- Design of dendrimer-based nanostructured catalyst systems and their catalytic activity in hydrogenation: Synthesis of ruthenium nanoparticles immobilized in dendrimer networks
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A new method has been proposed for immobilization of 3-nm ruthenium nanoparticles on special supports synthesized for this purpose, polymer networks based on poly(propylene imine) dendrimers. It has been shown that the structure of the support has a substantial effect on the size of particles and their catalytic activity in the hydrogenation reactions of unsaturated and aromatic compounds. The catalysts can be reused without loss of activity.
- Karakhanov,Maksimov,Zolotukhina,Kardashev
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- Selective hydrogenation of terminal alkynes over palladium nanoparticles within the pores of amino-modified porous aromatic frameworks
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Palladium catalysts, based on porous aromatic frameworks, synthesized via Suzuki cross-coupling reaction and further modified with amino groups, were prepared and tested in hydrogenation of several unsaturated compounds. Catalysts obtained were characterized by several techniques including IR spectroscopy, solid-state NMR spectroscopy, low-temperature nitrogen adsorption, transmission electron microscopy, atomic emission spectroscopy and X-ray photoelectron spectroscopy. It was shown that the amino-groups within the structure of aromatic frameworks interact with palladium nanoparticles and enhance their selectivity towards hydrogenation of terminal alkynes.
- Karakhanov, Edward,Maximov, Anton,Terenina, Maria,Vinokurov, Vladimir,Kulikov, Leonid,Makeeva, Daria,Glotov, Aleksandr
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p. 176 - 184
(2019/05/24)
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- Potassium Yttrium Ate Complexes: Synergistic Effect Enabled Reversible H2 Activation and Catalytic Hydrogenation
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A potassium yttrium benzyl ate complex was generated simply by mixing an yttrium amide and potassium benzyl. The benzyl ate complex could undergo peripheral deprotonation to produce a cyclometalated complex or hydrogenation to give a hydride ate complex. The latter hydride ate complex features a (KH)2 structure protected by two yttrium amide complexes. The synergistic effect between potassium hydride and the amide ligand enables the complex to deprotonate a methyl C-H bond. The combination of intramolecular deprotonation of the hydride ate complex and hydrogenation of the cyclometalated complex constitutes a reversible H2 activation process. Using this process involving formal addition and elimination of H2, we accomplished the catalytic hydrogenation of alkenes, alkynes, and imines.
- Zhai, Dan-Dan,Du, Hui-Zhen,Zhang, Xiang-Yu,Liu, Yu-Feng,Guan, Bing-Tao
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p. 8766 - 8771
(2019/09/30)
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- Electrochemical cross-coupling of biogenic di-acids for sustainable fuel production
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Direct electrocatalytic conversion of bio-derivable acids represents a promising technique for the production of value-added chemicals and tailor-made fuels from lignocellulosic biomass. In the present contribution, we report the electrochemical decarboxylation and cross-coupling of ethyl hydrogen succinate, methyl hydrogen methylsuccinate and methylhexanoic acid with isovaleric acid. The reactions were performed in aqueous solutions or methanol at ambient temperatures, following the principles of green chemistry. High conversions of the starting materials have been obtained with maximum yields between 42 and 61% towards the desired branched alkane products. Besides costly Pt electrodes also (RuxTi1-x)O2 on Ti electrodes exhibited a notable activity for cross-Kolbe electrolysis. As some of the products are insoluble in water, easy product isolation and reuse of the reaction solvent is enabled via phase separation. Several side products have been identified to evaluate the efficiency of the reaction and to elucidate the factors influencing the product selectivity. The yielded alkanes and esters were assessed with regard to their potential as fuels for internal combustion engines. While the longer alkanes constitute promising candidates for the compression-ignition engine, the smaller ester represents an interesting option for the spark-ignition engine.
- Holzh?user, F. Joschka,Creusen, Guido,Moos, Gilles,Dahmen, Manuel,K?nig, Andrea,Artz, Jens,Palkovits, Stefan,Palkovits, Regina
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p. 2334 - 2344
(2019/05/21)
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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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- Unsaturated-compound hydrogenation nanocatalysts based on palladium and platinum particles immobilized in pores of mesoporous aromatic frameworks
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Heterogeneous catalysts for the hydrogenation of unsaturated hydrocarbons have been synthesized on the basis of palladium and platinum nanoparticles immobilized in pores of mesoporous aromatic frameworks, which represent a new class of carbon supports with a diamond-like ordered structure. The resulting materials have been characterized by transmission electron microscopy, IR spectroscopy, and NMR spectroscopy. It has been shown that the catalyst activity in the hydrogenation reaction depends on the substrate molecule size and adsorbability on the surface of nanoparticles. Catalytic activity has been studied in the hydrogenation of a number of unsaturated compounds at temperatures of 60 and 80°C and pressures of 1.0 and 3.0 MPa.
- Kulikov,Terenina,Kryazheva, I. Yu.,Karakhanov
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p. 222 - 229
(2017/04/07)
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- IONIC LIQUID ALKYLATION OF 1-BUTENE TO PRODUCE 2,5-DIMETHYLHEXANE
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A process for producing dimethylhexanes (DMH) is provided. The DMH can be used to produce p-xylene. The process involves the alkylation of isobutane and 1-butene using an ionic liquid to produce naphtha that is rich in DMH. The DMH is then converted in high selectivity to xylene, including p-xylene, by dehydrocyclization.
