Efficient synthesis of 5-hydroxymethylfurfural from carbohydrates via SO₃H-containing dendrimer zeolite catalyst

A three-generation dendrimer beta zeolite catalyst (G3-beta-SO3H) was prepared by successfully growing a triazine dendrimer with a terminal sulfonic acid group on beta zeolite surface via a thiol-ene click reaction, which can be used as a bifunctional catalyst for the efficient conversion of carbohydrates to 5-hydroxymethylfurfural (HMF). The composition, structure, microscopic morphology and acidic sites of the G3-beta-SO3H zeolite were investigated by elemental analysis, EDS-Mapping, FTIR, XPS, SEM, XRD, N-2 adsorption-desorption isotherm, Py-FTIR and NH3-TPD. The catalytic performance of the catalyst was evaluated for the synthesis of HMF by converting carbohydrates in the H2O(NaCl)/tetrahydrofuran (THF) biphasic system. The G3-beta-SO3H zeolite catalyst gave remarkable HMF yields for the conversion of monosaccharides, disaccharides, polysaccharides, plant fibrous feedstock (moso bamboo), and waste biomass (wheat straw). By optimizing the reaction conditions, the catalyst achieved a maximum yield of 63.6% HMF from cellulose in H2O(NaCl)/THF system. Further, the catalytic system still resulted in 44% HMF yield from cellulose after five cycles, with acidic site leaching being the main factor in the decrease of the catalyst activity.