umu.sePublikationer
Ändra sökning
Avgränsa sökresultatet
123456 51 - 100 av 258
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 51.
    Eta, Valerie
    et al.
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Finland.
    Anugwom, Ikenna
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Finland.
    Virtanen, Pasi
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Finland.
    Mäki-Arvela, P
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Finland.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Finland.
    Enhanced mass transfer upon switchable ionic liquid mediated wood fractionation2014Ingår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 55, s. 109-115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fractionation of lignocellulosic biomass to its major components is the primary step towards the conversion of biomass-based biopolymers to commodity chemicals in the integrated biorefinery process. Wood chips encased in a SpinChem® device and attached to the stirrer of a batch autoclave were used together with switchable ionic liquids (SILs) for the selective fractionation of hemicelluloses and lignin. Stirring of the wood chips in the SpinChem® device facilitated the diffusion of SIL into the chips through forced recirculation and at the same time avoiding mechanical fibrillation. The treatment of birch chips (Betula pendula) with SILs comprising 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU), monoethanolamine (MEA) and CO2 at 120 °C in a SpinChem® device resulted in the fractionation of 82 wt.% hemicelluloses and 90 wt.% lignin, leaving the cellulose-rich non-dissolved material partially fibrillated and softened. The dissolved hemicelluloses and lignin were selectively precipitated using isopropanol and recovered from the spent SIL.

  • 52. Eta, Valerie
    et al.
    Maki-Arvela, Paivi
    Salminen, Eero
    Salmi, Tapio
    Murzin, Dmitry Yu.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    The Effect of Alkoxide Ionic Liquids on the Synthesis of Dimethyl Carbonate from CO2 and Methanol over ZrO2-MgO2011Ingår i: Catalysis Letters, ISSN 1011-372X, E-ISSN 1572-879X, Vol. 141, nr 9, s. 1254-1261Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 53.
    Eta, Valerie
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    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, Åbo-Turku, Finland.
    Deconstruction of Nordic hardwood in switchable ionic liquids and acylation of the dissolved cellulose2016Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 136, s. 459-465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nordic hardwood (Betula pendula) was fractionated in a batch autoclave equipped with a custom-made SpinChem® rotating bed reactor, at 120°C using CO2 and CS2-based switchable ionic liquids systems. Analyses of the non-dissolved wood after treatment showed that 64 wt% of hemicelluloses and 70 wt% of lignin were removed from the native wood. Long processing periods or successive short-time treatments using fresh SILs further decreased the amount of hemicelluloses and lignin in the non-dissolved fraction to 12 and 15 wt%, respectively. The cellulose-rich fraction was partially dissolved in an organic superbase and an ionic liquid system for further derivatization. Homogeneous acylation of the dissolved cellulose in the presence or absence of catalyst resulted in cellulose acetates with variable degree of substitution (DS), depending on the treatment conditions. By varying the reaction conditions, the cellulose acetate with the desired DS could be obtained under mild conditions.

  • 54. Eta, Valerie
    et al.
    Mäki-Arvela, Päivi
    Leino, Anne-Riikka
    Kordás, Krisztián
    Salmi, Tapio
    Murzin, Dmitry Yu
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Synthesis of dimethyl carbonate from methanol and carbon dioxide: Circumventing thermodynamic limitations2010Ingår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 49, nr 20, s. 9609-17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 55. Eta, Valerie
    et al.
    Mäki-Arvela, Päivi
    Murzin, Dmitry Yu
    Salmi, Tapio
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Synthesis of Dimethyl Carbonate from Methanol and Carbon Dioxide: the Effect of Dehydration2009Konferensbidrag (Refereegranskat)
  • 56.
    Eta, Valerie
    et al.
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, 20500 Turku/Åbo, Finland.
    Mäki-Arvela, Päivi
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, 20500 Turku/Åbo, Finland.
    Wärnå, Johan
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, 20500 Turku/Åbo, Finland.
    Salmi, Tapio
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, 20500 Turku/Åbo, Finland.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Murzin, Dmitry Yu
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, 20500 Turku/Åbo, Finland.
    Kinetics of dimethyl carbonate synthesis from methanol and carbon dioxide over ZrO2–MgO catalyst in the presence of butylene oxide as additive2011Ingår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 404, nr 1-2, s. 39-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 57.
    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%.

