3642-13-5Relevant academic research and scientific papers
Influence of iridium content on the behavior of Pt-Ir/Al2O 3 and Pt-Ir/TiO2 catalysts for selective ring opening of naphthenes
Vicerich, María A.,Benitez, Viviana M.,Especel, Catherine,Epron, Florence,Pieck, Carlos L.
, p. 167 - 174 (2013/03/29)
The influence of Ir content on the properties of Pt-Ir/Al2O 3 and Pt-Ir/TiO2 catalysts for selective ring opening of naphthenes was studied. It was found that these catalysts display a strong Pt-Ir interaction but only a weak metal-support interaction. Catalyst acidities depend on the metal loading, but opposite effects were observed on alumina (decrease) or titania (increase) as the metal loading increased. The results obtained from test reactions (cyclohexane dehydrogenation and cyclopentane hydrogenolysis) showed that titania supported catalysts were less active than their alumina supported counterparts. This behavior could be due to the partial blockage of metallic sites by migrated TiOx species and the sinterization of metallic phase during the reduction step. The methylcyclopentane ring opening reaction was found to occur through a partially selective mechanism, and an increase in activity as the Ir loading increased was observed. The selective mechanism was favored by higher total metal loadings, possibly due to an increase in the size of metallic aggregates. Alumina supported catalysts present higher ring opening selectivities. The activity for decalin ring opening increased both with metal loading and reaction temperature level.
Ring opening of decalin and methylcyclohexane over bifunctional Ir/WO 3/Al2O3 catalysts
Moraes, Rodrigo,Thomas, Karine,Thomas, Sebastien,Van Donk, Sander,Grasso, Giacomo,Gilson, Jean-Pierre,Houalla, Marwan
, p. 30 - 43 (2013/04/10)
Ring-opening reactions of decalin and methylcyclohexane (MCH) over bifunctional catalysts (1.2Ir/WO3/Al2O3) were investigated. A series of catalysts containing up to 5.3 at. W/nm2 and 1.2 wt.% Ir was prepared. The acidity of the solids was monitored by low-temperature CO adsorption followed by infrared spectroscopy. Characterization of the Ir metal phase was performed by H2 chemisorption and X-ray diffraction. The activity and product selectivity patterns obtained for the decalin ring-opening reaction were compared with those observed for MCH. For both naphthenes, ring contraction precedes ring opening, suggesting a similar ring-opening mechanism. Kinetic modeling based on the proposed reaction network allowed the determination of the activation energies and initial rates. Based on the yields and products distribution obtained for the decalin reaction, the potential for improvement of the cetane number is discussed.
Ring opening of decalin via hydrogenolysis on Ir/- and Pt/silica catalysts
Haas, Andreas,Rabl, Sandra,Ferrari, Marco,Calemma, Vincenzo,Weitkamp, Jens
experimental part, p. 97 - 109 (2012/07/13)
The catalytic conversion of cis-decalin was studied at a hydrogen pressure of 5.2 MPa and temperatures of 250-410 °C on iridium and platinum supported on non-acidic silica. The absence of catalytically active Br?nsted acid sites was indicated by both FT-IR spectroscopy with pyridine as a probe and the selectivities in a catalytic test reaction, viz. the hydroconversion of n-octane. On iridium/silica, decalin hydroconversion starts at ca. 250-300 °C, and no skeletal isomerization occurs. The first step is rather hydrogenolytic opening of one six-membered ring to form the direct ring-opening products butylcyclohexane, 1-methyl-2-propylcyclohexane and 1,2- diethylcyclohexane. These show a consecutive hydrogenolysis, either of an endocyclic carboncarbon bond into open-chain decanes or of an exocyclic carboncarbon bond resulting primarily in methane and C9 naphthenes. The latter can undergo a further endocyclic hydrogenolysis leading to open-chain nonanes. All individual C10 and C9 hydrocarbons predicted by this direct ring-opening mechanism were identified in the products generated on the iridium/silica catalysts. The carbon-number distributions of the hydrocracked products C9- show a peculiar shape resembling a hammock and could be readily predicted by simulation of the direct ring-opening mechanism. Platinum on silica was found to require temperatures around 350-400 °C at which relatively large amounts of tetralin and naphthalene are formed. The most abundant primary products on Pt/silica are spiro[4.5]decane and butylcyclohexane which can be readily accounted for by the well known platinum-induced mechanisms described in the literature for smaller model hydrocarbons, namely the bond-shift isomerization mechanism and hydrogenolysis of a secondary-tertiary carboncarbon bond in decalin.
