Influence of the operating conditions and kinetic analysis of the selective hydrogenation of oleic acid on Ru-Sn-B/Al2O3 catalysts

International audienceThe influence of the operating conditions on the selectivity and activity of Ru-Sn-B/Al2O3 catalysts for the hydrogenation of oleic acid to oleyl alcohol was studied. It was found that the Ru-Sn-B/Al2O3 catalyst is selective to oleyl alcohol while Ru or Ru-B/Al2O3 catalysts are not selective to produce oleyl alcohol. The electronic and catalytic properties of Ru are modified by the strong interaction between Sn and B. The incorporation of Sn leads to catalysts capable of producing oleyl alcohol. The experiments of oleic acid hydrogenation showed that an increase in reaction temperature leads to an increase in activity while the selectivity to oleyl alcohol goes through a maximum. This is because the reactions of hydrogenation of C=C double bond have lower activation energies than hydrogenolytic reactions. The increase in operating pressure has a positive effect on conversion and a more important effect on selectivity. A very simple first order kinetic model is proposed and reasonably represents the results obtained. This model can be useful to compare catalyst performance more rationally

Preparation and characterization oF Ru-Sn/Al2O3 catalysts for the hydrogenation of fatty acid methyl esters

Ru-Sn/Al2O3 catalysts with different Sn loadings were prepared by the coimpregnation method. Several characterization techniques such as TPR, pyridine TPD and catalytic tests for dehydrogenation and hydrogenolysis were used to evaluate and compare such catalysts. TPR results indicate that Sn is deposited both onto the support and as species strongly interacting with Ru. Such non selective deposition modifies the acid and metallic functions of the catalysts. Both total acidity and acid strength distribution are affected: total acidity decreases and new sites of lower acid strength are created. Both dehydrogenating and hydrogenolytic activities are strongly diminished by the addition of Sn. Results of catalytic tests for methyl oleate hydrogenation indicate that methyl stearate is the main product, with only minute amounts of oleyl alcohol produced, and that the addition of Sn diminishes the hydrogenation activity

Influence of gallium on the properties of Pt-Re/Al2O3 naphtha reforming catalysts

International audienceThe influence of gal lium on the properties of Pt-Re/Al2O3 catalysts used in naphtha reforming was studied. The catalysts were prepared by the coimpregnation method. It was found that the addition of gallium to the Pt-Re/Al2O3 catalyst diminishes its acidity (Bronsted and Lewis). It also produces an inhibition of the metal function, i.e. dehydrogenation and hydrogenolysis activity. Activity tests for n-C-5 isomerization showed that gallium addition decreases the total activity of the Pt-Re catalyst but increases its selectivity to i-C-5 isomers. The selectivity to low value light gases (C-1-C-3) is particularly decreased. Catalytic tests for n-C-7 reforming showed that addition of gallium increases both catalyst stability and selectivity to aromatics, and decreases the production of light gases

Chemical Structures of ZrO 2 -Supported V−Sb Oxides

The effect of the vanadium and/or antimony loading on the structure of zirconia and zirconium hydroxide on calcination is studied by X-ray diffraction and Raman spectroscopy. Vanadia promotes the transition of tetragonal to monoclinic zirconia at high temperatures. The interaction of dispersed vanadium oxide species with a zirconia support leads to the formation of ZrV2O7, which is easier on uncalcined zirconium hydroxide. Antimony tends to stabilize the tetragonal phase of zirconia and its specific area. The simultaneous presence of Sb and V on zirconia at low coverage leads to a preferential interaction of individual V and Sb oxides on the zirconia surface rather than the formation of a binary Sb−V oxide. However, at high Sb−V coverage, SbVO4 is formed at the expense of surface V oxide, while the transition to monoclinic polymorph is minimized. Simultaneously, the excess of antimony forms α-Sb2O4.Fil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentina. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; EspañaFil: Bañares, M. A.. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; EspañaFil: Vicente, M. A.. Universidad de Salamanca; EspañaFil: Fierro, J. L. G.. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; Españ

O-2 and O-3 regeneration of PtReSn/Al2O3 and PtReGe/Al2O3 naphtha reforming catalysts prepared by catalytic reduction

