| 1. |
- Kumar, Narendra, et al.
(författare)
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Synthesis and characterization of solid base mesoporous and microporous catalysts: Influence of the support, structure and type of base metal
- 2012
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 152, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of solid base Ce–H-MCM-41, Ce–Si-MCM-41, Cs-MCM-41, K-MCM-41 mesoporous materials and Na-ZSM-12, Cs-ZSM-12 microporous zeolites were carried out by means of evaporation impregnation and ion-exchange methods. The solid basecatalysts were characterized using X-ray powder diffraction, scanning electron microscope, nitrogen adsorption, FTIR of pyridine and temperature programmed desorption of CO2. The H-ZSM-12, Cs-ZSM-12 zeolite, H-MCM-41, Ce–H-MCM-41 and Ce–Si-MCM-41 mesoporous catalysts were studied for the synthesis of diethyl carbonate starting from ethanol and carbon dioxide, using butylene oxide as the dehydrating agent. Catalyst testing for the synthesis of diethyl carbonate was carried out at 170 °C and 4.5 MPa of initial CO2 pressure. 16 wt.% Ce–H-MCM-41 mesoporous material exhibited higher amount of weak, medium and strong basic sites than that of 32 wt.% Ce–Si-MCM-41. The presence of weak and strong basic sites was observed in the microporous 2 wt.% Cs-ZSM-12 catalyst. Diethyl carbonate formation was observed over Ce–H-MCM-41 and Ce–Si-MCM-41 mesoporous materials. Amount of basic sites and its strength influenced the synthesis of diethyl carbonate over the mesoporous materials.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Ahlkvist, Johan, et al.
(författare)
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Reaction Network upon One-pot Catalytic Conversion of Pulp
- 2013
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Konferensbidrag (refereegranskat)abstract
- Nordic sulphite and sulphate (Kraft) cellulose originating from 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. For this system, maximum yields of 53 mol-% and 57 mol-% were obtained for formic and levulinic acid, respectively. The reaction network of the various chemical species involved was investigated and a simple mechanistic approach involving first order reaction kinetics was developed. The prototype model was able to describe the behaviour of the system in a satisfactory manner.
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| 7. |
- Aldea, Steliana, et al.
(författare)
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Crystallization of Nano-Calcium Carbonate : The Influence of Process Parameters
- 2016
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Ingår i: Chemie Ingenieur Technik. - : Wiley-VCH Verlagsgesellschaft. - 0009-286X .- 1522-2640. ; 88:11, s. 1609-1616
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Tidskriftsartikel (refereegranskat)abstract
- Precipitated calcium carbonate was synthesized by carbonation of calcium hydroxide in the presence and absence of ultrasound (conventional stirring) at atmospheric as well as at elevated pressures and different initial concentrations of Ca(OH)2. Spherical morphology of the formed calcite was favored at high Ca(OH)2 concentrations and low CO2 pressures. The presence of ultrasound did not show any influence on the reaction rate in case of efficient mixing. A small increase of the reaction rate was observed at lower CO2 pressures. Elevated pressures in combination with ultrasound did not lead to notable changes of reaction rate or particle morphology.
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| 8. |
- Anugwom, I, et al.
(författare)
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Ionic liquid assisted extraction of nitrogen and sulphur-containing air pollutants from model oil and regeneration of the spent ionic liquid
- 2011
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Ingår i: Journal of Environmental Protection. - : Scientific Research Publishing. - 2152-2197 .- 2152-2219. ; 2:6, s. 796-802
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Tidskriftsartikel (refereegranskat)abstract
- Removal of air pollutants, such as nitrogen and sulphur containing compounds from a model oil (dodecane) was studied. An ionic liquid (1-ethyl-3-methylimidazolium chloride [C2mim] [Cl]) was used as an extractant. Liquid-liquid extraction by using 1-ethyl-3-methylimidazolium chloride [C2mim] [Cl] was found to be a very promising method for the removal of N- and S-compounds. This was evaluated by using a model oil (dodecane) with indole as a neutral nitrogen compound and pyridine as a basic nitrogen compound. Dibenzothiophene (DBT) was used as a sulphur compound. An extraction capacity of up to 90 wt% was achieved for the model oil containing pyridine, while only 76 wt% of indole in the oil was extracted. The extraction capacity of a model sulphur compound DBT was found to be up to 99 wt%. Regeneration of the spent ionic liquid was carried out with toluene back-extraction. A 1:1 toluene-to-IL wt ratio was performed at room temperature. It was observed that, for the spent ionic liquid containing DBT as a model compound more than 85 wt% (corresponding 3852 mg/kg) could be removed from the oil. After the second regeneration cycle, 86 wt% of the DBT was recovered from the ionic liquid to toluene. In the case of indole as the nitrogen containing species, more than 99 wt%, (corresponding to 2993 mg/kg) of the original indole was transferred from the model oil to the ionic liquid. After the first-regeneration cycle of the spent ionic liquid, 54 wt% of the indole–in-IL was transferred to toluene. Thus, both extractions of nitrogen and sulphur model compounds were successfully carried out from model oil and the back-extraction of these compounds from the ionic liquids to toluene demonstrated the proved the concept of the regeneration point of view.
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| 9. |
- Behravesh, Erfan, et al.
(författare)
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Synthesis and characterization of Au nano particles supported catalysts for partial oxidation of ethanol : Influence of solution pH, Au nanoparticle size, support structure and acidity
- 2017
-
Ingår i: Journal of Catalysis. - : Elsevier. - 0021-9517 .- 1090-2694. ; 353, s. 223-238
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Tidskriftsartikel (refereegranskat)abstract
- Partial oxidation of ethanol to acetaldehyde was carried out over gold catalysts supported on various oxides and zeolites by deposition precipitation. The special focus of this work was on the influence of H-Y zeolite surface charge on Au cluster size and loading linking it to activity and selectivity in ethanol oxidation and comparing with other studied catalysts. The catalysts were characterized by nitrogen physisorption, transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and zeta potential measurements. pH of the solution governed the Au NPs size within the range of 5.8–13.2 nm with less negatively charged surfaces leading to formation of smaller clusters. Au loading on H-Y zeolite with silica to alumina ratio of 80 was increased by raising the pH. In fact, H-Y-12 and H-Beta-25 were selective towards diethyl ether while acetaldehyde was the prevalent product on less acidic H-Y-80. The results demonstrated strong dependency of the catalytic activity on the Au cluster size. Namely turn over frequency (TOF) decreased with an increase in metal size from 6.3 to 9.3 nm on H-Y-80. Selectivity towards acetaldehyde and ethyl acetate did not change significantly on H-Y-80 within 6.3–9.3 nm Au particle size range. On Al2O3 support, however, selectivity towards acetaldehyde increased considerably upon diminishing Au average particle size from 3.7 to 2.1 nm.