  • 58. García, Alejandro
    et al.
    Hyvärinen, Sari
    Hemming, Jarl
    Carmona, René
    Lienqueo, María Elena
    Salazar, Oriana
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Murzin, Dmitry
    A chromatography approach applied to the biological pretreatment of lignocelluloses in order to produce bioethanol2009Konferensbidrag (Övrigt vetenskapligt)
  • 59.
    García-Serna, Juan
    et al.
    Department of Chemical Engineering and Environmental Technology, University of Valladolid, Spain .
    Moreno-Rueda, Teresa
    Department of Chemical Engineering and Environmental Technology, University of Valladolid, Spain .
    Biasi, Pierdomenico
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemical Engineering, Åbo Akademi University, Turku/Åbo, Finland.
    Cocero, María J.
    Department of Chemical Engineering and Environmental Technology, University of Valladolid, Spain .
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Finland.
    Salmi, Tapio O.
    Department of Chemical Engineering, Åbo Akademi University, Turku/Åbo, Finland.
    Engineering in direct synthesis of hydrogen peroxide: targets, reactors and guidelines for operational conditions2014Ingår i: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 16, nr 5, s. 2320-2343Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 60. Gavilà, Llorenç
    et al.
    Constantí, Magda
    Medina, Francisco
    Pezoa-Conte, Ricardo
    Anugwom, Ikenna
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lactic acid production from renewable feedstock: fractionation, hydrolysis, and fermentation2018Ingår i: Advanced Sustainable Systems, ISSN 2366-7486, Vol. 2, nr 3, artikel-id 1700185Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, an integrated fractionation with a switchable ionic liquid (SIL), pulp hydrolysis, and lactic acid fermentation is carried out. For this, SO2-swithced SIL is used for fractionation of sugar cane (Saccharum officinarum) bagasse and giant cane (Arundo donax, AD). SIL is able to extract ≈2/3 of lignin when relatively large wood chips (≈4 mm) are used without any mechanical agitation and just 1 h of treatment time for AD. Furthermore, SIL reuse is successfully demonstrated for four runs. Subsequently, the produced pulps are hydrolyzed within 15 min in a microwave reactor, producing a glucose rich hydrolysates. Finally, these hydrolysates are used as a carbohydrate source for Lactobacillus delbrueckii fermentation, which selectively transform all glucose present into optically pure D-lactic acid. Hence, the whole chain for lactic acid production from biomass is successfully demonstrated.

  • 61. Gemo, Nicola
    et al.
    Biasi, Pierdomenico
    Canu, Paolo
    Menegazzo, Federica
    Pinna, Francesco
    Ajaikumar, Samikannu
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordàs, Krisztián
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Electrical and Information Engineering, Microelectronics and Materials Physics Laboratories, University of Oulu, Oulu, Finland.
    Salmi, Tapio O.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemical Engineering, Process Chemistry Centre (PCC), Laboratory of Industrial Chemistry and Reaction Engineering, Åbo Akademi University, Åbo-turku, Finland.
    Reactivity aspects of SBA15-based doped supported catalysts: H2O2 direct synthesis and disproportionation reactions2013Ingår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, nr 9-10, s. 540-549Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 62. Gemo, Nicola
    et al.
    Menegazzo, Federica
    Biasi, Pierdomenico
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Turku/Åbo, Finland .
    Sarkar, Anjana
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Ajaikumar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Raut, Dilip G.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordás, Krisztián
    Rautio, Anne-Riikka
    Mohl, Melinda
    Boström, Dan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Turku/Åbo, Finland .
    TiO2 nanoparticles vs. TiO2 nanowires as support in hydrogen peroxide direct synthesis: the influence of N and Au doping2016Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, nr 105, s. 103311-103319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of Pd on titania support were evaluated in the direct synthesis of hydrogen peroxide. The equipment used was a high pressure, semi-batch apparatus equipped with a special injection system. Pd (1 wt%) catalysts on TiO2 materials with different nature were prepared by wet impregnation method. Three aspects were investigated: (a) the structure of the support (nanoparticles vs. nanowires); (b) the addition of a second active metal (Au); (c) the influence of N-doping of the support. All samples were characterized by means of XPS, TEM and XRD analyses. TiO2 nanoparticle supported catalyst demonstrated higher H2O2 selectivity and higher turnover frequency (TOF) than the catalysts based on TiO2 nanowires. The addition of Au to the Pd TiO2 nanowire catalyst improved the H2O2 selectivity due to altered particle size and electronic effects. Both N-doped versions of the catalysts gave rise to higher H2O2 selectivity than the parent non-doped ones. The synthetic procedure was the source of this observation: larger mean Pd nanoparticles were present, thus favouring the formation of H2O2 as the primary product.

  • 63. Gemo, Nicola
    et al.
    Sterchele, Stefano
    Biasi, Pierdomenico
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemical Engineering, Åbo Akademi University, Biskopsgatan 8, Åbo-Turku, Finland .
    Centomo, Paolo
    Canu, Paolo
    Zecca, Marco
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordas, Krisztian
    Salmi, Tapio Olavi
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemical Engineering, Åbo Akademi University, Biskopsgatan 8, Åbo-Turku, Finland .
    The influence of catalyst amount and Pd loading on the H2O2 synthesis from hydrogen and oxygen2015Ingår i: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 5, nr 7, s. 3545-3555Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 64.
    Goets, Mikhail
    et al.
    Åbo-Turku, Finland.
    Ajaikumar, Samikannu
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo-Turku, Finland.
    Catalytic Upgrading of Extractives to Chemicals: Monoterpenes to "EXICALS"2015Ingår i: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 115, nr 9, s. 3141-3169Artikel, forskningsöversikt (Refereegranskat)
  • 65.
    Golets, Mikhail
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Ajaikumar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Blomberg, David
    Processum Biorefinery Initiative AB, SE-89186, Örnsköldsvik, Sweden.
    Grundberg, H
    Aditya Birla Domsjö Fabriker AB, SE-89186, Örnsköldsvik, Sweden.
    Wärnå, J
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Salmi, T
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Liquid phase acetoxylation of α-pinene over Amberlyst-70 ion-exchange resin2012Ingår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 435-436, s. 43-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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 of the feasibility of batch acetoxylation of alpha-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.

