- Rational Preparation of Well-Defined Multinuclear Iridium-Aluminum Polyhydride Clusters and Comparative Reactivity
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We report an original alkane elimination approach, entailing the protonolysis of triisobutylaluminum by the acidic hydrides from Cp*IrH4. This strategy allows access to a series of well-defined tri- and tetranuclear iridium aluminum polyhydride clusters, depending on the stoichiometry: [Cp*IrH3Al(iBu)2]2(1), [Cp*IrH2Al(iBu)]2(2), [(Cp*IrH3)2Al(iBu)] (3), and [(Cp*IrH3)3Al] (4). Contrary to most transition-metal aluminohydride complexes, which can be considered as [AlHx+3]x-aluminates and LnM+moieties, the situation here is reversed: These complexes have original structures that are best described as [Cp*IrHx]n-iridate units surrounding cationic Al(III) fragments. This is corroborated by reactivity studies, which show that the hydrides are always retained at the iridium sites and that the [Cp*IrH3]-moieties are labile and can be transmetalated to yield potassium ([KIrCp*H3], 8) or silver (([AgIrCp*H3]n, 10) derivatives of potential synthetic interest. DFT calculations show that the bonding situation can vary in these systems, from 3-center 2-electron hydride-bridged Lewis adducts of the form Ir-H←Al to direct polarized metal-metal interaction from donation of d-electrons of Ir to the Al metal, and both types of interactions take place to some extent in each of these clusters.
- Camp, Clément,Del Rosal, Iker,Escomel, Léon,Jeanneau, Erwann,Maron, Laurent,Robin, Emmanuel,Soulé, Na?me,Thieuleux, Chloé
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- Synthesis and catalytic performance of zeolite-Y supported on silicon carbide in n-heptane cracking
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In this work, we demonstrate a facile approach for the synthesis of zeolite-Y crystals (size, ca. ～400 nm) supported on silicon carbide (SiC) with the assistance of the cationic template (polydiallyldimethylammonium chloride, PDDA). The polymeric cationic template used to treat SiC particles induces a positive charge on SiC surface which electrostatically attracts negatively charged aluminosilicate seeds and promotes the growth of zeolite (ZY) particles over SiC, thus leading to the formation of stable ZY?SiC supported catalysts. The supported ZY catalysts with different weight ratio of ZY and SiC were synthesized and characterized by various techniques such as XRD, SEM, SEM-EDX, SEM-mapping, TEM, STEM, FT-IR, 27Al MAS NMR and N2 sorption. The characterization of the supported ZY catalysts suggests the uniform growth of ZY particles over SiC together with the creation of hierarchical micro-mesopores assembly. In the catalytic cracking of n-heptane, the catalyst ZY?SiC-50 displayed a remarkable improvement in reaction rate when compared to commercial zeolite-Y (CBV-600) amounting to 3.5 folds enhancement. Interestingly, the light olefins yield is also substantially improved. At WHSV of 8 h?1 and 475 °C, the highest light olefin yield (24–36 %) was achieved over ZY?SiC-50 whereas the reference catalyst, CBV-600 produced lower light olefins yield (7–17 %). Moreover, the supported ZY catalyst exhibited less deactivation rates. This improved performance is attributed to the hierarchical micro-mesopores assembly created by the homogeneous dispersion of zeolite crystals on SiC which offers fast diffusion pathways for the reactants and enhanced accessibility to active sites thus leading to higher observed reaction rates and fast diffusion of products thus minimizing the occurrence of side reactions.
- Alhassan, Saeed M.,Berthod, Mikael,Dabbawala, Aasif A.,Joseph, Tony,Khan, Shaihroz,Mittal, Hemant,Morin, Stephane,Singaravel, Gnana,Vaithilingam, Balasubramanian V.,Wahedi, Yasser Al
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- PREPARATION METHOD FOR PREPARING A CATALYST BASED ON IRON NANOPARTICLES, COBALT NANOPARTICLES OR ALLOYS THEREOF, THE CATALYST THUS PREPARED AND USE OF THE CATALYST FOR THE SELECTIVE HYDROGENATION OF CARBON DIOXIDE TO ISOBUTANE
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The present invention describes a preparation method for preparing a catalyst made up of a Fe and Co metal alloy in several ratios in the form of nanoparticles embedded in a graphitic carbon matrix. Another object of the invention is also the prepared catalyst which in a surprising manner selectively catalyses the hydrogenation of carbon dioxide into isobutane.
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Page/Page column 14-15; 17-18
(2020/06/19)
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- Impact of the Spatial Organization of Bifunctional Metal–Zeolite Catalysts on the Hydroisomerization of Light Alkanes
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Improving product selectivity by controlling the spatial organization of functional sites at the nanoscale is a critical challenge in bifunctional catalysis. We present a series of composite bifunctional catalysts consisting of one-dimensional zeolites (ZSM-22 and mordenite) and a γ-alumina binder, with platinum particles controllably deposited either on the alumina binder or inside the zeolite crystals. The hydroisomerization of n-heptane demonstrates that the catalysts with platinum particles on the binder, which separates platinum and acid sites at the nanoscale, leads to a higher yield of desired isomers than catalysts with platinum particles inside the zeolite crystals. Platinum particles within the zeolite crystals impose pronounced diffusion limitations on reaction intermediates, which leads to secondary cracking reactions, especially for catalysts with narrow micropores or large zeolite crystals. These findings extend the understanding of the ??intimacy criterion” for the rational design of bifunctional catalysts for the conversion of low-molecular-weight reactants.
- Cheng, Kang,Harmel, Justine,Oenema, Jogchum,Sunley, Glenn,Yoshida, Hideto,Ze?evi?, Jovana,Zhang, Zhaorong,de Jong, Krijn P.,van der Wal, Lars I.
