| 1. |
- Pezoa-Conte, R., et al.
(författare)
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Deconstruction of the green alga Ulva rigida in ionic liquids : closing the mass balance
- 2015
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Ingår i: Algal Research. - : Elsevier. - 2211-9264. ; 12, s. 262-273
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Tidskriftsartikel (refereegranskat)abstract
- Algae are known to grow at high rates compared to terrestrial plants that contain comparable amounts of carbohydrates by weight. Therefore, this renders them attractive in terms of any biorefinery concept. In this work the green alga Ulva rigida, containing 40 wt.% of carbohydrates was pretreated with a switchable ionic liquid (SIL), distillable ionic liquid (DIL) and low-viscosity ionic liquid (LVIL). The SIL DBU–MEA–SO2 was prepared from a mixture of mono-ethanolamine (MEA) and 1,8-diazabicyclo-[5,4,0]-undec-7-ene (DBU) that was coupled with sulfur dioxide (SO2), whereas the DIL [TMGH+][EtCO2−] (1,1,3,3-tetramethylguanidine propionate) was synthesized by a simple acid–base neutralization reaction. Consequently, the LVIL [HDBU+][5OF−] protonated 1,8-diazabicyclo-[5,4,0]-undec-7-ene- 2,2,3,3,4,4,5,5-octafluoro-1-pentoxide was used as received. The treatments were carried out in the temperature range of 100–160 °C for 6 h. The products obtained after the treatments were analyzed using different techniques like ICP, OES, SEM, TEM, TGA, FTIR and carbohydrate determination by GC. Upon treatment with DIL up to 67 wt.% of carbohydrates could be dissolved. For the first time, processing of U. rigida was carried out in ionic liquids so that the mass balance of the process was obtained. It can be concluded that 1,1,3,3-tetramethylguanidine propionate shows significant potential when aiming at releasing carbohydrates from algal biomass that, consequently, can be applied in the production of platform chemicals and/or biofuels such as bioethanol.
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| 2. |
- Adeniyi, Omotayo, et al.
(författare)
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Engineering of layered iron vanadate nanostructure for electrocatalysis : simultaneous detection of methotrexate and folinic acid in blood serum
- 2023
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859.
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Tidskriftsartikel (refereegranskat)abstract
- In this study, nanostructure kazakhstanite-like iron vanadate (FexV3xOy.H2O) was synthesized and calcined at different temperatures (100-800 °C) in a nitrogen atmosphere. The material was used to modify screen-printed carbon electrodes to achieve an electrocatalytic effect on the surface. The relationship between calcination conditions and the catalytic performance of the electrode towards the oxidation of chemotherapeutic drugs, including methotrexate (MTX) and folinic acid (FA), was studied. Various spectroscopic, microscopic, and electrochemical methods were used to characterize the synthesized materials. The results show that calcination induces changes in the electronic structure, nanostructure morphology, electroactive surface area, and electrocatalytic performance of the material. Screen-printed carbon electrode modified with FexV3xOy calcinated at 450 °C (SPC/FexV3xOy-450) was used to develop a voltammetric sensor for the determination of MTX and FA in blood serum. The response of the SPC/FexV3xOy-450 towards the electrooxidation of MTX and FA was the highest in comparison to the bare SPC and SPC/FexV3xOy calcined at other temperatures. The SPC/FexV3xOy-450 exhibited a linear relationship over a wide concentration range: 0.005-200 µM for MTX and 0.05-200 µM for FA. The detection limit was 2.85 nM for MTX and 7.79 nM for FA. Compared to conventional methods, the SPC/FexV3xOy-450 sensor had a short response time (5 min) for simultaneous detection of MTX and FA without signal interferences from coexisting electroactive compounds. The accurate and precise determination of MTX in the presence of FA confirmed the potential clinical applications of SPC/FexV3xOy-450 for therapeutic drug monitoring during chemotherapy.
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| 3. |
- Adeniyi, Omotayo, et al.
