With the development of economies and the increase of populations, the growing demand of fossil fuels resulted in a great concern of global energy supply. Biomass is the largest source of renewable energy, currently supplying 3% of the total consumption of energy in the United States. As the second most abundant biomass, inedible lignin with plentiful benzene ring structure, draws much attention for its potential in the production of triditinoally petroleum-derived products. In this work, one-pot completely catalytic ethanolysis of Kraft lignin into C6-C10 chemicals (aliphatic alcohols, esters, phenols, benzyl alcohols, and arenes) is performed over a number of molybdenum-based catalysts with a batch reactor in supercritical ethanol. Metallic molybdenum, its carbide, and nitride all show remarkable activity, with the carbide and metallic catalyst exhibit the high yields, i.e. 1640 and 1390 mg/g lignin. The major phases composing the catalysts are well-recovered after the reaction. However, based on the EPR analysis, the detection of Mo(V) species verifies the partial oxidation of molybdenum, which leads to the formation of the dissociative Mo species, such as molybdenum V ethoxide, in the fluid phase. Through the product analysis and catalyst characterization, the common steps of lignin conversion to value added chemicals over the Mo-based catalyst is proposed. In our previous work, Kraft lignin was found to be degraded into fragments in a m/z range of 700−1400 in supercritical ethanol without a catalyst. After that, because of the existance of ethanol dissociation, the active Mo (V) species, such as Mo(OCH2CH3)5, dissociate from solid into the fluid. Afterwards, the dissociative Mo species catalyzes, with the paticipation of radicals, the further degradation of the segments into final products. Figure.1 gives part of the proposed scheme of the reaction. We then explored the catalytic behavior of Mo(OCH2CH3)5 with lignin model compounds in supercritical ethanol. The products distribution, to some extent, indicates that this complex is really one of the intermediates during the reaction.

Reaction pathways of Kraft lignin deploymerization to platform chemicals on molybdenum-based catalysts in supercritical ethanol

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.