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Royal Society of Chemistry, Green Chemistry, 11(17), p. 4921-4930

DOI: 10.1039/c5gc01641j

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Solvent Free Depolymerization of Kraft Lignin to Alkyl-phenolics using Supported NiMo and CoMo Catalysts

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This paper is available in a repository.

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Abstract

The catalytic hydrotreatment of Kraft lignin using sulfided NiMo and CoMo catalysts on different acidic and basic supports (Al2O3, ZSM-5, activated carbon (AC) and MgO-La2O3) was studied in the absence of a solvent. Experiments were carried out in a batch set-up at a reaction temperature of 350 °C, 4 h and 100 bar initial H2 pressure. The catalysts before and after reaction were characterized by X-ray diffraction, temperature programmed desorption of ammonia/CO2, BET surface area and scanning electron microscopy. The liquid products were fractionated and analyzed extensively by different techniques such as GPC, GC-MS-FID, GC-TCD, FT-IR, 13C-NMR and elemental analyses. Two dimensional gas chromatography (GCxGC-FID) was applied to identify distinct groups of compounds (aromatics, alkylphenolics, alkanes) after reaction, and product quantification was performed based on this method. Catalyst activity is a function of the support and increased in the order Al2O3 < ZSM-5 < AC=MgO-La2O3. In addition, the support also largely influenced the extent of depolymerization and monomer yield. The highest lignin oil yields were obtained using the sulfided NiMo supported on activated carbon and MgO-La2O3. The highest total monomer yield 26.4 wt.% on lignin intake, which included 15.7 wt.% alkyl-phenolics was obtained using the sulfided NiMo/MgO-La2O3 catalyst.