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  • 1.
    Lualdi, Matteo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lögdberg, Sara
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Regali, Francesco
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Investigation of mixtures of a Co-based catalyst and a Cu-based catalyst for the fischer-tropsch synthesis with Bio-Syngas: The importance of indigenous water2011In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 54, no 13-15, p. 977-985Article in journal (Refereed)
    Abstract [en]

    A series of different mechanical mixtures of a narrow-pore Co/γ-Al2O3 catalyst and a Cu-based WGScatalyst has been investigated in the low-temperature Fischer-Tropsch synthesis (483 K, 20 bar) with a model bio-syngas (H2/CO = 1.0) in a fixed-bed reactor. The higher the fraction of WGS-catalyst in the mixture, the lower is the Co-catalyst-time yield to hydrocarbons. This is ascribed to a strong positive kinetic effect of water on the Fischer-Tropsch rate of the Co-catalyst, showing the importance of the indigenously produced water, especially in fixed-bed reactors where the partial pressure of water is zero at the reactor inlet. A preliminary kinetic modeling suggests that the reaction order in PH2O is 0.3 for the Co/γ-Al2O3 catalyst in the range of the studied reactor-average partial pressures of water (i.e., 0.04-1.2 bar).

  • 2.
    Regali, Francesco
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Hydroconversion of model Fischer‑Tropsch wax over noble metal/silica-alumina catalysts2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Synthetic fuels produced using the Fischer-Tropsch technology will play an important role in the future of the transportation sector. The Fischer-Tropsch synthesis (FTS) allows converting synthesis gas (CO + H2) into fuels of outstanding quality. The synthesis gas can be obtained from different carbon sources: natural gas, coal and biomass. In order to maximize the yield of middle distillates, the process is carried out in two main steps: the FT-synthesis that produces long-chain hydrocarbons (waxes) and a hydrocracking step, to selectively convert the waxes into fuels. Diesel produced by this process is characterized by excellent combustion properties and reduced harmful tailpipe emissions compared to conventional diesel.

    Due to the growing interest in synthetic fuel production, from the industry and the academia, and to the peculiar characteristics of the Fischer-Tropsch products, research in hydrocracking has received renewed attention. Catalysts for the hydrocracking of long-chain paraffins have been the subject of the present work, which is the summary of four scientific publications.

    Noble metals supported on acid carriers have been compared, especially for what regards the mechanisms through which hydrocracking proceeds. The catalysts were synthesized and characterized by various techniques, including N2 physisorption, H2 chemisorption, TEM, pyridine adsorption FTIR, ammonia TPD, etc. It was shown that catalytic activity is mainly dependent on the acid support used; that selectivity is strongly dependent on conversion, high conversion favoring highly branched cracking products. Two main reaction routes were observed: bifunctional hydrocracking and hydrogenolytic cracking. Platinum-containing catalysts showed high selectivity towards the latter, while palladium/silica-alumina behaved as pure bifunctional catalysts. Catalyst deactivation was investigated and initial sintering of metal particles was observed. Coking was also a cause of deactivation. Formation of coke deposits was highly dependent on the metal loading of the catalysts. Metal loading also influenced catalyst selectivity, especially in the case of platinum/silica-alumina catalysts. Monofunctional hydrogenolysis on the platinum particles, superimposed to the bifunctional mechanism was observed. This route increased selectivity towards linear hydrocarbons and methane, with increasing amounts of platinum. The specific rate of hydrogenolysis was constant for different loadings of platinum on the same acid silica-alumina support. Using a different, less acid, support negatively affected the hydrogenolytic activity of the platinum catalytic sites. It was concluded that metal-support interactions might play an important role in the catalytic properties of platinum surfaces.

    This work has contributed to increasing the knowledge about hydrocracking of long-chain alkanes and pointed out some features that might have practical interest in the application of this technology to synthetic-fuel production.

  • 3.
    Regali, Francesco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Hydrocracking of Fischer-Tropsch waxes over Pt/Pd catalysts supported on amorphous silica-alumina2011In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 242, p. 63-PETR-Article in journal (Other academic)
  • 4.
    Regali, Francesco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Hydrocracking of n-hexadecane on noble metal/silica-alumina catalysts2013In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 214, no SI, p. 12-18Article in journal (Refereed)
    Abstract [en]

    Bifunctional catalysts consisting of platinum or palladium on amorphous silica-alumina were prepared and tested in the hydrocracking of n-hexadecane (n-C16H34). Product selectivities toward mono-branched and multi-branched feed isomers and cracking products have been determined in a wide range of conversions, varying liquid hourly space velocity at constant operating parameters (pressure = 30 bar; temperature = 310 C; H 2/n-C16H34 feed molar ratio = 10). A simple kinetic study is presented, in which the reactions are approximated by a network of pseudo first order irreversible reaction steps. The reaction network model was fitted to the experimental data, and kinetic constants for the different reaction steps were obtained. It could be concluded that mono-branched feed isomers are primary products in the hydrocracking/hydroisomerization reaction network; multi-branched isomers are formed mainly from mono-branched as a secondary product. On the platinum catalyst cracking products were formed as primary products, and it proved to be slightly more active than the palladium based one, at the same metallic molar loading. It could be shown that the platinum catalyst yields cracking products both via a bifunctional metal/acid mechanism and by monofunctional (metal only) hydrogenolysis. This second mechanism accounted for the higher activity of the platinum catalyst.

