after 6 times reusing.2?Novel solid acid catalyst PWAl-200 was synthesized by a new green method of electric-flocculation of phosphotungstic acid?PW?with aluminum as electrodes.Through electric-flocculation,PW was deposited in the hydrated aluminum received from electrolysis.Then the obtained floe was treated by hydrothermal process to get solid acid.Characterization results showed that after electric-flocculation,the electron-withdrawing influence of terminal W=O in the PW on hydrated aluminum formed Lewis?L?acid sites on these six-coordinated aluiminum.The H+ derived from PW could supply Bronsted?B?acid sites.In the further hydrothermal treatment,hydrated aluminum dehydrated to produce reformed six-coordinated aluminum.It was linked to heteropoly anions ligands through oxygen bridges.producing more L acid center.Besides,four-coordinated auminum formed from the hydrated aluminum.The positive charge it produced increased L acid sites due to the strong effect of nearby tungsten species,further adjusting to a moderate ratio of Lewis/Bronsted?L/B?on solid acid.The catalyst was applied on synthesis 5-HMF from glucose.The highest yield and selectivity were 61.7%and 64.9%at 170? for 4 hours,respectively.The catalyst could be recycled for five times and tend to stabilize.