- Alkali Metal-Naphthalene Adducts as Reagents for Neutralizing Oxide Surfaces, and the Effect of Alkali Metal Treated Surfaces in Rh-catalysed Synthesis Gas (CO + H2) Conversion
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M+C10H8.- adducts (M = Li, Na, K) are effective reagents for eliminating acidity from the surfaces of SiO2, ZrO2, or zeolite Y; the treated surfaces +, Na+, K+ from M+C10H8.-, SiO2 + Na+ from NaNO3, or ZrO2 + Na+ from Na+C10H8.-> function as novel supports for heterogeneous Rh catalysts in the conversion of CO + H2 into MeOH with >90percent selectivity at 40-95 bar and 250-300 deg C, which contrasts with the formation of CH4 over Rh on the untreated oxides.
- Dirkse, Hans A.,Lednor, Peter W.,Versloot, Peterina C.
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Read Online
- 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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- METHOD FOR THE PREPARATION OF A COMPOSITION ENRICHED IN 2-METHYL-BUT-2-ENE AND USE FOR MAKING A POLYMER
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Method for the preparation of a composition enriched in 2-methyl-but-2-ene and use for making a polymer.
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Page/Page column 7-8
(2021/04/01)
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- CATALYTIC HYDROCARBON DEHYDROGENATION
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A catalyst for dehydrogenation of hydrocarbons includes a support including zirconium oxide and Linde type L zeolite (L-zeolite). A concentration of the zirconium oxide in the catalyst is in a range of from 0.1 weight percent (wt. %) to 20 wt. %. The catalyst includes from 5 wt. % to 15 wt. % of an alkali metal or alkaline earth metal. The catalyst includes from 0.1 wt. % to 10 wt. % of tin. The catalyst includes from 0.1 wt. % to 8 wt. % of a platinum group metal. The alkali metal or alkaline earth metal, tin, and platinum group metal are disposed on the support.
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Paragraph 0056; 0122; 0123
(2021/03/13)
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- A Series of Crystallographically Characterized Linear and Branched σ-Alkane Complexes of Rhodium: From Propane to 3-Methylpentane
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Using solid-state molecular organometallic (SMOM) techniques, in particular solid/gas single-crystal to single-crystal reactivity, a series of σ-alkane complexes of the general formula [Rh(Cy2PCH2CH2PCy2)(ηn:ηm-alkane)][BArF4] have been prepared (alkane = propane, 2-methylbutane, hexane, 3-methylpentane; ArF = 3,5-(CF3)2C6H3). These new complexes have been characterized using single crystal X-ray diffraction, solid-state NMR spectroscopy and DFT computational techniques and present a variety of Rh(I)···H-C binding motifs at the metal coordination site: 1,2-η2:η2 (2-methylbutane), 1,3-η2:η2 (propane), 2,4-η2:η2 (hexane), and 1,4-η1:η2 (3-methylpentane). For the linear alkanes propane and hexane, some additional Rh(I)···H-C interactions with the geminal C-H bonds are also evident. The stability of these complexes with respect to alkane loss in the solid state varies with the identity of the alkane: from propane that decomposes rapidly at 295 K to 2-methylbutane that is stable and instead undergoes an acceptorless dehydrogenation to form a bound alkene complex. In each case the alkane sits in a binding pocket defined by the {Rh(Cy2PCH2CH2PCy2)}+ fragment and the surrounding array of [BArF4]- anions. For the propane complex, a small alkane binding energy, driven in part by a lack of stabilizing short contacts with the surrounding anions, correlates with the fleeting stability of this species. 2-Methylbutane forms more short contacts within the binding pocket, and as a result the complex is considerably more stable. However, the complex of the larger 3-methylpentane ligand shows lower stability. Empirically, there therefore appears to be an optimal fit between the size and shape of the alkane and overall stability. Such observations are related to guest/host interactions in solution supramolecular chemistry and the holistic role of 1°, 2°, and 3° environments in metalloenzymes.
- Bukvic, Alexander J.,Burnage, Arron L.,Tizzard, Graham J.,Martínez-Martínez, Antonio J.,Mckay, Alasdair I.,Rees, Nicholas H.,Tegner, Bengt E.,Kr?mer, Tobias,Fish, Heather,Warren, Mark R.,Coles, Simon J.,Macgregor, Stuart A.,Weller, Andrew S.
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supporting information
p. 5106 - 5120
(2021/05/04)
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- Experimental and Computational Studies of Palladium-Catalyzed Spirocyclization via a Narasaka-Heck/C(sp3or sp2)-H Activation Cascade Reaction
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The first synthesis of highly strained spirocyclobutane-pyrrolines via a palladium-catalyzed tandem Narasaka-Heck/C(sp3 or sp2)-H activation reaction is reported here. The key step in this transformation is the activation of a δ-C-H bond via an in situ generated σ-alkyl-Pd(II) species to form a five-membered spiro-palladacycle intermediate. The concerted metalation-deprotonation (CMD) process, rate-determining step, and energy barrier of the entire reaction were explored by density functional theory (DFT) calculations. Moreover, a series of control experiments was conducted to probe the rate-determining step and reversibility of the C(sp3)-H activation step.
- Wei, Wan-Xu,Li, Yuke,Wen, Ya-Ting,Li, Ming,Li, Xue-Song,Wang, Cui-Tian,Liu, Hong-Chao,Xia, Yu,Zhang, Bo-Sheng,Jiao, Rui-Qiang,Liang, Yong-Min
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supporting information
p. 7868 - 7875
(2021/05/27)
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- PREPARATION OF OLEFIN BY ALCOHOL DEHYDRATION, AND USES THEREOF FOR MAKING POLYMER, FUEL OR FUEL ADDITIVE.
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A process for the preparation of olefin by alcohol dehydration, for making polymer, fuel or fuel additive and use of olefin obtainable by said process for making polymer, fuel or fuel additive. Preferred olefin is C5 olefin obtained from dehydration of an alcohol or alcohol mixture, preferably from fusel oil.
