Abstract
Lignin modification opens the possibility of using it in polyol bio-based polymers, such as phenol–formaldehyde resins, polyurethanes, composites, and binders. Pine kraft lignin Indulin AT was partially depolymerized and the resulting products analyzed to determine their degree of valorization. Depolymerized lignin products were analyzed by GPC-SEC (molar mass), ∆ε-IDUS (phenolic hydroxyls), HACL (formaldehyde uptake), 13C-NMR (hydroxyl and methoxyl groups), and 1H-DOSY (molar mass distribution). The dominant parameter in lignin depolymerization by solvolysis was reaction temperature. According to the results, a higher reaction temperature decreases the average molar masses and PDI of lignin as well as the primary and secondary aliphatic hydroxyls, while simultaneously increasing the phenolic hydroxyls and formaldehyde uptake of lignin. Other variables (time, formic acid wt %, ethanol wt %, lignin load) had lesser effects. Partial depolymerization by solvolysis in mild conditions without catalyst is a viable valorization route for lignin, by which lignin properties can be significantly improved.
Highlights
The increasing environmental and political stress related to the valorization of fossil-derived feedstocks opens up an opportunity to use bio-derived resources for the production of value-added chemicals
In order to assess the effect of process conditions, each variable was studied while keeping all other variables constant according to Table 2
Depolymerization of lignin can be achieved by solvolysis with an ethanol–water mixture using formic acid as an insitu hydrogen donor
Summary
The increasing environmental and political stress related to the valorization of fossil-derived feedstocks opens up an opportunity to use bio-derived resources for the production of value-added chemicals. Lignocellulosic or woody biomass has the potential to be used as a renewable and alternative bioresource for the production of fuels and Faculty of Technology, Chemical Process Engineering, University of Oulu, P.O. Box 4300, 90014 Oulu, Finland. NMR Research Unit, Faculty of Science, University of Oulu, P.O. Box 3000, 90014 Oulu, Finland chemicals, which have conventionally been produced from fossil-derived feedstocks [1]. Lignin is remarkably underutilized in biorefineries, despite the fact that the lignin molecules could be broken into numerous valuable chemicals through bioand chemo–catalytic treatment [3, 4]. In order to improve lignin utilization, a techno-economically viable process needs to be developed to valorize lignin.
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