Kraft lignin valorization by hydrotreatment over Mo-based sulfided catalysts
Doktorsavhandling, 2022

The production of green fuels and chemicals from bio-based feedstock can suppress the dependency on fossil resources and help mitigate global climate challenges. Kraft lignin is a thermochemically modified natural lignin obtained from the pulping process as a byproduct. It is an underutilized fraction, often used to recover heat and energy in the current industrial practice. Chemically, it is highly rich in aromatics and thus has a huge potential to provide platform chemicals/fuels. However, the major challenge in the valorization of Kraft lignin is its recalcitrance to depolymerization due to the presence of strong interunit carbon-carbon linkages. Also, upon depolymerization, active monomeric fragments undergo repolymerization reactions forming undesired solid residue/char, thus making the transformation highly challenging.

In this context, Mo-based sulfide catalysts being sulfur tolerant and active for removing heteroatom-such as S, N, O, metals have been modified and studied with the aim to elucidate the selective cleavage of common lignin linkages, the hydrotreating potential of Kraft lignin, and upgrading of lignin derived bio-oil. The reactivity of lignin dimers, representing common lignin linkages, shows that NiMo sulfides over ultra-stable Y-zeolite support, with a higher amount of Brønsted acidity, can efficiently cleave both etheric and carbon-carbon linkages and yield deoxygenated aromatics and cycloalkanes by hydrodeoxygenation (HDO). Such hydrogenolysis, hydrocracking, and deoxygenation activity were also found to vary with the silica/alumina ratio of the Y-zeolites. The optimum activity was obtained with catalysts having a suitable balance of acidic and deoxygenation sites (metal sulfides). Additionally, one-pot hydrotreatment of Kraft lignin with a suitably functional catalyst shows a significant reduction in the repolymerization reactions, leading to a high yield of bio-oil rich in alkylbenzene and cycloalkane, a fraction suitable for example for jet fuel applications. Characterization reveals that the key function of a suitable catalyst is hydrogen activation at a lower temperature which facilitates stabilization of the lignin fragments, the moderate acidity of the catalysts, and high HDO activity of the catalyst. Furthermore, unsupported Ni/Mo-sulfides have been synthesized and found highly active for deoxygenation reaction and Kraft lignin hydrotreatment, resulting mainly from their defect-rich morphology.

Conventional Mo-based sulfide catalysts thus can be tailored to enable their effective application in the upgrading of complex biorefinery feedstocks to value added components.

Metal sulfide



Kraft Lignin





KA, Kemigården 4
Opponent: Associate Professor Päivi Mäki-Arvela, Industrial Chemistry and Reaction Engineering, Åbo Akademi University, Turku, Finland


Muhammad Abdus Salam

Chalmers, Kemi och kemiteknik, Kemiteknik

Cheah Y.W., Salam M.A., Sebastian J., Ghosh S., Arora P., Öhrman O., Olsson L., and Creaser D. Upgrading of triglycerides, pyrolysis oil, and lignin over metal sulfide catalysts: A review on the reaction mechanism, kinetics, and catalyst deactivation.

NiMoS on alumina-USY zeolites for hydrotreating lignin dimers: Effect of support acidity and cleavage of C-C bonds

Sustainable Energy and Fuels,; Vol. 4(2019)p. 149-163

Artikel i vetenskaplig tidskrift

Hydrotreatment of lignin dimers over NiMoS-USY: effect of silica/alumina ratio

SUSTAINABLE ENERGY & FUELS,; Vol. 5(2021)p. 3445-3457

Artikel i vetenskaplig tidskrift

Salam, M. A., Cheah, Y. W., Ho P. H., Bernin D., Achour A., Nejadmoghadam E., Öhrman O., Arora P., Olsson L., and Creaser D. Elucidating the role of NiMoS-USY during the hydrotreatment of Kraft lignin

Thermal annealing effects on hydrothermally synthesized unsupported MoS2 for enhanced deoxygenation of propylguaiacol and kraft lignin

Sustainable Energy and Fuels,; Vol. 5(2021)p. 5270-5286

Artikel i vetenskaplig tidskrift

The production of biofuels from renewable resources can make a vital contribution to meet the vision of a fossil-free transport sector by 2030 in Sweden. Conventional biofuels based on food-grade biomass like sugarcane, corn, or edible vegetable oil are not sustainable and risks food security. Therefore, the focus has been shifted to non-food based biomass to produce advanced biofuels. The biorefinery byproduct, lignin has good potential to be a source of advanced biofuel/platform chemicals. In the current biorefineries (e.g., pulp and paper industry), a large amount of lignin is separated as a byproduct during the production of cellulosic pulp from woody plant materials. The usual practice is to incinerate this carbon-rich fraction for heating purposes. Very few biorefineries utilize this product fraction to extract valuable products. Briefly, this thesis focuses on the use of this low-value fraction to produce value added fuel components via catalytic hydrotreatment, a technique used to remove sulfur, nitrogen, oxygen, etc. with hydrogen and in the presence of a robust catalyst.

Specifically, this thesis investigates the application of low-cost, sulfur tolerant supported and unsupported Mo-based transition metal sulfides and ultra-stable Y zeolite materials for the upgrading of lignin (Kraft) and lignin derived bio-oil. Since lignin is a heterogenous biopolymer having interunit carbon-carbon and carbon-oxygen-carbon linkages, the reactivity of these linkages was examined using model lignin dimers and sulfided catalysts with varying support acidity and textural properties. Later, Kraft lignin hydrotreatment was assessed using suitable catalysts based on their catalytic activity for the lignin dimers. Moreover, the role of the catalyst components was studied by comparing supported and unsupported Mo-based sulfided catalysts for Kraft lignin and lignin derived bio-oil. The analysis of the hydrotreated products revealed that lignin and lignin derived bio-oil can be upgraded to alkylbenzenes and cycloalkanes mixtures which can be suitable as jet fuel components. In addition, the thesis also outlined the current state of the art (in terms of reaction mechanism, kinetics, and catalyst deactivation) for catalytic upgrading of renewable feedstocks over sulfided catalysts.

Avancerade katalytiska material för uppgradering av lignin-oljor till biobränslen

Energimyndigheten (43212-1), 2017-01-01 -- 2019-12-31.

Kombinerade experiment och kinetikmodellering för ligninvalorisering till kemikalier och bränslen

Formas (2017-01392), 2018-01-01 -- 2020-12-31.


Hållbar utveckling








Chalmers materialanalyslaboratorium



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5088



KA, Kemigården 4


Opponent: Associate Professor Päivi Mäki-Arvela, Industrial Chemistry and Reaction Engineering, Åbo Akademi University, Turku, Finland

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