| 1. |
- 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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| 2. |
- Carrasco, Cristhian, et al.
(författare)
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SO2-catalysed steam pretreatment of quinoa stalks
- 2015
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Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575. ; 90:1, s. 64-71
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUNDQuinoa is a pseudo-cereal grown predominantly in South America. The quinoa stalks are lignocellulosic residues, which have a limited use today. The objective of the current study was to assess the potential of this material as a source of monosaccharides for fermentation purposes by means of steam pretreatment giving sugars from the hemicellulose part, and enzymatic hydrolysis of the solid fraction obtained. SO2 catalysed steam pretreatment was carried out with a holding time of 5min at temperatures between 180 and 220 degrees C. The pretreatment was carried out at two different scales, a small reactor of size 0.5L and a somewhat larger reactor of size 10L, to allow comparison of scale effects in the pretreatment. RESULTSThe highest xylose yield in the liquid phase, obtained after pretreatment at 210 degrees C, was 80%. In the smaller scale unit, longer residence times were needed. The enzymatic hydrolysis, at an enzyme loading of 15 FPU g(-1) glucan and a WIS loading of 2%, resulted in a glucose yield of 70% based on the original glucan. The overall sugar yield, including the xylan hydrolysed in the enzymatic treatment, at dilute conditions was 75%. CONCLUSIONSSO2 catalysed pretreatment of quinoa straw followed by enzymatic hydrolysis gave a relatively good sugar yield. However, the yield obtained was somewhat lower than previously reported for similar materials, such as wheat straw and sugarcane bagasse, steam pretreated with SO2. (c) 2013 Society of Chemical Industry
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| 3. |
- Chen, Genqiang, et al.
(författare)
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Scale-up of production of bacterial nanocellulose using submerged cultivation
- 2018
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Ingår i: Journal of chemical technology and biotechnology (1986). - : Wiley. - 0268-2575 .- 1097-4660. ; 93:12, s. 3418-3427
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: More extensive utilization of bacterial nanocellulose (BNC) is severely restricted by the low efficiency and small scale of the traditional static cultivation. Submerged fermentation in stirred-tank reactors (STRs) is potentially favourable for large-scale production of BNC, but scale-up of cultivation remains challenging. Even though the STR is most commonly used for submerged cultivation in the fermentation industry, there are few previous attempts to scale-up production of BNC to pilot scale using an STR. Furthermore, the question of how scale-up of submerged cultivation affects the properties of the BNC has received very little attention. RESULTS: Four strains were compared in 250-mL shake flasks. Strain DHU-ATCC-1 displayed the highest volumetric productivity, 0.56 g L−1 d−1, and was then cultivated in a 400-mL STR, showing a similar productivity of 0.55 g L−1 d−1. Scale-up using a 75-L STR pilot bioreactor resulted in enhancement of the BNC production rate from 0.056 g d−1 in the shake flasks to 17.3 g d−1 in the 75-L STR, although the productivity decreased to 0.43 g L−1 d−1. During scale-up from shake flasks to 400-mL STR and further on to 75-L STR, the BNC fibers formed more bundles, whereas the fiber diameter decreased from 25.6 to 21.7 nm. The BNC from the 75-L STR exhibited a higher degree of polymerization, specifically 3230, higher degree of crystallinity, specifically 83%, larger crystallites, and improved strength including higher tensile energy absorption index and superior stretch at break. CONCLUSION: It is possible to enhance BNC production, and maintain or improve its properties when scaling up submerged cultivation in STRs.
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| 4. |
- Eivazihollagh, Alireza, et al.