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supporting information
p. 3592 - 3600
(2020/02/05)
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- Decarbonylative ether dissection by iridium pincer complexes
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A unique chain-rupturing transformation that converts an ether functionality into two hydrocarbyl units and carbon monoxide is reported, mediated by iridium(i) complexes supported by aminophenylphosphinite (NCOP) pincer ligands. The decarbonylation, which involves the cleavage of one C-C bond, one C-O bond, and two C-H bonds, along with formation of two new C-H bonds, was serendipitously discovered upon dehydrochlorination of an iridium(iii) complex containing an aza-18-crown-6 ether macrocycle. Intramolecular cleavage of macrocyclic and acyclic ethers was also found in analogous complexes featuring aza-15-crown-5 ether or bis(2-methoxyethyl)amino groups. Intermolecular decarbonylation of cyclic and linear ethers was observed when diethylaminophenylphosphinite iridium(i) dinitrogen or norbornene complexes were employed. Mechanistic studies reveal the nature of key intermediates along a pathway involving initial iridium(i)-mediated double C-H bond activation. This journal is
- Yoo, Changho,Dodge, Henry M.,Farquhar, Alexandra H.,Gardner, Kristen E.,Miller, Alexander J.M.
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p. 12130 - 12138
(2020/11/26)
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- Hydrogenative metathesis of enynes via piano-stool ruthenium carbene complexes formed by alkyne gem-hydrogenation
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The only recently discovered gem-hydrogenation of internal alkynes is a fundamentally new transformation, in which both H atoms of dihydrogen are transferred to the same C atom of a triple bond while the other position transforms into a discrete metal carbene complex. [Cp?RuCl]4 is presently the catalyst of choice: the resulting piano-stool ruthenium carbenes can engage a tethered alkene into either cyclopropanation or metathesis, and a prototypical example of such a reactive intermediate with an olefin ligated to the ruthenium center has been isolated and characterized by X-ray diffraction. It is the substitution pattern of the olefin that determines whether metathesis or cyclopropanation takes place: a systematic survey using alkenes of largely different character in combination with a computational study of the mechanism at the local coupled cluster level of theory allowed the preparative results to be sorted and an intuitive model with predictive power to be proposed. This model links the course of the reaction to the polarization of the double bond as well as to the stability of the secondary carbene complex formed, if metathesis were to take place. The first application of "hydrogenative metathesis"to the total synthesis of sinularones E and F concurred with this interpretation and allowed the proposed structure of these marine natural products to be confirmed. During this synthesis, it was found that gem-hydrogenation also provides opportunities for C-H functionalization. Moreover, silylated alkynes are shown to participate well in hydrogenative metathesis, which opens a new entry into valuable allylsilane building blocks. Crystallographic evidence suggests that the polarized [Ru-Cl] bond of the catalyst interacts with the neighboring R3Si group. Since attractive interligand Cl/R3Si contacts had already previously been invoked to explain the outcome of various ruthenium-catalyzed reactions, including trans-hydrosilylation, the experimental confirmation provided herein has implications beyond the present case.
- Peil, Sebastian,Bistoni, Giovanni,Goddard, Richard,Fürstner, Alois
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supporting information
p. 18541 - 18553
(2020/11/17)
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- Room Temperature Acceptorless Alkane Dehydrogenation from Molecular σ-Alkane Complexes
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The non-oxidative catalytic dehydrogenation of light alkanes via C-H activation is a highly endothermic process that generally requires high temperatures and/or a sacrificial hydrogen acceptor to overcome unfavorable thermodynamics. This is complicated by alkanes being such poor ligands, meaning that binding at metal centers prior to C-H activation is disfavored. We demonstrate that by biasing the pre-equilibrium of alkane binding, by using solid-state molecular organometallic chemistry (SMOM-chem), well-defined isobutane and cyclohexane σ-complexes, [Rh(Cy2PCH2CH2PCy2)(η: η-(H3C)CH(CH3)2][BArF4] and [Rh(Cy2PCH2CH2PCy2)(η: η-C6H12)][BArF4] can be prepared by simple hydrogenation in a solid/gas single-crystal to single-crystal transformation of precursor alkene complexes. Solid-gas H/D exchange with D2 occurs at all C-H bonds in both alkane complexes, pointing to a variety of low energy fluxional processes that occur for the bound alkane ligands in the solid-state. These are probed by variable temperature solid-state nuclear magnetic resonance experiments and periodic density functional theory (DFT) calculations. These alkane σ-complexes undergo spontaneous acceptorless dehydrogenation at 298 K to reform the corresponding isobutene and cyclohexadiene complexes, by simple application of vacuum or Ar-flow to remove H2. These processes can be followed temporally, and modeled using classical chemical, or Johnson-Mehl-Avrami-Kologoromov, kinetics. When per-deuteration is coupled with dehydrogenation of cyclohexane to cyclohexadiene, this allows for two successive KIEs to be determined [kH/kD = 3.6(5) and 10.8(6)], showing that the rate-determining steps involve C-H activation. Periodic DFT calculations predict overall barriers of 20.6 and 24.4 kcal/mol for the two dehydrogenation steps, in good agreement with the values determined experimentally. The calculations also identify significant C-H bond elongation in both rate-limiting transition states and suggest that the large kH/kD for the second dehydrogenation results from a pre-equilibrium involving C-H oxidative cleavage and a subsequent rate-limiting β-H transfer step.
- McKay, Alasdair I.,Bukvic, Alexander J.,Tegner, Bengt E.,Burnage, Arron L.,Mart?nez-Mart?nez, Antonio J.,Rees, Nicholas H.,Macgregor, Stuart A.,Weller, Andrew S.