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Page/Page column 10; 11
(2019/10/04)
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- Oligomerization of Light Olefins Catalyzed by Br?nsted-Acidic Metal-Organic Framework-808
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Sulfated metal-organic framework-808 (S-MOF-808) exhibits strong Br?nsted-acidic character which makes it a potential candidate for the heterogeneous acid catalysis. Here, we report the isomerization and oligomerization reactions of light olefins (C3-C6) over S-MOF-808 at relatively low temperatures and ambient pressure. Different products (dimers, isomers, and heavier oligomers) were obtained for different olefins, and effective C-C coupling was observed between isobutene and isopentene. Among the substrates investigated, facile oligomerization occurred very specifically for the structures with an α-double bond and two substituents at the second carbon atom of the main carbon chain. The possible oligomerization mechanism of light olefins was discussed based on the reactivity and selectivity trends. Moreover, the deactivation and regeneration of S-MOF-808 were investigated. The catalyst deactivates via two mechanisms which predominance depends on the substrate and reaction conditions. Above 110 °C, a loss of acidic sites was observed due to water desorption, and the deactivated catalyst could be regenerated by a simple treatment with water vapor. For C5 substrates and unsaturated ethers, the oligomers with increased molecular weight caused deactivation via blocking of the active sites, which could not be readily reversed. These findings offer the first systematic report on carbocation-mediated olefin coupling within MOFs in which the Br?nsted acidity is associated with the secondary building units of the MOF itself and is not related to any guest substance hosted within its pore system.
- Liu, Ping,Redekop, Evgeniy,Gao, Xiang,Liu, Wen-Chi,Olsbye, Unni,Somorjai, Gabor A.
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supporting information
p. 11557 - 11564
(2019/08/20)
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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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- 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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- Revealing Hydrogenation Reaction Pathways on Naked Gold Nanoparticles
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Gold nanoparticles (AuNPs) display distinct characteristics as hydrogenation catalysts, with higher selectivity and lower catalytic activity than group 8-10 metals. The ability of AuNPs to chemisorb/activate simple molecules is limited by the low coordination number of the surface sites. Understanding the distinct pathways involved in the hydrogenation reactions promoted by supported AuNPs is crucial for broadening their potential catalytic applications. In this study, we demonstrate that the mechanism of the hydrogenation reactions catalyzed by AuNPs with "clean" surfaces may proceed via homolytic or heterolytic hydrogen activation depending on the nature of the support. The synthesis of naked AuNPs employing γ-Al2O3 and ionic liquid (IL)-hybrid γ-Al2O3 supports was accomplished by sputtering deposition using ultrapure gold foils. This highly reproducible and straightforward procedure furnishes small (～6.6 nm) and well-distributed metallic gold nanoparticles (Au(0)NPs) that are found to be active catalysts for the partial and selective hydrogenation of substituted conjugated dienes, alkynes, and α,β-unsaturated carbonyl compounds (aldehydes and ketones). Kinetic and deuterium labeling studies indicate that heterolytic hydrogen activation is the primary pathway occurring on the AuNPs imprinted directly on γ-Al2O3. In contrast, AuNPs supported on IL-hybrid γ-Al2O3 materials cause the reaction to proceed via a homolytic hydrogen activation pathway. The IL layer surrounds the AuNPs and acts as a cage, influencing the frequency of the interaction of the catalytically active species and the metal surface and, consequently, the catalytic performance of the AuNPs. The IL layer is shown to improve the product selectivity by the enhancement of the substrate/product discrimination, and to decrease the catalytic activity by shifting the rate-determining step to the H2 and substrate competitive adsorption/activation on the same active sites. A series of kinetic experiments suggest that AuNPs imprinted on an IL-hybrid γ-Al2O3 support are more efficient (lower activation energy, Ea) than group 8-10 metal based catalysts for hydrogenation reactions at moderate to high temperatures (75-150 °C).
- Luza, Leandro,Rambor, Camila P.,Gual, Aitor,Alves Fernandes, Jesum,Eberhardt, Dario,Dupont, Jairton
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p. 2791 - 2799
(2017/05/31)
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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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- Well-Defined Cobalt(I) Dihydrogen Catalyst: Experimental Evidence for a Co(I)/Co(III) Redox Process in Olefin Hydrogenation
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The synthesis of a cobalt dihydrogen CoI-(H2) complex prepared from a CoI-(N2) precursor supported by a monoanionic pincer bis(carbene) ligand, MesCCC (MesCCC = bis(mesityl-benzimidazol-2-ylidene)phenyl), is described. This species is capable of H2/D2 scrambling and hydrogenating alkenes at room temperature. Stoichiometric addition of HCl to the CoI-(N2) cleanly affords the CoIII hydridochloride complex, which, upon the addition of Cp2ZrHCl, evolves hydrogen gas and regenerates the CoI-(N2) complex. Furthermore, the catalytic olefin hydrogenation activity of the CoI species was studied by using multinuclear and parahydrogen (p-H2) induced polarization (PHIP) transfer NMR studies to elucidate catalytically relevant intermediates, as well as to establish the role of the CoI-(H2) in the CoI/CoIII redox cycle.
- Tokmic, Kenan,Markus, Charles R.,Zhu, Lingyang,Fout, Alison R.
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supporting information
p. 11907 - 11913
(2016/10/07)
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- Organic base-catalysed solvent-tuned chemoselective carbotrifluoromethylation and oxytrifluoromethylation of unactivated alkenes
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An unprecedented and efficient organic base-catalysed highly chemoselective carbo- and oxytrifluoromethylation of unactivated alkenes with Togni's reagent was developed. The switchable chemoselectivity was tuned by simply changing the organic base catalyst and solvent. Mechanistic studies indicated that a radical cyclization pathway for carbotrifluoromethylation in DMSO and a carbocation pathway for oxytrifluoromethylation in DCE were probably involved.
