Humins are an undesirable side product of acid-catalyzed carbohydrate conversion. With HMF, humins form via aldol addition/condensation involving 2,5-dioxo-6-hydroxy-hexanal (DHH) which forms from the HMF. This aldol chemistry can be manipulated leading to the incorporation of various functional groups in the humins. HMF is an intermediate product in the conversion of glucose and fructose. For those reactants, humins could form directly from the hexoses or from DHH. Infrared spectroscopy indicates similar features for humins from HMF, fructose and glucose. Microscopy shows that the size and the morphology of the humins changes over the course of the reaction and continues after all the original carbohydrate has been consumed. With glucose and fructose, it again is possible to incorporate different functional groups in the humins. An overall examination of the results suggests that for all three reactants the primary path to humins is through DHH.

Mechanism of humin formation and growth during acid-catalyzed conversion of glucose, fructose and HMF

243rd National Meeting (2012)

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