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supporting information
p. 11700 - 11712
(2019/08/20)
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- Hydrogen Activation and Hydrogenolysis Facilitated by Late-Transition-Metal-Aluminum Heterobimetallic Complexes
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Previously reported heterobimetallic rhodium-aluminum and iridium-aluminum alkyl complexes are shown to activate hydrogen, generating the corresponding alkane. Kinetic data indicate a mechanistic difference between the iridium- A nd rhodium-based systems. In both cases the transition metal is an active participant in the release of alkane from the aluminum center. For iridium-aluminum species, experimental mechanistic data suggest that multiple pathways occur concomitantly with each other: One being the oxidative addition of hydrogen followed by proton transfer resulting in alkane generation. Computational data indicate a reasonable barrier to formation of an iridium dihydride intermediate observed experimentally. In the case of the rhodium-aluminum species, hydrides are not observed spectroscopically, though a reasonable barrier to formation of this thermodynamically unstable species has been calculated. Alternative mechanistic possibilities are discussed and explored computationally. Cooperative hydrogenolysis mechanisms are computed to be energetically unfeasible for both metal centers.
- Charles, R. Malcolm,Yokley, Timothy W.,Schley, Nathan D.,Deyonker, Nathan J.,Brewster, Timothy P.
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p. 12635 - 12645
(2019/10/11)
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- Hydrocarbon Synthesis via Photoenzymatic Decarboxylation of Carboxylic Acids
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A recently discovered photodecarboxylase from Chlorella variabilis NC64A (CvFAP) bears the promise for the efficient and selective synthesis of hydrocarbons from carboxylic acids. CvFAP, however, exhibits a clear preference for long-chain fatty acids thereby limiting its broad applicability. In this contribution, we demonstrate that the decoy molecule approach enables conversion of a broad range of carboxylic acids by filling up the vacant substrate access channel of the photodecarboxylase. These results not only demonstrate a practical application of a unique, photoactivated enzyme but also pave the way to selective production of short-chain alkanes from waste carboxylic acids under mild reaction conditions.
- Zhang, Wuyuan,Ma, Ming,Huijbers, Mieke M. E.,Filonenko, Georgy A.,Pidko, Evgeny A.,Van Schie, Morten,De Boer, Sabrina,Burek, Bastien O.,Bloh, Jonathan Z.,Van Berkel, Willem J. H.,Smith, Wilson A.,Hollmann, Frank
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supporting information
p. 3116 - 3120
(2019/03/06)
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- Hydrogenation of CO2 into aromatics over a ZnCrO: X-zeolite composite catalyst
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A ZnCrOx-ZnZSM-5 composite catalyst was used for CO2 hydrogenation into hydrocarbons especially aromatics (Aro). 81.1% Aro selectivity in C5+ hydrocarbons (mainly C5-11) was obtained at 320 °C, corresponding to 19.9% CO2 conversion, 29.8% total hydrocarbons (HCt) selectivity and 69.7% C5+ selectivity in HCt. Our optimized STY of Aro is the highest ever reported.
- Zhang, Junfeng,Zhang, Meng,Chen, Shuyao,Wang, Xiaoxing,Zhou, Zeling,Wu, Yingquan,Zhang, Tao,Yang, Guohui,Han, Yizhuo,Tan, Yisheng
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supporting information
p. 973 - 976
(2019/01/23)
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- Conversion of n-Heptane, n-Butane, and Their Mixtures on Catalytic Systems Al2O3/WO 42– ?ZrO2 and HMOR/WO 42– ?ZrO2
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The conversion of n-C7H16, n-C4H10 and mixtures of C7H16: n-C4H10 = 1: 0.3 on the composite catalysts Al2O3/WO42– ?ZrO2 (A-WZ) and HMOR/ WO42– ? ZrO2 (M-WZ) at atmospheric pressure, H2/hydrocarbon = 3 and temperatures of 140°C-200°C was studied. A mixture of C7H16: n-C4H10 on M-WZ with high selectivity was converted into C5–C6 isomers. Systems, e.g., M-WZ can be promising catalysts for the joint processing of associated petroleum gas and gasoline into ecologically clean high-octane gasolines without aromatic components. However, the bifunctional interaction of n-heptane:n-butane was realized at certain lower temperatures.
- Abasov,Agayeva,Mamedova,Isayeva,Imanova,Iskenderova,Aliyeva,Zarbaliyev,Tagiyev
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p. 964 - 971
(2018/08/31)
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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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- Catalytic Conversion of Glycerol into Aromatic Hydrocarbons, Acrolein, and Glycerol Ethers on Zeolite Catalysts
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Abstract: The effect of the nature of zeolite catalysts H-ZSM-5, H-BETA, and SAPO-34 on the activity and selectivity in the conversion of glycerol into aromatic hydrocarbons, acrolein, and oxygenates (various glycerol ethers) was studied. H-ZSM-5 was foun
- Tarasov
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p. 2451 - 2454
(2019/01/03)
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- Reactions of the Ni(0) Compound Ni(PPh3)4 with Unactivated Alkyl Halides: Oxidative Addition Reactions Involving Radical Processes and Nickel(I) Intermediates
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Reactions of the nickel(0) compound NiL4 (L = PPh3) with alkyl halides RX involve initial inner-sphere halogen atom abstraction from the alkyl halides to form alkyl radicals R· and halonickel(I) metalloradical species NiX(PPh3)2,3. The radical pairs then undergo combination within the solvent cage to give the square planar nickel(II) compounds NiRX(PPh3)2. Radical intermediacy is demonstrated persuasively by observations that the relative rates vary in the orders tert-butyl > sec-butyl > n-butyl and RI > RBr > RCl, while density functional theory calculations indicate that the radical mechanism provides a lower energy pathway than do alternative, more conventional pathways. The product of the reaction of Ni(PPh3)4 with methyl iodide, NiMeI(PPh3)2, decomposes in solution to ethane and NiI(PPh3)2,3, but when RX = EtI, n-BuI, sec-BuI, tert-BuI, the alkyl-nickel products undergo rapid β-hydrogen elimination to give the hydride NiHI(PPh3)2 plus the corresponding alkene(s). Reactions also occur in which a portion of the alkyl radicals diffuses from the solvent cage and abstracts hydrogen from NiHI(PPh3)2 to form alkanes RH and Ni(I) species NiI(PPh3)2. As a result, NiHI(PPh3)2 is invariably a minor product while the major products are alkanes RH, alkenes R-H, and NiI(PPh3)2. Hydride NiHI(PPh3)2 is found to decompose to H2 and NiI(PPh3)2 but is stable at low temperatures where it exhibits unusual NMR behavior because of exchange involving free PPh3 and the bis- and trisphosphine species, NiHI(PPh3)2 and NiHI(PPh3)3. Present in all of the reactions are paramagnetic, substitution-labile Ni(I) metalloradical species. As a result, resonances of PPh3, ethylene, and the smaller iodoalkenes are generally broad and shifted because of exchange between free and coordinated ligands.