(författare)
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Electrochemical recovery of copper complexed by DTPA and C12-DTPA from aqueous solution using a membrane cell
- 2018
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Ingår i: Journal of chemical technology and biotechnology (1986). - : Wiley. - 0268-2575 .- 1097-4660. ; 93:5, s. 1421-1431
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUNDThe electrochemical recovery of copper from DTPA and C12-DTPA (a surface-active derivative of DTPA) complex solutions was investigated in a membrane flow cell. Electrolysis time, solution flow rate, applied current density, and solution pH were evaluated.RESULTSThe chelating surfactant C12-DTPA can promote the kinetics of copper electrodeposition more than DTPA depending on the experimental conditions. At a current density of 30 A m–2, a solution flow rate of 0.6 L min–1, and pH 10 after 180 min treatment, the copper recovery and current efficiency were 50% and 43.3%, respectively, in the Cu(II)-DTPA system and about 65% and 53.6%, respectively, in the Cu(II)-C12-DTPA system. The differences in the amount of recovery could be explained in terms of differences in the diffusion of copper complexes with DTPA and C12-DTPA to the cathode, as well as their solution behavior and pH-dependent conditional stability constants (log10 K’CuDTPA3-).CONCLUSIONElectrochemical methods could be effectively combined with foam flotation for the chelating surfactant C12-DTPA, to recover copper and C12-DTPA. This makes the overall treatment more sustainable, and can be helpful in complying with the increasingly stringent environmental regulations
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| 5. |
- Eivazihollagh, Alireza, et al.
(författare)
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Influences of the operational variables on electrochemical treatment of chelated Cu(II) in alkaline solutions using a membrane cell
- 2017
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Ingår i: Journal of chemical technology and biotechnology (1986). - : Wiley. - 0268-2575 .- 1097-4660. ; 92:6, s. 1436-1445
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUNDThe electrochemical recovery of copper and chelating agent from their complex solution using a membrane flow cell was investigated. The parameters electrolysis time, solution pH, current density, and temperature were investigated.RESULTSElectrochemical investigation indicated that chelating ligands can be recovered by the electrodeposition of copper ions on the cathode. For copper and EDTA recovery, the results indicated that recovery efficiency was affected by time, current density, and temperature. The recovery process was not influenced by pH in the range studied (pH 8–12), which can be explained by the low variation in the conditional stability constant, i.e. Δlog10 K' ≤ 0.7, over the pH range. However, when NTA, EDTA, and DTPA were compared, the results indicated that the recovery efficiency decreased as the conditional stability constant of the chelating agent–Cu(II) complex increased. The maximum current efficiency of copper and EDTA recovery after 5 h of treatment was approximately 85%, whereas the recovery was 80% of the initial concentration (0.05 mol L−1) at a current density of 1 A dm−2, temperature of 333 K, and pH of 10.CONCLUSIONRelatively high recovery efficiency makes the process fairly sustainable and hinders the discharge of copper ions and chelating ligands as pollutants into the environment.
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| 6. |
- Endrodi, Balázs, et al.
(författare)
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Suppressed oxygen evolution during chlorateformation from hypochlorite in the presenceof chromium(VI)
- 2019
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Ingår i: Journal of chemical technology and biotechnology (1986). - : Wiley. - 0268-2575 .- 1097-4660. ; 94:5, s. 1520-1527
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Chromium(VI) is a crucial electrolyte component in industrial chlorate production. Due to its toxicity, iturgently needs to be abandoned and its functions fulfilled by new solutions. In the industrial production of sodium chlorate,homogeneous decomposition of the hypochlorite intermediate to chlorate is a key step. As a competing loss reaction,hypochlorite can decompose to oxygen. How chromium(VI) affects these reactions is not well understood.RESULTS: This work shows, for the first time, that chromium(VI) selectively accelerates the chlorate formation from hypochloriteboth in dilute and concentrated, industrially relevant solutions. The effect of the ionic strength and the specific contributionof different electrolyte components were systematically studied. By simultaneously measuring the concentration decayof hypochlorite (UV–vis spectroscopy) and the oxygen formation (mass spectrometry), both the rate and the selectivity of thereactions were evaluated.CONCLUSION: In the presence of chromium(VI) the hypochlorite decomposition is described by the sum of an uncatalyzedand a parallel catalyzed reaction, where oxygen only forms in the uncatalyzed reaction. When removing chromium(VI),the homogeneous oxygen formation increases, causing economic and safety concerns. The need for a catalyst selectivefor chlorate formation is emphasized.