- Yang, Ning-Yuan,Li, Zhong-Liang,Ye, Liu,Tan, Bin,Liu, Xin-Yuan
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supporting information
p. 9052 - 9055
(2016/07/21)
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- PROCESSES FOR CONVERSION OF BIOLOGICALLY DERIVED MEVALONIC ACID
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The invention relates to a process comprising reacting mevalonic acid, or a solution comprising mevalonic acid, to yield a first product or first product mixture, optionally in the presence of a solid catalyst and/or at elevated temperature and/or pressure. The invention further relates to a process comprising: (a) providing a microbial organism that expresses a biosynthetic mevalonic acid pathway; (b) growing the microbial organism in fermentation medium comprising suitable carbon substrates, whereby biobased mevalonic acid is produced; and (c) reacting said biobased mevalonic acid to yield a first product or first product mixture.
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Paragraph 0148
(2016/06/13)
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- CATALYST AND PROCESS FOR THE CO-DIMERIZATION OF ETHYLENE AND PROPYLENE
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Disclosed are novel catalyst solutions comprising an organic complex of nickel, an alkyl aluminum compound, a solvent, and a phosphine compound, that are useful for the preparation of butenes, pentenes and hexenes by the co-dimerization or cross-dimerization of ethylene and propylene. Also disclosed are processes for the dimerization of ethylene and propylene that utilize these catalyst solutions. The catalyst systems described herein demonstrate that, depending on the choice of phosphine compound used with the catalytically active nickel, it is indeed possible to lower the concentration of hexene olefins relative to butenes and pentenes, even in the presence of excess propylene. The selectivity to the linear or branched pentene product can also be controlled by the selection of the phosphine compound. The catalyst solutions may be used with mixtures of olefins.
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Paragraph 0083
(2015/03/28)
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- Kinetics of the gas-phase elimination reaction of benzyl chloroformate and neopentyl chloroformate
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The gas-phase eliminations of benzyl chloroformate (475-523 K, 31-103 Torr) and neopentyl chloroformate (563-622 K, 37-70 Torr), in a deactivated static reaction vessel, and in the presence of a free radical suppressor, are homogeneous, unimolecular, and follow a first-order rate law. The rate coefficients are expressed by the following Arrhenius equations: Benzyl chloroformate log κI = (13.30 ± 0.38) - (152.9 ± 3.6) kJ mol-1(2.303RT)-1; r = 0.9989 Neopentyl chloroformate Formation of neopentyl chloride: log κI = (14.29 ± 0.48) - (196.3 ± 5.5) kJ mol-1(2.303RT)-1; r = 0.9986 Formation of 2-methylbutenes: log κII = (12.12 ± 0.73) - (178.2 ± 8.3) kJ mol-1(2.303RT)-1; r = 0.9960 The derived kinetic and thermodynamic parameters for benzyl chloroformate decomposition indicate the reaction proceeds through a concerted four-membered cyclic transition state to give benzyl chloride and CO2 gas. Neopentyl chloroformate undergoes a parallel reaction, where neopentyl chloride formation may arise from a polar-concerted four-membered cyclic transition state, whereas the mixture of olefins, 2-methyl-2-butene, and 2-methyl-1-butene appears to be produced from a carbene intermediate. This intermediate seems to be originated from a concerted five-membered cyclic transition state of the neopentyl substrate.
- Lezama, Jesus,Domnguez, Rosa M.,Chuchani, Gabriel
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p. 104 - 112
(2015/04/22)
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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)
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- Steric effects in reactions of decamethyltitanocene hydride with internal alkynes, conjugated diynes, and conjugated dienes
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Titanocene hydride [Cp*2TiH] (Cp* = η5-C5Me5) (1) readily inserts simple internal alkynes R1C≡CR2 into its Ti-H bond, yielding titanocene alkenyl Ti(III) compounds of two structural types. The less sterically congested products [Cp*2Ti(R1C=CHR 2)] (2a-e) contain a σ1-bonded alkenyl group, whereas the products bearing at least one trimethylsilyl substituent and other bulky substituents (R1 = SiMe3; R2 = SiMe 3, 4a; CMe3, 4b; and Ph, 4c) possess a remarkable Ti-H agostic bond of the σ1-bonded alkenyl group. This feature is consistent with solution EPR spectra of 4a-4c showing a doublet due to coupling of the hydrogen nucleus with the Ti(III) d1 electron. Compound 1 reacts with one molar equivalent of conjugated buta-1,3-diynes (RC≡C) 2 to give η3-butenyne complexes (R = SiMe3, 5a; CMe3, 5b). The Ti(III) complexes 2a-2e and 5a and 5b were oxidatively chlorinated with PbCl2 to give Ti(IV) chloro-alkenyl complexes [Cp*2TiCl(R1C=CHR2)] 3a-3e and chloro-alkenynes 6a and 6b, respectively. 1H and 13C NMR spectra of 3a-3e and 6a and 6b revealed that these compounds form equilibria of two atropisomers differing by the anti- and syn-position of the chlorine and the alkenyl hydrogen atoms. Such atropisomers are denoted by appended (a) and (b), respectively. Compound 1 reacted with 1,3-butadiene to give a thermally stable π-bonded 1-methylallyl complex (7) and with penta-1,3-diene to give a thermally labile 1,3-dimethylallyl complex (8). In toluene-d8 solutions 7 dissociated at 80 °C and 8 at room temperature to give [Cp*Ti(C5Me4CH2)] and corresponding alkenes. Other methyl-substituted dienes, isoprene, 4-methylpenta-1,3-diene, and 2,3-dimethylbuta-1,3-diene, did not yield observable π-bonded allyl products; the dienes were, however, hydrogenated to olefins with concomitant formation of [CpTi(C5Me4CH2)]. Compound 1 was shown to catalyze the hydrogenation of the alkynes and dienes to olefins and ultimately to alkanes under lower than atmospheric hydrogen pressure at room temperature. Single-crystal structures were determined for 3d(a), 3e(a), 4a-4c, 5a, 6b, and 7.