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| 10. |
- Bernardini, A., et al.
(författare)
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Direct synthesis of H2O2 over Pd supported on rare earths promoted zirconia
- 2015
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 256, s. 294-301
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Tidskriftsartikel (refereegranskat)abstract
- In this work Pd (0.3 or 0.6 wt.%) was supported on both ZrxM1-xO2 (M = La, Y, Ce) and on mechanical mixtures of CeO2 and ZrO2. The synthesized catalysts were characterized by XRD, TPR, AAS and CO chemisorption and tested for the direct synthesis of hydrogen peroxide in a high pressure semibatch apparatus. The reactants conversion was limited in order to avoid mass-transfer limitations. No selectivity enhancers of any kind were used and the all the materials were halide free. Small metal particles were obtained (1-2.6 nm). Supports with smaller pore diameters leaded to larger Pd particles, which in turn were found to preferentially support the formation of the peroxide. Moreover, supports with higher reducibility favored the production of H2O2, probably due to an easier reduction of the active metal, essential to achieve high selectivity. Notwithstanding the absence of enhancers, the specific activity and selectivity recorded were very high.
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| 11. |
- Bernas, Andreas, et al.
(författare)
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Catalytic transformation of abietic acid to hydrocarbons
- 2012
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Ingår i: Topics in catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 55:7-10, s. 673-679
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Tidskriftsartikel (refereegranskat)abstract
- Catalytic and thermal conversion of abietic acid was investigated in a laboratory scale high-pressure autoclave. Fractionation of crude tall oil produces rosin acids of which abietic acid is the main compound. Tall oil rosin acid, a forest product industry residue, is an abundant, inexpensive and chemically desirable feedstock for production of lighter hydrocarbons that can be used as diesel fuel additives. The carboxylic acid functionality of the main reactant, abietic acid, must first be removed, followed by double bond hydrogenation of the remaining aromatic rings. In this study, a number of catalytic and non-catalytic reaction steps in the conversion of abietic acid were investigated. The aim was to study hydrogenation and decarboxylation reactions of abietic acid in order to produce lighter hydrocarbons. The experiments were performed by using toluene as a solvent as well as with neat abietic acid, in the absence of any solvent. Hydrogenation of abietic acid to tetrahydroabietic acid in toluene was successfully performed over palladium on carbon catalyst at the temperature range of 100-200 A degrees C and at 30 bar hydrogen pressure. Thermal non-catalytic decarboxylation of abietic acid in toluene takes place at 200-300 A degrees C resulting in one main product. The hydrocarbon products were further hydrogenated under hydrogen pressure. Catalytic decarboxylation of abietic acid in toluene was achieved over 5 wt% Ru/C, giving a wider product distribution than thermal decarboxylation.
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| 12. |
- Biasi, Pierdomenico, et al.
(författare)
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Application of the Catalyst Wet Pretreatment Method (CWPM) for catalytic direct synthesis of H2O2
- 2015
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Ingår i: Catalysis Today. - : Elsevier. - 0920-5861 .- 1873-4308. ; 246:Special Issue, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- This work concerns a new technique to post-modify the catalytic material intended for use in H2O2 direct synthesis. The catalyst chosen was a commercially available 1 wt.% Pd/C. The catalyst was modified with the so-called Catalyst Wet Pretreatment Method (CWPM) that is used to post-modify prepared catalysts with aqueous solutions of NaBr, in different concentrations. The performance of pristine and the pretreated materials were then compared in the H2O2 direct synthesis and characterized before and after the catalytic tests in order to understand the role of the different concentrations of bromide in the CWPM procedure. The surface features of the different catalysts were analyzed with CO chemisorption (metal dispersion and mean particle size), Transmission Electron Microscopy (TEM, for Pd morphology and Pd particle size distributions), Inductive Coupled Plasma (ICP, for Pd content) and Ion Chromatography (IC, for bromide content). Various features of the materials prepared with the CWPM were correlated with the catalytic performance. It was found that the bromide has an active role in the reconstruction of metal phase and it does not only act as a poison for the most active catalytic sites as often reported in literature. By using this new protocol, the production H2O2 was almost doubled compared to the non-modified material when no direct promoters were added to the reaction environment.
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| 13. |
- Biasi, Pierdomenico, et al.
(författare)
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Hydrogen Peroxide Direct Synthesis : Enhancement of Selectivity and Production with non-Conventional Methods
- 2013
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Ingår i: ICHEAP-11. - : AIDIC - associazione italiana di ingegneria chimica. - 9788895608235 ; , s. 673-678
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Konferensbidrag (refereegranskat)abstract
- The present work is part of a comprehensive study on the direct synthesis of hydrogen peroxide in different fields, from chemistry to chemical engineering. Working on the different fields of the direct synthesis gave the possibility to look at the results and the challenges from different viewpoints. Here was investigated one parameter that enhances the direct synthesis. The H-2/Pd ratio is the key parameter that has to be investigated and optimize to enhance the hydrogen peroxide direct synthesis. Two reactors were built to study deeply the H-2/Pd ratio and to demonstrate how this parameter can affect the direct synthesis both in batch and continuous reactor with non-conventional experiments/methods. 1) A batch reactor was utilized as a "starving reactor" to enhance the productivity of hydrogen peroxide and to try to keep constant the selectivity. The starving method consists in refilling the hydrogen when it is consumed in the reactor. 2) A trickle bed reactor was utilized with a gradient of catalyst along the reactor to maximize both production and selectivity of hydrogen peroxide. The distribution of the catalyst along the bed gave the possibility to significantly improve the selectivity and the production of hydrogen peroxide (up to 0.5% in selected conditions). Higher production rate and selectivity were found when the catalyst concentration decreases along the bed from the top to the bottom compared to the uniformly dispersed catalyst. Selectivity in the batch reactor was enhanced by 5% and in the continuous reactor of 10%. The non-conventional experimental methods have been found to be novelty concepts to enhance the hydrogen peroxide direct synthesis.
