Efficient catalytic conversion of cellulose into 5-hydroxymethylfurfural by modified cerium zirconium phosphates in a biphasic system

Numerous metal phosphates have shown activity in the conversion of cellulose into 5-hydroxymethylfurfural (HMF). However, challenges persist due to low HMF yields and unclear structure-reactivity relationships. Herein, a series of zirconium-cerium phosphate-based catalysts were prepared by the co-precipitation method. These catalysts were sulfonated and loaded with tungsten to introduce Brønsted acidity. The effects of catalyst types and operating conditions on the production of HMF from cellulose using a biphasic system of tetrahydrofuran (THF) and water were systematically investigated in an autoclave reactor. The structure-reactivity relationship of these catalysts was subsequently elucidated using various catalyst characterization techniques. For an understanding of the reaction mechanism, in-situ attenuated total reflectance infrared spectroscopy (ATR-FTIR) was employed to monitor the reaction process. Experimental results revealed that the optimal HMF yield of 41.5% could be obtained using the 2W/CeZr2P + AC–SO3H–2 catalyst at 180 °C with a reaction time of 4 h. Compared to monometallic phosphate pairs of zirconium and cerium, this represents an enhancement in HMF yield by approximately 8%–20%. The enhancement could be attributed to the adequate acid amount and the balanced Brønsted/Lewis acid site ratio of this catalyst. These findings provide valuable guidance for future design and optimization of bimetallic phosphate catalysts.