(författare)
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Reagentless impedimetric immunosensor for monitoring of methotrexate in human blood serum using multiwalled carbon nanotube@polypyrrole/polytyramine film electrode
- 2024
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Ingår i: Talanta. - : Elsevier. - 0039-9140 .- 1873-3573. ; 268:Part 1
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Tidskriftsartikel (refereegranskat)abstract
- Ensuring effective monitoring of methotrexate (MTX) levels in the bloodstream of cancer patients undergoing high-dose methotrexate chemotherapy is crucial to prevent potentially harmful side effects. However, the absence of portable analytical devices suitable for point-of-care bedside monitoring has presented a significant obstacle to achieving real-time MTX monitoring. In this study, we developed an impedimetric immunosensor that doesn't require reagents for measuring MTX levels in undiluted human blood serum. This reagentless approach simplifies the assay process, enabling rapid and straightforward MTX quantification. The immunosensor transducer was fabricated by electrodepositing conductive network of porous multiwalled carbon nanotube@polypyrrole/polytyramine on screen-printed gold microchip electrode (SP–Au/MWCNT70@PPy-PTA). Polyclonal anti-MTX antibodies were immobilized on the film, acting as the immunorecognition element. Non-specific binding was prevented by blocking the transducer interface with denatured bovine serum albumin (dBSA) fibrils, resulting in SP-Au/MWCNT70@PPy-PTA/anti-MTXAb|dBSA film electrode. When MTX binds to the SP-Au/MWCNT70@PPy-PTA/anti-MTXAb|dBSA interface, the film conductance and electron transfer resistance changes. This conductivity attenuation allows for electrochemical impedimetric signal transduction without a redox-probe solution. The electrochemical impedance spectroscopy (EIS) results showed increased charge transfer resistance and phase angle as MTX concentrations increased. The SP-Au/MWCNT70@PPy-PTA/anti-MTXAb|dBSA demonstrated high sensitivity, with a linear response from 0.02 to 20.0 μM and a detection limit of 1.93 nM. The detection limit was 50 times lower than the intended safe level of MTX in human serum. The immunosensor exhibited minimal cross-reactivity with endogenous MTX analogs and serum proteins. The SP-Au/MWCNT70@PPy-PTA/anti-MTXAb|dBSA immunosensor presents a simple and rapid method for therapeutic drug monitoring compared to traditional immunoassay systems.
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| 4. |
- Aguilera, Adriana Freites, et al.
(författare)
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Epoxidation of fatty acids and vegetable oils assisted by microwaves catalyzed by a cation exchange resin
- 2018
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Ingår i: Industrial & Engineering Chemistry Research. - Washington : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 57:11, s. 3876-3886
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Tidskriftsartikel (refereegranskat)abstract
- Epoxidation of oleic acid and cottonseed oil was conducted in a semibatch reactor with in-situ-formed percarboxylic acid (peracetic acid or perpropionic acid), using hydrogen peroxide as an oxidizing agent and carboxylic acid (acetic acid or propionic acid) as oxygen carriers. Amberlite IR-120 was implemented as the catalyst. The system was comprised of a loop reactor, where the mixture was pumped through a single-mode cavity in which microwave irradiation was introduced. A heat exchanger was integrated into the system to replace microwave heating, to compare the results obtained via microwave heating versus conventional heating. The catalyst loading effect was studied, as well as the influence of microwave irradiation and the implementation of the SpinChem rotating bed reactor (RBR), in hopes of decreasing the influence of the internal mass transfer. The application of microwave irradiation results in an improvement of the reaction yield in the absence of a catalyst.
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| 5. |
- Aguilera, Adriana Freites, et al.
