| 1. |
- Cheah, You Wayne, 1993, et al.
(författare)
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Slurry co-hydroprocessing of Kraft lignin and pyrolysis oil over unsupported NiMoS catalyst: A strategy for char suppression
- 2023
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Ingår i: Chemical Engineering Journal. - 1385-8947. ; 475
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Tidskriftsartikel (refereegranskat)abstract
- Pyrolysis oil (PO) assisted Kraft lignin (KL) liquefaction over an unsupported NiMoS catalyst in a paraffin solvent was explored in this work. A paraffin solvent was used to represent hydrogenated vegetable oil (HVO) which is a biofuel. We have for the first time showed that when co-processing Kraft lignin with pyrolysis oil in a paraffin solvent the char formation could be completely suppressed. The complex composition of PO, containing various compounds with different functional groups, was able to aid the depolymerization pathways of lignin by obstructing the condensation path of reactive lignin derivatives. To further understand the role of different functional groups present in pyrolysis oil during lignin liquefaction, we investigate the co-hydroprocessing of Kraft lignin with various oxygenate monomers using unsupported NiMoS. 4-propylguaiacol (PG) was found to be the most efficient monomer for stabilizing the reactive lignin intermediates, resulting in a low char yield (3.7%), which was 4 times lower than the char production from Kraft lignin hydrotreatment alone. The suppressed rate of lignin fragment repolymerization can be attributed to the synergistic effect of functional groups like hydroxyl (-OH), methoxy (-OCH3), and propyl (-C3H7) groups present in PG. These groups were found to be able to stabilize the lignin depolymerized fragments and blocked the repolymerization routes enabling efficient lignin depolymerization. It was found that the presence of a co-reactant like PG during the heating period of the reactor acted as a blocking agent facilitating further depolymerization routes. Finally, a reaction network is proposed describing multiple routes of lignin hydroconversion to solid char, lignin-derived monomers, dimers, and oligomers, explaining why the co-processing of pyrolysis oil and Kraft lignin completely suppressed the solid char formation.
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| 2. |
- Cheah, You Wayne, 1993, et al.
(författare)
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Upgrading of triglycerides, pyrolysis oil, and lignin over metal sulfide catalysts: A review on the reaction mechanism, kinetics, and catalyst deactivation
- 2023
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437 .- 2213-2929. ; 11:3
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Forskningsöversikt (refereegranskat)abstract
- Human activities such as burning fossil fuels for energy production have contributed to the rising global atmospheric CO2 concentration. The search for alternative renewable and sustainable energy sources to replace fossil fuels is crucial to meet the global energy demand. Bio-feedstocks are abundant, carbon-rich, and renewable bioresources that can be transformed into value-added chemicals, biofuels, and biomaterials. The conversion of solid biomass into liquid fuel and their further hydroprocessing over solid catalysts has gained vast interest in industry and academic research in the last few decades. Metal sulfide catalysts, a common type of catalyst being used in the hydroprocessing of fossil feedstocks, have gained great interest due to their low cost, industrial relevance, and easy implementation into the current refining infrastructures. In this review, we aim to provide a comprehensive overview that covers the hydrotreating of various bio-feedstocks like fatty acids, phenolic compounds, pyrolysis oil, and lignin feed using sulfided catalysts. The main objectives are to highlight the reaction mechanism/networks, types of sulfided catalysts, catalyst deactivation, and reaction kinetics involved in the hydrotreating of various viable renewable feedstocks to biofuels. The computational approaches to understand the application of metal sulfides in deoxygenation are also presented. The challenges and needs for future research related to the valorization of different bio-feedstocks into liquid fuels, employing sulfided catalysts, are also discussed in the current work.
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| 3. |
- Nejadmoghadam, Elham, 1984, et al.
(författare)
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Stabilization of bio-oil from simulated pyrolysis oil using sulfided NiMo/Al 2 O 3 catalyst
- 2023
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Ingår i: Fuel. - 0016-2361. ; 353
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Tidskriftsartikel (refereegranskat)abstract
- Pyrolysis oil comprises compounds with a broad range of functional groups making its thermal/catalytic upgrading challenging due to the formation of undesired char. In this context, the current contribution addresses the thermal and catalytic hydrotreatment of a simulated pyrolysis oil containing all the representative groups of compounds under bio-oil stabilization conditions (180–300 °C, 60 bar, 4 h) using sulfided NiMo/Al2O3. The effect of reaction conditions and different oxygenated organic compounds on the yields and properties of products was compared thoroughly. Interestingly, a correlation between the presence/absence of oxygenated furan and sugar compounds was found to significantly affect the yield of liquid product containing stabilized compounds. The presence of such compound groups significantly enhances the solid formation via oligomerization and polymerization reactions. To gain further insight, the solid products were analyzed/characterized in detail to elucidate their characteristics by extracting them into a dimethyl sulfoxide (DMSO) soluble and insoluble solid fraction. It was found that in the presence of NiMo/Al2O3, increasing temperature from 180 to 300 °C enhances the formation of liquid product due to transformation of some of the soluble solids, while for experiments without the catalyst, the formation of solids was significantly higher. Oppositely, during heating up to 180 °C, no solids were found in the case without the catalyst, however the presence of the catalyst during heating resulted in solid formation due to various catalytic reactions that promoted char formation. Analysis of solids revealed that the structure of soluble solids at lower temperatures (180 °C) using the catalyst was closely related to sugar derivatives, whereas the corresponding insoluble solids with higher molecular weight were not fully char-like developed. However, at higher temperatures, the soluble and insoluble solid compositions were found to contain aliphatic compounds and fully developed char, respectively. Therefore, the stabilization of furan particularly with attached carbonyl groups and sugars derivatives in pyrolysis oil is of great importance to improve upgrading efficiency.
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