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Aqueous phase catalytic conversion of agarose to 5-hydroxymethylfurfural by metal chlorides

Yan, Lishi, Laskar, Dhrubojyoti D., Lee, Suh-Jane, Yang, Bin
RSC advances 2013 v.3 no.46 pp. 24090-24098
agarose, alkaline earth metals, byproducts, calcium chloride, catalysts, catalytic activity, chemical bonding, ferric chloride, galactose, hydroxymethylfurfural, isomerization, lactic acid, levulinic acid, magnesium chloride, sodium chloride, temperature, zinc chloride
The production of 5-hydroxymethylfurfural (5-HMF) from agarose catalyzed by metal chlorides was studied in aqueous phase. A series of metal chlorides, including NaCl, CaCl₂, MgCl₂, ZnCl₂, CrCl₃, CuCl₂ and FeCl₃, were comparatively investigated to catalyze agarose degradation for the production of 5-HMF at temperatures of 180 °C, 200 °C and 220 °C, catalyst concentration of 0.5% (w/w), 1% (w/w) and 5% (w/w), time of 0–50 min, and substrate concentration of 2% (w/w). Results revealed that alkali and alkaline earth metal chlorides, including NaCl, CaCl₂ and MgCl₂, resulted in higher 5-HMF yields from agarose with negligible amount of byproducts, such as levulinic acid and lactic acid, derived from further degradation reactions. 1% (w/w) MgCl₂ was the most efficient catalyst among the tested metal chlorides for 5-HMF production from agarose and resulted in both the highest yield of 40.7% and highest selectivity of 49.1% at 200 °C for 35 min. The cleavage of C–O–C bond in agarose with subsequent isomerization of galactose to its ketose was considered as a possible mechanism for formation of 5-HMF under MgCl₂ catalyzed conditions.