- Kehoe, Ryley,Mahadevan, Markshun,Manzoor, Adeela,McMurray, Gillian,Wienefeld, Patrick,Baird, Michael C.,Budzelaar, Peter H. M.
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supporting information
p. 2450 - 2467
(2018/08/21)
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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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- Selective conversion of bio-derived ethanol to renewable BTX over Ga-ZSM-5
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Selective conversion of bio-derived ethanol to benzene, toluene and xylenes (BTX) is desirable for producing renewable BTX. In this work, we show that addition of Ga to H-ZSM-5 leads to a two-fold increase in the BTX yield as compared with H-ZSM-5 when ethanol is converted over these zeolites at 450 °C and ambient pressure. Besides promoting BTX formation, Ga also plays an important role in enhancing molecular hydrogen production and suppressing hydrogen transfer reactions for light alkane formation. The ion exchange synthesis of Ga-ZSM-5 results in the majority of Ga at the outer surface of zeolite crystals as extra-zeolitic Ga2O3 particles and only a small fraction of Ga exchanging with the Br?nsted acid sites which appears to be responsible for higher ethanol conversion to BTX. The interface between H-ZSM-5 and Ga2O3 particles is not active since H-ZSM-5 and the physical mixture of β-Ga2O3/H-ZSM-5 furnish an almost identical product distribution. Hydrogen reduction of the physical mixtures facilitates movement of Ga to ion exchange locations and dramatically increases the BTX yield becoming comparable to those obtained over ion-exchanged Ga-ZSM-5, suggesting that exchanged Ga(iii) cations are responsible for the increased BTX production. A linear correlation between the BTX site time yield and exchanged Ga sites further confirms that Ga occupying cationic sites are active sites for enhancing BTX formation. Reduction of physical mixtures (β-Ga2O3/H-ZSM-5) also provides an economical and environmentally friendly non-aqueous method for large scale catalyst synthesis without sacrificing catalyst performance for ethanol conversion application.
- Li, Zhenglong,Lepore, Andrew W.,Salazar, Mariam F.,Foo, Guo Shiou,Davison, Brian H.,Wu, Zili,Narula, Chaitanya K.
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p. 4344 - 4352
(2017/09/28)
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- Production of Gasoline Fuel from Alga-Derived Botryococcene by Hydrogenolysis over Ceria-Supported Ruthenium Catalyst
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Hydrogenolysis of hydrogenated botryococcene (Hy-Bot) was conducted over various supported Ru catalysts, Ir/SiO2, and Pt/SiO2–Al2O3. Ru/CeO2 with very high dispersion showed the highest yield (70 %) of gasoline-range (C5–C12) alkanes at 513 K. The main gasoline-range products were dimethylalkanes. This yield is comparable to or higher than the gasoline yields from botryococcene in the literature, which were obtained at much higher temperature. Ir/SiO2 also showed a high fuel yield, but the activity was much lower than that with the Ru catalysts. The reaction over Pt/SiO2–Al2O3 slowed down before total conversion of Hy-Bot was achieved. Ru/CeO2 was stable in the hydrogenolysis of Hy-Bot without loss of activity and selectivity during reuses. The carbon balance was low for the hydrogenolysis of Hy-Bot over all catalysts if the main products are heavy hydrocarbons, whereas for the hydrogenolysis of squalane the carbon balance was kept near 100 %. 1H NMR spectra of the product mixture and thermogravimetric analyses of the product mixture and the recovered catalyst revealed that the formation of aromatic compounds, polymeric products, and coke was negligible for the carbon balance. In a model reaction using substrate compounds with a substructure of Hy-Bot, only 2,5-dimethylhexane, which has a C6 chain with two Cprimary?Ctertiary bonds, produced a cyclic product, 1,4-dimethylcyclohexane, which has a higher boiling point than the substrate. This dehydrocyclization reaction makes the product distribution in the hydrogenolysis of Hy-Bot more complex.
- Nakaji, Yosuke,Oya, Shin-Ichi,Watanabe, Hideo,Watanabe, Makoto M.,Nakagawa, Yoshinao,Tamura, Masazumi,Tomishige, Keiichi
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p. 2701 - 2708
(2017/07/28)
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- Effects of Co/Ce molar ratio and operating temperature on nanocatalyst performance in the Fischer-Tropsch synthesis
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Iron-cobalt-cerium three-metal nanoparticles have been obtained by a solvothermal method for converting synthesis gas into light olefins. The effect of various fabrication molar ratios of Co/Ce and the effect of the operating temperature (270-400 °C) on the activity and selectivity were demonstrated. The nanocatalyst with a 1:1/4 Co/Ce molar ratio at an operating temperature of 300 °C performed optimally in selectivity converting synthesis gas into light olefin. The nanocatalysts prepared with different Co/Ce molar ratios were characterized. The morphology, structure and magnetic behavior were established by SEM, EDX, FTIR, XRD and VSM ?techniques.
