Ni- and Ni/Pd-Catalyzed Reductive Coupling of Lignin-Derived Aromatics to Access Biobased Plasticizers

Zhi-Ming Su, Jack Twilton, Caroline Hoyt, Fei Wang, Lisa Stanley, Heather Mayes, Kai Kang, Daniel Weix, Gregg Beckham, Shannon Stahl

Research output: Contribution to journalArticlepeer-review

6 Scopus Citations


Lignin-derived aromatic chemicals offer a compelling alternative to petrochemical feedstocks, and new applications are the focus of extensive interest. 4-Hydroxybenzoic acid (H), vanillic acid (G), and syringic acid (S) are readily obtained via oxidative depolymerization of hardwood lignin substrates. Here, we explore the use of these compounds to access biaryl dicarboxylate esters that represent biobased, less toxic alternatives to phthalate plasticizers. Chemical and electrochemical methods are developed for catalytic reductive coupling of sulfonate derivatives of H, G, and S to access all possible homo- and cross-coupling products. A conventional NiCl2/bipyridine catalyst is able to access the H-H and G-G products, but new catalysts are identified to afford the more challenging coupling products, including a NiCl2/bisphosphine catalyst for S-S and a NiCl2/phenanthroline/PdCl2/phosphine cocatalyst system for H-G, H-S, and G-S. High-throughput experimentation methods with a chemical reductant (Zn powder) are shown to provide an efficient screening platform for identification of new catalysts, while electrochemical methods can access improved yields and/or facilitate implementation on larger scale. Plasticizer tests are performed with poly(vinyl chloride), using esters of the 4,4′-biaryl dicarboxylate products. The H-G and G-G derivatives, in particular, exhibit performance advantages relative to an established petroleum-based phthalate ester plasticizer.

Original languageAmerican English
Pages (from-to)159-165
Number of pages7
JournalACS Central Science
Issue number2
StatePublished - 2023

Bibliographical note

Publisher Copyright:
© 2023 The Authors. Published by American Chemical Society.

NREL Publication Number

  • NREL/JA-2A00-84895


  • depolymerization
  • lignin
  • lignin-derived


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