  • 66.
    Golets, Mikhail
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Ajaikumar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Larsson, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Blomberg, David
    Processum Biorefinery Initiative AB, 89186, Örnsköldsvik, Sweden.
    Grundberg, H
    Aditya Birla Domsjö Fabriker AB, 89186, Örnsköldsvik, Sweden .
    Wärnå, J
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Turku, Finland.
    Salmi, T
    Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Turku, Finland.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Turku, Finland.
    A kinetic study of the liquid phase acetoxylation of α-pinene2012Ingår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 55, nr 7-10, s. 649-656Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 67.
    Golets, Mikhail
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Ajaikumar
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mohln, M.
    University of Oulu, Oulu, Finland.
    Wärnå, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Åbo-Turku, Finland.
    Rakesh, S.
    Department of Chemistry, Podhigai College of Engineering and Technology, Tamilnadu, India.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Åbo-Turku, Finland.
    Continuous production of the renewable ρ-cymene from α-pinene2013Ingår i: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 307, s. 305-315Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this work was to demonstrate the feasibility to produce ρ-cymene, an important commodity chemical, in a continuous, one-pot reaction system from abundant α-pinene, available e.g. as a by-product of pulping industry. The isomerization reactions of α-pinene over bimetallic heterogeneous catalysts, 3 and 5 wt% Pd–Zn (1:1, 1:4, 4:1, 1:0, and 0:1), supported on Al-SBA15 were studied. The principal reaction products were identified as ρ- and m-cymenes, limonene, camphene, and ρ-menthene, respectively. The highest concentration of ρ-cymene reached 77 wt% under the optimized reaction conditions: 300 °C and α-pinene feed of 0.03 mL/min. Two main reaction pathways toward ρ- and m-cymenes were described, and a mechanistic kinetic model, based on a plausible reaction network in line with Langmuir–Hinshelwood approach, was developed. The catalyst characterization revealed the reduction in Pd(II) sites, catalyst coking, and decline of surface area over the course of time. The catalyst recovery and reuse was addressed.

  • 68.
    Gräsvik, John
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Eliasson, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Halogen-free ionic liquids and their utilization as cellulose solvents2012Ingår i: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1028, s. 156-163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work demonstrates a novel synthesis route to halogen-free ionic liquids. A one-pot synthetic reaction route avoiding the use of toxic and high-energetic alkyl halides was developed to reduce the environmental impact of the synthesis process of ionic liquids. However, the elimination of halogens and alkyl halides in the preparation of ionic liquids is not just an environmental issue: the aforementioned species are also among the most common and persistent contaminants in today’s Ionic Liquids (ILs). Thus, this paper introduces a range of quaternized nitrogen based ionic liquids, including both aromatic and non-aromatic components, all prepared without alkyl halides in any step of the process. Moreover, bio-renewable precursors such as (bio-)alcohols and carboxylic acids were employed as anion sources and alkylation media, thus avoiding halogen contamination or halogen-containing anions. The IL’s prepared were designed to dissolve cellulose, some of which was included in a cellulose dissolution study using a sulphite cellulose from the company Domsjö.

  • 69.
    Gräsvik, John
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Biomaterials dissolution using green ionic liquids2010Konferensbidrag (Övrigt vetenskapligt)
  • 70.
    Gräsvik, John
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ionic liquids for spectroscopy, Coil-32009Ingår i: 3rd Congress on Ionic Liquids May 31 - June 4 2009, Cairns Australia, 2009Konferensbidrag (Refereegranskat)
  • 71.
    Gräsvik, John
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Raut, Dilip G
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Challenges and perspectives of ionic liquids vs. traditional solvents for cellulose processing2012Ingår i: Handbook of ionic liquids: properties, applications & hazards / [ed] Jihoon Mun, Haeun Sim, New York: Nova Science Publishers, Inc., 2012, s. 1-34Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    It is commonly accepted that world-wide production of oil, coal and natural gas will eventually come to a halt, although we still heavily depend on these non-renewable feed stocks and their associated chemical derivatives. Therefore, new, sustainable resources for the production of industrially important chemicals are required. Biomaterials offer much promise in this regard, since they generally contain a lot of cellulose which can be transformed and potentially provide a great source of industrially important chemicals. Presently, only a small part of the annual biomass growth in the world is utilized by industry, while the rest is decaying along natural pathways. In order to effectively process cellulose, it needs to be dissolved in some liquid medium. Present state-of-the-art commercial technologies employ very toxic and hazardous processing with volatile organic solvents like CS2. However, this need not be the case. Ionic liquids (ILs) have shown great potential for the dissolution of cellulose. Some ILs also have attractive physical properties such as: low vapor pressure, high thermal stability and reusability. Thus, they are potentially viable and more environmentally friendly alternatives. Hereby, we present and discuss some of the challenges and perspectives for ILs in terms of their potential for cellulose processing. We briefly review the historical processes and current methods for cellulose processing, and look at alternative processes taking advantage of ILs.

