Functionalized Coal Fly Ash Is an Efficient Catalyst for Synthesizing Furfural from Xylose at a Low Catalyst Load

In this study, coal fly ash was functionalized, using a simple one-step process (loading with Al3+ and sulfonation), to yield a solid acid catalyst (S/Al-CFA) with strong acid sites. The catalyst was then used to produce furfural from xylose in a biphasic system (H2O(NaCl)/tetrahydrofuran). The furfural yield reached 82% at 180 °C–60 min with catalyst/xylose ratio of 0.2:1.0 (w/w). With the reaction completed, all of the components could be effectively separated, and the furfural was 97.6% pure. The cycle and regeneration of the catalyst were evaluated, and the catalyst deactivation mechanism was investigated.