(författare)
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Screening of ion exchange resin catalysts for epoxidation of oleic acid under the influence of conventional and microwave heating
- 2019
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Ingår i: Journal of chemical technology and biotechnology (1986). - : John Wiley & Sons. - 0268-2575 .- 1097-4660. ; 94:9, s. 3020-3031
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Tidskriftsartikel (refereegranskat)abstract
- Background: For many chemical systems, it is of great importance to find a durable, active and efficient catalyst that improves the process performance. Epoxidation of oleic acid with peracetic acid (Prilezhaev oxidation) was carried out in an isothermal loop reactor in the presence of heterogeneous catalysts. The kinetic experiments conducted under microwave heating (MW) were compared with identical experiments carried out under conventional (conductive/convective) heating. Extensive screening of heterogeneous catalysts was conducted and the influence of microwave irradiation on the reaction kinetics was studied. Several ion exchange resins were screened to explore their applicability and activity in the epoxidation of oleic acid. The perhydrolysis reaction (peracetic acid formed in situ from acetic acid and H2O2) was promoted with the use of various solid acid catalysts: Amberlite IR-120, Amberlyst 15, Smopex®, Dowex 50x8-100, Dowex 50x8-50, Dowex 50x2-100 and Nafion™.Results: From the selected group of catalysts, Dowex 50-x8100 and Dowex 50x8-50 produced the highest yield of epoxidized oil. Only minor differences in the reactant conversion and the product yield were found in the experiments carried out under microwave exposure compared to the conventionally heated experiments in the presence of several ion exchange resins.Conclusions: The catalytic effect was much more prominent than the microwave effect, because the solid acid catalysts enhanced the slow step of the process, the perhydrolysis of acetic acid. The catalytic effect was very dominant and a considerable improvement of the oleic acid conversion and the epoxide yield was observed in the presence of the top-performing catalysts.
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| 6. |
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| 7. |
- Ahlkvist, Johan, et al.
(författare)
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Experimental and Kinetic Modelling Studies upon Conversion of Nordic Pulp into Levulinic Acid
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, sulphite cellulose from a Swedish pulp mill was applied as the raw material upon catalytic, one-pot synthesis of green platform chemicals – levulinic and formic acids. Cationic ion-exchange resin, Amberlyst 70, was the catalyst of choice and the optimal reaction conditions leading to best yields were determined. The kinetic experiments were performed in a temperature range of 180–200 °C and an initial substrate concentration regime ranging from 0.7 to 6.0 wt %. For this system, maximum theoretical yields of around 59 mol % and 68 mol % were obtained for formic and levulinic acid, respectively. These yields were achieved at a reaction temperature of 180 °C and an initial cellulose intake of 0.7 wt %. A simplified reaction network of the various chemical species involved was investigated and a mechanistic approach involving first order reaction kinetics was developed. The model was able to describe the behaviour of the system in a satisfactory manner (degree of explanation 97.8 %). Since the solid catalyst proved to exhibit good mechanical strength under the experimental conditions applied here, the concept introduces a one-pot procedure providing a route to green platform chemicals from coniferous soft wood pulp to produce levulinic and formic acids, respectively.
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| 8. |
- Ahlkvist, Johan, 1970-
(författare)
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Formic and Levulinic Acid from Cellulose via Heterogeneous Catalysis
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The chemical industry of today is under increased pressure to develop novel green materials, bio-fuels as well as sustainable chemicals for the chemical industry. Indeed, the endeavour is to move towards more eco-friendly cost efficient production processes and technologies and chemical transformation of renewables has a central role considering the future sustainable supply of chemicals and energy needed for societies. In the Nordic countries, the importance of pulping and paper industry has been particularly pronounced and the declining European demand on these products as a result of our digitalizing world has forced the industry to look at alternative sources of revenue and profitability. In this thesis, the production of levulinic and formic acid from biomass and macromolecules has been studied. Further, the optimum reaction conditions as well as the influence of the catalyst and biomass type were also discussed.Nordic sulphite and sulphate (Kraft) cellulose originating from two Nordic pulp mills were used as raw materials in the catalytic synthesis of green platform chemicals, levulinic and formic acids, respectively. The