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| 14. |
- Biasi, P., et al.
(författare)
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Revealing the role of bromide in the H2O2 direct synthesis with the catalyst wet pretreatment method (CWPM)
- 2017
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Ingår i: AIChE Journal. - : American Institute of Chemical Engineers. - 0001-1541 .- 1547-5905. ; 63:1, s. 32-42
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Tidskriftsartikel (refereegranskat)abstract
- A tailor-made Pd0/K2621 catalyst was subjected to post synthesis modification via a wet treatment procedure. The aimwas the understanding of the role of promoters and how—if any—improvements could be qualitatively related to the cat-alyst performance for the H2O2direct synthesis. The Catalyst Wet Pretreatment Method was applied in different metha-nolic solutions containing H2O2, NaBr, and H3PO4, either as single modifiers or as a mixture. The catalyst wascharacterized by Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. It was concluded that themodified catalysts give rise to higher selectivities compared to the pristi ne reference catalyst thus opening a possibilityto exclude the addit ion of the undesirable selectivity enhancers in the reaction medium. This work provides original evi-dence on the role of promoter s, especially bromide, allowing the formulation of a new reaction mechanism for one ofthe most challenging reactions recognized by the world.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Damlin, Pia, et al.
(författare)
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Characterization of Hardwood-Derived Carboxymethylcellulose by High pH Anion Chromatography Using Pulsed Amperometric Detection
- 2010
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Ingår i: Cellulose Chemistry and Technology. - 0576-9787. ; 44:1-3, s. 65-69
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Tidskriftsartikel (refereegranskat)abstract
- An approach for the quantitative analysis of substituent distribution in carboxymethylcellulose (CMC) is presented. In short, the high-pH anion-exchange chromatography method, coupled to pulsed amperometric detection (PAD), is introduced. Each of the seven derivatives in CMC is presented by a single peak on the PAD trace, thus enabling an easy quantification. New inside information on monomer composition is obtained by this novel method, which is essential for understanding the structure versus property relationships in the CMC samples.
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| 19. |
- de Araujo Filho, Cesar A., et al.
(författare)
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A comprehensive study on the kinetics, mass transfer and reaction engineering aspects of solvent-free glycerol hydrochlorination
- 2014
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509 .- 1873-4405. ; 120, s. 88-104
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Tidskriftsartikel (refereegranskat)abstract
- The thorough kinetic study of the solvent-free hydrochlorination of glycerol using gaseous hydrogen chloride in a laboratory-scale semibatch reactor was carried out. A wide set of experiments was performed where reaction temperature (70–120 °C), catalyst concentration (0–50% by moles) and partial pressure (0.25, 0.5, 0.75 and 1.0 atm) were varied. Acetic acid was used as a homogenous catalyst. A more accurate approach was given to the semibatch reactor modeling since it was demonstrated that the liquid volume significantly increased along the reaction. The concentration of HCl was determined experimentally and it was possible to observe the influence of the reaction parameters on the HCl uptake. It was also evidenced that a non-catalytic hydrochlorination takes place in the system and its effect is non-negligible, especially at high temperatures. A new kinetic model was proposed and tested in order to explain the experimental observations. Non-linear regression analysis was successfully applied on the experimental data and the modeling results showed a satisfactory agreement. The model was able to estimate the activation energies for both catalyzed and non-catalyzed experiments. A new concept named Catalyst Modulus was derived from the kinetic equations and then verified with experimental data; the fit of this parameter was very high, thus, pointing out the validity of the model.
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| 20. |
- de Araujo Filho, Cesar A., et al.
(författare)
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Comparative Study of Reactive Flash Distillation vs Semibatch Reactor Technologies for the Glycerol Hydrochlorination with Gaseous HCl
- 2016
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 55:19, s. 5500-5513
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Tidskriftsartikel (refereegranskat)abstract
- The present work provides a systematic comparison of solvent-free glycerol hydrochlorination with semibatch and reactive flash distillation technologies. All the experiments were performed at atmospheric pressure and constant flow rate of gaseous HCl in the temperature range of 70 to 120 degrees C. Both acetic acid and adipic acid were used as homogeneous catalysts, separately, at a concentration of 12% by moles of each. In addition, a series of noncatalytic experiments was investigated. A comparative analysis between reactive flash distillation and semibatch operation suggested that reactive flash distillation only increases the production rate of the desired product 1,3-dichloropropan-2-ol (alpha gamma-DCP) for the highest temperature, i.e. 120 degrees C. Many aspects of the HCl liquid uptake were also exposed once water was allowed to leave the liquid phase, revealing that water also has a positive influence on the reaction rate because it promotes HCl solubility and hydrolysis. Such an important effect was not predicted by previous investigations, and it is hereby described for the first time. Additional semibatch experiments were conducted, in which different amounts of water and alpha gamma-DCP were initially added. It was found that, water exerts competing effects in the glycerol hydrochlorination; addition of alpha gamma-DCP showed an improvement of the reaction kinetics and decrease of HCl consumption. It is suggested that instead of using reactive distillation, a wiser choice to perform glycerol hydrochlorination would be to recycle large amounts of the product stream to achieve high conversion levels at milder temperatures and consuming less HCl gas.
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| 21. |
- de Araujo Filho, Cesar A., et al.
(författare)
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Dynamic modelling of homogeneously catalysed glycerol hydrochlorination in bubble column reactor
- 2016
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Ingår i: Chemical Engineering Science. - : Elsevier. - 0009-2509 .- 1873-4405. ; 149, s. 277-295
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Tidskriftsartikel (refereegranskat)abstract
- The homogeneously catalysed glycerol hydrochlorination was thoroughly investigated in a continuous isothermal co-current bubble column reactor over a wide range of reaction parameters, such as temperature (70–120 °C), catalyst concentration (3–12%), liquid flow rate (6–12 mL/min) and gas flow rate (0.4–1.0 L/min). The flow patterns inside the reactor were studied by means of step response residence time distribution experiments and by high-speed camera images. The fluid dynamics of the system presented an unusual behaviour due to the extremely high solubility of HCl in the reaction mixture. Interestingly, the fluid dynamics imposed severe limitations to the reaction conversion. The axial dispersion model was applied for describing the dynamic changes in concentrations of compounds. Kinetic and solubility data were collected from previous work on glycerol hydrochlorination in semi-batch reactor conducted by our research group. The bubble column model was able to successfully describe the dynamic behaviour of 29 experiments, as well as estimate hydrodynamics and mass transfer parameters.