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| 7. |
- Guo, Xiang, et al.
(författare)
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Production of bacterial nanocellulose and enzyme from [AMIM]Cl-pretreated waste cotton fabrics : effects of dyes on enzymatic saccharification and nanocellulose production
- 2016
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Ingår i: Journal of chemical technology and biotechnology (1986). - : Wiley. - 0268-2575 .- 1097-4660. ; 91:5, s. 1413-1421
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND Dyed used cotton textiles is a waste material associated with environmental problems. In this study, waste dyed cotton fabrics were used as feedstock for production of bacterial nanocellulose (BNC) with Gluconacetobacter xylinus and production of enzymes with Trichoderma reesei via enzymatic saccharification.RESULTS Reactive dyes caused almost no inhibition of the cellulase activity at a concentration of 5 g L-1, but decreased the BNC production at concentrations higher than 1 g L-1. The BNC yield reached 12.8 g L-1 with cotton hydrolysate, which was 48% higher than with glucose-based medium. The spent fermentation broth after BNC harvest was subsequently utilized for enzyme production. Cellulase activities produced by T. reesei reached 5.3 U mL(-1) with spent detoxified purple bed sheet (PBS) hydrolysate, and 8.2 U mL(-1) with 2-fold diluted spent PBS hydrolysate, which was almost the same or higher than with glucose medium (5.6 U mL(-1)). The xylanase activities (60.2 U mL(-1) and 88.0 U mL(-1)) obtained with the two media were 3-4 times higher than that obtained with glucose medium (21.0 U mL(-1)).CONCLUSION This approach could contribute to economical conversion of cellulosic waste to two high value-added microbial products, while also providing new raw materials for a more sustainable textile industry.
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| 8. |
- Heng, King Sern, et al.
(författare)
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Conversion of rice husks to polyhydroxyalkanoates (PHA) via a three-step process : optimized alkaline pretreatment, enzymatic hydrolysis, and biosynthesis by Burkholderia cepacia USM (JCM 15050)
- 2017
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Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575. ; 92:1, s. 100-108
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Rice husks (RH) are agricultural residues with abundant storage of cellulose and hemicellulose, making them a potential feedstock for polyhydroxyalkanoate (PHA) production. In this study, optimization of pretreatment with alkali under various conditions was performed before enzymatic hydrolysis using Celluclast 1.5 L (EC 3.2.1.4) and Novozyme 188 (EC 3.2.1.21). The hydrolysate was fed to two strains, Burkholderia cepacia USM (JCM 15050) and Cupriavidus necator NSDG-GG, an engineered strain of Cupriavidus necator H16, to evaluate their PHA production. RESULTS: Pretreatment of RH using 1.0 mol L−1 potassium hydroxide (KOH) at high temperature and pressure (HTP) (121 °C, 0.1 MPa) gave maximum sugar yield of up to 87% (per total carbohydrate content) after optimized enzymatic hydrolysis, whereby the undiluted hydrolysate contained approximately 20 g L−1 total reducing sugars (TRS). B. cepacia USM utilized the hydrolysate more efficiently compared with C. necator NSDG-GG, with a maximum cell dry weight (CDW) of 4.9 g L−1 and 40 wt% PHA at shake-flask scale. The CDW and PHA content of B. cepacia USM cultivated in a 5 L fermentor were 7.8 g L−1 and 50%, respectively. The decrease in total phenolics at the end of fermentation suggested that B. cepacia USM was able to metabolize phenolic compounds. CONCLUSION: Through optimized alkali pretreatment and enzymatic hydrolysis, RH has the potential to be converted to PHA by B. cepacia USM, thus valorizing this agricultural by-product.