  • 72.
    Gräsvik, John
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Winestrand, Sandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Normark, Monica
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Jönsson, Leif
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Evaluation of four ionic liquids for pretreatment of lignocellulosic biomass.2014Ingår i: BMC Biotechnology, ISSN 1472-6750, E-ISSN 1472-6750, Vol. 14, nr 1, s. 34-45Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND: Lignocellulosic biomass is highly recalcitrant and various pretreatment techniques are needed to facilitate its effective enzymatic hydrolysis to produce sugars for further conversion to bio-based chemicals. Ionic liquids (ILs) are of interest in pretreatment because of their potential to dissolve lignocellulosic materials including crystalline cellulose.

    RESULTS: Four imidazolium-based ionic liquids (ILs) ([C=C2C1im][MeCO2], [C4C1im][MeCO2], [C4C1im][Cl], and [C4C1im][HSO4]) well known for their capability to dissolve lignocellulosic species were synthesized and then used for pretreatment of substrates prior to enzymatic hydrolysis. In order to achieve a broad evaluation, seven cellulosic, hemicellulosic and lignocellulosic substrates, crystalline as well as amorphous, were selected. The lignocellulosic substrates included hybrid aspen and Norway spruce. The monosaccharides in the enzymatic hydrolysate were determined using high-performance anion-exchange chromatography. The best results, as judged by the saccharification efficiency, were achieved with [C4C1im][Cl] for cellulosic substrates and with the acetate-based ILs for hybrid aspen and Norway spruce. After pretreatment with acetate-based ILs, the conversion to glucose of glucan in recalcitrant softwood lignocellulose reached similar levels as obtained with pure crystalline and amorphous cellulosic substrates. IL pretreatment of lignocellulose resulted in sugar yields comparable with that obtained with acidic pretreatment. Heterogeneous dissolution with [C4C1im][HSO4] gave promising results with aspen, the less recalcitrant of the two types of lignocellulose included in the investigation.

    CONCLUSIONS: The ability of ILs to dissolve lignocellulosic biomass under gentle conditions and with little or no by-product formation contributes to making them highly interesting alternatives for pretreatment in processes where high product yields are of critical importance.

  • 73. Grénman, H
    et al.
    Salmi, Tapio
    Teknisk kemi och reaktionsteknik, Åbo akademi.
    Fardim, Pedro
    Teknisk kemi och reaktionsteknik, Åbo akademi.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Murzin, Dimtry Yu
    Teknisk kemi och reaktionsteknik, Åbo akademi.
    Towards new applications of chemical engineering: delignification2010Konferensbidrag (Övrigt vetenskapligt)
  • 74. Grénman, Henrik
    et al.
    Wärnå, Johan
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sifontes, Victor
    Fardim, Pedro
    Murzin, Dmitry Yu
    Salmi, Tapio
    Modeling the influence of wood anisotropy and internal diffusion on delignification kinetics2010Ingår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 49, nr 20, s. 9703-11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 75. Gulbrandsen, Torea A.
    et al.
    Johnsen, Ingvild A.
    Opedal, Mihaela Tanase
    Toven, Kai
    Oyaas, Karin
    Pranovich, Andrey
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Abo Akad Univ, Dept Chem Engn, Ind Chem & React Engn, Proc Chem Ctr, FI-20500 Turku, Finland.
    Hoff, Bard H.
    Extracting hemicelluloses from softwood and bagasse as oligosaccharides using pure water and microwave heating2015Ingår i: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 49, nr 2, s. 117-126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of the study was to identify conditions for hemicelluloses extraction in oligomeric form. Using microwave assisted hot water extraction (HWE), the effects of both retention time and temperature on hemicelluloses yields, as well as the degree of polymerization (DP) as analyzed by SEC-MALLS, were investigated using both softwood (sawmill shavings) and sugarcane bagasse. The results are discussed in the light of the unavoidable yield-DP compromise resulting from the application of batch mode operations. Nevertheless, significant differences between the two raw materials could be observed, as expected. For softwood shavings, data interpolation indicated that about 50% of the hemicelluloses could be obtained as oligomers at an average DP of 30 when extracted at 183 degrees C for 5 minutes. For bagasse, longer extraction times seemed optimal. After hot water extraction at 183 degrees C for 12 minutes, about 62% of the bagasse hemicelluloses were extracted as oligomers at an average DP of about 100.