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| 22. |
- de Araujo Filho, Cesar Augusto, et al.
(författare)
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Kinetic model for homogeneously catalyzed halogenation of glycerol
- 2013
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 52:4, s. 1523-1530
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Tidskriftsartikel (refereegranskat)abstract
- A new kinetic model for the halogenation of polyalcohols, e.g. chlorination of glycerol with gaseous HCl in the presence of homogeneous acid catalysts was developed. The model is based on a reaction mechanism, which includes esterification and epoxidation steps followed by halogenation steps. The principle of quasi-steady state was applied to the ester and ionic intermediates appearing in the model and rate equations were derived. Furthermore, some simplified cases of the rate equations were considered, such as immediate water removal from the reaction mixture and analytical solutions for the simplified kinetic models were derived. The model was verified against experimental data obtained from laboratory-scale semibatch reactors. The conclusion is that the model worked very well, predicting correctly the glycerol conversion and the product distribution of α-, β-, α,β- and α,γ-chlorinated products. The kinetic model can be used for design of reactors for homogeneously catalyzed halogenation.
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| 23. |
- Eta, Valerie, et al.
(författare)
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Kinetics of dimethyl carbonate synthesis from methanol and carbon dioxide over ZrO2–MgO catalyst in the presence of butylene oxide as additive
- 2011
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Ingår i: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 404:1-2, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- A kinetic investigation of dimethyl carbonate (DMC) synthesis from methanol and CO2 over ZrO2–MgO was performed by using butylene oxide as a chemical trap for the water formed during the reaction. The effect of the catalyst amount, the stirring speed, the temperature, as well as the amount of butylene oxide on the reaction rate and the selectivity to DMC was studied. The analysis of the reaction pathway suggests that DMC and butylene glycol are formed via the reaction of adsorbed mono-methoxycarbonate intermediate and methoxybutanol or methanol. A kinetic model was developed based on the reaction mechanism and it was in agreement with the experimental data. The apparent activation energy for the formation of DMC was 62 kJ/mol.
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| 24. |
- Eta, Valerie, et al.
(författare)
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Synthesis of dimethyl carbonate from methanol and carbon dioxide : Circumventing thermodynamic limitations
- 2010
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society. - 0888-5885 .- 1520-5045. ; 49:20, s. 9609-17
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of dimethyl carbonate from methanol and CO2 catalyzed by ZrO2 doped with KCl was investigated using chemical traps for water to circumvent thermodynamic limitations. The reaction, promoted by magnesium, occurred via the formation of carbonated magnesium methoxide (CMM) which adsorbed on the surface of ZrO2. The surface migration of the oxygen atom of ZrO2 to the surface methoxy groups of CMM resulted in the formation of dimethyl carbonate. The resulting MgO then reacted with methanol forming water and regenerating magnesium methoxide. The water formed reacted with the dehydrating agent, thus shifting the equilibrium toward a higher yield of DMC. The yield of 7.2 mol % DMC and 13.6 mol % conversion of methanol was obtained when methanol reacted with CO2 at 150 °C and 9.5 MPa for 8 h. The plausible reaction pathway is described.
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| 25. |
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| 26. |
- Eta, Valerie, et al.
(författare)
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The Effect of Alkoxide Ionic Liquids on the Synthesis of Dimethyl Carbonate from CO2 and Methanol over ZrO2-MgO
- 2011
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Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 141:9, s. 1254-1261
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Tidskriftsartikel (refereegranskat)abstract
- The use of carbon dioxide in the synthesis of chemicals, such as dimethyl carbonate (DMC), constitutes an environmentally attractive alternative to hazardous and toxic reagents. However, the direct synthesis of DMC from methanol and CO2 is characterized by low yields due to the reaction equilibrium and the thermodynamic limitations (Delta G(298K)(0) = + 26.3 kj/mol). Alkoxide ionic liquids possessing alkylimidazolium and benzalkonium cations were prepared, characterised and tested together with ZrO2-MgO catalyst for the synthesis of DMC from methanol and CO2. By using the novel ionic liquid as additives, ca. 12% conversion of methanol, and 90% selectivity to DMC was obtained at 120 A degrees C and 7.5 MPa. The water abstracting potential of the ionic liquids influenced the conversion of methanol and the selectivity to DMC. The alkoxide ionic liquids were recovered and reused in DMC synthesis without loss in activity and selectivity.
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| 27. |
- Freites Aguilera, A., et al.
(författare)
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Screening of heterogeneous catalysts for microwave assisted epoxidation of vegetable oils
- 2018
-
Ingår i: 23rd International Congress of Chemical and Process Engineering, CHISA 2018 and 21st Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, PRES 2018. - : Czech Society of Chemical Engineering. - 9781510881198 ; , s. 54-55
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Konferensbidrag (refereegranskat)
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| 28. |
- Gallina, Gianluca, et al.
(författare)
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Optimized H2O2 production in a trickled bed reactor, using water and methanol enriched with selectivity promoters
- 2015
-
Ingår i: Chemical Engineering Science. - : Elsevier. - 0009-2509 .- 1873-4405. ; 123, s. 334-340
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work a comparison between two different working solutions in the H2O2 catalytic direct synthesis (CDS) was studied in a continuous reactor. The two working solutions (i.e. water and methanol) were chosen due to their large use in the catalytic direct synthesis. Both the working solutions have advantages and drawbacks: it is well known that methanol is mainly used due to the possibility of higher H2 and O2 solubilization compared to water, while water is the “greenest” solvent for excellence. Different parameters such as temperature, gas flow rate and catalyst amount were studied in order to identify the major differences between water and methanol. A study to compare the gases solubility in our conditions in water and methanol was performed in order to understand how gas solubility can affect the reaction. Gas solubility was found to be 10 times higher in methanol compared to water. Consequently the consumption of the reagents was faster in methanol compared to water. Unexpectedly, the final concentration of H2O2 was comparable between water and methanol working solutions at the different operations conditions studied. This indicated that the transport phenomena are important to fine tune the reaction path. The maximum H2O2 was around 2.3 wt%.
