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  • 1. Riittonen, Toni
    et al.
    Eränen, Kari
    Mäki-Arvela, Päivi
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Rautio, Anne-Riikka
    Kordas, Krisztian
    Kumar, Narendra
    Salmi, Tapio
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Åbo Akademi University, Process Chemistry Centre, Laboratory of Industrial Chemistry & Reaction Engineering, Turku/Åbo, Finland.
    Continuous liquid-phase valorization of bio-ethanol towards bio-butanol over metal modified alumina2015Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 74, s. 369-378Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Commercial mixed-phase aluminum oxide was used as a heterogeneous catalyst support, providing slightly basic properties which are well-suited for the condensation of bio-ethanol to C-4 hydrocarbons, such as 1-butanol. Different metals (Cu, Ni and Co), at various metal loadings were deposited on the support. Consequently, the catalytic reactions were carried out in a continuous laboratory-scale fixed bed reactor operated at 240 degrees C and 70 bar. The catalysts were characterized by means of XRD, TEM, FT-IR, XPS and ICP-OES. Different metals were found to give entirely different product distributions. With the best catalysts, the selectivities towards 1-butanol close to 70% were reached, while the ethanol conversion typically varied between 10 and 30% - strongly depending on the metal applied. It was observed that low loading of copper and high loading of nickel were responsible for the formation of 1-butanol, whereas cobalt and high loading of copper resulted in the production of ethyl acetate. The reaction was found to be extremely sensitive to catalyst preparation conditions and procedures such as metal loading, calcination/reduction temperature and, thereby, to the formation of corresponding crystallite structure.

  • 2. Trubetskaya, Anna
    et al.
    Souihi, Nabil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Umeki, Kentaro
    Categorization of tars from fast pyrolysis of pure lignocellulosic compounds at high temperature2019Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 141, s. 751-759Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study presents how the yields of different tar compounds from pure lignocellulosic compounds respond to the change in temperature and residence time. Experiments were carried out with a drop tube furnace in the temperature range from 800 to 1250 °C. The tar composition was characterized by gas chromatography with a flame ionization detector and mass spectrometry using a dual detector system. Longer residence time and higher heat treatment temperatures increased the soot formation and decreased the tar yields. Soot yields from lignin samples were greater than soot yields from holocellulose pyrolysis. The dominating products in tars from pyrolysis of all lignocellulosic compounds were benzene and toluene. Cellulose and hemicellulose pyrolysis produced greater amount of oxygenates in tars, whereas lignin tar was rich in phenols, polycyclic hydrocarbons and naphthalenes. Simultaneous reduction of tar and soot was achieved by impregnation of lignin from wheat straw with alkali metals. The OPLS-DA model can accurately explain the differences in tar composition based on the experimental mass spectrometry data.

  • 3. Vicente, E.D.
    et al.
    Vicente, A.M.
    Evtyugina, M.
    Carvalho, Ricardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik. Centre for Environmental and Marine Studies, Department of Environment and Planning, University of Aveiro, Portugal.
    Tarelho, L.A.C.
    Paniagua, S.
    Nunes, T.
    Otero, M.
    Calvo, L.F.
    Alves, C.
    Emissions from residential pellet combustion of an invasive acacia species2019Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 140, s. 319-329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Currently, different types of raw materials are under investigation to fulfil the demand for pellet-based renewable energy. The aim of this study was to experimentally quantify and characterise the gaseous and particulate matter (PM10) emissions from the combustion of a pelletised invasive species growing in the Portuguese coastal areas. The combustion of acacia pellets in a stove used for domestic heating led to a noticeable production of environmentally relevant contaminants, such as carbon monoxide (CO, 2468 ± 485 mg MJ−1), sulphur dioxide (SO2, 222 ± 115 mg MJ−1) and nitrogen oxides (NOx, 478 ± 87 mg MJ−1). Besides gaseous pollutant emissions, substantial particle emissions (118 ± 14 mg MJ−1) were also generated. Particles consisted mostly of inorganic matter, mainly alkaline metals, sulphur and chlorine. About 25%wt. of the PM10 emitted had carbonaceous nature. The chromatographically resolved organic compounds were dominated by anhydrosugars, especially levoglucosan (284 μg g−1 PM10), and several types of phenolic compounds. Retene (8.77 μg g−1 PM10) was the chief compound among polyaromatic hydrocarbons.

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