- Pinkas, Jiri,Gyepes, Robert,Cisarova, Ivana,Kubista, Jiri,Horacek, Michal,Mach, Karel
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p. 3399 - 3413
(2014/08/05)
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- METHOD OF FORMING C5 DI-OLEFINS
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A process is disclosed that includes reacting a C1 source with n-butene to form a C-5 diolefin.
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Paragraph 0086; 0087
(2014/09/30)
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- Catalysis by coke deposits: Synthesis of isoprene over solid catalysts
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A help rather than a hindrance: Carbonaceous deposits have been found to play a key role in the selective synthesis of isoprene from formaldehyde and isobutene over solid catalysts. They accumulate on the catalyst surface during the induction period and promote the interaction of the substrates at the steady state. The proposed mechanism (see scheme) shows the way forward for the design of efficient solid catalysts for the synthesis of isoprene. Copyright
- Ivanova, Irina,Sushkevich, Vitaly L.,Kolyagin, Yury G.,Ordomsky, Vitaly V.
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supporting information
p. 12961 - 12964
(2014/01/06)
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- Characterization of phenylene-bridged hybrid mesoporous materials incorporating arenetricarbonyl complexes (-C6H4Me(CO) 3-; Me = Cr, Mo) and their catalytic activities
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The successful construction of arenetricarbonyl complexes (-C 6H4Me(CO)3-; Me = Cr, Mo) was achieved through the direct modification of phenylene (-C6H4-) moieties of phenylene-bridged hybrid mesoporous materials (HMM-ph) by the simple chemical vapor deposition (CVD) of corresponding metal hexacarbonyls. The pore structure as well as high surface area of HMM-ph were retained even after CVD treatment. It was found that HMM-ph incorporating an arenetricarbonyl molybdenum complex (HMM-phMo(CO)3) exhibited higher catalytic performance for the polymerization of phenylacetylene and dehydrochlorination of 2-chloro-2-methylbutane than HMM-phCr(CO)3. Various spectroscopic investigations revealed that the strength of the chemical bond between the phenylene ligand and metal center of the arenetricarbonyl complexes affects the catalytic performance of HMM-phMe(CO)3 (Me = Cr, Mo).
- Kamegawa, Takashi,Saito, Masakazu,Sakai, Takahiro,Matsuoka, Masaya,Anpo, Masakazu
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experimental part
p. 14 - 19
(2012/03/10)
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- PRODUCTION OF 3-METHYLBUT-1-EN BY MEANS OF DEHYDRATION OF 3-METHYLBUTANE-1-OL
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The invention relates to a process for preparing 3-methyl-1-butene by dehydration of 3-methyl-1-butanol over an aluminium-containing oxide in the temperature range from 200 to 450° C. in the gas phase or mixed liquid/gas phase, characterized in that an aluminium-containing oxide having a predominantly mesoporous pore structure whose: a) relative proportion of macropores is less than 15%; b) distribution of the pore diameter has a monomodal maximum in the range of mesopores from 3.6 to 50 nm; c) average pore diameter of all pores is in the range of mesopores and macropores from 5 to 20 nm; d) composition comprises more than 80% of gamma-aluminium oxide, is used.
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Page/Page column 4
(2012/06/16)
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- Metal-free catalytic olefin hydrogenation: Low-temperature H2 activation by frustrated lewis pairs
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Weak nucleophiles for strong activation: The reversible activation of dihydrogen by an electron-deficient phosphine, (C6F 5)PPh2, in combination with the Lewis acid B(C 6F5)3 at -80 °C was accomplished. The catalytic hydrogenation of olefins proceeds through protonation and subsequent hydride attack. Electron-deficient phosphines and diarlyamines were demonstrated to be viable Lewis bases for the reaction, thus allowing catalyst loadings of 10 to 5 mol %. Copyright
- Greb, Lutz,Paradies, Jan,Ona-Burgos, Pascual,Schirmer, Birgitta,Grimme, Stefan,Stephan, Douglas W.
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supporting information
p. 10164 - 10168,5
(2020/09/09)
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- ZEOLITIC CATALYTIC CONVERSION OF ALCOHOLS TO HYDROCARBONS
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A method for converting an alcohol to a hydrocarbon, the method comprising contacting said alcohol with a metal-loaded zeolite catalyst at a temperature of at least 100°C and up to 550°C, wherein said alcohol can be produced by a fermentation process, said metal is a positively-charged metal ion, and said metal-loaded zeolite catalyst is catalytically active for converting said alcohol to said hydrocarbon.
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Page/Page column 19
(2013/02/28)
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- Titration of nonstabilized diazoalkane solutions by fluorine NMR
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A new protocol for titrating nonstabilized diazoalkane solutions by quantitative 19F NMR is reported. An excess of 2-fluorobenzoic acid dissolved in CDCl3 is treated with the diazoalkane solution at a low temperature, immediately forming the corresponding 2-fluorobenzoate ester upon warming. A significant difference in the 19F chemical shift between the ester and acid is seen, allowing facile and accurate integration to determine titer. The procedure is safe, rapid, and indicates the active diazoalkane concentration with high precision.
- Rendina, Victor L.,Kingsbury, Jason S.
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experimental part
p. 1181 - 1185
(2012/03/12)
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- FUEL COMPOSITIONS COMPRISING ISOPRENE DERIVATIVES
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The invention provides for methods, compositions and systems using isoprene from a bioisoprene composition derived from renewable carbon for production of a variety of hydrocarbon fuels, fuel additives, and additives for fine chemistry and other uses.
