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  • 1.
    Bukhanko, Natalia
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wärnå, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, FIN-20500, Turku/Åbo, Finland.
    Samikannu, Ajaikumar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, FIN-20500, Turku/Åbo, Finland.
    Kinetic modeling of gas phase synthesis of ethyl chloride from ethanol and HCl in fixed bed reactor2016Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 142, s. 310-317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Kinetic modeling of gas-phase synthesis of ethyl chloride from ethanol and hydrochloric acid over high porous Al2O3 and 2 wt% ZnCl2/Al2O3 catalysts was studied in a continuous plug flow reactor in the temperature range of 200–325 °C. Two rival kinetic models were proposed that both describe the kinetics well. The kinetic parameters of the reaction were determined and activation energy values for ethyl chloride formation from ethyl alcohol and diethyl ether reactions were calculated.

  • 2. de Araujo Filho, Cesar A.
    et al.
    Eränen, Kari
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Salmi, Tapio
    A comprehensive study on the kinetics, mass transfer and reaction engineering aspects of solvent-free glycerol hydrochlorination2014Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 120, s. 88-104Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 3. de Araujo Filho, Cesar A.
    et al.
    Mondal, Debanga
    Haase, Stefan
    Wärnå, Johan
    Eränen, Kari
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemical Engineering, Johan Gadolin Process Chemistry Centre, Laboratory of Industrial Chemistry and Reaction Engineering, Åbo Akademi University, FI-20500 Turku/Åbo, Finland.
    Salmi, Tapio
    Dynamic modelling of homogeneously catalysed glycerol hydrochlorination in bubble column reactor2016Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 149, s. 277-295Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 4.
    Gallina, Gianluca
    et al.
    Process Chemistry Centre, Laboratory of Industrial Chemistry and Reaction Engineering, Åbo Akademi, Turku/Åbo, Finland.
    Biasi, Pierdomenico
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Process Chemistry Centre, Laboratory of Industrial Chemistry and Reaction Engineering, Åbo Akademi, Turku/Åbo, Finland.
    García-Serna, Juan
    Department of Chemical Engineering and Environmental Technology, High Pressure Processes Group, University of Valladolid, Spain.
    Salmi, Tapio
    Process Chemistry Centre, Laboratory of Industrial Chemistry and Reaction Engineering, Åbo Akademi, Turku/Åbo, Finland.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Process Chemistry Centre, Laboratory of Industrial Chemistry and Reaction Engineering, Åbo Akademi, Turku/Åbo, Finland.
    Optimized H2O2 production in a trickled bed reactor, using water and methanol enriched with selectivity promoters2015Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 123, s. 334-340Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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%.

  • 5. Jogunola, Olatunde
    et al.
    Salmi, Tapio
    Warna, Johan
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kinetic and diffusion study of acid-catalyzed liquid-phase alkyl formates hydrolysis2012Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 69, nr 1, s. 201-210Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 6. Johansson, Kristin
    et al.
    Kotkamo, Sami
    Rotabakk, Bjørn Tore
    Johansson, Caisa
    Kuusipalo, Jurkka
    Jönsson, Leif J.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Järnström, Lars
    Extruded polymer films for optimal enzyme-catalyzed oxygen scavenging2014Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 108, s. 1-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of enzymes as oxygen scavengers has a great potential in the food packaging industry. Enzymes can be incorporated into a coating layer that can be applied directly onto the packaging material. For the system to be fully functional, there is however a need for the packaging to have some barrier properties, to be sealable through heat, and to ensure low or no migration of the active coating to the food. Various combinations of polypropylene (PP), poly(lactic acid) (PLA) and low density polyethylene (LDPE) were extruded onto board coated with the oxygen-scavenging enzyme. Properties such as oxygen-transmission rate, water-vapor transmission rate, heat-sealability, migration and oxygen scavenging capacity were evaluated. All combinations of extruded material resulted in a packaging material able to scavenge the oxygen at both 84% and 100% relative humidity. The greatest decrease in oxygen concentration of the head space of air tight chambers was achieved with the material extruded with PLA on at least one side. It was found that the extruded plastic is necessary in order to meet the EU directives on migration from food packaging materials of not more than a total of 10 mg/dm(2) material. All plastics were heat sealable against themselves but not against any of the other plastics and only LDPE adhered strongly to the enzyme containing coating. (C) 2013 Elsevier Ltd. All rights reserved

