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Author: search.filters.author.Sooknoi, TawanSubject: search.filters.subject.Ceria

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    Production of liquid fuel from palmitic acid over nanocrystalline CeO2-based catalysts with minimal use of H2
    (2017-01-01)
    Maluangnont, Tosapol
    ;
    Dararat, Chalinee
    ;
    Kulrat, Teerapong
    ;
    Soontontaweesub, Surachet
    ;
    Anothaiwalaikul, Thitima
    The deoxygenation of palmitic acid into diesel-range hydrocarbons can be promoted over nanocrystalline ceria-based catalysts under atmospheric N<inf>2</inf> or 10% H<inf>2</inf>/N<inf>2</inf> in a fixed-bed flow reactor at 400 °C. Oxygen vacancy sites are active for ketonization of palmitic acid to C<inf>31</inf> ketone and also subsequent cracking of the formed ketone to hydrocarbons. The 22–31% selectivity of C<inf>9</inf> to C<inf>17</inf> liquid hydrocarbons can be achieved at 100% palmitic acid conversion. The deoxygenation under N<inf>2</inf> can be facilitated, presumably by hydrogen transfer from coke precursors. Catalytic activity of ceria-based catalysts can be tuned by pretreatment conditions, type of a carrier gas, or lattice modification.
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    Condensation reactions of propanal over CexZr 1-xO2 mixed oxide catalysts
    (2010-09-15)
    Gangadharan, Anirudhan
    ;
    Shen, Min
    ;
    Sooknoi, Tawan
    ;
    Resasco, Daniel E.
    ;
    Mallinson, Richard G.
    Vapor phase condensation reactions of propanal were investigated over Ce<inf>x</inf>Zr<inf>1-x</inf>O<inf>2</inf> mixed oxides as a model reaction to produce gasoline range molecules from short aldehydes found in bio-oil mixtures. Several operating parameters were investigated. These included the type of carrier gas used (H<inf>2</inf> or He) and the incorporation of acids and water in the feed. Propanal is converted to higher carbon chain oxygenates on Ce <inf>x</inf>Zr<inf>1-x</inf>O<inf>2</inf> by two pathways, aldol condensation and ketonization. The major products of these condensation reactions include 3-pentanone, 2-methyl-2-pentenal, 2-methylpentanal, 3-heptanone and 4-methyl-3-heptanone. It is proposed that the primary intermediate for the ketonization path is a surface carboxylate. The presence of acids in the feed inhibits the aldol condensation pathway by competitive adsorption that reduces the aldehyde conversion. Water also promotes ketonization and inhibits aldol condensation by increasing the concentration of surface hydroxyl groups that enhance the formation of surface carboxylates with the aldehyde. Hydrogen enhances cracking and production of light oxygenates and hydrocarbons. The light oxygenates may in turn be reincorporated into the reaction path, giving secondary products. However, the hydrocarbons do not react further. Analysis of the fresh and spent catalysts by XPS showed varying degrees of reduction of the oxide under different operating conditions that were consistent with the reaction results. Changing the proportion of the parent oxides showed that increased Zr favored formation of aldol products while increased Ce favored ketonization. This occurs by shifting the balance of the acid-base properties of the active sites. © 2010 Elsevier B.V.