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Page/Page column 70
(2012/01/06)
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- Selectivity patterns in heterogeneously catalyzed hydrogenation of conjugated ene-yne and diene compounds
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Selectivity control in heterogeneously catalyzed hydrogenation of conjugated hydrocarbons (ene-yne and diene compounds) is a challenging task. Available studies on the topic mainly encircle 1,3-butadiene as the substrate and palladium as the catalyst, while more elaborated playground molecules and other metals remain largely unexplored. This study investigates the gas-phase hydrogenation of valylene (2-methyl-1-butene-3-yne) and isoprene (2-methyl-1,3-butadiene) over Pd, Pb-poisoned Pd, CO-modified Pd, Cu, Ni, and bimetallic CuNi catalysts. Chemoselectivity, regioselectivity, full hydrogenation, and CC bond formation/scission footprints of the catalytic systems at different inlet hydrogen-to-hydrocarbon ratios and conversion degrees have been rationalized. Complementary studies of 3-methylbutyne and 1-penten-4-yne hydrogenation were carried out in order to analyze (i) the impact of isomerization on the observed mono-olefin distribution in valylene/isoprene hydrogenation and (ii) the conjugation issue in partial ene-yne hydrogenation. Our results lead to an improved understanding of hydrogenation of polyunsaturated hydrocarbons and open doors to design more selective heterogeneous catalysts and related processes for this practically important class of reactions.
- Bridier, Blaise,Perez-Ramirez, Javier
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experimental part
p. 165 - 175
(2012/02/02)
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- Thermal decomposition of t-amyl methyl ether (TAME) studied by flash pyrolysis/supersonic expansion/vacuum ultraviolet photoionization time-of-flight mass spectrometry
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Thermal decomposition of the oxygenated fuel component tert-amyl methyl ether (TAME) has been studied by flash pyrolysis up to 1250 K in a 20-100 μs time scale. Pyrolysis was followed by supersonic expansion to isolate intermediates and products, which are monitored by vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). The species detected, such as CH3, C2H4, C 2H5, C4H8, C5H 10, C3H6O, and C4H8O, show competition between molecular elimination and bond fission pathways. The alkenes 2-methyl-1-butene (1) and 2-methyl-2-butene (2), the primary molecular elimination products of TAME, were separately pyrolyzed to evaluate the extent of secondary decompositions, as were the ketones (acetone and 2-butanone) produced by losses of two alkyl radicals. While vicinal elimination of methanol from TAME to form 1 and 2 in an approximate 3:1 ratio begins around 600 K and continues to dominate at higher temperatures, homolysis of TAME to form radicals onsets >825 K, yielding more acetone than 2-butanone. Contributions from secondary dissociations of the ketone and alkene products are evaluated.
- Morton, Thomas Hellman,Weber, Kevin H.,Zhang, Jingsong
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experimental part
p. 210 - 218
(2012/07/17)
-
- Selective catalytic C-H alkylation of alkenes with alcohols
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Alkenes and alcohols are among the most abundant and commonly used organic feedstock in industrial processes. We report a selective catalytic alkylation reaction of alkenes with alcohols that forms a carbon-carbon bond between vinyl carbon-hydrogen (C-H) and carbon-hydroxy centers with the concomitant loss of water. The cationic ruthenium complex [(C6H6)(PCy 3)(CO)RuH]+BF4- (Cy, cyclohexyl) catalyzes the alkylation in solution within 2 to 8 hours at temperatures ranging from 75° to 110°C and tolerates a broad range of substrate functionality, including amines and carbonyls. Preliminary mechanistic studies are inconsistent with Friedel-Crafts-type electrophilic activation of the alcohols, suggesting instead a vinyl C-H activation pathway with opposite electronic polarization.
- Lee, Dong-Hwan,Kwon, Ki-Hyeok,Yi, Chae S.
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scheme or table
p. 1613 - 1616
(2012/02/01)
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- Polymers as novel modifiers for supported metal catalyst in hydrogenation of benzaldehydes
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Polyethylene glycol (PEG) was impregnated on a palladium metal supported on silica gel and used in a catalyst for hydrogenation of benzaldehydes. In the vapor-phase flow reaction, the PEG modification improved catalytic activity and selectivity for a partially hydrogenated product, benzyl alcohol. In isoprene hydrogenation, selectivity for partially hydrogenated products, monoenes, was also enhanced. X-ray photoelectron spectroscopy (XPS) analysis of the modified catalysts revealed that the modification with PEG makes the palladium surface negatively charged, possibly leading to an increase in the selectivity for the partially hydrogenated product caused by enhancement of its desorption from the surface. In the liquid-phase hydrogenation of benzaldehyde, the PEG modification also increased the selectivity for benzyl alcohol.
- Okamoto, Masaki,Hirao, Tomoyuki,Yamaai, Tatsuya
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experimental part
p. 423 - 428
(2011/02/27)
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- Isomerization of neopentyl chloride and neopentyl bromide by a 1,2-Interchange of a halogen atom and a methyl group
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The recombination of chloromethyl and t-butyl radicals at room temperature was used to generate neopentyl chloride molecules with 89 kcal mol-1 of internal energy. The observed unimolecular reactions, which give 2-methyl-2-butene and 2-methyl-1-butene plus HCl, as products, are explained by a mechanism that involves the interchange of a methyl group and the chlorine atom to yield 2-chloro-2-methylbutane, which subsequently eliminates hydrogen chloride by the usual four-centered mechanism to give the observed products. The interchange isomerization process is the rate-limiting step. Similar experiments were done with CD2Cl and C(CH3)3 radicals to measure the kinetic-isotope effect to help corroborate the proposed mechanism. Density functional theory was employed at the B3PW91/6-31G(d',p') level to verify the Cl/CH3 interchange mechanism and to characterize the interchange transition state. These calculations, which provide vibrational frequencies and moments of inertia of the molecule and transition state, were used to evaluate the statistical unimolecular rate constants. Matching the calculated and experimental rate constants, gave 62 ± 2 kcal mol -1 as the threshold energy for interchange of the Cl atom and a methyl group. The calculated models also were used to reinterpret the thermal unimolecular reactions of neopentyl chloride and neopentyl bromide. The previously assumed Wagner-Meerwein rearrangement mechanism for these reactions can be replaced by a mechanism that involves the interchange of the halogen atom and a methyl group followed by HCl or HBr elimination from 2-chloro- 2-methylbutane and 2-bromo-2-methylbutane. Electronic structure calculations also were done to find threshold energies for several related molecules, including 2-chloro-3,3-dimethylbutane, 1-chloro-2-methyl-2-phenylpropane, and 1-chloro-2-methyl-2-vinylpropane, to demonstrate the generality of the interchange reaction involving a methyl, or other hydrocarbon groups, and a chlorine atom. The interchange of a halogen atom and a methyl group located on adjacent carbon atoms can be viewed as an extension of the halogen atom interchange mechanisms that is common in 1,2-dihaloalkanes.