Ring opening of decalin and methylcyclohexane over alumina-based monofunctional WO3/Al2O3 and Ir/Al 2O3 catalysts
Moraes, Rodrigo,Thomas, Karine,Thomas, Sebastien,Van Donk, Sander,Grasso, Giacomo,Gilson, Jean-Pierre,Houalla, Marwan
scheme or table, p. 62 - 77 (2012/03/11)
Ring-opening reactions of decalin and MCH were studied over monofunctional acid (WO3/Al2O3) and metal (Ir/Al 2O3) catalysts containing, respectively, up to 5.3 at. W/nm2 and 1.8 wt% Ir. The catalysts were characterized by X-ray diffraction, Raman spectroscopy, low-temperature CO adsorption followed by infrared spectroscopy, and H2 chemisorption. A reaction network was proposed for both molecules and used to determine the kinetic parameters. Kinetic modeling allowed relating characterization results and catalytic performance. For WO3/Al2O3 catalysts, ring contraction precedes ring opening of both molecules. The evolution of ring contraction activity was consistent with the development of relatively strong Bronsted acid sites. Ring opening occurs according to a classic acid mechanism. For Ir/Al2O3 catalysts, only direct ring opening was observed. Ring opening proceeds mostly via dicarbene mechanism. Analysis of products indicated that monofunctional metal catalysts are better suited than acid solids for upgrading LCO.
Efficient thermochemical alkane dehydrogenation and isomerization catalyzed by an iridium pincer complex
Liu, Fuchen,Goldman, Alan S.
, p. 655 - 656 (2007/10/03)
((i-Pr)PCP)IrH2 is found to be a remarkably effective solution-phase catalyst for the 'acceptorless' thermochemical dehydrogenation of cycloalkanes (and isomerization in the case of cyclodecane), and the first such catalyst reported to effect the dehydrogenation of n-alkanes.
Catalytic Hydrogenation of Some Hydrocarbons with Spiroanellated Bicyclopropyl Units
Kaufmann, Dieter,Meijere, Armin de
, p. 833 - 837 (2007/10/02)
The spirocyclopropyl groups of dispirodec-8-ene (1) and dispirohexane-3',1''-cyclopropane> (11) both upon catalytic hydrogenation are ringopened to ethyl groups rather than gem-dimethyl groups as would be expected
Synthesis and Characterization of Representative Octa-1,3,5,7-tetraenes and Deca-1,3,5,7,9-pentaenes
Spangler, Charles W.,Little, David A.
, p. 2379 - 2386 (2007/10/02)
Several representative conjugated linear tetraenes and pentaenes were prepared by a variety of synthetic methods including Wittig condensation, 1,8-Diazabicycloundec-7-ene (DBU)-induced dehydrobromination, and Hofmann elimination.For the preparation of (E,E)- and (Z,E)-octa-1,3,5,7-tetraene, the Hofmann elimination sequence is by far the most convenient method by synthesis, while DBU-induced dehydrobromination of (E,E)-4-bromonona-1,5,7-triene, produces excellent yields of (E,E,E)- and (3Z,5E,7E)-nona-1,3,5,7-tetraene.Deca-1,3,5,7,9-pentaene can be produced by several methods, but not in high yield.Undeca-1,3,5,7,9-pentaene and trideca-1,3,5,7,9,11-hexaene can also be prepared in low yield by the Wittig reaction.All the polyenes produced in this study polymerize rapidly in the crystalline state.
