Production of Furan Compounds from Sugarcane Bagasse Using a Catalytic System Containing ZnCl2/HCl or AlCl3/HCl in a Biphasic System

In this work, two catalytic systems combining Lewis and Brønsted acids (ZnCl2/HCl and AlCl3/HCl) were applied in a tetrahydrofuran (THF)/NaClaq biphasic system to produce furan compounds from plant polysaccharides. The following cellulosic matrices were applied for this purpose: α-cellulose, microcrystalline cellulose and both native and steam-exploded sugarcane bagasse. The AlCl3/HCl catalytic system afforded the best yields for α-cellulose conversion to furan compounds (hydrolysis followed by dehydration). The highest yields of 5-(hydroxymethyl)-furfural (HMF) and furfural were 44.0 and 92.2% for AlCl3/HCl and 36.5 and 81.4% for ZnCl2/HCl, respectively. Cellulosic materials with lower crystallinity indexes afforded the best performance in hydrolysis followed by dehydration, giving relatively high yields of HMF and furfural. The HMF yields were similar for both native and steam-exploded sugarcane bagasse and the presence of lignin had a negative effect on HMF production. The highest furfural yield from native sugarcane bagasse was 60.6% with AlCl3/HCl catalytic system.

本研究采用两种路易斯酸（Lewis acid）与布朗斯特酸（Brønsted acid）复配催化体系（ZnCl₂/HCl与AlCl₃/HCl），在四氢呋喃（tetrahydrofuran, THF）/氯化钠水溶液双相反应体系中，以植物多糖为原料制备呋喃类化合物。本研究选用如下纤维素基质开展实验：α-纤维素、微晶纤维素，以及天然甘蔗渣与蒸汽爆破甘蔗渣。AlCl₃/HCl催化体系对α-纤维素经水解-脱水级联反应转化为呋喃类化合物的过程展现出最优产率。其中AlCl₃/HCl体系下5-羟甲基糠醛（5-(hydroxymethyl)-furfural, HMF）与糠醛的最高产率分别为44.0%与92.2%，ZnCl₂/HCl体系下对应产率分别为36.5%与81.4%。结晶度更低的纤维素基质在水解-脱水级联反应中表现更优，可获得相对更高的HMF与糠醛产率。天然甘蔗渣与蒸汽爆破甘蔗渣的HMF产率相近，而木质素的存在对HMF的生成具有负面影响。采用AlCl₃/HCl催化体系时，天然甘蔗渣的糠醛最高产率可达60.6%。