In this presentation, I will describe maleic acid hydrotropic fractionation (MAHF) of wood for producing highly reactive lignin for efficient conversion to lignin aromatics. MAHF can achieve rapid (~ 30 min) dissolution of wood lignin at ~100°C at high yield in aqueous systems. The dissolved lignin can be easily separated through precipitation by simply diluting the spent liquor with water to the minimal hydrotrope concentration (MHC). The dissolved xylose can be efficiently dehydrated into furfural, a high value chemical, using the acid hydrotrope (maleic acid) in the spent liquor without additional catalyst. The rapid solubilization of lignin at low temperatures resulted in lignin with low degree of condensation and highly reactive, which facilitated catalytic conversion to lignin aromatics. We will compare the properties, especially reactivity and conversion yields of MA hydrotropic lignin (MAHL) from batch reaction with those from flow through reaction. Both catalytic oxidative depolymerization and supercritical methanol dehydration hydrodeoxygenation processes were applied to MAHL from batch and flow through reactions. The results show MAHL can be efficiently converted to lignin monophenols. MAHL from flow through reaction are even more reactive with higher conversion yield due to the high content beta-O-4 linkages retained. MA is a US FDA approved indirect food additive, the low solubility of MA also facilitates MA recovery, therefore MAHF has significant advantages over most existing fractionation processes especially those solvent-based processes.

Maleic acid hydrotropic lignin (MAHL) for efficient conversion to lignin aromatics: Production, characterization, conversion

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