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| 29. |
- García-Serna, Juan, et al.
(författare)
-
Engineering in direct synthesis of hydrogen peroxide : targets, reactors and guidelines for operational conditions
- 2014
-
Ingår i: Green Chemistry. - : Royal Society of Chemistry. - 1463-9262 .- 1463-9270. ; 16:5, s. 2320-2343
-
Tidskriftsartikel (refereegranskat)abstract
- The demand for hydrogen peroxide is booming since it is considered as one of the most environmentally friendly and versatile chemical oxidants available and with a wide range of applications. The annual market close to 3000 kt/y being produced via the auto-oxidation process (with 2-ethyl anthraquinone (traditional) or amyl anthraquinone for mega-plants) is mostly supplied by the company Solvay (30%), followed by Evonik (20%) and Arkema (13%) as key intermediate. Nevertheless, the dream of direct synthesis process is close to a century year-old and it has gained momentum in research effort during the last decade with more than 15 groups active in the world. In this review, we focus the discussion on the targets, e.g. plant tonnage, the reactors and the most feasible industrial operational conditions, based on our experience, and from the point of view using the chemical engineering tools available. Thus, direct synthesis can be competitive when on-site production is required and capacities less than 10 kt/y are demanded. The total investment cost should be approximately in between 40.3±12.1 MM$ (in 2012) for a 10 kt/y size process to be comparable to the traditional process in terms of costs. Moreover, all kinds of reactors used are hereby discussed emphasizing the pros and cons; the most common ones are batch and semicontinous modes of operations. However, at the moment, demonstrations of continuous operations as well as carefully determined kinetics are needed in order to scale up the process. Finally, operational conditions, including the catalyst composition (active metal, oxidation state and support), promoters (halides and acids-pH-isoelectric point), solvents, pressure and temperature need to be carefully analysed. In our opinion, as we try to show here, H2O2 direct synthesis is a competitive process and ready for larger scale demonstration. Also, more than a hundred patents within the area support this claim, although the barries of technology demonstration and further licensing are still pending.
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| 30. |
- Gemo, Nicola, et al.
(författare)
-
Reactivity aspects of SBA15-based doped supported catalysts : H2O2 direct synthesis and disproportionation reactions
- 2013
-
Ingår i: Topics in catalysis. - New York : Springer. - 1022-5528 .- 1572-9028. ; 56:9-10, s. 540-549
-
Tidskriftsartikel (refereegranskat)abstract
- Pd and PdAu catalysts supported on SBA15 and SiO2 were prepared and investigated for H2O2 direct synthesis in a batch autoclave (10 °C and 17.5 bar) and in the absence of halides and acids. The SiO2 supported catalysts exhibited inferior performances compared to the mesoporous ordered SBA15. A good control of both the catalysts dispersion and nanoparticle stability was achieved using SBA15. Catalysts were doped with bromine, a promoter in the H2O2 direct synthesis. Productivity and selectivity decreased when bromine was incorporated in the catalysts, thus indicating a possible poisoning due to the grafting process. A synergetic effect between Pd and Au was observed both in presence and absence of bromopropylsilane grafting on the catalyst surface. Three modifiers of the SBA15 support (Al, CeO2 and Ti) were chosen to elucidate the influence of the surface properties on metal dispersion and catalytic performance. Higher productivity and selectivity were achieved incorporating Al into the SBA15 framework, whereas neither Ti nor CeO2 improved H2O2 yields. The enhanced performance observed for the Prau/Al–SBA15 catalysts was attributed to the increased number of Brønsted acid sites. A modification of this catalyst with bromine was confirmed to impair both productivity and selectivity, possibly due to the broader particle size distribution and the poor stability of the metal nanoparticles, as demonstrate by transmission electron microscopy (TEM) images. H2O2 disproportionation was also investigated. A much slower reaction rate was observed compared to the H2O2 production, suggesting that the major contributor in the process of H2O2 destruction must be connected to the hydrogenation reaction.
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| 31. |
- Gemo, Nicola, et al.
(författare)
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The influence of catalyst amount and Pd loading on the H2O2 synthesis from hydrogen and oxygen
- 2015
-
Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 5:7, s. 3545-3555
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Tidskriftsartikel (refereegranskat)abstract
- Palladium catalysts with an active metal content from 0.3 to 5.0 wt.% and supported on a strongly acidic, macroporous resin were prepared by ion-exchange/reduction method. H2O2 direct synthesis was carried out in the absence of promoters (acids and halides). The total Pd amount in the reacting environment was varied by changing A) the catalyst concentration in the slurry and B) the Pd content of the catalyst. In both cases, smaller amounts of the active metal enhance the selectivity towards H2O2, at any H-2 conversion, with option B) better than A). In case A), the Pd(II)/Pd(0) molar ratio (XPS) in the spent catalysts was found to decrease at lower catalyst Pd content. With these catalysts and this experimental set-up the dynamic H-2(1)/Pd molar ratio, the metal loading and the metal particle size were the key factors controlling the selectivity, which reached 57% at 60% H-2 conversion, and 80% at lower conversion.
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| 32. |
- Golets, Mikhail, 1987-, et al.
(författare)
-
A kinetic study of the liquid phase acetoxylation of α-pinene
- 2012
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Ingår i: Topics in catalysis. - : Springer. - 1022-5528 .- 1572-9028. ; 55:7-10, s. 649-656
-
Tidskriftsartikel (refereegranskat)abstract
- The present study introduces kinetic modeling of liquid phase α-pinene acetoxylation with acetic acid over an ion-exchange resin catalyst. The reaction was carried out in a laboratory scale high-pressure autoclave. α-terpinyl (35 wt%) and bornyl (40 wt%) acetates were the primary products. The predominant reaction pathways were identified and evaluated.
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| 33. |
- Golets, Mikhail, 1987-, et al.
