| 1. |
- Achour, Abdenour, 1980, et al.
(författare)
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Evaluation of kraft and hydrolysis lignin hydroconversion over unsupported NiMoS catalyst
- 2023
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 453
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Tidskriftsartikel (refereegranskat)abstract
- Catalytic hydroconversion of Kraft and hydrolysis lignins was for the first time compared in a batch reactor over an unsupported NiMoS-SBA catalyst. We also report the effect of key reaction parameters on the yields and properties of the products. The results obtained at 20 wt% catalyst loading for hydrolysis lignin showed the highest monomer yield of 76.0 wt%, which consisted of 39 wt% aromatics with the lowest alkylphenolics yield of 10.1 wt%. Identical operating conditions, 400 °C, 80 bar, 5 h at 10 wt% catalyst loading, were used to compare both lignins and the highest monomer yield (64.3 wt%) was found for the hydrolysis lignin, consisting of 16.0 wt% alkylphenolics and 20.1 wt% aromatic compounds. These values are considerably higher than those for Kraft lignin with its 47.0 wt% monomer yield. We suggest that the reason for high yields of monomeric units from hydrolysis lignin is that it is more reactive due to its lower ash and sulfur contents and the chemical structural differences compared to the Kraft lignin. More precisely, the bio-oil from hydrolysis lignin contained higher yields of small molecules, sourced from ring-opening of cellulose in the hydrolysis lignin, which could stabilize the reactive oligomeric groups. These yields were two to seven times higher from kraft and hydrolysis lignin, respectively, compared to those obtained without catalyst. The results showed that the NiMoS-SBA catalyst is a promising catalyst for reductive depolymerization of lignin and in addition that the regenerated catalyst had good stability for multiple reaction cycles.
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| 2. |
- Achour, Abdenour, 1980, et al.
(författare)
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Towards stable nickel catalysts for selective hydrogenation of biomass-based BHMF into THFDM
- 2023
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437 .- 2213-2929. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Selective transformation of BHMF (2,5-bis(hydroxymethyl)furan) to THFDM (tetrahydrofuran-2,5-dimethanol) over a variety of structured Ni/Sx-Z1−x catalysts was investigated. The effects of support, Ni loading, solvent, temperature, pressure, and particle size on the conversion and selectivity were studied. Among them, the 10 wt% Ni catalyst supported on the SiO2:ZrO2 weight ratio of 90:10 (10NiS90Z10) exhibits the best performance in terms of BHMF conversion and THFDM selectivity. Its good performance was attributed to its well-balanced properties, that depend upon the ZrO2 content of the support in combination with SiO2, the active Ni sites-support interaction, and acidity/basicity ratio of each catalyst resulting in different Ni dispersions. Importantly, the 10NiS90Z10 catalyst showed a stable selectivity to THFDM (>94%), with 99.4% conversion of BHMF during 2 h reaction time. Poor catalytic activity resulted from excessive ZrO2 content (>10 wt%). The structural, textural, and acidity properties of NiSi100−y-Zry catalysts, tuned by selectively varying the Ni amount from 5 to 15 wt%, were critically investigated using numerous material characterization techniques. Catalyst recycling experiments revealed that the catalyst could be recycled several times without any measurable loss of catalytic activity.
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| 3. |
- Arora, Prakhar, 1987, et al.
(författare)
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The role of catalyst poisons during hydrodeoxygenation of renewable oils
- 2021
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 367, s. 28-42
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodeoxygenation (HDO) activity of NiMo catalysts have been evaluated in the presence of catalyst poisons in bio-based feedstocks. An in-house synthesized NiMo/Al2O3 catalyst was placed in a refinery unit for biofuel production. Iron (Fe), phosphorus (P) and metals were identified as major contaminants. Calcination treatment was explored to recover the activity of spent catalysts. The effect of Fe, K and phospholipid containing P and Na on catalyst deactivation during hydrodeoxygenation of stearic acid was simulated at lab-scale. Fe caused the most deactivation where the highest feed concentration of the Fe compound resulted in 1480 ppm Fe deposited on the catalyst. Elemental distribution along the radial axis of spent catalysts indicated: Fe deposited only to a depth of 100 μm irrespective of concentration while P and Na from phospholipid and K penetrated deeper in catalyst particles with a distribution profile that was found to be concentration dependent.
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| 4. |
- Bergvall, Niklas, et al.