- Taherzadeh Lari, Tahereh,Mirzaei, Ali Akbar,Atashi, Hossein
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p. 34497 - 34507
(2017/07/22)
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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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- Effect of CO2on hydrogen absorption in Ti-Zr-Mn-Cr based AB2type alloys
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The effect of CO2on hydrogen absorption has been investigated for AB2type alloys of Ti0.515Zr0.485Mn1.2Cr0.8(Ti-Zr-Mn-Cr) and Ti0.515Zr0.485Mn1.2Cr0.8M0.1(Ti-Zr-Mn-Cr-M, M?=?Fe, Co, or Ni) in order to develop metal hydrides for a hydrogen purification and storage system. A magnitude of CO2poisoning tolerance was evaluated by comparing hydrogen absorption properties before and after CO2exposure. As the results, an order of CO2tolerance was Ti-Zr-Mn-Cr-Ni?2alloys have dependence of additive 3d-transition elements on CO2tolerance. Ti-Zr-Mn-Cr-Fe has the highest CO2tolerance among them. The additive of Fe and Co improves tolerance of CO2poisoning for hydrogen absorption properties. On the other hand, Ni element in AB2alloy decreases CO2tolerance. The estimated enthalpy change between CO2and the alloys surface was comparable to the formation of metal oxide. And the CO2-exposed AB2alloys after reacting with hydrogen desorbed methane gas. Therefore, CO2would dissociate to CO and O on the surface of alloys, and then oxygen atom reacts with the alloys.
- Hanada, Nobuko,Asada, Hirotaka,Nakagawa, Tessui,Higa, Hiroki,Ishida, Masayoshi,Heshiki, Daichi,Toki, Tomohiro,Saita, Itoko,Asano, Kohta,Nakamura, Yumiko,Fujisawa, Akitoshi,Miura, Shinichi
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p. 507 - 516
(2017/03/02)
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- Transition-Metal Oxos as the Lewis Basic Component of Frustrated Lewis Pairs
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The reaction of oxorhenium complexes that incorporate diamidopyridine (DAP) ligands with B(C6F5)3 results in the formation of classical Lewis acid-base adducts. The adducts effectively catalyze the hydrogenation of a variety of unactivated olefins at 100 °C. Control reactions with these complexes or B(C6F5)3 alone did not yield any hydrogenated products under these conditions. Mechanistic studies suggest a frustrated Lewis pair is generated between the oxorhenium DAP complexes and B(C6F5)3, which is effective at olefin hydrogenation. Thus, we demonstrate for the first time that the incorporation of a transition-metal oxo in a frustrated Lewis pair can have a synergistic effect and results in enhanced catalytic activity.
- Lambic, Nikola S.,Sommer, Roger D.,Ison, Elon A.
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supporting information
p. 4832 - 4842
(2016/05/09)
-
- 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 0082
(2016/07/05)
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- Synthesis of Al-MTW with low Si/Al ratios by combining organic and inorganic structure directing agents
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A rationalized combination of alkali cations and bulky dicationic organic structure directing agents (OSDAs) has allowed the synthesis of the Al-rich MTW zeolites with Si/Al ratios of ～12 and large pore accessibility. 27Al MAS NMR spectroscopy indicates that most of the aluminum atoms are in tetrahedral coordination in framework positions, and in situ infrared pyridine adsorption/desorption spectroscopy reveals strong Br?nsted acidity after cationic exchange for the Al-rich MTW. In addition, another MTW material with a Si/Al ratio of 30 has been synthesized under alkali-free conditions using a bulky dicationic molecule such as OSDA, the lowest Si/Al ratio being achieved for a MTW zeolite synthesized in the absence of alkali-cations in the synthesis media. The catalytic activity of these MTW materials has been tested for the n-decane cracking reaction, achieving higher catalytic activities and olefin yields than other related large pore zeolites.
- Paris, Cecilia,Martín, Nuria,Martínez-Triguero, Joaquín,Moliner, Manuel,Corma, Avelino
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p. 4140 - 4145
(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)
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- Tungsten(VI) Carbyne/Bis(carbene) Tautomerization Enabled by N-Donor SBA15 Surface Ligands: A Solid-State NMR and DFT Study
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Designing supported well-defined bis(carbene) complexes remains a key challenge in heterogeneous catalysis. The reaction of W(≡CtBu)(CH2tBu)3with amine-modified mesoporous SBA15 silica, which has vicinal silanol/silylamine pairs [(≡SiOH)(≡SiNH2)], leads to [(≡SiNH2?)(≡SiO?)W(≡CHtBu)(CH2tBu)2] and [(≡SiNH2?)(≡SiO?)W(=CHtBu)2(CH2tBu). Variable temperature,1H–1H 2D double-quantum,1H–13C HETCOR, and HETCOR with spin diffusion solid-state NMR spectroscopy demonstrate tautomerization between the alkyl alkylidyne and the bis(alkylidene) on the SBA15 surface. Such equilibrium is possible through the coordination of W to the surface [(≡Si?OH)(≡Si?NH2)] groups, which act as a [N,O] pincer ligand. DFT calculations provide a rationalization for the surface–complex tautomerization and support the experimental results. This direct observation of such a process shows the strong similarity between molecular mechanisms in homogeneous and heterogeneous catalysis. In propane metathesis (at 150 °C), the tungsten bis(carbene) tautomer is favorable, with a turnover number (TON) of 262. It is the highest TON among all the tungsten alkyl-supported catalysts.