(författare)
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Liquid phase acetoxylation of α-pinene
- 2012
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Ingår i: NWBC 2012. - : VTT. - 9789513878801 - 9789513878818 ; , s. 339-341
-
Konferensbidrag (refereegranskat)abstract
- Chemical pulping and bio-refining results in many fractions such as. tall oil and turpentine that contain substantial amounts of α-pinene and other terpenes. Today these fractions are usually burned in the recovery boilers. However, the northern forest industry, primarily utilizing the boreal forests, faces serious challenges from developing markets (South America, Asia), because of lower cost of raw material resources and labor. At the same time, there is a growing concern about emissions of greenhouse gases and security of supply connected to the use of fossil oil for transportation and as a feedstock for the chemical industry. The mentioned fact renders the substitution of petrochemical-related raw materials an important field of research.The flavor and fragrance industry is one of the main users of terpene esters. From those esters, α-terpinyl and bornyl acetates are produced from α-pinene and commonly used for bath products and perfumes. Due to the imperfection of conventional two-stage production method of the mentioned esters, which lays in the equipment corrosion, environmental pollution, large load and nonrecyclability of a catalyst, the novel one-stage catalytic process is always of high priority.The possibility of α-pinene liquid phase catalytic acetoxylation is introduced in the present study. The complex product distribution and reaction network analysis, influent reaction and catalytic factors optimization, combined with the reaction kinetic modeling were the main aims of research. The ion-exchange resin catalyst Amberlyst 70 was characterized as the catalyst used in the studied reaction and compared with the solvent-catalyzed mode. Valuable combinations of acetates were obtained for both studied modes. A wide range of process factors were studied in the batch (Parr) reactor used. The mentioned type of reactor is suitable for the consequent industrial operations scale-up calculations.
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| 34. |
- Golets, Mikhail, 1987-, et al.
(författare)
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Liquid phase acetoxylation of α-pinene over Amberlyst-70 ion-exchange resin
- 2012
-
Ingår i: Applied Catalysis A: General. - : Elsevier BV. - 0926-860X .- 1873-3875. ; 435-436, s. 43-50
-
Tidskriftsartikel (refereegranskat)abstract
- Heterogeneously-catalyzed and solvent-catalyzed liquid phase acetoxylation of α-pinene with acetic acid acting as both a solvent and a reagent was studied. Both solvent-catalyzed and catalytic experiments were carried out and various reaction conditions were studied. The influence of temperature, pressure, solvent and gas milieu were taken into account. Bornyl, fenchyl, verbenyl as well as α-terpinyl acetates, limonene, camphene and γ-terpinene were found among reaction products. The addition of the catalyst allowed for maximization of the yield of bornyl acetate. The predominant products obtained were α-terpinyl, verbenyl and bornyl acetates. The reaction pathways were identified and evaluated. The aim of this work was to study the feasibility of batch acetoxylation of α-pinene. The analysis of the complex product distribution is not trivial and, consequently, resolving the reaction network was important. The optimized reaction conditions were searched for aiming at an efficient conversion of α-pinene to a mixture of valuable products.
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| 35. |
- Grénman, Henrik, et al.
(författare)
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Modeling the influence of wood anisotropy and internal diffusion on delignification kinetics
- 2010
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society. - 0888-5885 .- 1520-5045. ; 49:20, s. 9703-11
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Tidskriftsartikel (refereegranskat)abstract
- A general mathematical model for the chemical pulping of wood including coupled chemical reactions and diffusion limitations in anisotropic wood chips was developed. The model, which consists of coupled parabolic partial differential equations (PDEs) and ordinary differential equations (ODEs), describes the time-dependent behavior of wood chips as they are exposed to chemicals in the liquid phase. In addition to the reaction−diffusion phenomena, the model describes the change of the wood chip porosity during the process. A numerical algorithm that combines spatial discretization by finite differences with a stiff ODE solver based on the backward difference method was used as an efficient strategy to solve the mass balances of wood chips in batch reactors. Numerical simulations with the software can be used to predict the progress of industrial delignification, that is, production of primarily cellulose through chemical pulping. The effect of the reaction parameters, such as the temperature and the concentrations of the alkaline delignification chemicals, as well as the sizes of the wood chips, can be evaluated with the model, the final goal being the intensification of the chemical pulping process. The model can be used to describe both the current kraft pulping (sulfate pulping) technique, as well as other processes, such as sulfite pulping and pulping in nonaqueous solvents.
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| 36. |
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| 37. |
- Hajek, Jan, et al.
(författare)
-
Interconversion of Lactose to Lactulose in Alkaline Environment : Comparison of Different Catalysis Concepts
- 2013
-
Ingår i: Topics in catalysis. - : Springer/Plenum Publishers. - 1022-5528 .- 1572-9028. ; 56:9-10, s. 839-845
-
Tidskriftsartikel (refereegranskat)abstract
- Interconversion of lactulose to lactulose with the aim to determine and optimize the yield of ketose was carried out. Various homogenous and heterogeneous alkaline catalysts were applied (NaOH, MgO, hydrotalcite etc.). The selectivity and activity of the catalysts were compared. The results gave insight to the performance differences among the screened catalysts under the various reaction conditions. From the activity performance point of view, the conversion was limited by the formation of acidic end-products. In general, the selectivity decreased with conversion and the conversion-selectivity pattern was independent of the catalyst.
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| 38. |
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| 39. |
- Hajek, J., et al.
(författare)
-
Processing of gluconic acid derivatives to value added monosaccharides via oxidative degradation
- 2012
-
Konferensbidrag (refereegranskat)abstract
- One of the components that can be efficiently obtained, e.g., via fermentation of polysaccharide containing waste or biomass, is glucose and some of its derivatives. Degradation of C6 carbohydrates yields corresponding C5 sugars. In case of gluconic acid, the product is arabinose. The reaction, illustrating a valuable synthetic route, e.g., for the abatement of waste streams containing gluconic acid is shown. In spite of high yields, the reaction is characterized by complex analytics due to the presence of organic as well as inorganic by-products. Under optimized conditions, yields between 70-80% could be achieved. This is an abstract of a paper presented at the CHISA 2012 - 20th International Congress of Chemical and Process Engineering and PRES 2012 - 15th Conference PRES (Prague, Czech Republic 8/25-29/2012).
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| 40. |
- Hernandez Carucci, José R, et al.