(författare)
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Upgrading of fast pyrolysis bio-oils to renewable hydrocarbons using slurry- and fixed bed hydroprocessing
- 2024
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Ingår i: Fuel processing technology. - : Elsevier B.V.. - 0378-3820 .- 1873-7188. ; 253
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Tidskriftsartikel (refereegranskat)abstract
- Liquefaction of lignocellulosic biomass through fast pyrolysis, to yield fast pyrolysis bio-oil (FPBO), is a technique that has been extensively researched in the quest for finding alternatives to fossil feedstocks to produce fuels, chemicals, etc. Properties such as high oxygen content, acidity, and poor storage stability greatly limit the direct use of this bio-oil. Furthermore, high coking tendencies make upgrading of the FPBO by hydrodeoxygenation in fixed-bed bed hydrotreaters challenging due to plugging and catalyst deactivation. This study investigates a novel two-step hydroprocessing concept; a continuous slurry-based process using a dispersed NiMo-catalyst, followed by a fixed bed process using a supported NiMo-catalyst. The oil product from the slurry-process, having a reduced oxygen content (15 wt%) compared to the FPBO and a comparatively low coking tendency (TGA residue of 1.4 wt%), was successfully processed in the downstream fixed bed process for 58 h without any noticeable decrease in catalyst activity, or increase in pressure drop. The overall process resulted in a 29 wt% yield of deoxygenated oil product (0.5 wt% oxygen) from FPBO with an overall carbon recovery of 68%.
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| 5. |
- Bjerregaard, Joachim, 1996, et al.
(författare)
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Interpretation of H 2 -TPR from Cu-CHA Using First-Principles Calculations
- 2024
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Ingår i: Journal of Physical Chemistry C. - 1932-7447 .- 1932-7455. ; 128:11, s. 4525-4534
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Tidskriftsartikel (refereegranskat)abstract
- Temperature-programmed reduction and oxidation are used to obtain information on the presence and abundance of different species in complex catalytic materials. The interpretation of the temperature-programmed reaction profiles is, however, often challenging. One example is H2 temperature-programmed reduction (H2-TPR) of Cu-chabazite (Cu-CHA), which is a material used for ammonia assisted selective catalytic reduction of NOx (NH3-SCR). The TPR profiles of Cu-CHA consist generally of three main peaks. A peak at 220 °C is commonly assigned to ZCuOH, whereas peaks at 360 and 500 °C generally are assigned to Z2Cu, where Z represents an Al site. Here, we analyze H2-TPR over Cu-CHA by density functional theory calculations, microkinetic modeling, and TPR measurements of samples pretreated to have a dominant Cu species. We find that H2 can react with Cu ions in oxidation state +2, whereas adsorption on Cu ions in +1 is endothermic. Kinetic modeling of the TPR profiles suggests that the 220 °C peak can be assigned to Z2CuOCu and ZCuOH, whereas the peaks at higher temperatures can be assigned to paired Z2Cu and Z2CuHOOHCu species (360 °C) or paired Z2Cu and Z2CuOOCu (500 °C). The results are in good agreement with the experiments and facilitate the interpretation of future TPR experiments.
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| 6. |
- Cheah, You Wayne, 1993, et al.
(författare)
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Role of transition metals on MoS 2 -based supported catalysts for hydrodeoxygenation (HDO) of propylguaiacol
- 2021
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Ingår i: Sustainable Energy and Fuels. - : Royal Society of Chemistry (RSC). - 2398-4902. ; 5:7, s. 2097-2113
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal sulfides (TMSs) are typically used in the traditional petroleum refining industry for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) applications. Bio-oils require an upgrading process like catalytic hydrodeoxygenation (HDO) to produce advanced biofuels and chemicals. Herein, MoS /γ-Al O promoted by transition metals like nickel (Ni), copper (Cu), zinc (Zn), and iron (Fe) was evaluated for the HDO of a bio-oil model compound, 4-propylguaiacol (PG) in a batch reactor at 340 °C under 50 bar H pressure. The catalyst screening results showed that the sulfided Ni-promoted catalyst gave a high 94% yield of deoxygenated cycloalkanes, however for the sulfided Cu-promoted catalyst, 42% of phenolics remain in the reaction medium after 5 h. The results also revealed that the sulfided Zn and Fe-promoted catalysts gave a final yield of 16% and 19% at full PG conversion, respectively, for deoxygenated aromatics. A kinetic model considering the main side reactions was developed to elucidate the reaction pathway of demethoxylation and dehydroxylation of PG. The developed kinetic model was able to describe the experimental results well with a coefficient of determination of 97% for the Ni-promoted catalyst system. The absence of intermediates like 4-propylcyclohexanone and 4-propylcyclohexanol during the reaction implies that direct deoxygenation (DDO) is the dominant pathway in the deoxygenation of PG employing sulfided catalysts. The current work also demonstrated that the activity of the transition metal promoters sulfides for HDO of PG could be correlated to the yield of deoxygenated products from the hydrotreatment of Kraft lignin. 2 2 3 2
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| 7. |
- 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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| 8. |
- Cheah, You Wayne, 1993, et al.