- Bendjeriou-Sedjerari, Anissa,Sofack-Kreutzer, Julien,Minenkov, Yury,Abou-Hamad, Edy,Hamzaoui, Bilel,Werghi, Baraa,Anjum, Dalaver H.,Cavallo, Luigi,Huang, Kuo -Wei,Basset, Jean -Marie
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supporting information
p. 11162 - 11166
(2016/10/13)
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- Catalytic: N -pentane conversion on H-ZSM-5 at high pressure
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The effect of temperature (633-723 K), pressure (10-60 bar) and weight hourly space velocity (WHSV) (400-1500 gC5 gcat-1 h-1) on the conversion of n-pentane on H-[Al]ZSM-5 type catalysts has been investigated. Catalyst properties were tested using a packed-bed laboratory microreactor and reaction products were analyzed via online gas chromatography. 5-25% pentane conversion was observed at a pressure of 40 bar and temperatures in the range of 633-723 K. Reactant consumption rate approached saturation kinetics at pressures above 30 bar (～14% conversion, 673 K). At 40 bar and 673 K, increasing WHSV (400-1500 gC5 gcat-1 h-1) resulted in a reduction in pentane conversion (26-10%). In all cases, propane and butane were the major products, followed by heavier C6+ compounds and other lighter products (C1-C4 paraffins and olefins). Propane carbon selectivity increased from 24% at 633 K to 34% at 723 K, while butane carbon selectivity (～40%) was nearly constant. An inverse relationship between the production of C6+ and light products was observed with changes in reaction conditions. The carbon selectivity to C6+ compounds increased from 20% at 10 bar to 27% at 60 bar and decreased from 28% at 633 K to 18% at 723 K. At all reaction conditions, the observed product distribution can be explained as the result of fast bimolecular reactions, including hydride transfer and alkylation.
- Schreiner, Edward P.,Teketel, Shewangizaw,Lobo, Raul F.
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supporting information
p. 4245 - 4251
(2016/06/09)
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- Scandium, yttrium, and ytterbium bisalkyl complexes stabilized by monoanionic amidopyridinate ligands
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A reaction of Sc, Y, and Yb amidopyridinate dichlorides with the corresponding amount of LiCH2SiMe3 was used to synthesize bis(trimethylsilylmethyl) complexes (Ap)Ln(CH2SiMe3)2-(THF) (Ap is N-mesityl-6-(2,4,6-triisopropylphenyl)pyridine-2-amide (Ap9Me), Ln = Y (2); Ap is N-(2,6-diisopropylphenyl)-6-(2,4,6-triisopropylphenyl)pyridine-2-amide (Ap*), Ln = Sc (3), Yb (4)). An exchange reaction of yttrium amidopyridinate dichloride derivative 1 with 4 equiv. of ButLi in hexane gave the corresponding di-tert-butyl derivative Ap9MeY(But)2(THF) (5). Molecular structures of complexes 3 and 4 were established by X-ray diffraction. A method of the ligand solid angles was used to calculate the completion degree of the metal atom coordination sphere for the series of isomorphic derivatives (Ap*)Ln(CH2SiMe3)2(THF) containing the central metal ions with different ionic radii (Sc, Y, Yb, Lu). According to this method, the amidopyridinate ligand solid angle in these complexes virtually does not vary, while the solid angles of coordinated THF molecule and alkyl ligands vary within a wide range.
- Lyubov,Rad’kov, V. Yu.,Cherkasov,Fukin,Trifonov
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p. 2594 - 2600
(2017/05/19)
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- 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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- HMT continuous synthesis apparatus and method
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The present invention provides an HMT continuous synthesis apparatus and method. The method comprises: taking p-cymene, 2,3-dimethyl-1-butylene, tert-butylchloride cyclohexane as raw materials to prepare a liquid mixture; stirring the mixture uniformly and then placing the mixture into a tubular reactor containing aluminium trichloride; obtaining an HMT reaction liquid in the tubular reactor; carrying out heat insulation while stirring in a transfer kettle and then overflowing the liquid into a hydrolysis kettle; after water washing and alkaline washing, obtaining an HMT crude product by rectification; and obtaining HMT with high purity degree by recrystallization. According to the method provided by the present invention, the process safety is good, the reaction conditions are easy to control, and the product quality is stable, so that HMT continuous large-scale production can be achieved.
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Paragraph 0035; 0036
(2016/10/10)
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- Synthesis of isoalkanes over a core (Fe-Zn-Zr)-shell (zeolite) catalyst by CO2 hydrogenation
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A kind of core-shell catalyst with Fe-Zn-Zr as the core and a zeolite (HZSM-5, Hbeta, and HY) as the shell was synthesized by a simple cladding method. The catalyst has an obvious confinement effect on the synthesis of isoalkanes by CO2 hydrogenation. Especially, the Fe-Zn-Zr@HZSM-5-Hbeta catalyst with a double-zeolite shell exhibits an extraordinary high i-HC/t-HC ratio.
