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Insight into Aluminum Sulfate‐Catalyzed Xylan Conversion into Furfural in a γ‐Valerolactone/Water Biphasic Solvent under Microwave Conditions
Author(s) -
Yang Tao,
Zhou YiHan,
Zhu ShengZhen,
Pan Hui,
Huang YaoBing
Publication year - 2017
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201701290
Subject(s) - furfural , chemistry , catalysis , xylose , xylan , yield (engineering) , isomerization , organic chemistry , lignocellulosic biomass , lewis acids and bases , hydrolysis , inorganic chemistry , fermentation , materials science , metallurgy
A simple and efficient biphasic system with an earth‐abundant metal salt catalyst was used to produce furfural from xylan with a high yield of up to 87.8 % under microwave conditions. Strikingly, the metal salt Al 2 (SO 4 ) 3 exhibited excellent catalytic activity for xylan conversion, owing to a combination of Lewis and Brønsted acidity and its ability to promote good phase separation. The critical role of the SO 4 2− anion was first analyzed, which resulted in the aforementioned characteristics when combined with the Al 3+ cation. The mixed solvent system with γ‐valerolactone (GVL) as the organic phase provided the highest furfural yield, resulting from its good dielectric properties and dissolving capacity, which facilitated the absorption of microwave energy and promoted mass transfer. Mechanistic studies suggested that the xylan‐to‐furfural conversion proceeded mainly through a hydrolysis–isomerization–dehydration pathway and the hexa‐coordinated Lewis acidic [Al(OH) 2 (aq)] + species were the active sites for xylose–xylulose isomerization. Detailed kinetic studies of the subreaction for the xylan conversion revealed that GVL regulates the reaction rates and pathways by promoting the rates of the key steps involved for furfural production and suppressing the side reactions for humin production. Finally, the Al 2 (SO 4 ) 3 catalyst was used for the production of furfural from several lignocellulosic feedstocks, revealing its great potential for other biomass conversions.