catalyst of choice used in this study was a macro-porous, cationic ion-exchange resin, Amberlyst 70, for which the optimal reaction conditions leading to best yields were determined. Cellulose from Nordic pulp mills were used as raw materials in the catalytic one-pot synthesis of ‘green’ levulinic and formic acid. The kinetic experiments were performed in a temperature range of 150–200 °C and an initial substrate concentration regime ranging from 0.7 to 6.0 wt %. It was concluded that the most important parameters in the one-pot hydrolysis of biomass were the reaction temperature, initial reactant concentration, acid type as well as the raw material applied. The reaction route includes dehydration of glucose to hydroxymethylfurfural as well as its further rehydration to formic and levulinic acids. The theoretical maximum yield can hardly be obtained due to formation of humins. For this system, maximum yields of 59 mol % and 68 mol % were obtained for formic and levulinic acid, respectively. The maximum yields were separately obtained in a straight-forward conversion system only containing cellulose, water and the heterogeneous catalyst. These yields were achieved at a reaction temperature of 180 °C and an initial cellulose intake of 0.7 wt % and belong to the upper range for solid catalysts so far presented in the literature.The reaction network of the various chemical species involved was investigated and a simple mechanistic approach involving first order reaction kinetics was developed. The concept introduces a one-pot procedure providing a feasible route to green platform chemicals obtained via conversion of coniferous soft wood pulp to levulinic and formic acids, respectively. The model was able to describe the behaviour of the system in a satisfactory manner (degree of explanation 97.8 %). Since the solid catalyst proved to exhibit good mechanical strength under the experimental conditions applied here and a one-pot procedure providing a route to green platform chemicals was developed. A simplified reaction network of the various chemical species involved was investigated and a mechanistic approach involving first order reaction kinetics was developed.
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| 9. |
- Ahlkvist, Johan, et al.
(författare)
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Heterogeneously catalyzed conversion of nordic pulp to levulinic and formic acids
- 2016
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Ingår i: Reaction Kinetics, Mechanisms and Catalysis. - : Springer. - 1878-5190 .- 1878-5204. ; 119:2, s. 415-427
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Tidskriftsartikel (refereegranskat)abstract
- Herein, one-pot conversion of cellulose to platform chemicals, formic and levulinic acids was demonstrated. The catalyst selected was an affordable, acidic ion-exchange resin, Amberlyst 70, whereas the cellulose used was sulfite cellulose delivered by a Swedish pulp mill. Furthermore, in an attempt to better understand the complex hydrolysis network of the polysaccharide, kinetic experiments were carried out to pinpoint the optimal reaction conditions with an initial substrate concentration of 0.7–6.0 wt% and a temperature range of 180–200 °C. Higher temperatures could not be used due to the limitations in the thermal stability of the catalyst. Overall, maximum theoretical yields of 59 and 68 mol% were obtained for formic and levulinic acid, respectively. The parameters allowing for the best performance were reaction temperature of 180 °C and initial cellulose concentration of 0.7 wt%. After studying the behavior of the system, a simplified reaction network in line with a mechanistic approach was developed and found to follow first order reaction kinetics. A satisfactory fit of the model to the experimental data was achieved (97.8 % degree of explanation). The catalyst chosen exhibited good mechanical strength under the experimental conditions and thus, a route providing green platform chemicals from soft wood pulp from coniferous trees (mixture of Scots Pine and Norway Spruce) was demonstrated.
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| 10. |
- Ahlkvist, Johan, et al.
(författare)
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Macro-molecules as a source of levulinic acid
- 2014
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Ingår i: International Review of Chemical Engineering. - : Praise Worthy Prize. - 2035-1755. ; 16:1, s. 44-58
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Tidskriftsartikel (refereegranskat)abstract
- The production of levulinic acid from biomass and macromolecules has been reviewed. It was concluded that the most important parameters in the one-pot hydrolysis of biomass, also including dehydration of glucose to hydroxymethylfurfural as well as its further rehydration to formic and levulinic acids, respectively, are the reaction temperature, initial reactant concentration, acid type as well as the raw material applied. The theoretical maximum yield can hardly be obtained due to formation of humins. Further, the optimum reaction conditions as well as the influence of the catalyst and biomass type are also discussed.
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