Valorizing lignin is important to achieving economically-viable conversion of biomass to fuels and chemicals. However, due to its complex structure and resistance to breakdown, generating a high value from lignin is difficult and success to date has been limited. We describe a method to treat lignin using a room-temperature, one-step oxidative process to selectively open the aromatic rings and generate carboxylic acid groups. The approach results in a water-soluble polyacid that constitutes a valuable product, for example as a dispersant, without need for further upgrading. Polymeric dispersants are used extensively in dyes, paints, concrete, pharmaceuticals, cosmetics, paper and paperboard, ceramics processing, and to inhibit fouling in cooling water systems. Our approach uses chelator-mediated Fenton chemistry (e.g., Fe + chelator + H2O2).1 The Fenton reaction, reaction of hydrogen peroxide and ferrous salt, is used to treat industrial waste and organic contaminants in groundwater and has been employed in biomass pretreatment strategies. Use of an Fe chelator in the Fenton system leads to substantially higher yields of solubilized polyacid product per amount of oxidant (H2O2) consumed. We also show that the amount of aromatic ring opening can be controlled by the reaction conditions. By controlling the extent of ring opening, the relative amounts of hydrophobic and charged groups can be tailored to produce polyacids with properties optimized for specific applications. The economic feasibility of this process depends on maximizing the yield of solubilized lignin-derived product per amount of H2O2 consumed and also minimizing or eliminating separation steps. We will describe progress on those aspects and report the best results achieved to date. We will also show that the material solublized by this reaction behaves as an effective dispersant.

Polyacids from lignin

ACS Spring Meeting 2021

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