Potential of catalytic oxidation of Kraft black liquor for the production of biosourced compounds

Abstract

Industrial Kraft black liquor from maritime pine was oxidized in aqueous, alkaline medium, under air, at 150C, with or without CuO/TiO2 catalyst. The oxidation products were analyzed by HPLC, elemental analysis, SEC, FTIR, NMR. The results showed the depolymerisation of lignin, the formation of phenolic compounds in low yields, with vanillin being the major phenolic compound, and the formation of aliphatic compounds in higher yields, with formic, succinic and tartronic acids being the major identified aliphatic compounds. The presence of catalyst favoured the formation of phenolic and aliphatic compounds. Replacing Kraft black liquor by pure Kraft lignin as a starting material did not enhance the performances of catalytic oxidation, showing that lignin purification may not be necessary in our conditions. Switching from a batch reactor to a fixed bed reactor, working under similar conditons, did not increase the yields in oxidation products but increased the productivity. This work shows the potential of Kraft black liquor to produce a large panel of compounds, including phenolics, aliphatic acids and oxidized lignin, all being valuable in chemical industry.

Potential of catalytic oxidation of kraft black liquor for the production of biosourced compounds

“…The reaction conditions were chosen on the basis of previous studies by our teams on pure lignin transformation. 12,40,41 The temperature was set at 150 °C, the pressure at 20 bar, stirring rate 1800 rpm and the copper/dry matter ratio at 5 wt%.…”

Potential of catalytic oxidation of Kraft black liquor for the production of biosourced compounds

“…The reaction conditions were chosen on the basis of previous studies by our teams on pure lignin transformation. 12,40,41 The temperature was set at 150°C, the pressure at 20 bar, stirring rate 1800 rpm and the copper/dry matter ratio at 5 wt.%. Effect of reaction time on lignin conversion and phenolics.…”