- Lisowski, Carmen E.,Duncan, Juliana R.,Ranieri, Anthony J.,Heard, George L.,Setser,Holmes, Bert E.
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scheme or table
p. 10395 - 10402
(2011/02/18)
-
- Propylene and isoprene production
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A process for producing propylene and isoprene from a feed stream comprising 1-butene and isobutene is disclosed. The feed stream is reacted in a catalytic distillation reactor containing an olefin isomerization catalyst to produce an overhead stream comprising 2-butene and isobutene and a bottoms stream comprising 2-butene. The overhead stream is reacted in the presence of a metathesis catalyst to produce propylene and isoamylenes. Isoprene is produced by dehydrogenation of isoamylenes.
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Page/Page column 3-4
(2009/03/07)
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- High yield of liquid range olefins obtained by converting i-propanol over zeolite H-ZSM-5
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Methanol, ethanol, and i-propanol were converted under methanol-to-gasoline (MTH)-like conditions (400°C, 1-20 bar) over zeolite H-ZSM-5. For methanol and ethanol, the catalyst lifetimes and conversion capacities are comparable, but when i-propanol is use
- Mentzel, Uffe V.,Shunmugavel, Saravanamurugan,Hruby, Sarah L.,Christensen, Claus H.,Holm, Martin S.
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experimental part
p. 17009 - 17013
(2010/03/23)
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- PROCESS FOR CRACKING TERT-ALKYL ETHERS THAT USE A MESOSTRUCTURED HYBRID ORGANIC-INORGANIC MATERIAL
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A process for cracking tert-alkyl ether(s) selected from among tert-amyl methyl ether (TAME) and ethyl tert-amyl ether (ETAE) for the production of tertiary olefins comprising bringing said tert-alkyl ether(s) into contact with at least one catalyst that is formed by at least one mesostructured hybrid organic-inorganic material that consists of at least two spherical elementary particles, whereby each of said spherical particles consists of a mesostructured matrix with a silicon oxide base to which are linked organic groups with acid terminal reactive functions, said groups representing less than 20 mol % of said matrix that is present in each of said spherical elementary particles, which have a maximum diameter of between 50 nm and 200 μm.
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Page/Page column 10-11
(2010/01/31)
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- Method of selectively hydrogenating conjugated diene by using supported ionic liquid nano-pd catalyst
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A method of selectively hydrogenating a conjugated diene by using a supported ionic liquid nano-palladium catalyst. The supported ionic liquid nano-palladium catalyst, hydrogen and a reactant having the conjugated diene react at a temperature ranging from 40 to 120° C. and a pressure ranging from 100 to 400 psig. A ratio of the catalyst to the reactant ranges from 1/20 to 1/250 (g/ml).
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Page/Page column 3-4
(2008/12/04)
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- Thermodynamic parameters of the single-stage dehydrogenation of isopentane to isoprene
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From the results of experiments with platinum-containing catalysts operating in the steady mode, adiabatic changes in temperature in the course of 2-metylbutane dehydrogenation to monoolefins and isoprene were calculated. Dehydrogenation of 2-methylbutane
- Romanova,Lamberov,Shaikhutdinova,Gil'Manov,Gil'Mullin
-
body text
p. 1583 - 1591
(2009/05/06)
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- Catalytic dehydrogenation of isopentane with iridium catalysts
-
(Graph Presented) Activation by adding PPh3: The catalytic dehydrogenation of isopentane to give isopentene and hydrogen with iridium catalysts ona silica gel support at 450°C proceeds with impressive conversion whenthe support is impregnated w
- Alt, Helmut G.,Boehmer, Ingrid K.
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p. 2619 - 2621
(2008/12/23)
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- DEHYDRATION PROCESS
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A process for producing an olefin and/or an ether is described, which comprises heating an alcohol in the presence of an acidic ionic compound which exists in a liquid state at a temperature of below 150°C.
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Page/Page column 16
(2008/06/13)
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- Moving bed process for producing propylene, recycling a fraction of used catalyst
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The invention concerns a process for producing propylene from a steam cracking and/or catalytic cracking light olefinic cut, said process comprising a moving bed catalytic cracking step with a catalyst regeneration loop. The process recycles a portion of the used catalyst to the inlet of the moving bed reactor. The conversion is high using the process of the invention, with a good yield and good propylene selectivity.
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Page/Page column 5-6
(2008/06/13)
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- Sorption, acid, and catalytic properties of a sulfonic cation exchanger supported on the carbon fiber
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Distribution in strength of the acid centers in sulfonic cation in the form of exchanger granules and fibers was studied by the novel modification of the thermal desorption method.