- Wang, Xiaoxing,Yang, Guohui,Zhang, Junfeng,Chen, Shuyao,Wu, Yingquan,Zhang, Qingde,Wang, Junwei,Han, Yizhuo,Tan, Yisheng
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supporting information
p. 7352 - 7355
(2016/06/14)
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- Conversion of biomass derived valerolactone into high octane number gasoline with an ionic liquid
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Conversion of biomass into gasoline of high octane number is challenging. In this study, conversion of biomass-derived γ-valerolactone into gasoline was achieved by decarboxylation of valerolactone to produce butenes and alkylation of the produced butenes with butane using [CF3CH2OH2][CF3CH2OBF3] as an efficient catalyst. The obtained gasoline was rich in trimethylpentane with a high research octane number of 95.4. This journal is
- Xin, Jiayu,Yan, Dongxia,Ayodele, Olubunmi,Zhang, Zhan,Lu, Xingmei,Zhang, Suojiang
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supporting information
p. 1065 - 1070
(2015/03/04)
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- Efficient hydrodesulfurization catalysts based on Keggin polyoxometalates
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Bulk and supported hydrodesulfurization catalysts based on Mo and W and containing Co or Ni as promoters and phosphorus as a modifier are prepared through the polyoxometalate route using Keggin type phosphomolybdates and phosphotungstates and tested in the HDS of thiophene at 350-400°C and 1 bar pressure. The corresponding oxidic pre-catalysts retain intact Keggin structure of the parent polyoxometalates and possess Br?nsted and Lewis acidity. In the course of sulfidation, the oxidic pre-catalysts transform into an active sulfidic phase with the loss of Keggin structure and catalyst acidity. Catalyst activity increases in the order of supports: SiO2 2 2O3. CoMoP/γ-Al2O3 catalyst prepared through the polyoxometalate route shows higher HDS activity and butene selectivity than industrial catalyst of comparable composition. The results indicate that polyoxometalate catalyst preparation route can be considered a performance enhancement methodology for HDS catalysis.
- North, Jocelyn,Poole, Olivia,Alotaibi, Abdullah,Bayahia, Hossein,Kozhevnikova, Elena F.,Alsalme, Ali,Siddiqui, M. Rafiq H.,Kozhevnikov, Ivan V.
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- Why are organotin hydride reductions of organic halides so frequently retarded? kinetic studies, analyses, and a few remedies
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Kinetic data for reduction of organic halides (RX) by tri-n-butylstannane (SnH) reveal a serious flaw in the current view of the kinetic radical chain: the tacit but unproven assumption that the speed of reaction is determined by the slowest propagation step. Our results show this is rarely true for reductive chains and that the observed rate is in fact controlled by unseen side-reactions of propagating R? and Sn? radicals with the solvent (notably, benzene!) or solvent impurities (e.g., trace benzophenone dryness indicator in THF) or, crucially, with allylic-CH and conjugated unsaturated groups in substrates and products. Most R? and/or Sn? radicals are therefore converted into relatively inert delocalized species A? and/or B? that inhibit the chain. Retardation in the degraded chain is given by a simple sum of terms, each being the ratio of the chain-transfer rate divided by the rate of chain-return. The model kinetic equation is linear and easy to ratify, interpret, and apply: to calculate retarding rate constants, optimize reaction conditions, and identify additives or "remedies" that repair the chain and accelerate reaction. The present work is thus expected to have a helpful impact on the practice and design of SnH radical chain based (and related) syntheses.
- Ingold,Bowry, Vincent W.
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p. 1321 - 1331
(2015/02/19)
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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.
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Paragraph 0103
(2015/02/05)
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- CATALYTIC ISOMERIZATION 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.
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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.
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Paragraph 0102
(2015/02/05)
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- CATALYTIC DISPROPORTIONATION 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 carbocation promoter are described. The ionic liquid is unsupported, and the reactions occur at temperatures below about 200° C.
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Paragraph 0102
(2015/02/05)
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- 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.
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Paragraph 0103
(2015/02/05)
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- CATALYTIC DISPROPORTIONATION 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.
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Paragraph 0102
(2015/02/05)
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- 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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- A comparative study of PdZSM-5, Pdβ, and PdY in hybrid catalysts for syngas to hydrocarbon conversion
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The catalytic conversion of syngas into hydrocarbons over hybrid catalysts consisting of a methanol synthesis catalyst and Pd modified zeolites (PdZSM-5, Pdβ, and PdY) was investigated. The results indicate that the intermediate dehydration step of DME in the syngas to hydrocarbon process mainly occurs on the Bronsted acid sites of the Pd zeolite. The large pores and cavities of Pdβ and PdY promote the formation of C4+ hydrocarbons, which are mainly gasoline-type branched hydrocarbons. Moreover, the large pores and cavities provide enough space for the formation of higher aromatics which are the precursor of coke. The blockage of micropores of the Pd zeolites by hydrocarbon-type coke results in the deactivation of the hybrid catalysts.
- Wang, Chun,Ma, Xiangang,Ge, Qingjie,Xu, Hengyong
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p. 1847 - 1853
(2015/04/27)
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- 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.
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Paragraph 0062; 0063
(2015/01/16)
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- PROCESS FOR SELECTIVE RING OPENING OF CYCLIC HYDROCARBONS
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PURPOSE: A process for ring opening is provided to obtain improved conversion ratio and selectivity in comparison with the case of using hydrogen as a reducing agent. CONSTITUTION: A cyclic hydrocarbon and a reducing agent are provided as supplying materials. The supplying materials are transferred into a reactor (5) and reacted under the presence of a catalyst. A product is separated from the effusion of reaction zone. The catalyst is a heterogeneous catalyst having both acid site and metallic component. The product is obtained by evaporating and heating a mixture containing 100 parts by weight of porous molecular sieve and 0.01-20 parts by weight of water soluble metallic salt. The cyclic hydrocarbon is a naphthene group cyclic hydrocarbon which is pentagonal or hexagonal compound, or an alkyl derivative thereof selected from cyclopentane and cyclohexane. The alkyl derivative is methyl, ethyl, profile, butyl, isopropyl or an isobutyl derivative.
