Highly efficient preparation of HMF from cellulose using temperature-responsive heteropolyacid catalysts in cascade reaction

• Temperature-responsive heteropolyacid presents the highest yield of HMF (75.0%).
• Easy preparation of catalyst using choline chloride and H3PW12O40 by coprecipitate.
• Temperature-responsibility links the gap of heterogeneous and homogeneous catalyst.
• Easy separation of HMF using MIBK and prevent HMF further rehydration.
• Microwave improved HMF yield from cellulose at short time or low temperature.

A series of heteropolyacid catalysts (HOCH2CH2N(CH3)3) xH3−xPW12O40 (abbreviated as ChxH3−xPW12O40, x = 1, 2 and 3) had been synthesized using choline chloride and H3PW12O40 as the raw materials, which were used as heterogeneous catalysts in one-pot conversion of cellulose to 5- hydroxymethylfurfural (abbreviated as HMF) in double solvent system containing methyl isobutyl ketone (abbreviated as MIBK) and H2O. A remarkable HMF yield of 75.0% was achieved catalyzed by ChH2PW12O40 within 8 h at 140 °C attributed to its higher Brønsted acidity and thermoregulate property comparable to its homogeneous form H3PW12O40. To the best of our knowledge, it was almost the highest yield of HMF from cellulose by now, while the best yield of 64.0% was reported so far over AlCl3 in biphasic system. Using our biphasic reaction protocol, even raw lignocellulosic biomass straw, gave HMF yields of 27.6%. Moreover, such heteropolyacid catalysts could be recycled under simply lowering the reaction temperature to room temperature without loss of its weight, which were reused for more than 10 times.

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