- Egiazarov,Shachenkova,Radkevich,Cherches,Gorbatsevich,Ermolenko
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p. 1761 - 1764
(2007/10/03)
-
- Remarkably Facile Solvolyses of Triflates via Carbocationic Processes in Dimethyl Sulfoxide
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A number of triflates have been shown to undergo clean pseudo-first-order solvolysis reactions in DMSO-d6 to give products derived from carbocationic intermediates. Thus, t-BuCH(OTf)CO-t-Bu (5) and t-BuCH 2OTf (9) react readily in DMSO-d6 at 25 °C to give a rearranged oxosulfonium salts, and subsequent alkene products where methyl migration to the incipient cationic center occurs. t-BuCH(OTf)CO 2CH3 (14) gives analogous rearranged products, and 1-methylcyclopropyl triflate (21) gives a ring-opened allylic oxosulfonium salt. These triflates react primarily via kΔ pathways. 6-Methylbicyclo[3.1.0]hex-6-yl triflate (23), bicyclo[2.2.1hept-1-yl triflate (24), 1,6-methano[10]-annulen-11-yl triflate (25), (CH3) 2C(OTf)CO2CH3 (26), and (CH3) 2CCN(OTf) (29) all react in DMSO-d6 to give carbocation-derived products. PhCH(OTf)CF3 (33) and substituted analogues also react readily in DMSO-d6, and the Hammett ρ + value is -3.7. This suggests a "borderline" mechanism where the transition state has substantial charge development. The primary feature of these solvolyses is the high reactivity of all of these triflates in DMSO-d6. Thus, these triflates are all more reactive in DMSO-d 6 than in HOAc, and for most, rates are faster than in CF 3CH2OH. Triflates 5, 21, 29, and 33 are 10 8-109 times more reactive in DMSO-d6 than the corresponding mesylates. It is suggested that the decreased need for electrophilic solvation of trifiate anion, and the high cation solvating ability of DMSO, are the reasons for the high triflate reactivity in DMSO-d 6.
- Creary, Xavier,Burtch, Elizabeth A.
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p. 1227 - 1234
(2007/10/03)
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- METHODS FOR PRODUCING ALKYLARYL SULFONATES BY USING MODIFIED DIMERIZED OLEFINS
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The invention relates to methods for producing alkylaryl sulfonates by: a) reacting a C4-olefin mixture on a metathesis catalyst in order to produce a 2-pentene and/or an olefin mixture containing 3-hexene, and optionally separating out 2-pentene and/or 3-hexene; b) dimerizing the 2-pentene and/or 3-hexene obtained in step a) in the presence of a dimerization catalyst to form a mixture containing C10-12-olefins and optionally separating out the C10-12-olefins; c) reacting the C10-12-olefin mixtures obtained in step b) with an aromatic hydrocarbon in the presence of an alkylation catalyst in order to form alkyl-aromatic compounds, whereby linear olefins can be additionally added before the reaction; d) sulfonating the alkyl-aromatic compounds obtained in step c) and neutralizing them in order to form alkylaryl sulfonates, whereby linear alkyl benzenes can be additionally added before the sulfonation; e) optionally mixing the alkylaryl sulfonates obtained in step d) with linear alkylaryl sulfonates.
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Page/Page column 31
(2008/06/13)
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- Development of a novel mesoporous catalyst UDCaT-6: Kinetics of synthesis of tert-amyl methyl ether (TAME) from tert-amyl alcohol and methanol
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UDCaT-6, a novel active mesoporous and stable catalyst, was synthesized by generating in situ nanosized acidic centers of chlorosulfonic acid treated zirconia in the pores of highly ordered hexagonal mesoporous silica (HMS). For the first time, we have used chlorosulfonic acid as a source of sulfating agent to treat zirconia in pores of the HMS. The catalyst is characterized by XRD, FTIR, EDAX, SEM, and BET surface area and pore size analysis, and probe reactions. The structural integrity of HMS is maintained in UDCaT-6. The activity and stability of UDCaT-6 was tested in liquid phase alkylation of toluene with benzyl chloride and vapor phase synthesis of tert-amyl methyl ether (TAME) from ferf-amyl alcohol (TAA) and methanol where corrosive acid HCl and water are generated as biproducts. A complete theoretical and experimental analysis is presented and kinetics are evaluated. The model explains the experimental data very well.
- Yadav, Ganapati D.,Murkute, Ambareesh D.
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p. 9557 - 9566
(2008/04/18)
-
- Synthesis of methyl tert-amyl ether in the presence of a fibrous sulfonated cation exchanger
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The influence of exchange capacity of the fibrous sulfonated cation exchanger FIBAN K-1 and the main process parameters of iso-amyl methyl ether production on the yield of the desired product was examined. It was shown that, under the experimental conditions (temperature 60-100°C, the feed weight hour space velocity 2-6 g/(gcath), and CH3OH to iso-C5H10 molar ratio 1: 2), 2-methyl-1-butene can transform into 2-methyl-2-butene, and 3-methyl-1-butene almost does not isomerize and remains uninvolved in the ether synthesis. At a temperature of 80°C and above, the fibrous sulfonated cation exchanger is superior to the beaded resin in activity.
