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Zhang, L., and Yu, H. (2013). "Conversion of xylan and xylose into furfural in biorenewable deep eutectic solvent with trivalent metal chloride added," BioRes. 8(4), 6014-6025.


Transformation of the hemicellulose fraction in an environmentally benign manner to deliver high value-added chemicals is critical for the integrated utilization of biomass. Amongst all the chemicals derived from hemicellulose, furfural (produced by hydrolysis of xylan into xylose and successive dehydration of the latter) is a promising option. In this manuscript, a catalytic approach for converting xylan and xylose into furfural co-catalyzed by choline chloride-citric acid·H2O, a deep eutectic solvent (DES) synthesized from biorenewable building blocks, and trivalent metal chloride was developed. Choline chloride-citric acid·H2O acted as both reaction medium and Brønsted acid catalyst. Both monophasic route and biphasic route (with methyl isobutyl ketoneas extractant for in situ extraction of furfural) were proposed. The highest furfural yields obtained from xylose and xylan in monophasic approach were 59.3% and 54.2%, respectively, at 140 °C, and these values increased to 73.1% and 68.6% when biphasic system was applied for the reaction. Moreover, in biphasic system, choline chloride-citric acid and metal chloride could be recycled and reused for 5 runs with stable catalytic ability.
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