Novel synthesis of Lewis and Bronsted acid sites incorporated CS-Fe3O4@SO3H catalyst and its application in one-pot synthesis of tri(furyl)methane under aqueous media

A sustainable chitosan (CS)-derived magnetic solid acid catalyst (CS-Fe3O4@SO3H) incorporated by Lewis and Bronsted acid sites was synthesized in an eco-friendly manner through the preloading of iron on CS and one-pot low-temperature carbonization/sulfonation. The carbonization/sulfonation of CS-Fe3O4 using p-Toluenesulfonic acid (p-TSA) at 140 oC resulted in the loss of ammonia in some extent and provided bifunctional sites on the catalyst. This heterogeneous catalyst was found to be highly selective for the conversion of xylose and arabinose to furfural (FF) and subsequent tri(furyl)methane (TFM) formation by the condensation with furan in the same reaction vessel without any purification. The outcome of optimization under different reaction parameters showed that only 20 wt.% of CS-Fe3O4@SO3H catalyst resulted in 81% TFM yield from xylose while arabinose gave a 70% TFM yield in dimethyl sulfoxide (DMSO):water with high selectivity. This green protocol provides an easy isolation of products and minimizes the formation of polymerized by-products. The catalyst can be readily recovered and efficiently reused for three consecutive catalytic cycles without any significant loss on product yields.