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Paragraph 0057; 0060-0067
(2020/04/29)
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- Platinum-tin nano-catalysts supported on alumina for direct dehydrogenation of n-butane
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Al2O3 supports were prepared by a precipitation method using various basic solutions (NaOH, KOH, NH4OH, and Na2CO3) as precipitation agents, and Pt/Sn/Al2O3 nano-catalysts were then prepared by a sequential impregnation method. The prepared catalysts were applied to the direct dehydrogenation of n-butane to n-butenes and 1,3-butadiene. The effect of precipitation agents on the physicochemical properties and catalytic activities of Pt/Sn/Al2O3 nano-catalysts in the direct dehydrogenation of n-butane was investigated. Catalytic performance of Pt/Sn/Al2O3 nanocatalysts decreased in order of Pt/Sn/Al2O3 (NaOH) > Pt/Sn/Al2O3 (KOH) > Pt/Sn/Al2O3 (NH4OH) > Pt/Sn/Al2O3 (Na2CO3). Among the catalysts tested, Pt/Sn/Al2O3 (NaOH) nano-catalyst showed the best catalytic performance in ter ms of yield for total dehydrogenation products (TDP, n-butenes and 1,3-butadiene). Hydrogen chemisorption experiments revealed that platinum surface area of the catalyst was closely related to the catalytic performance. Yield for TDP increased with increasing platinum surface area of the catalyst.
- Lee, Jong Kwon,Seo, Hyun,Hong, Ung Gi,Park, Gle,Yoo, Yeonshick,Lee, Jinsuk,Chang, Hosik,Song, In Kyu
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p. 8305 - 8310
(2015/11/27)
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- Insight into the mechanism of hydrogenation of amino acids to amino alcohols catalyzed by a heterogeneous MoOx-modified Rh catalyst
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Hydrogenation of amino acids to amino alcohols is a promising utilization of natural amino acids. We found that MoOx-modified Rh/SiO2 (Rh-MoOx/SiO2) is an efficient heterogeneous catalyst for the reaction at low temperature (323 K) and the addition of a small amount of MoOx drastically increases the activity and selectivity. Here, we report the catalytic potential of Rh-MoOx/SiO2 and the results of kinetic and spectroscopic studies to elucidate the reaction mechanism of Rh-MoOx/SiO2 catalyzed hydrogenation of amino acids to amino alcohols. Rh-MoOx/SiO2 is superior to previously reported catalysts in terms of activity and substrate scope. This reaction proceeds by direct formation of an aldehyde intermediate from the carboxylic acid moiety, which is different from the reported reaction mechanism. This mechanism can be attributed to the reactive hydride species and substrate adsorption caused by MoOx modification of Rh metal, which results in high activity, selectivity, and enantioselectivity.
- Tamura, Masazumi,Tamura, Riku,Takeda, Yasuyuki,Nakagawa, Yoshinao,Tomishige, Keiichi
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p. 3097 - 3107
(2015/02/05)
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- Reductive cleavage of inert aryl C-O bonds to produce arenes
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Reductive cleavage of the aryl C-O bonds in various phenolic compounds and aryl ethers was achieved using LiAlH4 combined with KOtBu and without any other catalysts or additives, solely producing arenes in high yields.
- Xu, Huanjun,Yu, Bo,Zhang, Hongye,Zhao, Yanfei,Yang, Zhenzhen,Xu, Jilei,Han, Buxing,Liu, Zhimin
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supporting information
p. 12212 - 12215
(2015/07/27)
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- Effect of steam during catalytic cracking of n-hexane using P-ZSM-5 catalyst
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Phosphorus-modified ZSM-5 (P-ZSM-5) catalyst was active for steam cracking of n-hexane to produce propylene and ethylene; however, the P-ZSM-5 catalyst deactivated because of both dealumination and coke deposition, which were strongly influenced by the steam to n-hexane ratio in the reactant flow. The amount of coke deposition increased with decreasing the steam to n-hexane ratio from the TG-DTA measurement. The steam could reduce the reactions of the light olefins to BTX and coke and enhance the yield of the light olefins; however, the excess steam deactivated the ZSM-5 catalysts irreversibly via dealumination.
- Yamaguchi, Aritomo,Jin, Dingfeng,Ikeda, Takuji,Sato, Koichi,Hiyoshi, Norihito,Hanaoka, Takaaki,Mizukami, Fujio,Shirai, Masayuki
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- Enhancement of dehydrogenation and hydride transfer by La3+ cations in zeolites during acid catalyzed alkane reactions
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La3+ cations exchanged into ultrastable zeolite Y and zeolite X promote catalytic isomerization, cracking, and alkylation of alkanes. La 3+ cations stabilize the zeolite lattices and, more importantly, polarize alkane C-H bonds to enhance the rates of all three reactions. This unique activity leads to stable cracking and isomerization of reactive alkanes, with polarizable C-H bonds with adjacent tertiary or quaternary carbon atoms below 370 K. The presence of La3+ cations also enhances the zeolite catalyzed hydride transfer rate for isobutane alkylation with 2-butene leading to high catalyst stability. Solid state MAS NMR shows that the strongest positive effects are associated with nonhydroxylated La3+ cations accessible to the reacting molecules in supercages of the zeolite. The high activity is the result of a cooperative polarization of C-H bonds of alkanes by La3+ cations and the presence of stable and strong Bronsted acid sites.
- Schuessler, Florian,Schallmoser, Stefan,Shi, Hui,Haller, Gary L.,Ember, Erika,Lercher, Johannes A.
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p. 1743 - 1752
(2014/06/24)
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- Sulfated Zirconia-catalyzed Alkylation of Phenol with Camphene and Isomerization of n-butane
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Sulfated zirconia modified with polyvalent cations is capable of catalyzing alkylation of phenol with camphene and isomerization of utane into isobutane.
- Popova, Svetlana A.,Chukicheva, Irina Yu.,Kutchin, Alexander V.,Tarasov, Andrei L.,Kustov, Leonid M.
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