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  • 1. Behravesh, Erfan
    et al.
    Kumar, Narendra
    Balme, Quentin
    Roine, Jorma
    Salonen, Jarno
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Process Chemistry Centre, Åbo Akademi University, FI-20500 Turku/Åbo, Finland.
    Peurla, Markus
    Aho, Atte
    Eränen, Kari
    Murzin, Dmitry Yu.
    Salmi, Tapio
    Synthesis and characterization of Au nano particles supported catalysts for partial oxidation of ethanol: Influence of solution pH, Au nanoparticle size, support structure and acidity2017In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 353, p. 223-238Article in journal (Refereed)
    Abstract [en]

    Partial oxidation of ethanol to acetaldehyde was carried out over gold catalysts supported on various oxides and zeolites by deposition precipitation. The special focus of this work was on the influence of H-Y zeolite surface charge on Au cluster size and loading linking it to activity and selectivity in ethanol oxidation and comparing with other studied catalysts. The catalysts were characterized by nitrogen physisorption, transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and zeta potential measurements. pH of the solution governed the Au NPs size within the range of 5.8–13.2 nm with less negatively charged surfaces leading to formation of smaller clusters. Au loading on H-Y zeolite with silica to alumina ratio of 80 was increased by raising the pH. In fact, H-Y-12 and H-Beta-25 were selective towards diethyl ether while acetaldehyde was the prevalent product on less acidic H-Y-80. The results demonstrated strong dependency of the catalytic activity on the Au cluster size. Namely turn over frequency (TOF) decreased with an increase in metal size from 6.3 to 9.3 nm on H-Y-80. Selectivity towards acetaldehyde and ethyl acetate did not change significantly on H-Y-80 within 6.3–9.3 nm Au particle size range. On Al2O3 support, however, selectivity towards acetaldehyde increased considerably upon diminishing Au average particle size from 3.7 to 2.1 nm.

  • 2.
    Golets, Mikhail
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Samikannu, Ajaikumar
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mohln, M.
    University of Oulu, Oulu, Finland.
    Wärnå, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Åbo Akademi University, Åbo-Turku, Finland.
    Rakesh, S.
    Department of Chemistry, Podhigai College of Engineering and Technology, Tamilnadu, India.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Åbo Akademi University, Åbo-Turku, Finland.
    Continuous production of the renewable ρ-cymene from α-pinene2013In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 307, p. 305-315Article in journal (Refereed)
    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.

  • 3. Konwar, Lakhya Jyoti
    et al.
    Mäki-Arvela, Päivi
    Begum, Pakiza
    Kumar, Narendra
    Thakur, Ashim Jyoti
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Finland.
    Deka, Ramesh Chandra
    Deka, Dhanapati
    Shape selectivity and acidity effects in glycerol acetylation with acetic anhydride: selective synthesis of triacetin over Y-zeolite and sulfonated mesoporous carbons2015In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 329, p. 237-247Article in journal (Refereed)
    Abstract [en]

    Abstract 100% triacetin selectivity was achieved in glycerol acetylation with acetic anhydride in 20–50 min in the presence of catalytic amounts of mesoporous sulfonated carbons and zeolite H-Y. Experimental results obtained over a range of solid acids with varying structure and acidic properties indicate that selectivity to triacetin was influenced mainly by the pore structure and catalyst surface acid site density. The shape selectivity effect over microporous zeolites was verified from the molecular dimensions of glycerol, monoacetin, diacetin and triacetin obtained from DFT calculations; on the contrary in mesoporous catalyst surface acid site density was responsible for determining triacetin selectivity.