  • 76. Hajek, J
    et al.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Salmi, T
    Isomerisation of saccharides2010Konferensbidrag (Övrigt vetenskapligt)
  • 77. Hajek, Jan
    et al.
    Murzin, Dmitry Yu.
    Salmi, Tapio
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Turku, Finland.
    Interconversion of Lactose to Lactulose in Alkaline Environment: Comparison of Different Catalysis Concepts2013Ingår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, nr 9-10, s. 839-845Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 78. Halonen, Niina
    et al.
    Sapi, Andras
    Nagy, Laszlo
    Puskas, Robert
    Leino, Anne-Riikka
    Maklin, Jani
    Kukkola, Jarmo
    Toth, Geza
    Wu, Ming-Chung
    Liao, Hsueh-Chung
    Su, Wei-Fang
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kukovecz, Akos
    Konya, Zoltan
    Kordas, Krisztian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Low-temperature growth of multi-walled carbon nanotubes by thermal CVD2011Ingår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 248, nr 11, s. 2500-2503Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low-temperature thermal chemical vapor deposition (thermal CVD) synthesis of multi-walled carbon nanotubes (MWCNTs) was studied using a large variety of different precursor compounds. Cyclopentene oxide, tetrahydrofuran, methanol, and xylene: methanol mixture as oxygen containing heteroatomic precursors, while xylene and acetylene as conventional hydrocarbon feedstocks were applied in the experiments. The catalytic activity of Co, Fe, Ni, and their bi-as well as tri-metallic combinations were tested for the reactions. Low-temperature CNT growth occurred at 400 degrees C when using bi-metallic Co-Fe and tri-metallic Ni-Co-Fe catalyst (on alumina) and methanol or acetylene as precursors. In the case of monometallic catalyst nanoparticles, only Co (both on alumina and on silica) was found to be active in the low temperature growth (below 500 degrees C) from oxygenates such as cyclopentene oxide and methanol. The structure and composition of the achieved MWCNTs products were studied by scanning and transmission electron microscopy (SEM and TEM) as well as by Raman and X-ray photoelectron spectroscopy (XPS) and by X-ray diffraction (XRD). The successful MWCNT growth below 500 degrees C is promising from the point of view of integrating MWCNT materials into existing IC fabrication technologies. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  • 79. Hara, Piia
    et al.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Murzin, Dmitry Yu
    Kanerva, Liisa T
    Supported ionic liquids in Burkholderia cepacia lipase-catalyzed asymmetric acylation2010Ingår i: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 67, nr 1-2, s. 129-134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lipase PS from Burkholderia cepacia was successfully immobilized on Kynol™ ACC 507-15 active carbon cloth with and without ionic liquids as SILE catalysts. Activity, enantioselectivity and reuse of the catalysts were evaluated in the acylation of 1-phenylethanol with vinyl acetate in toluene and in hexane over the temperature range 25 - 60 °C. The presence of [EMIM][NTf2] clearly stabilized the enzyme against inactivation and preserved enantioselectivity in reuse in a process which is affected by the nature of the IL, solvent and substrate structure.

  • 80. Hernandez Carucci, José R
    et al.
    Sosa, Jhosmar
    Arve, Kalle
    Karhu, Hannu
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Eränen, Kari
    Salmi, Tapio
    Murzin, Dmitry Yu
    Preparation and characterization of coated microchannels for the selective catalytic reduction of NOx2012Ingår i: Focus on Catalysis Research: New Developments / [ed] Minjae Ghang and Bjørn Ramel, New York: Nova Science Publishers , 2012, s. 209-236Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    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.

  • 81. Herrara, Victor A. Sifontes
    et al.
    Mendoza, Daniel E. Rivero
    Leino, Anne-Riika
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Finland.
    Zolotukhin, Aleksey
    Eränen, Kari
    Salmi, Tapio
    Sugar hydrogenation in continuous reactors: from catalyst particles towards structured catalysts2016Ingår i: Chemical Engineering and Processing, ISSN 0255-2701, E-ISSN 1873-3204, Vol. 109, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 82. Horacek, J.
    et al.
    St'avova, Gabriela
    Hora, Lukas
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akad Univ, Proc Chem Ctr, Ind Chem & React Engn, FIN-20500 Turku, Finland.
    Kubicka, David
    Lignin transformations to chemicals2013Ingår i: Proceedings of the 1st INTERNATIONAL CONFERENCE ON CHEMICAL TECHNOLOGY / [ed] Kalenda, P., Lubojacky, J., Czech Chemical Society , 2013, s. 382-388Konferensbidrag (Refereegranskat)
    Abstract [en]

    Sodium lignosulfonate was decomposed at 320 degrees C and 130 bar over various catalysts. Zeolites Beta modified with 0.5 % of Pt showed important effect of Al content in the support on product yields. Alumina-supported NiO was also found as active in lignosulfonate decomposition to guaiacol: Moreover, the contact time of substrate with the active centers was identified as the key reaction factor in lignosulfonate decomposition. Model compounds of lignin decomposition were hydrodeoxygenated at 180 degrees C and 5 MPa over Pt modified zeolites Beta. Dealuminated zeolite was found as more active in phenol conversion than zeolite with similar Si/Al ratio obtained by direct synthesis. Reactivity of cresols increased in order m>o>p for catalyst with higher Si/Al ratio, decrease of Al content resulted in lower reactivity of cresols and change of reactivity order of isomers to o>m>p.

