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  • 251. Virtanen, Pasi
    et al.
    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, Piispankatu 8, FI-20500 Turku/Åbo, Finland.
    Kinetics of cinnamaldehyde hydrogenation by supported ionic liquid catalysts (SILCA)2009Ingår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 48, nr 23, s. 10335-10342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The research of ionic liquids and their applications in catalysis are attracting increasing attention in chemistry and chemical engineering. A supported ionic liquid catalyst (SILCA) consists of immobilized catalytic species (e.g., transition-metal particles, metal complexes, or enzymes) residing in an ionic liquid layer immobilized on a porous solid support. The kinetics of cinnamaldehyde hydrogenation over SILCAs that contained palladium nanoparticles in ionic liquid, which, in turn, was immobilized oil active carbon cloth (ACC), was studied and modeled in detail. A mechanistic kinetic model, which describes the differences of the activity and selectivity of the catalysts consisting of different ionic liquids, was developed. The model explained the experimental results well.

  • 252. Virtanen, Pasi
    et al.
    Salmi, Tapio O
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Supported ionic liquid catalysts (SILCA) for preparation of organic chemicals2010Ingår i: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 53, nr 15-18, s. 1096-1103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Supported Ionic Liquid Catalysts (SILCA) designed by immobilization of catalytic species residing in an ionic liquid layer, which in turn was immobilized on a solid support, were applied on the selective hydrogenation of citral in a batch reactor and in a continuous reactor. Different ionic liquids with and without addition of acid modificators were studied in terms of the catalyst activity and product selectivity. Consequently, mechanistic kinetic models describing the differences in the activity and selectivity of the catalysts consisting different ionic liquids, were developed.

  • 253. Virtanen, Pasi
    et al.
    Salminen, Eero
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Industrial Chemistry & Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University.
    Modeling of Supported Ionic Liquid Catalysts Systems: From Idea to Applications2017Ingår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 56, nr 45, s. 12852-12862Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The modeling of chemical reactions studied in small scale, often carried out in Academia, is very important since it gives more information about the system and better possibilities to scale-up the processes in the future. Supported ionic liquid catalysts (SILCAs) have been studied in a number of different processes. However, the modeling of these processes have been studied only in a few cases. In this paper the sample cases are reviewed. These processes include hydrogenation of unsaturated aldehydes as well as isomerization of terpenes, α- and β-pinene oxides.

  • 254. Virtanen, Pasi
    et al.
    Salminen, Eero
    Mäki-Arvela, Päivi
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Selective Hydrogenation for Fine Chemical Synthesis2014Ingår i: Supported Ionic Liquids: Fundamentals and Applications / [ed] Rasmus Fehrmann, Anders Riisager, and Marco Haumann, Wiley-VCH Verlagsgesellschaft, 2014, s. 251-262Kapitel i bok, del av antologi (Refereegranskat)
  • 255. Vucetic, Nemanja
    et al.
    Virtanen, Pasi
    Nuri, Ayat
    Mattsson, Ida
    Aho, Atte
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Johan Gadolin Process Chemistry Centre, Laboratory of Industrial Chemistry and Reaction Engineering, Turku, Finland.
    Salmi, Tapio
    Preparation and characterization of a new bis-layered supported ionic liquid catalyst (SILCA) with an unprecedented activity in the Heck reaction2019Ingår i: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 371, s. 35-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new bis-layered supported ionic liquid catalyst (SILCA) loaded with palladium was designed and successfully applied for the Heck reaction of iodobenzene and methyl acrylate. The silica modified catalyst consisting of the first ionic liquid layer - covalently anchored imidazolium bromide - on which the second layer, made of pyridine-carboxylic acid balanced with tetramethylguanidinium cation was attached, resulted in a catalyst with high activity. High turnover frequencies of 22,000 h(-1) were achieved in reactions with a low palladium loading as 0.009 mol %. Lower TOFs, indicating on palladium dimerization was detected when higher amounts were used. The TMG cation had a purpose to recapture and stabilize the Pd nanoparticles thus followed a release and catch mechanism. In order to get a full understanding of the catalyst structure and behaviour, the catalyst was characterized by means of nitrogen physisorption, thermal gravimetric analysis, infrared spectroscopy, scanning electron and transmission electron microscopes, solid-state NMR, X-ray photoelectron spectroscopy and inductively coupled plasma spectroscopy. The catalyst preserved good activity in five cycles.

