| 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. |
- Dhakal, Prabin, 1994, et al.
(författare)
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Producing upgradeable bio-oil from food bio-waste via hybrid-assisted pretreatment coupled with catalytic hydrotreatment
- 2023
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Ingår i: Bioresource Technology Reports. - 2589-014X. ; 24
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Tidskriftsartikel (refereegranskat)abstract
- Slurry food waste sourced from Renova (Gothenburg, Sweden) was investigated as a model for generating upgradeable bio-oil via a hybrid-assisted pretreatment along with a catalytic hydrotreatment process. Hybrid-assisted pretreatment has been examined for extracting and stabilizing of reactive-derived substances. For the resulting bio-crude and residual solids, the properties of the heteroatoms were also examined prior to the catalytic hydrotreatment experiments. Hybrid-assisted pretreatment is an interesting solution in that it maximizes the bio-crude yield and transfers significant amounts of the nitrogenous content (De-N ∼83.3 %, dry basis) into the residual solids. Nearly 87 wt% of the oxygenated monomers were found in the obtained bio-crude, which possessed 52.0 wt% of alcohols. The highest upgradeable bio-oil of 86.0 wt% was achieved during catalytic hydrotreatment of the bio-crude and residual solids jointly: producing blends of up to 78 wt% of hydrocarbons, 14 wt% oxygenated and <6 wt% of cyclic, aromatics, N-containing components.
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| 4. |
- 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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| 5. |
- Di, Wei, 1986, et al.
(författare)
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Modulating the Formation of Coke to Improve the Production of Light Olefins from CO2 Hydrogenation over In2O3 and SSZ-13 Catalysts
- 2023
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Ingår i: Energy & Fuels. - 1520-5029 .- 0887-0624. ; 37:22, s. 17382-17398
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Tidskriftsartikel (refereegranskat)abstract
- Moderately acidic aluminophosphates (SAPOs) are often integrated with methanol synthesis catalysts for the hydrogenation of CO2 to olefins, but they suffer from hydrothermal decomposition. Here, an alternative SSZ-13 zeolite with high hydrothermal stability is synthesized and coupled with an In2O3 catalyst in a hybrid system. Its performance regarding selectivity for olefins and coke formation was investigated for CO2 hydrogenation under varying temperatures and pressures. Various reactions occur, producing mainly CO and different hydrocarbons. The results indicate that the hydrogenation of hydrocarbons are dominant at high temperatures (around 400 °C) over SSZ-13 zeolite with a high acid density and that the coke deposition rate is slow. Polymethylbenzenes are the main coke species, but the selectivity for light olefins is low among hydrocarbons at high temperatures. However, at low temperatures (around 325 °C), and especially under high pressure (40 bar), methanol disproportionation becomes significant. This results in an increased selectivity for light olefins; however, it also leads to a rapid coke deposition, which gives inactive adamantanes as the main coke species that block the pores and cause rapid deactivation. However, after coking at 325 °C and regeneration at 400 °C under the reaction atmosphere, the accumulated adamantanes can be decomposed into smaller coke species, which reopens the channel structure and generates modulated active sites within the zeolite, resulting in a higher yield of olefins without deactivation. The performances of acidic SSZ-13 zeolites, with varying ratios of Si/Al in transient experiments, further verified that a dynamic balance exists between the formation and degradation of coke within the SSZ-13 zeolite during a long-term CO2 hydrogenation reaction. This balance can be achieved by optimizing the reaction conditions to match the acid density of the catalyst. Using the conditions of 20 bar and 375 °C, with a H2 to CO2 mole ratio of 3, the results obtained for the precoked hybrid catalysts of In2O3 and SSZ-13 (Si/Al = 25) exhibited very stable activity, with the selectivity for light olefins (based on hydrocarbons formed) of max. 70% after 100 h time-on-stream. This work provides new insights into the design of stable hybrid catalysts, especially the influence of a precoking process for SSZ-13 zeolite in the production of light olefins.
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| 6. |
- Hynynen, Jonna, 1987, et al.
(författare)
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'Lignin and extractives first' conversion of lignocellulosic residual streams using UV light from LEDs
- 2021
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Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 23, s. 8251-8259
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Tidskriftsartikel (refereegranskat)abstract
- Lignocellulosic biomass, especially lignin and extractives, has the potential to substitute fossil precursors in the chemical industry. The conversion of lignin has been intensively researched, but challenges remain as high temperatures and increased pressure are commonly used, which is not energy efficient. Lignin and wood extractives bear chromophoric groups that can absorb light in the ultraviolet (UV) region, which enables photochemical reactions. Ultraviolet light emitting diodes (UV-LEDs) are an emerging technology; they are cheap, versatile, and energy-efficient compared to existing mercury lamps. UV-LEDs were used in this study as a proof of concept for the valorisation of a lignocellulosic residual stream from the pulp and paper industry, sawdust. In a process at ambient temperature and pressure and without the use of a catalyst, we have shown that lignin and extractives can be valorised using light from UV-LEDs. Simplified lignin model compounds were used to pinpoint chemical reactions during irradiation, and to ease the analysis of the sawdust samples. The rate of conversion upon irradiation of the model compounds was found to be 0.7-2.3 g L-1 h(-1), depending on the concentration of the starting compounds.
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| 7. |
- 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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| 8. |
- Nejadmoghadam, Elham, 1984, et al.