  • 83. Horáček, Jan
    et al.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry & Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Ajaikumar, Samikannu
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Šťávová, Gabriela
    Larsson, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Hora, Lukáš
    Kubička, David
    Studies on sodium lignosulfonate depolymerization over Al2O3 supported catalysts loaded with metals and metal oxides in a continuous flow reactor2013Ingår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, nr 9-10, s. 794-799Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this work was to study the how various heterogeneous catalysts perform upon lignosulfonate decomposition reactions. The main target of the study was to obtain extractable phenolic compounds as potential renewable chemicals for the production of fuel components and chemicals. The nature of the heterogeneous catalyst was found to have a great impact on the obtained product yields and the composition of the product mixture. Initially, a nickel–tungsten on alumina (NiW/Al2O3) reference catalyst was applied upon screening the influence of catalyst particle size and various reaction parameters. Significantly increasing product yields with decreasing catalyst particle size indicated that the lignosulfonate transformation takes place on the external catalyst surface due to large macromolecular structure of the feedstock. The contact time (space time velocity) and catalyst particle size were the most important factors influencing the selectivity profiles towards various products as well as the yields observed. The highest conversion to phenolics was obtained over in-house-prepared NiO/Al2O3 and NiMo/Al2O3 catalysts with various NiO and MoO3 loadings.

  • 84. Huang, B. T.
    et al.
    Leveneur, S.
    Zamar, T.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Taouk, B.
    Towards Production of gamma-valerolactone via Hydrogenation of Aqueous Levulinic Acid2015Ingår i: International journal of Chemical Reactor Engineering, ISSN 1542-6580, E-ISSN 1542-6580, Vol. 13, nr 1, s. 119-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synthesis of GVL (gamma-valerolactone) via hydrogenation of aqueous LA (levulinic acid) with H-2 over heterogeneous catalyst (Ru/C) was investigated. In the first part, a study of the influence of various operating conditions was conducted including that of temperature (90-180 degrees C), stirring rate (500-1200 rpm), catalyst loading (0.1-2.0 g), hydrogen pressure (0.4-2.8 MPa) and initial LA concentration (0.5-2 M). In the second part, influence of supercritical CO2 (scCO(2)) on hydrogenation rate and GVL yield were investigated. Hydrogenation of aqueous LA under scCO(2) and under N-2 atmosphere was carried out in batch reactor at 150 degrees C and was compared with the case when no additional gases were present. The result indicated that the use of scCO(2) had no beneficial effect neither in terms of LA conversion nor hydrogenation rate when the amount of hydrogen was relatively low compared to the stoichiometry. This effect was mitigated when more hydrogen was present.

  • 85. Huang, B.T
    et al.
    Leveneur, S.
    Zamar, T.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, FI-20500 Åbo-Turku, Finland.
    Taouk, B.
    Towards Production of γ-valerolactone via Hydrogenation of Aqueous Levulinic Acid2015Ingår i: International journal of Chemical Reactor Engineering, ISSN 1542-6580, E-ISSN 1542-6580, Vol. 13, nr 1, s. 119-127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synthesis of GVL (γ-valerolactone) via hydrogenation of aqueous LA (levulinic acid) with H2 over heterogeneous catalyst (Ru/C) was investigated. In the first part, a study of the influence of various operating conditions was conducted including that of temperature (90–180°C), stirring rate (500–1200 rpm), catalyst loading (0.1–2.0 g), hydrogen pressure (0.4–2.8 MPa) and initial LA concentration (0.5–2 M). In the second part, influence of supercritical CO2 (scCO2) on hydrogenation rate and GVL yield were investigated. Hydrogenation of aqueous LA under scCO2 and under N2atmosphere was carried out in batch reactor at 150°C and was compared with the case when no additional gases were present. The result indicated that the use of scCO2 had no beneficial effect neither in terms of LA conversion nor hydrogenation rate when the amount of hydrogen was relatively low compared to the stoichiometry. This effect was mitigated when more hydrogen was present.