  • 256. Wu, Ming-Chung
    et al.
    Hiltunen, Jussi Tapio
    Sápi, András
    Avila, Anna
    Larsson, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Liao, Hsueh-Chung
    Huuhtanen, Mika
    Tóth, Géza
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Laufer, Noémi
    Kukovecz, Akos
    Konya, Zoltan
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Keiski, Riitta
    Su, Wei-Fang
    Chen, Yang-Fang
    Jantunen, Heli
    Ajayan, Pulickel M
    Vajtai, Robert
    Kordás, Krisztián
    Nitrogen-doped anatase nanofibers decorated with noble metal nanoparticles for photocatalytic production of hydrogen2011Ingår i: ACS NANO, Vol. 5, nr 6, s. 5025-5030Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report the synthesis of N-doped TiO2 nanofibers and high photocatalytic efficiency in generating hydrogen from ethanol-water mixtures under UV-A and UV-B irradiation. Titanate nanofibers synthesized by hydrothermal method are annealed in air and/or ammonia to achieve N-doped anatase fibers. Depending on the synthesis route, either interstitial N atoms or new N-Ti bonds appear in the lattice resulting in slight lattice expansion as shown by XPS and HR-TEM analyses, respectively. These nanofibers were then used as support for Pd and Pt nanoparticles deposited with wet impregnation followed by calcination and reduction. In the hydrogen generation tests the N-doped samples were clearly outperforming their un-doped counterparts showing remarkable efficiency not only under UV-B but also with UV-A illumination. Applying 100 mg catalyst (N-doped TiO2 nanofiber decorated with Pt nanoparticles) in 1 L water-ethanol mixture the H2 evolution rates were as high as 700 μmol/h (UV-A) and 2250 μmol/h (UV-B) corresponding to photo energy percentages of ~3.6% and ~12.3%, respectively.

  • 257. Wu, Ming-Chung
    et al.
    Liao, Hsueh-Chung
    Cho, Yu-Cheng
    Hsu, Che-Pu
    Lin, Ting-Han
    Su, Wei-Fang
    Sapi, Andras
    Kukovecz, Akos
    Konya, Zoltan
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sarkar, Anjana
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Larsson, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Åbo-Turku, Finland.
    Mohl, Melinda
    Toth, Geza
    Jantunen, Heli
    Valtanen, Anna
    Huuhtanen, Mika
    Keiski, Riitta L.
    Kordas, Krisztian
    Photocatalytic activity of nitrogen-doped TiO2-based nanowires: a photo-assisted Kelvin probe force microscopy study2013Ingår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 16, nr 1, s. Article Number: UNSP 2143-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, a set of nitrogen-doped TiO2-based nanomaterials demonstrating photocatalytic activity was developed by combining the efforts of lattice doping and metal nanoparticle decoration and tested for photo-degradation of methylene blue dye by applying solar simulator irradiation. The surface potential shifts of these TiO2-based photocatalytic nanomaterials measured by Kelvin probe force microscope have been used to study the degree of electron generation of the photocatalysts after irradiation and were well correlated with the photocatalytic activity. The nitrogen-doped TiO2 nanowires decorated with Pt nanoparticles can induce obvious electron accumulation and result in a large shift of surface potential. The analysis shows a clear correlation between the surface potential shift and the photodegradation activity. Furthermore, a thorough comparative photocatalytic activity study combined with X-ray photoelectron spectroscopy analysis of the materials-doped with nitrogen under various conditions-reveals that the photocatalytic efficiency of the catalysts is maintained even if the lattice doping is leached e.g., by thermal treatments after doping. By monitoring the surface potential shifts of various TiO2-based photocatalysts by photo-assisted Kelvin probe force microscopy, we obtain a useful tool for developing novel materials with high photocatalytic activity.

  • 258. Xie, Yujiao
    et al.
    Raut, Dilip G.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Samikannu, Rakesh
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    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.
    Ji, Xiaoyan
    A Thermodynamic Study of Aqueous 1-Allyl-3-Methylimidazolium Formate Ionic Liquid as a Tailored Sorbent for Carbon Dioxide Separation2017Ingår i: Energy Technology, ISSN 2194-4296, Vol. 5, nr 8, s. 1464-1471Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, aqueous 1-allyl-3-methylimidazolium formate ([Amim][HCOO]) was studied as a potential sorbent for CO2 separation. The density and viscosity of aqueous [Amim][HCOO] were measured at temperatures ranging from 293.15 to 333.15 K at atmospheric pressure. The solubility of CO2 and CH4 in dry [Amim][HCOO] as well as the CO2 solubility in aqueous [Amim][HCOO] were measured at pressures up to 1.8 MPa and temperatures of 298.2, 313.2, and 333.2 K. The results showed that the density and viscosity of aqueous [Amim][HCOO] as well as the CO2 solubility in aqueous [Amim][HCOO] decreased upon increasing the water concentration and temperature. The viscosity was very sensitive to the water concentration. The experimental density and viscosity of aqueous [Amim][HCOO] were fitted to semiempirical equations, and the excess molar volume and viscosity deviations were calculated to investigate the interaction between the [Amim][HCOO] ionic liquid and water. The experimental vapor–liquid equilibrium was represented with the nonrandom two-liquid and Redlich–Kwong model. The model parameters can be further implemented into Aspen Plus software to conduct process simulations.

3456 251 - 258 av 258
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