  • 7.
    Ma, Charlie
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Skoglund, Nils
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Carlborg, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Broström, Markus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Viscosity of molten CaO-K2O-SiO2 woody biomass ash slags in relation to structural characteristics from molecular dynamics simulation2020Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 215, artikel-id 115464Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molten compositions in the CaO-K2O-SiO2 system relevant to woody biomass ash slags were simulated with molecular dynamics to extract structural characteristics. Multivariate analysis elucidated correlations of these structural characteristics with viscosity measurements. The simulations show SiO4/silicate tetrahedral units (STUB) diffusing slowly and forming flexible networks via oxygen bridges. The degree of STU polymerization varies linearly with the (K2O + CaO)/SiO2 ratio. Ca depolymerises stronger than K, but K diffuses quicker. Depolymerization and diffusion cause network disruptions and agitations that promote collective atomic mobility of the system. This imposes structural characteristics in the slag that correlate with viscosity. The inter-STU Si-O-Si angle narrows with decreasing viscosity, while the Si-O bond length of these bridges increases. Attributes related to atomic mobility, such as the variations in the Si-O-Si angle and the distance of nearest Si-Si pairs, also correlate with viscosity. The discussion provides insight into the connection between structural characteristics and viscosity.

  • 8. Russo, Vincenzo
    et al.
    Salmi, Tapio
    Mammitzsch, Frank
    Jogunola, Olatunde
    Lange, Rüdiger
    Wärnå, Johan
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi, Process Chemistry Centre, Laboratory of Industrial Chemistry and Reaction Engineering, FI-20500 Åbo/Turku, Finland.
    First, second and nth order autocatalytic kinetics in continuous and discontinuous reactors2017Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 172, s. 453-462Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Autocatalytic phenomena in chemical kinetics originate from various reasons, such as acid-catalytic effects of reaction products or change of the physical properties of the reaction mixture. The impact of autocatalytic kinetics on the chemical reactor design is crucially important leading to deviations from standard design rules. The impact of autocatalytic effects on first, second and nth order kinetics was investigated for batch, plug flow, backmixed, axial dispersion and recycled plug flow reactors was analyzed by classical approach and numerical simulations. Efficient numerical strategies were developed for the different reactor models. The results showed how an optimal degree of backmixing (Péclet number) and optimal recycle ratio can be determined for tubular reactors and how the reactor volume can be minimized for specific cases. Generic examples as well as hydrolysis of alkyl formate were considered as case studies.

  • 9. Salmi, Tapio
    et al.
    Damlin, Pia
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kangas, Matias
    Modelling and experimental verification of cellulose substitution kinetics2011Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 66, nr 2, s. 171-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose and starch derivatives are often prepared by substitution reactions to the hydroxyl groups (OH-2, OH-3 and OH-6) of the corresponding anhydroglucose units. A general kinetic model for the substitution of cellulose and starch was developed. The model assumes different reactivities of the hydroxyl groups and a decrease in the reactivity as the substitution proceeds. Both phenomena are taken into account in the model. The model predicts the detailed distribution of the different mono (2, 3, 6)-, di (23, 26, 36)—and trisubstituted (236) units as a function of the reaction time. The classical Spurlin distribution is obtained as a special case of the general model. Numerical strategies were developed for the solution and computer simulation of the model. Simulation results were shown to be valid for various reactivity ratios of the hydroxyl groups. The modelling concept was verified with experimental data obtained for carboxymethylation of cellulose. It should be emphasized, however, that the same general approach is also applicable in studies of any hemicelluloses or oligo- or monosaccharides. The detailed data, which revealed the non-uniform reactivities of the different hydroxyl groups and the decline of the substitution rate with time, were successfully described by the mathematical model.

  • 10. Salmi, Tapio
    et al.
    Eränen, Kari
    Tolvanen, Pasi
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Johan Gadolin Process Chemistry Centre (PCC), Laboratory of Industrial Chemistry and Reaction Engineering, Turku/Åbo, Finland.
    Russo, Vincenzo
    Determination of kinetics and equilibria of heterogeneously catalyzed gas-phase reactions in gradientless autoclave reactors by using the total pressure method: Methanol synthesis2019Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rapid methods are very valuable in the determination of the kinetic and mass transfer effects for heterogeneously catalyzed reactions. The total pressure method is a classical tool in the measurement of the kinetics of gas-phase reactions, but it can be successfully applied to the kinetic measurements of gas-phase processes enhanced by solid catalysts. A general theory for the analysis of heterogeneously catalyzed gas-phase kinetics in gradientless batch reactors was presented for the case of intrinsic kinetic control and combined kinetic-diffusion control in porous catalysts. The concept was applied to gas-phase synthesis of methanol from carbon monoxide and hydrogen on a commercial copper-based catalyst (CuO/ZnO/Al2O3 R3-12 BASF). The reaction temperature was 180–210 °C and the initial total pressure was varied between 11 and 21 bar in a laboratory-scale autoclave reactor equipped with a rotating basket for the catalyst particles. The initial molar ratios CO-to-H2 were approximately 1:2, 1:3 and 1:4. The experimental data from methanol synthesis were compared with numerical simulations and a good agreement between the experiments and model simulations was achieved. The predicted equilibrium agrees with previously reported values.

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