  • 86. Huerta, I.
    et al.
    Biasi, P.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Garcia-Serna, J.
    Cocero, M. J.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Salmi, T.
    Effect of low hydrogen to palladium molar ratios in the direct synthesis of H2O2 in water in a trickle bed reactor2015Ingår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 248, s. 91-100Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 87. Huerta, Irene
    et al.
    Pierdomenico, Biasi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry and Reaction Engineering, Process Chemistry Center (PCC) Department of Chemical Engineering, Åbo Akademi University, FI-20500, Turku/Åbo, Finland.
    Juan-Garcia, Serna
    Cocero, Mária
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry and Reaction Engineering, Process Chemistry Center (PCC) Department of Chemical Engineering, Åbo Akademi University, FI-20500, Turku/Åbo, Finland.
    Salmi, Tapio
    Continuous H2O2 direct synthesis process: an analysis of the process conditions that make the difference2016Ingår i: Green Processing and Synthesis, ISSN 2191-9542, E-ISSN 2191-9550, Vol. 5, nr 4, s. 341-351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 88. Hyvärinen, S
    et al.
    Leino, E
    Eta, V
    Privalova, E
    Salminen, E
    Gräsvik, John
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Virtanen, P
    Mäki-Arvela, P
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ionic liquids as catalytic medium for biomass transformations2011Ingår i: Heterogeneous catalysis in biomass to chemicals and fuels / [ed] David Kubicka and Iva Kubicková, Research Signpost, 2011, s. 65-102Kapitel i bok, del av antologi (Refereegranskat)
  • 89. Hyvärinen, S
    et al.
    Virtanen, P
    Hemming, J
    Reunanen, M
    Leppänen, A S
    Murzin, D Yu
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ionic liquid fractionation of lignocellulosics2009Konferensbidrag (Övrigt vetenskapligt)
  • 90. Hyvärinen, S
    et al.
    Virtanen, P
    Murzin, DYU
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Towards ionic liquid fractionation of lignocellulosics for fermentable sugars2010Ingår i: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 44, nr 4-6, s. 187-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present study investigates wood fractionation through ionic liquid (IL) mediated pretreatment, for obtaining simple fermentable sugars, namely oligo- and monosaccharides, and in particular hexoses (andpentoses). The study focuses on softwood, Scots Pine (Pinus sylvestris) and Norway Spruce (Picea abies), exposed to ionic liquid 1-ethyl-3-methylimidazolium chloride (EmimCl). Since both EmimCl and the monosaccharides are water-soluble and dissolve readily in similar solvents, the separation of this hydrophilic IL from sugars is difficult. Moreover, the analytics of monosaccharides released from lignocellulosics with the help of EmimCl is challenging. Sufficiently diluted samples, with low enough EmimCl concentrations, tolerated by GC sugar columns, can be also analyzed by GC. The results obtained suggest that some IL-tolerating HPLC columns can be utilized for a quantitative determination of monosaccharides. However, frequently, these columns have low separation ability for monosaccharides and, consequently, the retention time values are very close to each other. So far, the best results on HPLC utilization were obtained with isocratic elution, using a refractive index detector and a diode array UV detector in series.

  • 91. Hyvärinen, Sari
    et al.
    Damlin, Pia
    Gräsvik, John
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Murzin, Dmitry Yu
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ionic liquid fractionation of woody biomass for fermentable monosaccharides2011Ingår i: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 45, nr 7-8, s. 483-486Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The goal of the present study, devoted to wood fractionation, was to obtain monosaccharides, hexoses and pentoses by means of an ionic liquid (IL) based pre-treatment procedure. Softwood sawdust (maximum particle size of 2 mm) of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) were exposed to ionic liquids – 1-ethyl-3-methylimidazolium acetate (C2mimAce) and 1-ethyl-3-methylimidazolium chloride (C2mimCl) – and thermal treatment (80-150 °C), for various time intervals (0-72 h). Furthermore, cellulose of various origins (plants, wood pulps) was dissolved in C2mimAce and 1-butyl-3-methylimidazolium chloride (C4 mimCl) for the study of the dissolved fractions, stress being laid on monosaccharides and possible by-products, 5-hydroxymethylfurfural and furfural. Knowing the challenges in analysis techniques when ILs and sugars are involved, the present work focuses on the development of suitable analysis methods. To this end, a Hewlett Packard 1100 series HPLC equipped with a refractive index (RI), detector model HP1047 A and a diode array UV detector (DAD) fitted with a carbohydrate column HPX-87K was utilized. Challenges and improvements are discussed.

     

  • 92. Hyvärinen, Sari
    et al.
    Virtanen, P
    Pranovich, S A
    Leppänen, A-S
    Hemming, J
    Reunanen, M
    Willför, D
    Murzin, Yu
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Towards improved fractionation of lignocellulosics via integrated ionic liquid-thermal pretreatment: The analysis challenge2009Konferensbidrag (Övrigt vetenskapligt)
  • 93. Hyvärinena, S.
    et al.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Åbo/Turku, Finland.
    Murzin, D. Yu.
    Kaljurand, M.
    Koel, M.
    Sugars and sugar derivatives in ionic liquid media obtained from lignocellulosic biomass: comparison of capillary electrophoresis and chromatographic analysis2014Ingår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 223, s. 18-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Processing of woody lignocellulosic biomass, under heating in combination with ionic liquids (ILs) was studied in order to obtain simple (fermentable) sugars. Due to the new environmental challenges, finding greener ways to produce platform chemicals and/or bio-fuels has become a popular research area. Various industrial, pilot or laboratory scale technologies for the depolymerization or fractionation of lignocellulosic polysaccharides to monomers are known. One of the new, interesting, methods is to utilize ILs in biomass pre-treatment procedures with an aim to bypass other pre-treatment methods. Furthermore, in order even to initiate studies whether ILs can contribute to catalytic depolymerization, there has to be a robust way to analyze the IL-treated lignocellulosics. This is a major issue since woody samples that contain any salts such as ILs can indeed be quite challenging from the analytic point of view. The applied capillary electrophoresis was found to be an excellent analytical method providing substantial improvements compared to the earlier used chromatographic methods.

    In this work it was demonstrated that application of ILs, at elevated temperatures, contributes to hydrolysis and depolymerization of lignocellulose. The effect is time and temperature dependent: in harsh conditions sugars degrade but too low processing temperatures or short treatment times result in no meaningful effect. The formation of the degradation products of the monosaccharides is a good indicator of the harshness of the applied chemical conditions. Evidently, furfural and 5-(hydroxymethyl)furfural formed in rather short treatment times.