(författare)
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Stabilization of fresh and aged simulated pyrolysis oil through mild hydrotreatment using noble metal catalysts
- 2024
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Ingår i: Energy Conversion and Management. - 0196-8904. ; 313
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Tidskriftsartikel (refereegranskat)abstract
- The nature and reactivity of the oxygenates, containing different functional chemical groups, and especially carbonyl compounds, render pyrolysis oil unstable. Alterations in physical and chemical properties of pyrolysis oil during storage and the catalytic stabilization of this oil is therefore critical and is the objective of the current work. In this study, Pd/Al2O3, Pt/Al2O3, Rh/Al2O3, Re/Al2O3 and sulphided NiMo/Al2O3 catalysts were employed in the hydrotreatment (180 °C, 60 bar H2, 4 h) of simulated pyrolysis oil to examine their effect on stabilization and potential polymerization routes. Of all the catalysts used, Pd/Al2O3 with well-dispersed metal particles, and a high char-suppressing potential was the most effective catalyst. It had the highest bio-liquid yield and the highest selectivity to low molecular weight stabilized oxygenates and deoxygenated products. In addition, the acidity in the light fraction was low and a very low solid product formation was found that consisted mainly of soluble polymers composed predominantly of aliphatic compounds and sugars, whereas insoluble polymers were not fully developed char. The solid yield increased in the following order: Pd (3.3 wt%) < Rh (13.3 wt%) < NiMo (13.6 wt%) < Pt (21.5 wt%) < Re (25.8 wt%) < Blank (27.4 wt%). This trend was also accompanied by an enhanced yield of heavy oligomers in the corresponding liquid phase abundant in phenolic compounds compared to carboxylic acids and aliphatic compounds based on GPC and P-NMR analyses. The Pd loading necessary to obtain a high-quality product was also assessed, and the lower carbon loss when using catalysts with smaller contents of metal was revealed. Based on the results a detailed reaction network was proposed regarding the reactions during stabilization of sugars, aldehydes, ketones, furans, acids and phenols present in pyrolysis oil. To delve deeper into the simulated pyrolysis oil properties, it was subjected to accelerated aging. Interestingly as much as 79 % of the feed was converted during aging. According to GC/MS analysis only large oligomers were formed that could not be detected. When removing the most reactive components from the feed, i.e. the sugar and furan, the conversion was lowered to 53 %. Catalytic stabilization was conducted on the aged oil and compared with stabilization followed by aging. The results showed that the solid formation increased from 5.1 to 9.1 % when the pyrolysis oil was first aged, followed by stabilization. A suggested reason for this is the large amount of oligomers that were formed during the aging. Thus, aging before stabilization is very negative for an industrial process.
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| 9. |
- Ojagh, Houman, 1976, et al.
(författare)
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Effect of DMSO on the catalytical production of 2,5-bis(hydoxymethyl)furan from 5-hydroxymethylfurfural over Ni/SiO2 catalysts
- 2022
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Ingår i: Reaction Chemistry and Engineering. - : Royal Society of Chemistry (RSC). - 2058-9883. ; 7:1, s. 192-200
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Tidskriftsartikel (refereegranskat)abstract
- Hydroconversion of 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydoxymethyl)furan (BHMF) was studied over mono- and bimetallic supported catalysts. It was found that monometallic Ni/SiO2 catalysts exhibited superior performance with a total yield of BHMF of up to 99 wt%. This excellent performance may be attributed to higher Ni dispersion and low acidity of the support. Dimethyl sulfoxide (DMSO) is often present in HMF, due to the route used for its synthesis. DMSO adsorption caused a clear reduction of Ni/SiO2 performance for the HMF hydrodeoxygenation reaction. Characterization of the spent catalysts was performed using HAADF-STEM-EDX, Raman, ICP, and XPS spectroscopies, and showed the presence of sulfur and graphitic carbon, which could explain the deactivation.
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| 10. |
- Olsson Månsson, Emma, 1992, et al.
(författare)
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Removal of Inorganic Impurities in the Fast Pyrolysis Bio-oil Using Sorbents at Ambient Temperature
- 2024
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Ingår i: Energy & Fuels. - 1520-5029 .- 0887-0624. ; 38:1, s. 414-4254
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Tidskriftsartikel (refereegranskat)abstract
- Fast pyrolysis bio-oil (FPBO) sourced from residual biomass waste (such as sawdust) is a promising feedstock that may be used for biofuel production. Their inorganic elements may, however, vary and cause deactivation of the catalysts in the hydrodeoxygenation (HDO) upgrading biorefinery unit. It was found that the use of zeolite Y and strong acidic ion-exchange resins as adsorbents was almost equally efficient in lowering the concentrations of Ca from <10 to <1 ppm and of Fe, K, and Mg to <0.3 ppm in FPBO at 30 °C, atmospheric pressure, and 4 h adsorption time. The removal efficiency of zeolite and resins exceeded 85–98% (detection limit) of these particular elements. For the first time for the FPBO, phosphorus was reported as being successfully targeted by aluminum oxide, being lowered from 1 ppm to <0.1 ppm, which is a reduction of at least 90%. Characterization of the oil and sorbents suggests that the surface acidity affects the removal efficiency of these elements from FPBO. Organic compounds in the pyrolysis oil, including isopropanol, lactic acid, hydroxy acetone, furfural, guaiacol, and levoglucosan, were semiquantified using two-dimensional gas chromatography coupled with mass spectrometry (GCxGC-MS). Compared to the fresh oil, the compositions and contents of these organic compounds were not impacted significantly by the sorbents under these mild operating conditions. This research indicates that inorganic impurities present in bio-oils can be removed, and thus, they may be considered feedstocks for producing biofuels with less deactivation of HDO catalysts.
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