(författare)
-
Preparation and characterization of coated microchannels for the selective catalytic reduction of NOx
- 2012
-
Ingår i: Focus on Catalysis Research. - New York : Nova Science Publishers. - 9781621004776 ; , s. 209-236
-
Bokkapitel (refereegranskat)abstract
- Shallow microchannels (Ø= 460 m) were successfully coated with different catalytically active phases, e.g., Cu-ZSM-5, Cu/(ZSM-5+Al2O3), Au/Al2O3, Ag/(Al2O3+Ionic liquid) and Ag/Al2O3, and tested on the hydrocarbon-assisted selective catalytic reduction of NOx (HC-SCR) with different model bio-derived fuels, i.e., methyl- and ethyl laurate produced by transesterification and hexadecane, a paraffinic component that can be produced by decarboxylation and/or decarbonylation of natural oils and fats. Characterization of the washcoats was done by means of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDXA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), showing a dependence of the metal loading with the impregnation time and the precursor concentration. The Ag/Al2O3 catalysts exhibited, in general, the highest activities towards the NOx reduction. Optima in impregnation time and concentration of AgNO3 solution displaying the highest activity in HC-SCR among the prepared Ag/Al2O3 washcoats were established. A combination of Cu-ZSM-5 or Cu/(ZSM-5+Al2O3) and the optimum Ag/Al2O3 catalyst were tested in order to improve the low temperature reduction in SCR with hexadecane as a reducing agent. The enhancement of the activity at low temperatures (< 350 °C) was up to seven-fold compared to the case when only Ag/alumina was used. The effect of the hydrocarbon concentration (hexadecane) and the presence of water in the feed were also investigated.
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| 41. |
- Herrara, Victor A. Sifontes, et al.
(författare)
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Sugar hydrogenation in continuous reactors : from catalyst particles towards structured catalysts
- 2016
-
Ingår i: Chemical Engineering and Processing. - : Elsevier BV. - 0255-2701 .- 1873-3204. ; 109, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- The density, viscosity and hydrogen solubility of selected sugars (l-arabinose, d-galactose, d-maltose and l-rhamnose) were determined at different temperatures (generally 60, 90 and 130 °C). The role of internal diffusion resistance in porous catalyst layers for sugar hydrogenation was confirmed by numerical simulations based on kinetic data and physical properties. The simulations suggested the use of small catalyst particles or structured catalysts in continuous hydrogenation of the sugars to sugar alcohols. Continuous hydrogenation of l-arabinose was carried out in a laboratory-scale fixed bed reactor with ruthenium catalysts on three different supports (active carbon clothes, carbon nanotubes on sponge-like metallic structures, conventional active carbon catalyst particles). It was proved that continuous hydrogenation is a feasible alternative to batch technology for sugar hydrogenation over conventional catalyst particles and structured catalysts: l-arabinose was converted to arabitol with a very high selectivity.
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| 42. |
- Huerta, Irene, et al.
(författare)
-
Continuous H2O2 direct synthesis process : an analysis of the process conditions that make the difference
- 2016
-
Ingår i: Green Processing and Synthesis. - : Walter de Gruyter. - 2191-9542 .- 2191-9550. ; 5:4, s. 341-351
-
Tidskriftsartikel (refereegranskat)abstract
- A trickle bed reactor (TBR) was used to study different process parameters upon hydrogen peroxide direct synthesis. The catalysts used were commercial palladium on active carbon. The influence of pressure (1.75–25 barg), temperature (5–60°C), liquid flow rate (2–13.8 ml·min-1), gas flow rate (3.4–58.5 ml·min-1), catalyst amount (90–540 mg), Pd percentage on the support (5% wt., 10% wt. and 30% wt. Pd/C) as well as promoter concentrations (0.0005–0.001 m) were all varied as process parameters to better understand the behaviour of the system. By contrast, the gas phase molar composition of the feed (4:20:76=H2:O2:CO2) was kept constant. The strong influence between liquid flow rate, gas flow rate and catalyst amount were identified as the key parameters to tune the reaction, and related to the activity of the catalyst. In essence, these parameters must be carefully tuned to control the hydrogen consumption. The maximum productivity (289 μmol H2O2·min-1) and yield (83.8%) were obtained when a diluted bed of 30% Pd/C was applied. The H2O2 hydrogenation was studied in order to understand its role in the H2O2 direct synthesis reaction network. The hydrogenation reaction mechanism and the role of NaBr were identified thanks to the experiment proposed in the present work. Consequently, understanding the whole reaction mechanism from the process conditions studied led to a deeper understanding of all of the phenomena involved in the H2O2 direct synthesis.
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| 43. |
- Huerta, I., et al.
(författare)
-
Effect of low hydrogen to palladium molar ratios in the direct synthesis of H2O2 in water in a trickle bed reactor
- 2015
-
Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 248, s. 91-100
-
Tidskriftsartikel (refereegranskat)abstract
- Application of a trickle bed reactor (TBR) renders a very compact solution to carry out direct synthesis of hydrogen peroxide in water over a carbon supported palladium. The laboratory scale reactor was filled with silica particles (50-70 mesh) physically mixed with 37.5 to 75 mg of 5%Pd/C particles. The reaction conditions applied were 15 degrees C, 15-28 barg, 0.5 to 6 mL min(-1) of liquid and 4.0-4.5 mL min(-1) of gas flowrate (86.7/11/2.23 mol% of CO2/O-2/H-2). Thus, we demonstrated that the ratio between H-2 and Pd is one of the key factors to achieve optimized, higher yields of hydrogen peroxide. Consequently, low H-2 concentrations lead to low productivities. One of the least studied parameters, addressed here, is the ratio between the bed filling (SiO2) and the catalyst; i.e. the active catalytic species dilution effect. In short, it was found that when the amount of Pd was reduced below 0.094 mg Pd cm(-3) SiO2 the highest productivity of H2O2 could be achieved. The selectivity obtained were between 5.3 and 38.0%, respectively, corresponding to turn-over-frequencies (TOF) ranging from 65 to 921 mmol H2O2 gPd(-1) h(-1). (C) 2014 Elsevier B.V. All rights reserved.
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| 44. |
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| 45. |
- Jogunola, O., et al.