  • 94. Jogi, Ramakrishna
    et al.
    Mäki-Arvela, Päivi
    Virtanen, Pasi
    Kumar, Narendra
    Hemming, Jarl
    Smeds, Annika
    Lestander, Torbjörn A.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry & Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Biocrude production through hydro‐liquefaction of wood biomass in supercritical ethanol using iron silica and iron Beta zeolite catalysts2019Ingår i: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 94, nr 11, s. 3736-3744Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 95.
    Jogunola, Olatunde
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Eta, Valerie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, 20500 Åbo/Turku, Finland.
    Hedenström, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sundman, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Salmi, Tapio
    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, 20500 Åbo/Turku, Finland.
    Ionic liquid mediated technology for synthesis of cellulose acetates using different co-solvents2016Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 135, s. 341-348Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 96. Jogunola, Olatunde
    et al.
    Salmi, Tapio
    Eranen, Karl
    Warna, Johan
    Kangas, Matias
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Reversible Autocatalytic Hydrolysis of Alkyl Formate: Kinetic and Reactor Modeling2010Ingår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 49, nr 9, s. 4099-4106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The kinetics and thermodynamics of alkyl formate hydrolysis in liquid phase were studied in a laboratory-scale autoclave at temperatures between 333 and 383 K using different molar ratios of the reactants. The process was found to exhibit an autocatalytic effect due to the acid formed. More so, the rate of neutral hydrolysis of ethyl formate is faster compared to methyl formate in the uncatalyzed reaction. However, the autocatalytic effect is more pronounced in methyl formate hydrolysis. In addition, the effect of adding a small amount of formic acid as an initial charge upon the equilibrium conversion and kinetics was investigated, and it was found that the addition improved the reaction rate by reducing the induction period but it suppressed slightly the equilibrium conversion. A kinetic model was proposed to explain these experimental trends, and the model agreed well with the experimental results.

  • 97. Jogunola, Olatunde
    et al.
    Salmi, Tapio
    Eränen, Kari
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Qualitative treatment of catalytic hydrolysis of alkyl formates2010Ingår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 384, nr 1-2, s. 36-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Liquid-phase hydrolysis of alkyl formates was performed in a stirred batch reactor using formic acid as a homogenous catalyst, cation exchange resin as heterogeneous catalyst and an additive as a complexation agent. The catalysts increased the rate of the reaction considerably, but the equilibrium conversion was slightly suppressed by the homogenous catalyst. The additive not only accelerated the reaction rate, but also improved the yield significantly. The effect of external and internal mass transfer limitations present in the heterogeneous reaction steps was investigated and it was observed that there is the existence of internal diffusion limitation for the largest catalyst particles. Other parameters such as temperature, catalyst pre-treatment, catalyst loading and stirring speed were investigated in order to optimize the process. The experiments also demonstrated that the ion exchange resin can be reused more than once.

  • 98. Jogunola, Olatunde
    et al.
    Salmi, Tapio
    Eränen, Kari
    Wärnå, Johan
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Rates and equilibria of ester hydrolysis: Combination of slow and rapid reactions2011Ingår i: Chemical Engineering and Processing, ISSN 0255-2701, E-ISSN 1873-3204, Vol. 50, nr 7, s. 665-674Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The kinetics and thermodynamics of ester hydrolysis were studied experimentally in a laboratory-scale batch reactor by using ethyl formate as the model molecule. The effects of the reaction conditions, such as temperature, excess water, complexing agent and initial acid charge upon the ester hydrolysis process were investigated and a kinetic model was developed for the system. Autocatalytic kinetics was observed experimentally, which was due to the carboxylic acid formed during the reaction. The reaction rate was further enhanced and the equilibrium was shifted to the product side by adding a complexing agent into the reaction mixture. A mathematical model comprising the mass balances and rate equations were developed for the system by assuming quasi-equilibrium hypothesis for the reaction involving the complexing agent. A robust calculation scheme was developed for the estimation of the kinetic and thermodynamic parameters from experimental data. The proposed model was able to predict the experimental results satisfactorily.

  • 99.
    Jogunola, Olatunde
    et al.
    Åbo Akad Univ, Proc Chem Ctr, FI-20500 Turku, Finland .
    Salmi, Tapio
    Åbo Akad Univ, Proc Chem Ctr, FI-20500 Turku, Finland .
    Kangas, Matias
    Åbo Akad Univ, Proc Chem Ctr, FI-20500 Turku, Finland .
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Determination of the kinetics and mechanism of methyl formate synthesis in the presence of a homogeneous catalyst2012Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 203, s. 469-479Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 100. Jogunola, Olatunde
    et al.
    Salmi, Tapio
    Leveneur, Sébastien
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi, Johan Gadolin Process Chemistry Centre, Laboratory of Industrial Chemistry and Reaction Engineering, Åbo/Turku, Finland.
    Complexation equilibria studies of alkyl formate hydrolysis in the presence of 1-butylimidazole2017Ingår i: Thermochimica Acta, ISSN 0040-6031, E-ISSN 1872-762X, Vol. 652, s. 62-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

123456 51 - 100 av 258
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf