- Effect of External Surface Diffusion Barriers on Platinum/Beta-Catalyzed Isomerization of n-Pentane
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We have developed a generalizable strategy to quantify the effect of surface barriers on zeolite catalysis. Isomerization of n-pentane, catalyzed by Pt/Beta, is taken as a model reaction system. Firstly, the surface modification by chemical liquid deposition of SiO2 was carried out to control the surface barriers on zeolite Beta crystals. The deposition of SiO2 leads to a very slight change in the physical properties of Beta crystals, but an obvious reduction in Br?nsted acid sites. Diffusion measurements by the zero-length column (ZLC) method show that the apparent diffusivity of n-pentane can be more than doubled after SiO2 deposition, indicating that the surface barriers have been weakened. Catalytic performance was tested in a fixed-bed reactor, showing that the apparent catalytic activity improved by 51–131 % after SiO2 deposition. These results provide direct proof that reducing surface barriers can be an effective route to improve zeolite catalyst performance deteriorated by transport limitations.
- Hu, Shen,Liu, Junru,Ye, Guanghua,Zhou, Xinggui,Coppens, Marc-Olivier,Yuan, Weikang
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- Ir/Pt-HZSM5 for n-pentane isomerization: Effect of iridium loading on the properties and catalytic activity
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The effects of iridium loading on the properties of Ir/Pt-HZSM5 and n-pentane isomerization were studied. XRD, IR, and NMR results indicated that increasing iridium loading did not much change the properties of catalysts, but eliminated the perturbed silanol groups at 3700 and 3520 cm-1, whereas IR and ESR spectroscopy confirmed that increasing iridium loading continuously decreased the permanent Lewis and Bronsted acid sites and inhibited the formation of protonic acid sites induced by hydrogen. At low iridium loading (0-0.3 wt%), cracking process proceed through dimerization-cracking step, whereas high iridium loading (0.5-2.0 wt%) reduces the contribution of dimerization-cracking step and promotes the contribution of hydrogenolysis. The excessive amount of iridium loading, with the presence of a low amount of active protonic acid sites and hydrogen gas, accelerated the hydrogenolysis process. The activity of Ir/Pt-HZSM5 was marginal in the absence of hydrogen, showing the dependence of activity on promotive effect of hydrogen.
- Setiabudi,Jalil,Triwahyono
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- Catalytic activity of H-forms of zeolites in the isomerization of supercritical n-pentane and their physicochemical properties
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The acidic properties of the H-forms of zeolites ZSM-5, Beta, Y, and mordenite are studied by diffuse reflectance IR spectroscopy using n-pentane as a probe molecule. The decreasing order of Bronsted acid site strengths is constructed. The isopentane selectivity in n-pentane isomerization under supercritical conditions (260°C, 130 atm) increases in the order H-ZSM-5 H-Beta H-mordenite(11) ≈ H-Y with decreasing strength of Bronsted sites. Catalytic data are analyzed jointly with the results of physicochemical studies of H-mordenite (temperature-programmed ammonia desorption, benzene adsorption, and IR spectroscopy). Under the supercritical conditions, the conversion of n-pentane on mordenite is determined by the total acidity of the zeolite and also by the accessibility of the acid sites inside the zeolite channels to the reactant.
- Bogdan,Koklin,Kazanskii
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- Skeletal Isomerization of n-Butane over Caesium Hydrogen Salts of 12-Tungstophosphoric Acid
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Skeletal isomerization of n-butane to isobutane has been studied with a flow reactor, mainly at 573 K, over caesium hydrogen salts of 12-tungstophosphoric acid (trihydrogen phosphododecatungstate), CsxH3-xPW12O40.The activity was highly dependent on the caesium content, being a maximum for x = 2.5 where the number of acid sites on the surface was greatest.The initial rate was first order with respect to the butane pressure (ca. 0.05-0.5 atm) at both 423 and 573 K on Cs2.5H0.5PW12O40*Cs2.5H0.5PW12O40 was found to be much more active and selective (83percent cf. 60percent) than SO4(2-)/ZrO2 at the steady state at 573 K.H-ZSM-5 showed a higher activity than Cs2.5H0.5PW12O40 and SO4(2-)/ZrO2 but the selectivity was only 14percent.Cs2.5H0.5PW12O40 is a promising catalyst for this reaction and the low deactivation of Cs2.5H0.5PW12O40 is probably responsible for the high catalytic activity.
- Na, Kyutae,Okuhara, Toshio,Misono, Makoto
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- Isomerization of n-pentane over platinum promoted tungstated zirconia supported on mesoporous SBA-15 prepared by supercritical impregnation
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Tungstated zirconia was supported on mesoporous SBA-15 by impregnation in supercritical ethanol. The resultant catalyst promoted with 1 wt% of Pt shows 100% selectivity of iso-pentane and two times higher conversion in n-pentane isomerization than the one prepared by conventional impregnation. Supercritical impregnation exerts no destruction of the porous silica and offers better dispersion of tungstated zirconia than conventional impregnation. Optimized loading of WO3/ZrO2/SBA-15 is 20/40/40 wt%, which infers to 2.4 W-atoms/nm2 and 8.9 Zr-atoms/nm2 dispersed on the SBA-15 support. Moreover, introducing a proper mole fraction of hydrogen in the reactants markedly improves the catalytic activity in n-pentane isomerization. The role of hydrogen was not only served as the reactants, it also acted to regenerate Br?nsted acid sites during n-pentane isomerization. However, overdose of hydrogen leaded to a leveling-off in the rate of isomerization and enhanced hydrogenolysis reaction. The in situ IR spectroscopic studies suggested that Br?nsted acid sites were the active centers for the isomerization. A reaction mechanism was, therefore, proposed that heterolytic fission of hydrogen and dehydrogenation of n-pentane took place over Pt. The secondary carbocation formed over Br?nsted acid sites was rearranged to a tertiary carbocation by methyl migration, followed by reacting with a hydride to generate iso-pentane.
- Cheng, Soofin,Lee, Wenchao,Yang, Chieh-Chao
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- Catalytic performance of nanostructured Pt/ZSM-5 catalysts synthesized by extended Charnell's method in hydroisomerization of n-pentane
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Na-ZSM-5 zeolite, synthesized by extended Charnell's method was used to prepare Pt/ZSM-5 catalyst for n-pentane hydroisomerization. The influence of ion exchange, alkaline treatment and method of platinum incorporation on the Na-ZSM-5 zeolite was investigated. It was found that the presence of Trien affected the physicochemical properties of the synthesized catalyst. The synthesized catalysts showed high performance so that the sample prepared in rotating mode at 24 h and Pt loaded via impregnation showed conversion and selectivity about 75 and 97%, respectively. Also, a maximum yield for this catalyst was achieved at 250 °C.
- Charchi Aghdam,Ejtemaei,Sharafi,Babaluo,Tavakoli,Bayati
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- La-Ni modified S2O82-/ZrO2-Al2O3 catalyst in n-pentane hydroisomerization
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The LaNiS2O8 2?/ZrO2Al2O3 (LaNiSZA) was prepared and the effect of La and Ni on the structure and isomerization performance of catalyst was investigated. The addition of La could lead to a higher dispersion of metal and more acid sites. The addition of Ni can promote redox performance of catalyst and formation of Lewis acid sites. The highest isopentane yield of 66.5% at a lower reaction temperature of LaNiSZA can be attributed to the synergistic interaction between La and Ni.
- Song, Hua,Wang, Na,Song, Hua-Lin,Li, Feng
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- Aluminum fluoride-supported platinum and palladium as highly efficient catalysts of n-pentane hydroisomerization
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Catalytic isomerization of n-pentane was studied over novel high surface area (HS) aluminum fluoride supported palladium and platinum catalysts, prepared by the nonaqueous fluorolytic sol-gel synthesis. HS-AlF3 maintained well its nanoscopic, mesoporous, and highly acidic character at higher temperatures, up to 350 °C. Both Pt/HS-AlF3 and Pd/HS-AlF 3 catalysts, characterized by very small metal particle sizes (≈2 nm) maintained very good activity, stability, and selectivity towards isomerization (up to nearly 100 %) at up to 350 °C. Very strong acidity of HS-AlF3 is the prerequisite for isomerization but the presence of the metal is also essential to maintain a high conversion level. The effect of metal-acid balance in Pd/HS-AlF3 catalysts, important for bifunctional isomerization, was tested by screening three differently metal-loaded catalysts. The performance of the 0.5 wt % Pd/HS-AlF3 appeared as good as that of 2.0 wt % Pd. The properties of the HS-AlF 3 support, catalyst precursors, and catalysts were characterized by XRD, TEM, H2 chemisorption, and FTIR photoacustic spectroscopy of adsorbed pyridine, and NH3 temperature programmed desorption. The first three methods allowed evaluating the state of the metal in the reduced catalysts. The suppressed chemisorption of H2 must result from different factors, such as carbon presence in Pd introduced during catalyst synthesis and activation, metal-acidic support interaction, and, partially, metal encapsulation in AlF3 during sol-gel synthesis. Lewis and Bronsted acidity was detected in activated catalysts and both types of acid sites were assumed to play a role in bifunctional isomerization. NH 3 effectively blocks the strongest acid sites and drastically limits the overall catalytic performance. Introduction of water to the reaction system also degrades, but to a lesser extent, the Pd(Pt)/HS-AlF3 catalyst performance, most probably because of poisoning of only the strongest Lewis acid sites. A week-long performance: High surface area(HS) aluminum fluoride-supported palladium and platinum catalysts are used in the isomerization of n-pentane. The activity, stability, and selectivity of Pt/HS-AlF3 and Pd/HS-AlF3 catalysts is maintained at temperatures of up to 350 °C over reaction times of up to a week. Both Lewis and Bronsted acidity is detected in the activated catalysts, evidencing bifunctional isomerization. Copyright
- Machynskyy, Ostap,Kemnitz, Erhard,Karpinski, Zbigniew
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- IR study of iridium bonded to perturbed silanol groups of Pt-HZSM5 for n-pentane isomerization
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The Ir/Pt-HZSM5 catalyst was prepared by impregnation of iridium on Pt-HZSM5. The activity of Ir/Pt-HZSM5 was tested for n-pentane isomerization under hydrogen stream. The introduction of iridium did not change the bands observed at 3740, 3665 and 3610 cm-1 indicating that neither non-acidic terminal silanol groups nor acidic bridging hydroxyl groups interacted with the iridium. Additionally, the peaks corresponding to the perturbed silanol groups at 3700 and 3520 cm-1 decreased significantly. X-ray photoelectron spectroscopy (XPS) analysis revealed that the iridium is in the form of IrO2. 27Al MAS NMR confirmed the elimination of distorted tetrahedral aluminum. The presence of iridium slightly increased the acidity of Pt-HZSM5 and its selectivity for iso-pentane. Hydrogen adsorption FTIR indicated that iridium enhanced the formation of protonic acid sites which may participate in the isomerization, and inhibited the formation of hydroxyl groups at 3380, 3600 and 3680 cm-1 which may participate in the enhancement of the cracking reaction.
- Setiabudi, Herma Dina,Jalil, Aishah Abdul,Triwahyono, Sugeng,Kamarudin, Nur Hidayatul Nazirah,Mukti, Rino R.
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- New Perspectives in the Formation of the Grignard Reagent
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Inhibitors, in very low concentration, inhibit the reaction between 1-bromo-3-methylbutane and magnesium obtained by vaporization of metal.For such a magnesium derivative, the inhibitors cannot play the role of "killers" for active sites.A chain reaction for the formation of the Grignard reagent is proposed.
- Peralez, Eric,Negrel, Jean-Claude,Chanon, Michel
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- alpha , beta -SUBSTITUTED BIS(CYCLOPENTADIENYL)TITANACYCLOBUTANES AND THEIR ROLE IN PRODUCTIVE METATHESIS.
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The synthesis and reactions of the alpha , beta -disubstituted titanacyclobutanes, are reported. The cis isomer is the less stable and at room temperature isomerizes to the trans isomer and unidentified products. The cis- alpha , beta -dimethylmetallacycle produces a variety of C//1 to C//5 hydrocarbons upon thermal decomposition. Evidence for competitive cleavage of the cis- alpha , beta -dimethylmetallacycle to give a titanocene ethylidene or a titanocene methylene is presented. The mechanism of these olefin metathesis reactions is discussed in terms of the chemistry of the model intermediates, the cis- and trans- alpha , beta -dimethyltitanacycles.
- Straus,Grubbs
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- Mechanisms of Methylenecyclobutane Hydrogenation over Supported Metal Catalysts Studied by Parahydrogen-Induced Polarization Technique
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In this work the mechanism of methylenecyclobutane hydrogenation over titania-supported Rh, Pt and Pd catalysts was investigated using parahydrogen-induced polarization (PHIP) technique. It was found that methylenecyclobutane hydrogenation leads to formation of a mixture of reaction products including cyclic (1-methylcyclobutene, methylcyclobutane), linear (1-pentene, cis-2-pentene, trans-2-pentene, pentane) and branched (isoprene, 2-methyl-1-butene, 2-methyl-2-butene, isopentane) compounds. Generally, at lower temperatures (150–350 °C) the major reaction product was methylcyclobutane while higher temperature of 450 °C favors the formation of branched products isoprene, 2-methyl-1-butene and 2-methyl-2-butene. PHIP effects were detected for all reaction products except methylenecyclobutane isomers 1-methylcyclobutene and isoprene implying that the corresponding compounds can incorporate two atoms from the same parahydrogen molecule in a pairwise manner in the course of the reaction in particular positions. The mechanisms were proposed for the formation of these products based on PHIP results.
- Salnikov, Oleg G.,Burueva, Dudari B.,Kovtunova, Larisa M.,Bukhtiyarov, Valerii I.,Kovtunov, Kirill V.,Koptyug, Igor V.
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- Dendrimer-Encapsulated Pd Nanoparticles, Immobilized in Silica Pores, as Catalysts for Selective Hydrogenation of Unsaturated Compounds
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Heterogeneous Pd-containing nanocatalysts, based on poly (propylene imine) dendrimers immobilized in silica pores and networks, obtained by co-hydrolysis in situ, have been synthesized and examined in the hydrogenation of various unsaturated compounds. The catalyst activity and selectivity were found to strongly depend on the carrier structure as well as on the substrate electron and geometric features. Thus, mesoporous catalyst, synthesized in presence of both polymeric template and tetraethoxysilane, revealed the maximum activity in the hydrogenation of various styrenes, including bulky and rigid stilbene and its isomers, reaching TOF values of about 230000 h?1. Other mesoporous catalyst, synthesized in the presence of polymeric template, but without addition of Si(OEt)4, provided the trans-cyclooctene formation with the selectivity of 90–95 %, appearing as similar to homogeneous dendrimer-based catalysts. Microporous catalyst, obtained only on the presence of Si(OEt)4, while dendrimer molecules acting as both anchored ligands and template, demonstrated the maximum activity in the hydrogenation of terminal linear alkynes and conjugated dienes, reaching TOF values up to 400000 h?1. Herein the total selectivity on alkene in the case of terminal alkynes and conjugated dienes reached 95–99 % even at hydrogen pressure of 30 atm. The catalysts synthesized can be easily isolated from reaction products and recycled without significant loss of activity.
- Karakanov, Edward A.,Zolotukhina, Anna V.,Ivanov, Andrey O.,Maximov, Anton L.
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p. 358 - 381
(2019/04/04)
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- Competitive adsorptions between thiophenic compounds over a CoMoS/Al2O3 catalyst under deep HDS of FCC gasoline
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The transformation of various model sulfur compounds (2-methylthiophene: 2MT, 3-methylthiophene: 3MT and benzothiophene: BT) representative of sulfur compounds in FCC gasoline was investigated over a CoMoS/Al2O3 catalyst. More specifically, a quantitative reactivity scale was established with BT being more reactive than 3MT and 2MT. In mixture, their reactivity was reduced due to the presence of the other sulfur compound, the scale of reactivity being preserved. BT strongly inhibits the transformation of 2MT. With a single kinetic model based on a Langmuir Hinshelwood formalism, kinetic and adsorption parameters were calculated and the results explained by mutual competitive adsorption between 2MT and BT with a higher adsorption constant for BT compared to that of 2MT.
- dos Santos, Alan Silva,Girard, Etienne,Leflaive, Philibert,Brunet, Sylvette
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p. 292 - 298
(2018/12/11)
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- High-Quality Gasoline Directly from Syngas by Dual Metal Oxide–Zeolite (OX-ZEO) Catalysis
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Despite significant efforts towards the direct conversion of syngas into liquid fuels, the selectivity remains a challenge, particularly with regard to high-quality gasoline with a high octane number and a low content of aromatic compounds. Herein, we show that zeolites with 1D ten-membered-ring (10-MR) channel structures such as SAPO-11 and ZSM-22 in combination with zinc- and manganese-based metal oxides (ZnaMnbOx) enable the selective synthesis of gasoline-range hydrocarbons C5–C11 directly from syngas. The gasoline selectivity reached 76.7 % among hydrocarbons, with only 2.3 % CH4 at 20.3 % CO conversion. The ratio of isoparaffins to n-paraffins was as high as 15, and the research octane number was estimated to be 92. Furthermore, the content of aromatic compounds in the gasoline was as low as 16 %. The composition and structure of ZnaMnbOx play an important role in determining the overall activity. This process constitutes a potential technology for the one-step synthesis of environmentally friendly gasoline with a high octane number from a variety of carbon resources via syngas.
- Li, Na,Jiao, Feng,Pan, Xiulian,Chen, Yuxiang,Feng, Jingyao,Li, Gen,Bao, Xinhe
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supporting information
p. 7400 - 7404
(2019/05/10)
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- Rh(iii)-Catalysed solvent-free hydrodehalogenation of alkyl halides by tertiary silanes
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Efficient catalytic reduction of CDCl3 and other alkyl halides, including persistent organic pollutants, by different tertiary silanes using the unsaturated silyl-hydrido-Rh(iii) complex {Rh(H)[SiMe2(o-C6H4SMe)](PPh3)2}[BArF4] as a pre-catalyst is accomplished. The reactions are performed in a solvent-free manner. On account of experimental evidence, a simplified catalytic cycle is suggested for the hydrodehalogenation of CDCl3.
- Almenara,Azpeitia,Garralda,Huertos
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supporting information
p. 16225 - 16231
(2018/11/30)
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- Cobalt-Iron-Manganese Catalysts for the Conversion of End-of-Life-Tire-Derived Syngas into Light Terminal Olefins
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Co-Fe-Mn/γ-Al2O3 Fischer–Tropsch synthesis (FTS) catalysts were synthesized, characterized and tested for CO hydrogenation, mimicking end-of-life-tire (ELT)-derived syngas. It was found that an increase of C2-C4 olefin selectivities to 49 % could be reached for 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn/γ-Al2O3 with Na at ambient pressure. Furthermore, by using a 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al2O3 catalyst the selectivity towards the fractions of C5+ and CH4 could be reduced, whereas the selectivity towards the fraction of C4 olefins could be improved to 12.6 % at 10 bar. Moreover, the Na/S ratio influences the ratio of terminal to internal olefins observed as products, that is, a high Na loading prevents the isomerization of primary olefins, which is unwanted if 1,3-butadiene is the target product. Thus, by fine-tuning the addition of promoter elements the volume of waste streams that need to be recycled, treated or upgraded during ELT syngas processing could be reduced. The most promising catalyst (5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al2O3) has been investigated using operando transmission X-ray microscopy (TXM) and X-ray diffraction (XRD). It was found that a cobalt-iron alloy was formed, whereas manganese remained in its oxidic phase.
- Falkenhagen, Jan P.,Maisonneuve, Lise,Paalanen, Pasi P.,Coste, Nathalie,Malicki, Nicolas,Weckhuysen, Bert M.
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supporting information
p. 4597 - 4606
(2018/03/06)
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- Synthesis of Densely Packaged, Ultrasmall Pt02 Clusters within a Thioether-Functionalized MOF: Catalytic Activity in Industrial Reactions at Low Temperature
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The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt02 clusters, homogenously distributed and densely packaged within the channels of a metal–organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO2 methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal clusters in solids for technically easier, cheaper, and dramatically less-dangerous industrial reactions.
- Mon, Marta,Rivero-Crespo, Miguel A.,Ferrando-Soria, Jesús,Vidal-Moya, Alejandro,Boronat, Mercedes,Leyva-Pérez, Antonio,Corma, Avelino,Hernández-Garrido, Juan C.,López-Haro, Miguel,Calvino, José J.,Ragazzon, Giulio,Credi, Alberto,Armentano, Donatella,Pardo, Emilio
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supporting information
p. 6186 - 6191
(2018/05/30)
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- Alkanethiolate-capped palladium nanoparticles for selective catalytic hydrogenation of dienes and trienes
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Selective hydrogenation of dienes and trienes is an important process in the pharmaceutical and chemical industries. Our group previously reported that the thiosulfate protocol using a sodium S-alkylthiosulfate ligand could generate catalytically active Pd nanoparticles (PdNP) capped with a lower density of alkanethiolate ligands. This homogeneously soluble PdNP catalyst offers several advantages such as little contamination via Pd leaching and easy separation and recycling. In addition, the high activity of PdNP allows the reactions to be completed under mild conditions, at room temperature and atmospheric pressure. Herein, a PdNP catalyst capped with octanethiolate ligands (C8 PdNP) is investigated for the selective hydrogenation of conjugated dienes into monoenes. The strong influence of the thiolate ligands on the chemical and electronic properties of the Pd surface is confirmed by mechanistic studies and highly selective catalysis results. The studies also suggest two major routes for the conjugated diene hydrogenation: the 1,2-addition and 1,4-addition of hydrogen. The selectivity between two mono-hydrogenation products is controlled by the steric interaction of substrates and the thermodynamic stability of products. The catalytic hydrogenation of trienes also results in the almost quantitative formation of mono-hydrogenation products, the isolated dienes, from both ocimene and myrcene.
- Chen, Ting-An,Shon, Young-Seok
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p. 4823 - 4829
(2017/10/19)
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- Flexible gasoline process using multiple feedstocks
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A flexible process for gasoline refineries is described. The process can vary depending on the available feedstock and the desired products. At one time, the process can involve disproportionating pentanes to a product mixture including isobutane and isohexane. At other times, by switching the feedstock and operating conditions, the process can convert a mixture of C4 and C7 paraffins to a low aromatic blendstock with suitable octane and a vapor pressure lower than butanes. The process can be performed in separate stand-alone units operated at different times, or a single unit can be operated according to one process at one time and according to the other process at another time.
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Paragraph 15; 16
(2017/03/08)
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- Hydrodeoxygenation of Phenol over Zirconia-Supported Catalysts: The Effect of Metal Type on Reaction Mechanism and Catalyst Deactivation
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This work aims at investigating the effect of the type of metal (Pt, Pd, Rh, Ru, Cu, Ni, Co) on the performance of ZrO2-supported catalysts for the hydrodeoxygenation of phenol in the gas phase at 573 K and 1 atm. Two different reaction pathways take place depending on the type of the metal. For Pt/ZrO2 and Pd/ZrO2 catalysts, phenol is mainly tautomerized, followed by hydrogenation of the C=C bond of the tautomer intermediate formed, producing cyclohexanone and cyclohexanol. By contrast, the direct dehydroxylation of phenol followed by hydrogenolysis might also occur over more oxophilic metals such as Rh, Ru, Co, and Ni. In addition to the metals, the oxophilic sites of this support represented by Zr4+ and Zr3+ cations near the perimeter of the metal particles also increased the selectivity to deoxygenated products. All catalysts were significantly deactivated mainly owing to the growth of metal particle size and the decrease in the density of oxophilic sites.
- Teles, Camila A.,Rabelo-Neto, Raimundo C.,Jacobs, Gary,Davis, Burtron H.,Resasco, Daniel E.,Noronha, Fábio B.
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p. 2850 - 2863
(2017/07/28)
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- PROCESS OF MAKING OLEFINS OR ALKYLATE BY REACTION OF METHANOL AND/OR DME OR BY REACTION OF METHANOL AND/OR DME AND BUTANE
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Methods of simultaneously converting butanes and methanol to olefins over Ti-containing zeolite catalysts are described. The exothermicity of the alcohols to olefins reaction is matched by endothermicity of dehydrogenation reaction of butane(s) to light olefins resulting in a thermo- neutral process. The Ti-containing zeolites provide excellent selectivity to light olefins as well as exceptionally high hydrothermal stability. The coupled reaction may advantageously be conducted in a staged reactor with methanol/DME conversion zones alternating with zones for butane(s) dehydrogenation. The resulting light olefins can then be reacted with iso-butane to produce high-octane alkylate. The net result is a highly efficient and low cost method for converting methanol and butanes to alkylate.
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Page/Page column 15; 25; 26; 31; 32
(2017/05/10)
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- METHOD FOR METHANOL CONVERSION TO PROPYLENE OVER A MONOLITHIC CATALYST SYSTEM
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A catalyst system and a process for methanol to light olefin conversion with enhanced selectivity towards propylene. The catalyst system comprises a honeycomb monolith catalyst support coated with aluminosilicate nanozeolite catalysts on the edges and inside the channels of the support structure. The aluminosilicate nanozeolite catalysts have not been pre-modified with a promoter metal. The catalyst system gives higher hydrothermal stability to the catalyst compared to randomly packed pellet catalysts and allows methanol to be converted to predominantly propylene at a low temperature, with decreased selectivity towards C2, higher olefins and paraffinic hydrocarbons.
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Paragraph 0075-0078
(2017/12/27)
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- Transfer Hydrogenation of Nitriles, Olefins, and N-Heterocycles Catalyzed by an N-Heterocyclic Carbene-Supported Half-Sandwich Complex of Ruthenium
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In the presence of KOBut, N-heterocyclic carbene-supported half-sandwich complex [Cp(IPr)Ru(pyr)2][PF6] (3) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) catalyzes transfer hydrogenation (TH) of nitriles, activated N-heterocycles, olefins, and conjugated olefins in isopropanol at the catalyst loading of 0.5%. The TH of nitriles leads to imines, produced as a result of coupling of the initially formed amines with acetone (produced from isopropanol), and showed good chemoselectivity. Reduction of N-heterocycles occurs for activated polycyclic substrates (e.g., quinoline) and takes place exclusively in the heterocycle. The TH also works well for linear and cyclic olefins but fails for trisubstituted substrates. However, the C = C bond of α,β-unsaturated esters, amides, and acids is easily reduced even for trisubstituted species, such as isovaleriates. Mechanistic studies suggest that the active species in these catalytic reactions is the trihydride Cp(IPr)RuH3 (5), which can catalyze these reactions in the absence of any base. Kinetic studies are consistent with a classical inner sphere hydride-based mechanism of TH.
- Mai, Van Hung,Nikonov, Georgii I.
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p. 943 - 949
(2016/05/09)
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- Ferrocenyl-derived electrophilic phosphonium cations (EPCs) as Lewis acid catalysts
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Oxidation of diphenylphosphinoferrocene and 1,1′-bis(diphenylphosphino)ferrocene with XeF2, resulted in the formation of CpFe(η5-C5H4PF2Ph2) 1 and Fe(η5-C5H4PF2Ph2)22 respectively. Subsequent reactions with [SiEt3][B(C6F5)4] yielded [CpFe(η5-C5H4PFPh2)][B(C6F5)4] 3 and [Fe(η5-C5H4PFPh2)2] [B(C6F5)4]24. PhP(η5-C5H4)2Fe 5 was prepared, converted to [PhMeP(η5-C5H4)2Fe][O3SCF3] 6 and then to [PhMeP(η5-C5H4)2Fe][B(C6F5)4] 7. The ability of the salts 3, 4 and 7 to catalyze Friedel-Crafts dimerization of 1,1-diphenylethylene, dehydrocoupling of phenol and triethylsilane, deoxygenation of acetophenone and hydrodefluorination of 1-fluoropentane were probed. While compound 7 proved to be ineffective, compounds 3 and 4 were useful Lewis acid catalysts. Compounds 3 and 4 were shown to catalyze the deoxygenation of a series of ketones.
- Mallov, Ian,Stephan, Douglas W.
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supporting information
p. 5568 - 5574
(2016/04/09)
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- INTEGRATED PROCESS FOR GASOLINE PRODUCTION
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An integrated process for gasoline production is described. The process includes introducing a feed comprising n-C5 hydrocarbons into a disproportionation reaction zone in the presence of a disproportionation catalyst to form a disproportionation mixture comprising iso-C4 and C6+ disproportionation products and unreacted n-C5 hydrocarbons. An iso-C4 hydrocarbon stream and an olefin feed are introduced into an alkylation reaction zone in the presence of an alkylation catalyst to produce an alkylation mixture comprising alkylate and unreacted iso-C4 paraffins. The disproportionation mixture and the alkylation mixture are combined, and the combined mixture is separated into at least a stream comprising the alkylate product, an iso-C4 stream, and an unreacted n-C5 hydrocarbon stream. The iso-C4 stream is recycled to the alkylation reaction zone, and the unreacted n-C5 hydrocarbon stream is recycled to the disproportionation reaction zone. The stream comprising the alkylate product is recovered.
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Paragraph 0086
(2016/07/05)
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- The Effect of Metal Type on Hydrodeoxygenation of Phenol Over Silica Supported Catalysts
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Abstract: Different metals supported on SiO2 were tested for the hydrodeoxygenation of phenol. For Pt/SiO2, Pd/SiO2 and Rh/SiO2 catalysts, phenol is mainly tautomerized, followed by hydrogenation of the aromatic ring. The direct dehydroxylation of phenol followed by hydrogenolysis is favored over more oxophilic metals (Ru, Co and Ni). Graphical Abstract: [Figure not available: see fulltext.]
- Teles, Camila A.,Rabelo-Neto, Raimundo C.,de Lima, Jerusa R.,Mattos, Lisiane V.,Resasco, Daniel E.,Noronha, Fabio B.
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p. 1848 - 1857
(2016/10/18)
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- Cross-Linked "poisonous" Polymer: Thermochemically Stable Catalyst Support for Tuning Chemoselectivity
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Designed catalyst poisons can be deliberately added in various reactions for tuning chemoselectivity. In general, the poisons are "transient" selectivity modifiers that are readily leached out during reactions and thus should be continuously fed to maintain the selectivity. In this work, we supported Pd catalysts on a thermochemically stable cross-linked polymer containing diphenyl sulfide linkages, which can simultaneously act as a catalyst support and a "permanent" selectivity modifier. The entire surfaces of the Pd clusters were ligated (or poisoned) by sulfide groups of the polymer support. The sulfide groups capping the Pd surface behaved like a "molecular gate" that enabled exceptionally discriminative adsorption of alkynes over alkenes. H2/D2 isotope exchange revealed that the capped Pd surface alone is inactive for H2 (or D2) dissociation, but in the presence of coflowing acetylene (alkyne), it becomes active for H2 dissociation as well as acetylene hydrogenation. The results indicated that acetylene adsorbs on the Pd surface and enables cooperative adsorption of H2. In contrast, ethylene (alkene) did not facilitate H2-D2 exchange, and hydrogenation of ethylene was not observed. The results indicated that alkynes can induce decapping of the sulfide groups from the Pd surface, while alkenes with weaker adsorption strength cannot. The discriminative adsorption of alkynes over alkenes led to highly chemoselective hydrogenation of various alkynes to alkenes with minimal overhydrogenation and the conversion of side functional groups. The catalytic functions can be retained over a long reaction period due to the high thermochemical stability of the polymer.
- Yun, Seongho,Lee, Songhyun,Yook, Sunwoo,Patel, Hasmukh A.,Yavuz, Cafer T.,Choi, Minkee
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p. 2435 - 2442
(2016/04/26)
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- Fischer–Tropsch synthesis with cobalt catalyst and zeolite multibed arrangement
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The role of zeolite in transformations of hydrocarbons produced from CO and H2 over a Fischer–Tropsch cobalt catalyst under the conditions of multibed arrangement of the cobalt catalyst and the zeolite has been determined. Hydrocarbon conversion over the HBeta zeolite occurs via the bimolecular mechanism, as evidenced by a low methane yield and a high yield of unsaturated gaseous and liquid hydrocarbons. The conversion over the CaA zeolite obeys the unimolecular mechanism, as evidenced by the formation of increased amounts of methane and saturated gaseous C2–C4 hydrocarbons.
- Asalieva, E. Yu.,Kul’chakovskaya,Sineva,Mordkovich,Bulychev
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p. 275 - 280
(2016/06/09)
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- Palladium-gold catalyst for the electrochemical reduction of CO2 to C1-C5 hydrocarbons
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Copper is a unique electrocatalyst for CO2 reduction, since it is one of the few catalysts able to produce methane, ethylene and ethane from CO2 with decent faradaic efficiencies. Here we report on the design and synthesis of a new non-copper-containing catalyst able to reduce CO2 to C1 to C5 hydrocarbons. This catalyst was designed by combining a metal that binds CO strongly, Pd, with a metal that binds CO weakly, Au, in an attempt to tune the binding energy of CO. We show that a mixture of C1-C5 hydrocarbons and soluble products are produced from an onset potential of -0.8 VRHE. We propose that the higher hydrocarbons are formed via a polymerization of -CH2 groups adsorbed on the catalyst surface.
- Kortlever,Peters,Balemans,Kas,Kwon,Mul,Koper
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supporting information
p. 10229 - 10232
(2016/08/23)
-
- Understanding reaction processes for n-heptane over 10Mo2C/SZ catalyst
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Supported carbided molybdena catalysts was prepared by treating MoO3/sulfated zirconia in methane/hydrogen (1:4 volumetric ratio) at 923?K. Characterisation shows the oxide to be different from the carbide phase. Carburisation did not induce phase change of the support with the tetragonal phase remaining dominant but did results in some changes to the textural properties. Lewis acid site density was constant in transforming from oxide to carbide forms while Br?nsted acidity site densities was diminished by ca 10% to give a Br?nsted/Lewis density ratio 2.46 in the carbide form. The ratio of hydrogenation sites to (Br?nsted) acid sites on the carbidic form of the catalyst was 0.12. Increasing temperature and decreasing WHSV augmented heptane conversion but leads to multiple cracking. Analysis of the product distribution as a function of conversion or as a function of temperature implied that the reaction did not simply proceed via a single consecutive reaction pathway Conversion increased the research octane number (RON) due to of the increased fraction of pentane isomers.
- Oloye,McCue,Anderson
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p. 246 - 256
(2016/10/05)
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- Cyclic bent allene hydrido-carbonyl complexes of ruthenium: Highly active catalysts for hydrogenation of olefins
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A new family of ruthenium complexes bearing the carbodicarbene-type ligand "cyclic bent allene" (CBA) have been synthesized from the common precursor RuHCl(CO)(PPh3)3. Complexes were evaluated for catalytic activity in the room-temperature hydrogenation of unactivated olefins and were found to be significantly more active than known ruthenium hydrido-carbonyl phosphine or NHC complexes. In particular, RuH(OSO2CF3)(CO)(SIMes)(CBA) was found to be among the most active hydrogenation catalysts, achieving comparable activity to Crabtree's catalyst in the hydrogenation of unactivated trisubstituted olefins and superior activity in the hydrogenation of styrene derivatives in side-by-side catalytic runs. RuH(OSO2CF3)(CO)(SIMes)(CBA) was also found to be highly active in olefin selective hydrogenation in the presence of a variety of unsaturated functional groups, and can achieve exceptional diastereoselectivity in functional-group-directed hydrogenations at very low catalyst loadings.
- Pranckevicius, Conor,Fan, Louie,Stephan, Douglas W.
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p. 5582 - 5589
(2015/05/13)
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- Cyclic bent allene metal complexes
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The present invention provides stable, cyclic bent allene metal complexes and methods of conducting chemical processes, preferably olefin hydrogenation, comprising contacting an olefin substrate, preferably an unsaturated polymer, with a cyclic bent allene metal complex as described herein, under hydrogenation conditions. wherein M is a transition metal selected from Groups 6-11 of the periodic table, L1 is a cyclic bent allene ligand according to the general formula (II)
- -
-
Paragraph 0189
(2015/12/18)
-
- Catalytic Ketone Hydrodeoxygenation Mediated by Highly Electrophilic Phosphonium Cations
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Ketones are efficiently deoxygenated in the presence of silane using highly electrophilic phosphonium cation (EPC) salts as catalysts, thus affording the corresponding alkane and siloxane. The influence of distinct substitution patterns on the catalytic effectiveness of several EPCs was evaluated. The deoxygenation mechanism was probed by DFT methods.
- Mehta, Meera,Holthausen, Michael H.,Mallov, Ian,Pérez, Manuel,Qu, Zheng-Wang,Grimme, Stefan,Stephan, Douglas W.
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p. 8250 - 8254
(2015/07/07)
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- Mechanism of n-butane skeletal isomerization on H-mordenite and Pt/H-mordenite
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Kinetics and isotope labeling experiments were used to investigate the reaction pathways of n-butane on H-mordenite and Pt/H-mordenite at atmospheric pressure and temperatures of 543-583 K. Butenes, either formed on the catalyst or present in the feed, controlled the relative rates of mono- and bimolecular reaction pathways. The true activation energy for isobutane formation was found to be 120-134 kJ/mol. The reaction order for isobutane formation with respect to n-butene on Pt/H-mordenite was 1.0-1.2, consistent with a predominately monomolecular route of formation. An order close to 2 for disproportionation products indicated a bimolecular route of formation. An increase of the butene concentration from less than 20 ppm to about 120 ppm greatly increased the rate of bimolecular skeletal isomerization, as determined from conversion of 1,4-13C2-n-butane. The findings explain how reaction conditions affect product selectivity and clarify the controversy around butane isomerization on solid acids.
- Wulfers, Matthew J.,Jentoft, Friederike C.
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p. 507 - 519
(2015/03/18)
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- CATALYTIC ISOMERIZATION OF PENTANE USING IONIC LIQUIDS
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Processes for the disproportionation and isomerization of a C5 hydrocarbon feed using a liquid catalyst comprising an ionic liquid and a halocarbon carbocation promoter are described. The ionic liquid is unsupported, and the reactions occur at temperatures below about 200° C.
- -
-
Paragraph 0103
(2015/02/05)
-
- CATALYTIC ISOMERIZATION OF HEPTANE USING IONIC LIQUIDS
-
Processes for the disproportionation and isomerization of a C7 hydrocarbon feed using a liquid catalyst comprising an ionic liquid and a carbocation promoter are described. The ionic liquid is unsupported, and the reactions occur at temperatures below about 200° C.
- -
-
Paragraph 104
(2015/02/05)
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- CATALYTIC DISPROPORTIONATION OF HEPTANE USING IONIC LIQUIDS
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Processes for the disproportionation and isomerization of a C7 hydrocarbon feed using a liquid catalyst comprising an ionic liquid and a carbocation promoter are described. The ionic liquid is unsupported, and the reactions occur at temperatures below about 200° C.
- -
-
Paragraph 0102
(2015/02/05)
-
- CATALYTIC DISPROPORTIONATION OF PENTANE USING IONIC LIQUIDS
-
Processes for the disproportionation and isomerization of a C5 hydrocarbon feed using a liquid catalyst comprising an ionic liquid and a carbocation promoter are described. The ionic liquid is unsupported, and the reactions occur at temperatures below about 200° C.
- -
-
Paragraph 0102
(2015/02/05)
-
- CATALYTIC ISOMERIZATION OF PARAFFINS USING IONIC LIQUIDS
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Processes for the disproportionation and isomerization of a hydrocarbon feed using a liquid catalyst comprising an ionic liquid and a carbocation promoter are described. The ionic liquid is unsupported, and the reactions occur at temperatures below about 200° C.
- -
-
Paragraph 0103
(2015/02/05)
-
- CATALYTIC DISPROPORTIONATION OF PARAFFINS USING IONIC LIQUIDS
-
Processes for the disproportionation and isomerization of a hydrocarbon feed using a liquid catalyst comprising an ionic liquid and a carbocation promoter are described. The ionic liquid is unsupported, and the reactions occur at temperatures below about 200° C.
- -
-
Paragraph 0102
(2015/02/05)
-
- CATALYTIC CONVERSION OF ALCOHOLS HAVING AT LEAST THREE CARBON ATOMS TO HYDROCARBON BLENDSTOCK
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A method for producing a hydrocarbon blendstock, the method comprising contacting at least one saturated acyclic alcohol having at least three and up to ten carbon atoms with a metal-loaded zeolite catalyst at a temperature of at least 100°C and up to 550°C, wherein the metal is a positively-charged metal ion, and the metal-loaded zeolite catalyst is catalytically active for converting the alcohol to the hydrocarbon blendstock, wherein the method directly produces a hydrocarbon blendstock having less than 1 vol% ethylene and at least 35 vol% of hydrocarbon compounds containing at least eight carbon atoms.
- -
-
Paragraph 0062; 0063
(2015/01/16)
-
- Catalytic Production of Branched Small Alkanes from Biohydrocarbons
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Squalane, C30 algae-derived branched hydrocarbon, was successfully converted to smaller hydrocarbons without skeletal isomerization and aromatization over ruthenium on ceria (Ru/CeO2). The internal CH2-CH2 bonds located between branches are preferably dissociated to give branched alkanes with very simple distribution as compared with conventional methods using metal-acid bifunctional catalysts.
- Oya, Shin-Ichi,Kanno, Daisuke,Watanabe, Hideo,Tamura, Masazumi,Nakagawa, Yoshinao,Tomishige, Keiichi
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p. 2472 - 2475
(2015/08/24)
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- Evidence for geometric effects in neopentane conversion on PdAu catalysts
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Silica-supported Pd and shell/core PdAu nanoparticles of a similar size were evaluated for neopentane conversion. Monometallic Pd exhibited poor neopentane isomerization selectivity in favor of high selectivity to primary and secondary hydrogenolysis products. Similarly sized PdAu catalysts of increasing Pd weight loading were synthesized to evaluate the effect of increasing Pd monolayers on neopentane conversion. All PdAu catalysts had neopentane conversion selectivity within the range of monometallic Pd catalysts from previous work (~5-30%). However, there was an inverse relationship between Pd weight loading and neopentane isomerization selectivity. The increase in isomerization selectivity did not correlate to a decrease in heats of adsorption as seen with monometallic Pd catalysts, but was correlated with the catalyst surface structure which suggests a geometric effect as the cause for changes in catalytic performance rather than an electronic effect.
- Childers, David J.,Schweitzer, Neil M.,Shahri, Seyed Mehdi Kamali,Rioux, Robert M.,Miller, Jeffrey T.,Meyer, Randall J.
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p. 4366 - 4377
(2015/02/19)
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- Half sandwich ruthenium(ii) hydrides: Hydrogenation of terminal, internal, cyclic and functionalized olefins
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Bis(1,2,3-triazolylidene) silver(i) complex 1a was reacted with [RuCl2(p-cymene)]2 to give the ruthenium complex [PhCH2N2(NMe)C2(C6H4CF3)]RuCl2(p-cymene) (2a) as major product in addition to the minor C(sp2)-H activated product [PhCH2N2(NMe)C2(C6H3CF3)]RuCl(p-cymene) (2a′). Similar ruthenium complexes 2b, 2c, 2d and 2e with general formula RuCl2(p-cymene)(NHC) (NHC = MesCH2N2(NMe)C2Ph 2b, PhCH2N2(NMe)C2Ph 2c, TripCH2N2(NMe)C2Ph 2d, IMes 2e) were also synthesized. Subsequent reaction of Me3SiOSO2CF3 with 2a and 2b resulted in cationic ruthenium species [(PhCH2N2(NMe)C2(C6H4CF3))RuCl(p-cymene)][OSO2CF3] (3a) and [(MesCH2N2(NMe)C2Ph)RuCl(p-cymene)][OSO2CF3] (3b), respectively. Complexes 3a and 3b dissolved in CD3CN to give [(PhCH2N2(NMe)C2(C6H4CF3))RuCl(CD3CN)(p-cymene)][OSO2CF3] (4a) and [(MesCH2N2(NMe)C2Ph)RuCl(CD3CN)(p-cymene)][OSO2CF3] (4b), respectively. Cationic ruthenium species 4a and 4b failed to show catalytic activity towards hydrogenation of olefins. Ruthenium(ii) complexes 2b-e with the general formula RuCl2(p-cymene)(NHC) were reacted with Et3SiH to generate a series of ruthenium(ii) hydrides 5b-e. These compounds 5b-e are effective catalysts for the hydrogenation of terminal, internal and cyclic and functionalized olefins.
- Bagh, Bidraha,Stephan, Douglas W.
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p. 15638 - 15645
(2015/01/08)
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- Mesoporous organic Pd-containing catalysts for the selective hydrogenation of conjugated hydrocarbons
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Palladium catalysts supported on ordered organic mesoporous polymers were synthesized. The catalysts are characterized by the narrow size distribution of palladium nanoparticles with an average particle size of 2.2-5.2 nm. They demonstrate high catalytic activity and selectivity in phenylacetylene hydrogenation (896-2590 min-1, selectivity 89-98%). High activity and selectivity for alkenes are observed in the hydrogenation of conjugated dienes (for isoprene, TOF = 1850-5000 min-1, selectivity 99%; for 2,5-dimethyl-2,4-hexadiene, TOF = = 1294-2400 min-1, selectivity 100%; for 1,4-diphenyl-1,3-butadiene, TOF = 14-22 min-1, selectivity 7-16%). A dependence of the selectivity on the nature of the support and substrate was found for the hydrogenation of 1,4-diphenyl-1,3-butadiene.
- Karakhanov,Maksimov,Aksenov,Kuznetsov,Filippova,Kardashev,Volkov
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p. 1710 - 1716
(2015/05/20)
-
- Synthesis and hydrogenation activity of iron dialkyl complexes with chiral bidentate phosphines
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The activity of bis(phosphine) iron dialkyl complexes for the asymmetric hydrogenation of alkenes has been evaluated. High-throughput experimentation was used to identify suitable iron-phosphine combinations using the displacement of pyridine from py2Fe(CH2SiMe3)2 for precatalyst formation. Preparative-scale synthesis of a family of bis(phosphine) iron dialkyl complexes was also achieved using both ligand substitution and salt metathesis methods. Each of the isolated organometallic iron complexes was established as a tetrahedral and hence high-spin ferrous compound, as determined by M?ssbauer spectroscopy, magnetic measurements, and, in many cases, X-ray diffraction. One example containing a Josiphos-type ligand, (SL-J212-1)Fe(CH2SiMe3)2, proved more active than other isolated iron dialkyl precatalysts. Filtration experiments and the lack of observed enantioselectivity support dissociation of the phosphine ligand upon activation with dihydrogen and formation of catalytically active heterogeneous iron. The larger six-membered chelate is believed to reduce the coordination affinity of the phosphine for the iron center, enabling metal particle formation.
- Hoyt, Jordan M.,Shevlin, Michael,Margulieux, Grant W.,Krska, Shane W.,Tudge, Matthew T.,Chirik, Paul J.
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p. 5781 - 5790
(2015/02/19)
-
- Modifying structure-sensitive reactions by addition of Zn to Pd
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Silica-supported Pd and PdZn nanoparticles of a similar size were evaluated for neopentane hydrogenolysis/isomerization and propane hydrogenolysis/ dehydrogenation. Monometallic Pd showed high neopentane hydrogenolysis selectivity. Addition of small amounts of Zn to Pd lead Pd-Zn scatters in the EXAFS spectrum and an increase in the linear bonded CO by IR. In addition, the neopentane turnover rate decreased by nearly 10 times with little change in the selectivity. Increasing amounts of Zn lead to greater Pd-Zn interactions, higher linear-to-bridging CO ratios by IR and complete loss of neopentane conversion. Pd NPs also had high selectivity for propane hydrogenolysis and thus were poorly selective for propylene. The PdZn bimetallic catalysts, however, were able to preferentially catalyze dehydrogenation, were not active for propane hydrogenolysis, and thus were highly selective for propylene formation. The decrease in hydrogenolysis selectivity was attributed to the isolation of active Pd atoms by inactive metallic Zn, demonstrating that hydrogenolysis requires a particular reactive ensemble whereas propane dehydrogenation does not.
- Childers, David J.,Schweitzer, Neil M.,Shahari, Seyed Mehdi Kamali,Rioux, Robert M.,Miller, Jeffrey T.,Meyer, Randall J.
-
-
- Bis(imino)pyridine cobalt-catalyzed dehydrogenative silylation of alkenes: Scope, mechanism, and origins of selective allylsilane formation
-
The aryl-substituted bis(imino)pyridine cobalt methyl complex, ( MesPDI)CoCH3 (MesPDI = 2,6-(2,4,6-Me 3C6H2-N=CMe)2C5H 3N), promotes the catalytic dehydrogenative silylation of linear α-olefins to selectively form the corresponding allylsilanes with commercially relevant tertiary silanes such as (Me3SiO) 2MeSiH and (EtO)3SiH. Dehydrogenative silylation of internal olefins such as cis- and trans-4-octene also exclusively produces the allylsilane with the silicon located at the terminus of the hydrocarbon chain, resulting in a highly selective base-metal-catalyzed method for the remote functionalization of C-H bonds with retention of unsaturation. The cobalt-catalyzed reactions also enable inexpensive α-olefins to serve as functional equivalents of the more valuable α, ω-dienes and offer a unique method for the cross-linking of silicone fluids with well-defined carbon spacers. Stoichiometric experiments and deuterium labeling studies support activation of the cobalt alkyl precursor to form a putative cobalt silyl, which undergoes 2,1-insertion of the alkene followed by selective β-hydrogen elimination from the carbon distal from the large tertiary silyl group and accounts for the observed selectivity for allylsilane formation.
- Atienza, Crisita Carmen Hojilla,Diao, Tianning,Weller, Keith J.,Nye, Susan A.,Lewis, Kenrick M.,Delis, Johannes G. P.,Boyer, Julie L.,Roy, Aroop K.,Chirik, Paul J.
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supporting information
p. 12108 - 12118
(2014/10/16)
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- METHOD OF FORMING C5 DI-OLEFINS
-
A process is disclosed that includes reacting a C1 source with n-butene to form a C-5 diolefin.
- -
-
Paragraph 0086; 0087
(2014/09/30)
-
- Effects of oxidant acid treatments on carbon-templated hierarchical SAPO-11 materials: Synthesis, characterization and catalytic evaluation in n-decane hydroisomerization
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Hierarchical SAPO-11 was synthesized using a commercial Merck carbon as template. Oxidant acid treatments were performed on the carbon matrix in order to investigate its influence on the properties of SAPO-11. Structural, textural and acidic properties of the different materials were evaluated by XRD, SEM, N2 adsorption, pyridine adsorption followed by IR spectroscopy and thermal analyses. The catalytic behavior of the materials (with 0.5 wt.% Pt, introduced by mechanic mixture with Pt/Al2O3), were studied in the hydroisomerization of n-decane. The hierarchical samples showed higher yields in monobranched isomers than typical microporous SAPO-11, as a direct consequence of the modification on both porosity and acidity, the later one being the most predominant.
- Bértolo, Raquel,Silva, Jo?o M.,Ribeiro, Filipa,Maldonado-Hódar, Francisco J.,Fernandes, Auguste,Martins, Angela
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p. 230 - 237
(2014/12/10)
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- Catalytic hydrogenation activity and electronic structure determination of bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes
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The bis(arylimidazol-2-ylidene)pyridine cobalt methyl complex, ( iPrCNC)CoCH3, was evaluated for the catalytic hydrogenation of alkenes. At 22 C and 4 atm of H2 pressure, ( iPrCNC)CoCH3 is an effective precatalyst for the hydrogenation of sterically hindered, unactivated alkenes such as trans-methylstilbene, 1-methyl-1-cyclohexene, and 2,3-dimethyl-2-butene, representing one of the most active cobalt hydrogenation catalysts reported to date. Preparation of the cobalt hydride complex, (iPrCNC)CoH, was accomplished by hydrogenation of (iPrCNC)CoCH3. Over the course of 3 h at 22 C, migration of the metal hydride to the 4-position of the pyridine ring yielded (4-H2-iPrCNC)CoN2. Similar alkyl migration was observed upon treatment of (iPrCNC)CoH with 1,1-diphenylethylene. This reactivity raised the question as to whether this class of chelate is redox-active, engaging in radical chemistry with the cobalt center. A combination of structural, spectroscopic, and computational studies was conducted and provided definitive evidence for bis(arylimidazol-2- ylidene)pyridine radicals in reduced cobalt chemistry. Spin density calculations established that the radicals were localized on the pyridine ring, accounting for the observed reactivity, and suggest that a wide family of pyridine-based pincers may also be redox-active.
- Yu, Renyuan Pony,Darmon, Jonathan M.,Milsmann, Carsten,Margulieux, Grant W.,Stieber, S. Chantal E.,Debeer, Serena,Chirik, Paul J.
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supporting information
p. 13168 - 13184
(2013/09/24)
-
- A novel monolith catalyst of plate-type anodic alumina for the hydrolysis of dimethyl ether
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A novel monolith catalyst of plate-type anodic alumina was applied in the dimethyl ether (DME) hydrolysis reaction system. The reactivity of the anodic alumina with hydration treatments in DME hydrolysis reaction was investigated. The preferred hydration-treated temperature was found to be 80 C and the anodic Al2O3/Al monolith exhibited higher activity than the commercial Al2O3 in DME hydrolysis reaction. Meanwhile, the anodic Al2O3/Al monolith was proven to have higher MeOH effluent mole percentage with less unfavorable side reactions than the ZSM-5 catalyst. The anodic γ-Al2O3/Al monolith had just 0.85% coking while the ZSM-5 catalyst had 8.81% after 100 h of continuous experiments.
- Zhang, Qi,Sun, Dongmei,Fan, Feiyue,Zhang, Qinghui,Zhu, Zibin
-
-
- The methylation of alkenes to triptyls with dimethyl carbonate
-
A series of methylating reagents: methanol, dimethylether and dimethylcarbonate, have been evaluated for their ability to methylate 2,3-dimethylbut-2-ene to yield triptyls (a mixture of triptane and triptene). The results presented highlight that dimethylcarbonate is a far superior methylating agent compared to methanol or dimethylether, providing a higher yield of triptyls.
- Armitage, Gareth G.,Bonati, Matteo L. M.,Guo, Neng,Gaemers, Sander,Shabaker, John W.
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p. 370 - 374
(2013/05/21)
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- A descriptor for the relative propagation of the aromatic- and olefin-based cycles in methanol-to-hydrocarbons conversion on H-ZSM-5
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The observed product distribution in methanol-to-hydrocarbons (MTH) catalysis can be rationalized based on the relative rates of propagation of the aromatic- and olefin-based cycles that operate on the zeolite catalyst. We report that the ratio of ethene to 2-methylbutane + 2-methyl-2-butene (ethene/2MB) yield can be used to describe the propagation of aromatic and olefin methylation/cracking cycles. The co-reaction of 12C-ethene with 13C-dimethyl ether (DME) shows that the rate of DME conversion (1.62 mol C (mol Al s)-1) is ~20 times faster than ethene conversion (0.08 mol C (mol Al s)-1), suggesting that ethene can be considered as terminal product for MTH at 623 K. At iso-conversion conditions at 548 K, propene is co-fed with DME to increase propagation of the olefin-based cycle and correspondingly a 1.7-fold decrease in the ethene/2MB yield is observed. Similarly, the co-reaction of toluene with DME increases propagation of the aromatic-based cycle and a 2.1-fold increase in the ethene/2MB yield is observed. The ethene/2MB yield also increased by a factor of 2 as DME conversion increased from 5% to 62%, which is consistent with the observed concurrent increase in selectivity to ethene and methylbenzenes. For the reaction of DME alone, increasing the temperature from 548 K to 723 K increases the propagation of the olefin-based cycle and a corresponding decrease in the ethene/2MB yield from 4.7 to 1.3 is also observed. The ethene/2MB yield varies systematically with feed composition, conversion, and temperature, showing that this ratio describes the relative propagation of the aromatic to olefin methylation/cracking cycles in MTH conversion on H-ZSM-5.
- Ilias, Samia,Khare, Rachit,Malek, Andre,Bhan, Aditya
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p. 135 - 140
(2013/07/05)
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- Identification of carbonaceous deposits formed on H-mordenite during alkane isomerization
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To identify hydrocarbon surface species accumulating during alkane isomerization, a strategy involving in situ UV-vis and FTIR spectroscopies, reaction of formed species with various bases, adsorption of reference compounds, and extraction of spent catalysts was applied. During conversion of n-butane or n-pentane on H-mordenite at reaction temperatures below ≈550 K, species characterized by an intense absorption band at a wavelength of 292-296 nm were observed by in situ diffuse reflectance UV-vis spectroscopy. Species with a comparable electronic signature formed after adsorption of 1-butene, 1-pentene, or 1-hexene, indicating that olefins are intermediates in the formation of carbonaceous deposits from alkanes. The chromophore was largely invariant to the carbon chain length and the species were identified as alkyl-substituted cyclopentenyl cations. Carbonaceous deposits formed at temperatures higher than ≈550 K consisted of methyl-substituted naphthalenes, anthracenes, and tetracenes; these species also existed as stable cations on the zeolite during catalysis, producing a broad absorption at 350-500 nm. The polycyclic aromatic species were neutralized by water vapor, whereas the alkyl-substituted cyclopentenyl cations required a stronger base, such as ammonia.
- Wulfers, Matthew J.,Jentoft, Friederike C.
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p. 204 - 213
(2013/09/23)
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