Two-step conversion of Kraft lignin to nylon precursors under mild conditions

Abstract

<p>Treatment of Kraft lignin, massive byproduct of pulping industry, with dilute aqueous base followed by catalytic hydrogenation of the extracted monomers at ambient pressure yields KA oil, the precursor of high demand nylon polymer.</p>

Catalytic Liquefaction of Kraft Lignin with Solvothermal Approach

“…The total of monomers increased drastically at long reaction times and reached 14.6 mg•g lignin −1 after 24 h. In the literature, Kraft lignin hydrolysis in basic solution in medium basic solution (pH = 10) yielded 1.1%wt monomers at 200 • C in 8 h, in accordance with our results. Higher pH gave higher monomers yields, up to 13%wt [23]. Noticeably, for reaction time above 7 h, new products were detectable in traces, namely phenol and p-ethylguaiacol.…”

“…To minimize such undesired reaction, the use of ethanol was proven to be effective [14] as alcohol act as hydrogen transfer agents stabilizing reactive phenolics as well as helping to depolymerization through hydrogenolysis [14][15][16]. Solvolysis results in partial or complete solubilization of Kraft lignin (e.g., Kraft lignin is 90% soluble at 200 • C in basic aqueous solution, and 33% soluble at 200 • C in methanol) [23]. In the absence of catalyst, the production of monomers during solvolysis is generally inferior to 4%wt for Kraft lignin.…”

Vacancy Engineering in Transition Metal Sulfide and Oxide Catalysts for Hydrodeoxygenation of Lignin‐Derived Oxygenates

“…There is also the use of CS 2 ‐H 2 to sulfide Mo‐based sulfides, this high‐temperature vulcanization will form larger particle size and orderly multilayer MoS 2 crystals, reducing unsaturated sulfur atoms on the edge [71] . It is worth that the nature of the solvent will affect the synthesis of the catalyst, and the difference in the solvent will also affect the generation of sulfur vacancies [54a,72] . Wang et al [73] .…”

Recent Catalytic Approaches for the Production of Cycloalkane Intermediates from Lignin‐Based Aromatic Compounds: A Review

“…Slowing research group reported Kraft lignin conversion to KA oil (cyclohexanol/cyclohexanone) in two‐steps [74] . In the first step, depolymerization of kraft lignin to phenolic monomers was performed using 100 mM NaOH at 200 °C for 16 h and in this case, they observed ∼13 % monomer production based on lignin (82 % guaiacol selectivity).…”