International audienceThe deactivation and regeneration of naphtha reforming PtReGe/Al2O3 and PtReSn/Al2O3 catalysts prepared by catalytic reduction were studied. The extent and nature of coke deposition as determined by TPO were related to catalyst properties such as dispersion, acidity and Cl content. The PtReSn catalyst was the most resistant to coke deactivation. Regeneration was performed by calcination in oxygen at 450 degrees C or ozone at 125 degrees C at variable regeneration times. Regenerated catalysts were evaluated by cyclopentane hydrogenolysis, cyclohexane dehydrogenation and n-heptane reaction tests. Regeneration by oxygen burning-off was the most effective for decoking. However, oxygen combustion produced more segregation of the metal function than ozone regeneration. With the regeneration conditions used in this work, the original acidity of the catalysts cannot be recovered

Influence of Support Acidity and Ir Content on the Selective Ring Opening of Decalin over Ir/SiO₂–Al₂O₃

The influence of the addition of HCl and Ir (1 wt %) to different SiO₂–Al₂O₃ supports of varying silica content was studied in the reaction of selective ring opening of decalin. The addition of HCl to silica–alumina supports containing 70 and 80 wt % SiO₂ was found to have little influence in the distribution of reaction products compared to the calcined supports. The incorporation of Ir to the silica–alumina catalysts has a beneficial effect, increasing the decalin conversion, being this effect more noticeable in the low acidity supports, i.e., those containing 30–40 wt % SiO₂. The iridium-containing materials display the highest yield of cracking products, ring opening products, and ring contraction products. Increasing the reaction temperature promotes cracking and dehydrogenation but markedly decreases the selectivity to ring contraction products. At 350 °C a slight decrease in selectivity to ring opening products occurs, though the overall increase in conversion results in an increased yield of these products. An optimum ratio between the acid sites and metal activity that favors the formation of ring opening products was found. At lower acid sites/metal activity ratios the isomerization reaction which leads to C₅ cycle isomers is low, and ring opening by hydrogenolysis is limited as a consequence. On the other hand, at high acid sites/metal activity ratios the cracking reactions are favored, decreasing the yield of RO products

Bulk and Surface Structures of V2 O5 /ZrO2 Systems and Their Relevance for o -Xylene Oxidation

Zirconia-supported vanadium oxide systems, with V2O5 loadings ranging from V/Zr ) 0.033-0.270 atom ratios (0.2-2 monolayers), were prepared by impregnation of a porous ZrO2 substrate with ammonium metavanadate solutions. The surface structures of air-calcined samples were elucidated by Raman and X-ray photoelectron spectroscopic techniques and thermal desorption methods. Some insight into how the bulk structures of these materials developed upon thermal treatment was derived from the X-ray diffraction patterns and temperature-programmed reduction. At low V content, surface-dispersed vanadium oxide species were formed, which produced the transformation of the ZrO2 support from the tetragonal phase into the monoclinic one. At higher vanadium oxide contents, a solid-state reaction between V2O5 and ZrO2 occurred, with subsequent formation of the ZrV2O7 phase, this being the major V-containing phase. The reactivity of these surface structures was examined by looking at their performance for the oxidation of o-xylene to phthalic anhydride. Activity tests indicated that surface vanadium oxide species were more active for the oxidation of o-xylene but had a lower selectivity to phthalic anhydride.Fil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentina. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; EspañaFil: Del Val, S.. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; EspañaFil: López Granados, M.. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; EspañaFil: Bañares, M. A.. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; EspañaFil: Fierro, J. L. G.. Consejo Superior de Investigaciones Científicas. Instituto de Catálisis y Petroleoquímica; Españ

Influence of the Ir content and the support on the thiotolerance of the Ir/SiO2-Al2O3 catalysts used in selective ring opening of decalin

International audienceThe influence of Ir content on sulphur tolerance for the selective ring opening of decalin was investigated. Ir/SiO2-Al2O3 catalysts (70 and 80 wt% SiO2) were used. In the absence of sulphur, slight differences were observed on the yields according to the metallic content regardless of the support used. Although the results of cyclopentane hydrogenolysis showed that the metallic function acquires importance as the metal content increases, for these metal percentages the acid function limits the rate of decalin opening reaction. Products distribution are strongly modified using decalin with S content compared to pure decalin. The formation of dehydrogenated products is virtually null due to S adsorbed on the metal sites. The support has low influence on the thiotolerance. The results related to the amount of S per Ir surface atom, showed that for a moderate S content (S/Irsurf 0.30) 1.5 Ir/Sy appears to be less poisoned than 1Ir/Sy and 2Ir/Sy