- Cherches,Kovalenko,Shunkevich,Soldatov,Egiazarov
-
-
- Flash vacuum pyrolysis over magnesium. Part 1 - Pyrolysis of benzylic, other aryl/alkyl and aliphatic halides
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Flash vacuum pyrolysis over a bed of freshly sublimed magnesium on glass wool results in efficient coupling of benzyl halides to give the corresponding bibenzyls. Where an ortho halogen substituent is present further dehalogenation gives some dihydroanthracene and anthracene. Efficient coupling is also observed for halomethylnaphthalenes and halodiphenylmethanes while chlorotriphenylmethane gives 4,4′-bis(diphenylmethyl)biphenyl. By using α,α′-dihalo-o-xylenes, benzocyclobutenes are obtained in good yield, while the isomeric α,α′-dihalo-p-xylenes give a range of high thermal stability polymers by polymerisation of the initially formed p-xylylenes. Other haloalkylbenzenes undergo largely dehydrohalogenation where this is possible, in some cases resulting in cyclisation. Deoxygenation is also observed with haloalkyl phenyl ketones to give phenylalkynes as well as other products. With simple alkyl halides there is efficient elimination of HCl or HBr to give alkenes. For aliphatic dihalides this also occurs to give dienes but there is also cyclisation to give cycloalkanes and dehalogenation with hydrogen atom transfer to give alkenes in some cases. For 5-bromopent-1-ene the products are those expected from a radical pathway but for 6-bromohex-1-ene they are clearly not. For 2,2-dichloropropane and 1,1-dichloropropane elimination of HCl occurs but for 1,1-dichlorobutane, -pentane and -hexane partial hydrolysis followed by elimination of HCl gives E, E-, E,Z- and Z,Z- isomers of the dialk-1-enyl ethers and fully assigned 13C NMR data are presented for these. With 6-chlorohex-1-yne and 7-chlorohept-1-yne there is cyclisation to give methylenecycloalkanes and -cycloalkynes. The behaviour of 1,2-dibromocyclohexane and 1,2-dichlorocyclooctane under these conditions is also examined. Various pieces of evidence are presented that suggest that these processes do not involve generation of free gas-phase radicals but rather surface-adsorbed organometallic species.
- Aitken, R. Alan,Hodgson, Philip K.G.,Morrison, John J.,Oyewale, Adebayo O.
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p. 402 - 415
(2007/10/03)
-
- Push-pull mechanism of hydrodenitrogenation over silica-supported MoP, WP, and MoS2 hydroprocessing catalysts
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The mechanism of liquid-phase catalytic hydrodenitrogenation at 3.1 MPa on silica-supported molybdenum phosphide, MoP/SiO2, and tungsten phosphide, WP/SiO2, was studied using a series of pentylamines of different structures. The reactivity pattern suggested that removal of nitrogen occurred primarily by an E2 elimination mechanism involving acidic and base sites on the catalyst surfaces in a push-pull process. Infrared spectroscopy and temperature-programmed reaction studies of ethylamine indicated that alkyl ammonium species formed on Bronsted acid sites were intermediates in the reaction. Similar results were obtained with a reference MoS2/SiO2 sample tested at the same conditions. This suggested that sulfur was probably present on the active surface and assisted in the removal of sulfur.
- Clark,Wang,Deck,Oyama
-
p. 116 - 126
(2007/10/03)
-
- Laser powered homogeneous pyrolysis of ethyne, propyne, and propadiene initiated by methyl radicals: Formation and degradation of hydrocarbons at 800-950 K
-
Applying laser heating by fast vibrational-translational energy transfer in a quasi-wall-free reactor the pyrolysis of ethyne (C2H2), propyne (p-C3H4), and propadiene (a-C3H4) was studied experimentally at 0.13 bar in the medium temperature range of 800-950 K with respect to the degradation and formation of hydrocarbons. The radical/hydrocarbon chemistry was chemically induced via CH3 radicals produced by the fast thermal dissociation of di-tert-butyl-peroxide DTBP ((tert-C4H9O)2 → 2 CH3 + 2 CH3COCH3). Complete analysis of the product yields was achieved by means of GC-MS with special attention to isomeric product and benzene formation. The product distribution, the temperature dependence and the underlying reaction schemes were analyzed by kinetic models developed for high temperature alkane oxidation/pyrolysis and aromatic formation in premixed ethene and ethyne flames. The primary attack of the unsaturated hydrocarbons by CH3 radicals in the studied temperature range occurs via the addition to the double/triple bond and via hydrogen atom abstraction, leading to different classes of radicals. For the reaction system C2H2 + CH3 high yields of C6H6 with a marked negative temperature dependence were observed. A semi-quantitative description of the C6H6 yield was obtained by a reaction sequence of successive addition of C2H2 to the radicals C2H3 (from C2H2 + H) and C4H5, being consistent with recent discussed reaction networks. For the reaction systems p-C3H4 + CH3 and a-C3H4 + CH3 only qualitative agreement between measured and modelled product yields was found, pointing to a lack of reliable data of the reactions of p-C3H4/a-C3H4/C3H 3/H. Modified mechanisms are presented for the radical rich reaction systems C2H2 + CH3, p-C3H4 + CH3, and a-C3H4 + CH3 experimentally studied.
- Goos, Elke,Hippler, Horst,Hoyermann, Karlheinz,Juerges, Bettina
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p. 2011 - 2018
(2007/10/03)
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- Selective hydrogenation of diene hydrocarbons to olefins with mono- and bimetallic complexes of transition metals with oligoallene ligands
-
Mono- and bimetallic catalysts based on complexes of palladium and some base transition metals (Ni, Co, and Fe) with oligoallene ligands were synthesized and were shown to be very active and selective in the hydrogenation of linear and cyclic dienes to olefins. The optimal conditions of the synthesis were established. The bimetallic systems were found to display synergism of the activity. The isomeric composition of the isoprene and butadiene hydrogenation products was studied.
- Khar'kova,Rozantseva,Frolov
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p. 262 - 267
(2007/10/03)
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- Etherification of tert-amyl alcohol with methanol over ion-exchange resin
-
tert-Amyl methyl ether (TAME) is a proven high octane additive. The synthesis of tert-amyl methyl ether from tert-amyl alcohol and methanol has been carried out in the presence of a variety of solid acid catalysts. Amberlyst-36 was found to be very effective in comparison with other solid acids. A complete theoretical and experimental analysis is presented for the model studies of tert-amyl alcohol with methanol. The parallel reactions of tert-amyl alcohol adsorbed on the sites were found to control the overall rate of reaction, which led to the formation of TAME, 2-methyl-1-butene (2MB1), and 2-methyl-2-butene (2MB2). The reaction follows pseudo-first-order kinetics at a fixed catalyst loading. The individual rate constants for the formation of TAME, 2MB1, and 2MB2 were also evaluated from the same data.
- Yadav,Joshi
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p. 408 - 414
(2013/09/07)
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