  • 5.
    Regali, Francesco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liotta, Leonarda Francesca
    Istituto per lo Studio dei Materiali Nanostrutturati, ISMN CNR, Palermo, Italy.
    Venezia, Anna Maria
    Istituto per lo Studio dei Materiali Nanostrutturati, ISMN CNR, Palermo, Italy.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Hydroconversion of n-hexadecane on Pt/silica-alumina catalysts: Effect of metal loading and support acidity on bifunctional and hydrogenolytic activity2014In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 469, p. 328-339Article in journal (Refereed)
    Abstract [en]

    Bifunctional catalysts based on platinum and amorphous silica-alumina were studied in the hydroconversion of n-hexadecane. The influence of platinum loading and support acidity on activity and selectivity were assessed. The contribution of hydrogenolysis reactions on top of bifunctional hydrocracking was shown to depend not only on metal loading, but also on the effect of support acidity on the intrinsic activity of the platinum sites. The yield of cracking products, and their linear alkane fraction, increased with metal loading, while the isomerization yield was practically independent of the metal content. On a support of high Bronsted acidity, the rate of formation of methane was proportional to the platinum surface area, indicating that dernethylation occurred by metal-cataly ed hydrogenolysis. On the other hand, the methane site-time yield was one order of magnitude lower on a catalyst with negligible Bronsted acidity. Pt-catalyzed hydrogenolysis was also investigated during selective poisoning of acid sites by cofeeding pyridine and comparing the effect of hydrogen partial pressure on reaction rates. In the presence of pyridine, total hydroconversion activity was reduced by one order of magnitude while rates to methane and linear cracking products remained relatively high. These observations indicate that acid sites do not intervene in the mechanism, but that support acidity affects the hydrogenolytic activity of platinum sites.

  • 6.
    Regali, Francesco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liotta, Leonarda Francesca
    Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Palermo, Italy.
    Venezia, Anna Maria
    Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Palermo, Italy.
    Montes, Vicente
    Organic Chemistry Department, University of Córdoba, Córdoba, Spain.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Effect of metal loading on activity, selectivity and deactivation behavior of Pd/silica-alumina catalysts in the hydroconversion of n-hexadecane2014In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 223, p. 87-96Article in journal (Refereed)
    Abstract [en]

    Bifunctional catalysts consisting of palladium on amorphous silica-alumina with different metal loadings (0 wt% to 1.2 wt%) were compared in the hydrocracking/hydroisomerization of n-hexadecane. The reaction conditions were: pressure = 30 bar; temperature = 310 degrees C; hydrogen-to-hexadecane feed molar ratio = 10. Metal loading was found to have a remarkable influence on the initial deactivation rate, which could be related to the formation of carbonaceous deposits. The dependence of activity on the metal-acid site ratio was the typical one for bifunctional hydrocracking where, after reaching a threshold value, the catalytic activity does not appreciably increase with increasing metal loading. On the Pd-containing catalysts, the methane space-time-yield showed a strong dependence on conversion, but no clear relationship with metal surface area, indicating that the formation of methane might not proceed by purely metal-catalyzed hydrogenolysis.

  • 7.
    Regali, Francesco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Suaréz París, Rodrigo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Aho, Atte
    Åbo Akademi.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Deactivation of a Pt/Silica–Alumina Catalyst and Effecton Selectivity in the Hydrocracking of n-Hexadecane2013In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, no 9-10, p. 594-601Article in journal (Refereed)
    Abstract [en]

    The deactivation behavior of a bifunctionalcatalyst consisting of platinum on amorphous silica–aluminawas studied in the hydrocracking of n-hexadecane.The initial decline in activity and the change in selectivitywere monitored at the following reaction conditions:pressure = 30 bar; temperature = 310 C; hydrogen-tohexadecanefeed molar ratio = 10. Initially, hexadecaneconversion and selectivity to cracking products decreasedrapidly with time-on-stream, and stabilized after 40 h onstream. This could be related to an initial loss of metalsurface area, which decreased the activity of monofunctionalhydrogenolysis generating cracking products. Theacidic function seemed to be unaffected under these reactionconditions. The stable catalyst was exposed to a lowerhydrogen-to-hexadecane ratio to accelerate deactivation bycoking. A decline in the activity of both functions wasobserved. The activity of the acidic function could bealmost completely recovered by oxidative regeneration,while the metal activity was only partially recovered.

1 - 7 of 7
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