(författare)
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Thermal annealing effects on hydrothermally synthesized unsupported MoS2 for enhanced deoxygenation of propylguaiacol and kraft lignin
- 2021
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Ingår i: Sustainable Energy and Fuels. - 2398-4902. ; 5:20, s. 5270-5286
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Tidskriftsartikel (refereegranskat)abstract
- Catalytic hydrodeoxygenation (HDO) is an important hydrotreating process that is used to improve the quality of bio-oils to produce biomass-derived fuel components and chemicals. Molybdenum disulfide (MoS2) has been widely used as a catalyst in hydrodesulfurization (HDS) applications for several decades, which can be further improved for effective unsupported catalyst synthesis. Herein, we studied a universally applicable post-annealing treatment to a hydrothermally synthesized MoS2 catalyst towards developing efficient unsupported catalysts for deoxygenation. The effect of the annealing treatment on the catalyst was studied and evaluated for HDO of 4-propylguaiacol (PG) at 300 °C with 50 bar H2 pressure. The annealing of the as-synthesized catalyst under nitrogen flow at 400 °C for 2 h was found to enhance the HDO activity. This enhancement is largely induced by the changes in the microstructure of MoS2 after the annealing in terms of slab length, stacking degree, defect-rich sites and the MoS2 edge-to-corner site ratio. Besides, the effect of hydrothermal synthesis time and acid addition combined with the annealing treatment on the MoS2 catalytic activity was also studied for the same model reaction. The annealed MoS2 with a synthesis time of 12 h under an acidic environment was found to have improved crystallinity and exhibit the highest deoxygenation degree among all the studied catalysts. An acidic environment during the synthesis was found to be crucial in facilitating the growth of MoS2 micelles, resulting in smaller particles that affected the HDO activity. The annealed unsupported MoS2 with the best performance for PG hydrodeoxygenation was further evaluated for the hydrotreatment of kraft lignin and demonstrated a high deoxygenation ability. The results also indicate a catalyst with high activity for deoxygenation and hydrogenation reactions can suppress char formation and favor a high lignin bio-oil yield. This research uncovers the importance of a facile pretreatment on unsupported MoS2 for achieving highly active HDO catalysts.
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| 9. |
- 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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| 10. |
- Di, Wei, 1986, et al.
(författare)
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CO2 hydrogenation to light olefins using In2O3 and SSZ-13 catalyst-Understanding the role of zeolite acidity in olefin production
- 2023
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Ingår i: Journal of CO2 Utilization. - 2212-9820. ; 72
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Tidskriftsartikel (refereegranskat)abstract
- With the aim to explore the effect of acidic properties of zeolites in tandem catalysts on their performance for CO2 hydrogenation, two types of SSZ-13 zeolites with similar bulk composition, but different arrangements of framework Al, were prepared. Their morphology, pore structure, distribution of framework Al, surface acid strength and density, were explored. The results showed that SSZ-13 zeolites with isolated aluminum distribution could be successfully synthesized, however, they contained structural defects. During calcination, the framework underwent dealumination, resulting in weaker Brønsted acidity and lower crystallinity. The morphologies were, however, well preserved. Compared with the SSZ-13 zeolites, synthesized conventionally, these low acidity SSZ13 zeolites with isolated aluminum were good zeolite components in bifunctional catalysts for CO2 hydrogenation to light olefins. By combining with In2O3, they exhibited better catalytic performance for light olefin production during CO2 hydrogenation at low temperatures. Na+ cation exchange was used to adjust the Brønsted acid site (BAS) density with only minor changes to the cavity structure. Comparative experiments established that the BAS density of the zeolite, rather than the framework Al distribution (BAS distribution), overwhelmingly affected catalyst stability and product selectivity. A higher acid density reduced the selectivity for light olefins, while lower acid density tended to form inert coke species leading to rapid deactivation. The ideal amount of BAS density in the bifunctional catalyst was approximately 0.25 mmol/g, which exhibited 70% selectivity for light olefins among hydrocarbons, and 74% selectivity for CO without deactivation, after 12 h reaction at 325 celcius and 10 bar.
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