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| 9. |
- Jogi, Ramakrishna, et al.
(författare)
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Biocrude production through hydro‐liquefaction of wood biomass in supercritical ethanol using iron silica and iron Beta zeolite catalysts
- 2019
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Ingår i: Journal of chemical technology and biotechnology (1986). - : John Wiley & Sons. - 0268-2575 .- 1097-4660. ; 94:11, s. 3736-3744
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: In the production of biofuels from lignocellulosic material, biocrude plays a key role. The present work deals with the biocrude production through hydrothermal liquefaction (HTL) of birch wood in supercritical ethanol over 5 wt. % Fe‐H‐Beta‐150 (SiO2 to Al2O3 ratio of 150) or 5 wt. % Fe‐SiO2 catalyst.RESULTS: The liquid and solid products were characterized with various analytical techniques such as GC‐MS, GC‐FID, SEC, ICP‐MS, p‐XRD, SEM, and solid‐state 13C MAS NMR respectively. The results revealed that 5 wt. % Fe‐H‐Beta‐150, a strongly Brønsted acidic catalyst, enhanced the biocrude formation when compared with a non‐acidic 5 wt. % Fe‐SiO2 catalyst. Hemicellulose and lignin degradation occurred resulting in formation of mainly sugars, acids‐esters and phenolic compounds in liquid phase. The gaseous atmosphere of hydrogen also enhanced the degradation of biomass. The biocrude yield from birch was 25 wt. % over 5 wt. % Fe‐H‐Beta‐150. The Brønsted acidic catalyst gave higher dissolution efficiency and its clear catalytic effect was observed in comparison to non‐acidic 5 wt. % Fe‐SiO2. The degradation level of lignin in presence of 5 wt. % Fe‐H‐Beta‐150 was high 68 wt. % aromatic products were formed, while only 38 wt. % was obtained with 5 wt. % Fe‐SiO2.CONCLUSIONS: Hydrogen atmosphere enhances the fractionation of birch wood when compared to argon atmosphere. 5 wt. % Fe‐H‐Beta‐150 catalyst enhanced very strongly the degradation of hemicellulose and lignin in biomass to sugars and acid‐esters as well as phenolic compounds, respectively compared to the non‐acidic 5 wt. % Fe‐SiO2 catalyst.
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| 10. |
- Kadic, Adnan, et al.
(författare)
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Does sugar inhibition explain mixing effects in enzymatic hydrolysis of lignocellulose?
- 2017
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Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575. ; 92:4, s. 868-873
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Enzymatic hydrolysis of lignocellulose is associated with mixing issues, which are likely to affect process performance. The aim of this study was to investigate how viscosity and sugar inhibition influence the mixing-dependence in hydrolysis of steam-pretreated spruce. RESULTS: The effect of agitation on low-viscosity, low-solid hydrolysis (5% water insoluble solid (WIS)) was marginal, as the conversion after 72 h decreased by 9% when decreasing the agitation rate from 600 to 100 rpm. However, when the viscosity at 5% WIS was increased by Xanthan addition, the effect of agitation was greater, and conversion decreased by 21% when decreasing agitation from 600 to 100 rpm. For high-viscosity, high-solid hydrolysis (16% WIS), the conversion decreased by 54% when decreasing the agitation from 600 to 100 rpm. However, when the product concentration was kept low by simultaneous saccharification and fermentation (SSF), the effect of agitation was weaker, and conversion decreased by only 14%. CONCLUSION: The results of this study strongly suggest that poor mixing in viscous lignocellulose hydrolysis causes local product accumulation, leading to increased inhibition and decreased hydrolysis rates. Decreasing the glucose and cellobiose concentration removes the mixing-dependence, highlighting SSF as an attractive option for large-scale hydrolysis and fermentation of steam-pretreated softwood.
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