Key words: hydrolysis lignin, depolymerization, n-hexane, supercritical conditions, hydrogenation, Ru/C
Depolymerization of hydrolysis lignin in supercritical n-hexane medium was carried out in two stages: 1) lignin treatment in an autoclave at 250°C and 15 MPa; 2) hydrogenation of the solution obtained in the first stage at 250°C and 9 MPa on a Ru/C catalyst. The products of the first and second stages were analyzed by HPLC, GPC, gas chromatography, chromatography-mass spectrometry, and elemental analysis. At the first stage, the degree of depolymerization was 17 %, the mono- and oligomeric fragments of lignin that passed into solution as a result of depolymerization have an MMD from 65 Da to 270 kDa. Monomer composition of the solution: mono-, di-, tri- and tetraalkyl derivatives of benzene (2.8 wt. %), guaiacol and its alkyl derivatives (0.6 wt. %), including coniferyl alcohol (0.06 wt. %). At the second stage of transformation the following processes occur: 1) depolymerization of oligomers to monomers; 2) hydrogenation of monomeric phenols to derivatives of cyclohexane and its oxo derivatives; 3) formation of gas products, mainly methane (95 vol. %), as a result of hydrocracking of the solvent.
doi:10.34984/SCFTP.2023.19.2.006