(författare)
-
Carbonylation of methanol using potassium methoxide: Kinetic and mechanistc studies
- 2012
-
Konferensbidrag (refereegranskat)abstract
- Carbonylation of methanol (MeOH) to methyl formate (MeFo) process step was studied using potassium methoxide (KOMe) as catalyst. The reaction was almost exclusively selective to methyl formate but traces of dimethyl ether and trimethoxylmethane were detected. The mass and volume of the reaction mixture increased with as the reaction advanced. The addition of CO to methanol changed the mass. The mass and mole balances of each sample were solved separately by adjusting the total mass. This was possible by assuming that all MeOH consumed was transformed to MeFo and the rest of the components in the system were inert. The model, which consisted of kinetics and mass transfer limitation, predicted the experimental results successfully. This is an abstract of a paper presented at the CHISA 2012 - 20th International Congress of Chemical and Process Engineering and PRES 2012 - 15th Conference PRES (Prague, Czech Republic 8/25-29/2012).
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| 46. |
- Jogunola, Olatunde, et al.
(författare)
-
Complexation equilibria studies of alkyl formate hydrolysis in the presence of 1-butylimidazole
- 2017
-
Ingår i: Thermochimica Acta. - : Elsevier. - 0040-6031 .- 1872-762X. ; 652, s. 62-68
-
Tidskriftsartikel (refereegranskat)abstract
- Formic acid production by ethyl or methyl formate hydrolysis was improved using 1-butylimidazole as a complexing agent. The chemical process involved both hydrolysis and complexation steps. The complexation equilibria were investigated by deriving theoretical equations using the equilibrium constant of the hydrolysis step, the apparent formation constant of the complexation process and the initial concentration of the complexing agent. The treatment of the experimental results within the experimental domain indicated that an equimolar amount of the acid and the base did not lead to the complex formation. Experimental observation suggested that the derived equation could be simplified by assuming that the stoichiometric coefficient of the complexing agent was 0.5. The apparent reaction enthalpy obtained from this equation was compared to the experimental one using a Tian-Calvet calorimeter and a good agreement was found between them. FTIR spectroscopy was used to confirm the existence of the complex between formic acid and 1-butylimidazole.
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| 47. |
- Jogunola, O., et al.
(författare)
-
Complexation equilibria studies of alkyl formate hydrolysis using butyllimidazole
- 2014
-
Ingår i: 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, PRES 2014. - : Czech Society of Chemical Engineering. - 9781510828131 ; , s. 103-
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Konferensbidrag (refereegranskat)
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| 48. |
- Jogunola, Olatunde, et al.
(författare)
-
Determination of the kinetics and mechanism of methyl formate synthesis in the presence of a homogeneous catalyst
- 2012
-
Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 203, s. 469-479
-
Tidskriftsartikel (refereegranskat)abstract
- The kinetics and mechanism of methyl formate synthesis, the key intermediate of the formic acid process was determined. Methyl formate was prepared from carbon monoxide and methanol in the presence of potassium methoxide as a homogeneous catalyst. Experimental work was carried out in a laboratory-scale semi-batch autoclave to obtain the intrinsic reaction kinetics. The experimental results were described with a plausible reaction mechanism comprising the reaction of potassium methoxide with carbon monoxide, followed by the proton transfer from methanol to the reaction intermediate to restore the catalyst. It was observed that simple first order kinetics fits the experimental data of the catalyst decomposition. A model for the gas-liquid mass transfer, coupled to the synthesis reaction was developed and the reaction of potassium methoxide was assumed to be the rate-determining step. The equilibrium, mass transfer and rate parameters included in the completely new kinetic model were determined with non-linear regression analysis. A comparison of the modeling results with the experimental data illustrated a good agreement between the model and the actual data. The kinetic and mass transfer models can be used for the scale-up of the methyl formate synthesis.
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| 49. |
- Jogunola, Olatunde, et al.
(författare)
-
Ionic liquid mediated technology for synthesis of cellulose acetates using different co-solvents
- 2016
-
Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 135, s. 341-348
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, cellulose acetate was synthesized under homogeneous conditions. Cellulose was first dispersed in acetone, acetonitrile, 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) or dimethyl sulphoxide (DMSO) and the resulting suspension was dissolved in an ionic liquid, 1,5-diazabicyclo(4.3.0)non-5-enium acetate [HDBN][OAc] at 70 °C for 0.5 h. It was possible to dissolve more than 12 wt% cellulose with a degree of polymerization in the range of 1000–1100. The dissolved cellulose was derivatized with acetic anhydride (Ac2O) to yield acetylated cellulose. As expected, the use of the co-solvents improved the acetylation process significantly. In fact, cellulose acetates with different properties could be obtained in half an hour, thus facilitating rapid processing. When DBN was used as the dispersing agent (the precursor of the ionic liquid), the problems associated with recycling of the ionic liquid were significantly reduced. In fact, additional [HDBN][OAc] was obtained from the interaction of the DBN and the by-product, acetic acid (from Ac2O). However, the cellulose acetate obtained in this manner had the lowest DS. Consequently, the native cellulose and acetylated celluloses were characterized by means of 1H- and 13C-NMR, FT-IR, GPC/SEC and by titration. The cellulose acetates produced were soluble in organic solvents such as acetone, chloroform, dichloromethane and DMSO which is essential for their further processing. It was demonstrated that the ionic liquid can be recovered from the system by distillation and re-used in consecutive acetylation batches.
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| 50. |
- Jogunola, Olatunde, et al.
(författare)
-
Kinetic and diffusion study of acid-catalyzed liquid-phase alkyl formates hydrolysis
- 2012
-
Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509 .- 1873-4405. ; 69:1, s. 201-210
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Tidskriftsartikel (refereegranskat)abstract
- Alkyl formates are typically hydrolyzed with the aid of homogeneous catalysts, but heterogeneous catalysts provide a promising pathway for the process. The hydrolysis of alkyl formates by a solid acid catalyst, ion-exchange resin was accomplished in a batch reactor, a stirred autoclave operating isothermally at 60 degrees C and 90 degrees C with a constant initial water-to-ester molar ratio. A mathematical model, which incorporates the particle size distribution of the solid catalyst, was developed to study the kinetics and internal mass transfer effects in the porous particles and it was able to predict the concentrations in the bulk phase and inside the catalyst particles. A combined reaction-diffusion model is necessary to describe the behavior of the system. The model was able to predict well the experimental results. (C) 2011 Elsevier Ltd. All rights reserved.
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