  • 4. Kwong, Wai Ling
    et al.
    Lee, Cheng Choo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry-Ångström Laboratory, Molecular Biomimetics, Uppsala University, 75120 Uppsala, Sweden.
    High-performance iron (III) oxide electrocatalyst for water oxidation in strongly acidic media2018In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 365, p. 29-35Article in journal (Refereed)
    Abstract [en]

    Stable and efficient oxygen evolution reaction (OER) catalysts for the oxidation of water to dioxygen in highly acidic media are currently limited to expensive noble metal (Ir and Ru) oxides since presently known OER catalysts made of inexpensive earth-abundant materials generally suffer anodic corrosion at low pH. In this study, we report that a mixed-polymorph film comprising maghemite and hematite, prepared using spray pyrolysis deposition followed by low-temperature annealing, showed a sustained OER rate (>24 h) corresponding to a current density of 10 mA cm−2 at an initial overpotential of 650 mV, with a Tafel slope of only 56 mV dec−1 and near-100% Faradaic efficiency in 0.5 M H2SO4 (pH 0.3). This performance is remarkable, since iron (III) oxide films comprising only maghemite were found to exhibit a comparable intrinsic activity, but considerably lower stability for OER, while films of pure hematite were OER-inactive. These results are explained by the differences in the polymorph crystal structures, which cause different electrical conductivity and surface interactions with water molecules and protons. Our findings not only reveal the potential of iron (III) oxide as acid-stable OER catalyst, but also highlight the important yet hitherto largely unexplored effect of crystal polymorphism on electrocatalytic OER performance.

  • 5. Murzin, Dmitry Yu.
    et al.
    Kusema, Bright
    Murzina, Elena V.
    Aho, Atte
    Tokarev, Anton
    Boymirzaev, Azamat S.
    Wärnå, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Department of Chemical Engineering, Åbo Akademi University.
    Dapsens, Pierre Y.
    Mondelli, Cecilia
    Perez-Ramirez, Javier
    Salmi, Tapio
    Hemicellulose arabinogalactan hydrolytic hydrogenation over Ru-modified H-USY zeolites2015In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 330, p. 93-105Article in journal (Refereed)
    Abstract [en]

    The hydrolytic hydrogenation of hemicellulose arabinogalactan was investigated in the presence of protonic and Ru (1-5 wt.%)-modified USY zeolites (Si/Al ratio = 15 and 30). The use of the purely acidic materials was effective in depolymerizing the macromolecule into free sugars. While the latter partly dehydrated into 5-hydroxymethylfurfural and furfural, the generation of high molecular-weight compounds (aggregates of sugars and humins) was not favored, in contrast to previous evidences over beta zeolites. Application of the bifunctional Ru/USY catalyst, comprising well-dispersed metallic nanopartides on the aluminosilicate support, resulted in the formation of galactitol and arabitol, in the suppression of dehydration side products, and further inhibition of polymerization reactions, which only yielded low molecular-weight oligomers. Detailed analysis of the reaction pathways as well as kinetic modeling of hydrolytic hydrogenation was performed with an advanced reaction mechanism.

  • 6. Rozmyslowicz, Bartosz
    et al.
    Kirilin, Alexey
    Aho, Atte
    Manyar, Haresh
    Hardacre, Christopher
    Wärnå, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Salmi, Tapio
    Murzin, Dmitry Yu.
    Selective hydrogenation of fatty acids to alcohols over highly dispersed ReOx/TiO2 catalyst2015In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 328, p. 197-207Article in journal (Refereed)
    Abstract [en]

    Production of fatty alcohols through selective hydrogenation of fatty acids was studied over a 4% ReOx/TiO2 catalyst. Stearic acid was hydrogenated to octadecanol at temperatures and pressures between 180-200 degrees C and 2-4 MPa, with selectivity reaching 93%. A high yield of octadecanol was attributed to a strong adsorption of the acid compared to alcohol on the catalyst, which inhibits further alcohol transformation to alkanes. Low amounts (<7%) of alkanes (mainly octadecane) were formed during the conversion of stearic acid. However, it was found that the catalyst could be tuned for the production of alkanes. The reaction intermediates were octadecanal and stearyl stearate. Based on the reaction products analysis and catalyst characterization, a reaction mechanism and possible pathways were proposed.

  • 7. Vucetic, Nemanja
    et al.
    Virtanen, Pasi
    Nuri, Ayat
    Mattsson, Ida
    Aho, Atte
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. 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 reaction2019In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 371, p. 35-46Article in journal (Refereed)
    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.

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