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Page/Page column 17
(2015/09/23)
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- IONIC LIQUID ALKYLATION OF 1-BUTENE TO PRODUCE 2,5-DIMETHYLHEXANE
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A process for producing dimethylhexanes (DMH) is provided. The DMH can be used to produce p-xylene. The process involves the alkylation of isobutane and 1-butene using an ionic liquid to produce naphtha that is rich in DMH. The DMH is then converted in high selectivity to xylene, including p-xylene, by dehydrocyclization.
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Paragraph 0072
(2015/08/04)
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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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- 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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- Impact of cationic surfactant chain length during SAPO-11 molecular sieve synthesis on structure, acidity, and n-octane isomerization to di-methyl hexanes
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The structure, acidity, and n-octane di-branched isomerization of SAPO-11 synthesized with surfactants of different chain lengths in water-propanol system were investigated. The results showed that with the increasing chain length of surfactants, the crys
- Guo, Lin,Bao, Xiaojun,Fan, Yu,Shi, Gang,Liu, Haiyan,Bai, Danjiang
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p. 161 - 170
(2012/11/07)
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- Paraffin alkylation
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A liquid acid process is disclosed in which a hydrocarbon component containing an olefin, an olefin precursor or mixture and an isoalkane and a liquid acid catalyst is fed to a downflow reaction zone containing a disperser, under conditions to induce pulse flow at or near the outlet to react the isoalkane and olefin to produce a reaction product and feeding the reaction product to a vaporization zone containing a disperser under conditions to induce pulse flow at or near the outlet of the vaporization zone. A pressure drop across the disperser in the vaporization zone causes partial vaporization of the hydrocarbon which quench es the heat reaction and cooling the unvaporized portion of said reaction product, which is recovered and allowed to separate into an acid phase and hydrocarbon phase containing the alkylate. The acid catalyst and hydrocarbons may be fractally fed to the reaction zone.
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Page/Page column 7
(2008/06/13)
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- Alkylation process with recontacting in settler
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A system and/or process for decreasing the level of at least one organic fluoride present in a hydrocarbon phase contained in an alkylation settler by contacting the hydrocarbon phase with an HF containing stream, containing greater than about 80 wt. % and less than about 94 wt. % HF, in the intermediate portion of the settler which contains at least one tray system, with each tray system comprising a perforated tray defining a plurality of perforations and a layer of packing below the perforated tray, are disclosed.
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Page/Page column 3-5
(2008/06/13)
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- Alkene oligomerization process
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A process for oligomerising alkenes having from 3 to 6 carbon atoms which comprises contacting a feedstock comprising a) one or several alkenes having x carbon atoms, and, b) optionally, one or several alkenes having y carbon atoms, x and y being different, with a catalyst containing a zeolite of the MFS structure type, under conditions to obtain selectively oligomeric product containing predominant amounts of certain oligomers. The process is carried out at a temperature comprised between 125 and 175° C. when the feedstock contains only alkenes with 3 carbon atoms and between 140 and 240° C., preferably between 140 and 200° C. when the feedstock contains comprises at least one alkene with 4 or more carbon atoms.
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- Catalyst and process for contacting a hydrocarbon and ethylene
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A process of contacting at least one feed hydrocarbon, containing three to about seven carbon atoms per molecule, and ethylene in a hydrocarbon-containing fluid in the presence of a catalyst composition to provide at least one product hydrocarbon isomer containing about four to about nine carbon atoms per molecule is provided. The at least one feed hydrocarbon can be selected from paraffins, isoparaffins, and the like and combinations thereof. The catalyst composition contains a hydrogen halide component, a sulfone component, and a metal halide component.
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- Disproportionation of hydrocarbons
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A novel hydrocarbon disproportionation process is provided and includes contacting a hydrocarbon feed comprising at least one paraffin with a disproportionation catalyst comprising a support component, a metal, and a halogen in a disproportionation reaction zone under disproportionation reaction conditions.
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- Ionic liquid-catalyzed alkylation of isobutane with 2-butene
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A detailed study of the alkylation of isobutane with 2-butene in ionic liquid media has been conducted using 1-alkyl-3-methylimidazolium halides-aluminum chloride encompassing various alkyl groups (butyl-, hexyl-, and octyl-) and halides (Cl, Br, and I) on its cations and anions, respectively. The emphasis has been to delineate the role of both cations and anions in this reaction. The ionic liquids bearing a larger alkyl group on their cation ([C8mim]) displayed relatively higher activity than a smaller one ([C6 or C4mim]) with the same anionic composition, due to the high solubility of reactants in the former. Among the ionic liquids with different halide groups, bromides ([C8mim]Br-AlCl3) showed outstanding activity, because of the higher inherent acidity relative to others. From the 27Al NMR study, a major peak at ～99.5 ppm corresponding to [AlCl3Br]- (～99.5 ppm) was observed. Moreover, the anion showed a strong acidity based on FT-IR characterization; the largest peak related to acidity (1570 cm-1) was detected. Under various composition conditions, catalytic activity and amount of TMPs increased with concentration of anion. This is mainly attributed to a higher amount of strong acid ions [Al2Cl6Br]- which can react with hydrogen atoms at the 2-position of an imidazolium ion to form Bronsted acid. However, the ionic liquid with strong acidity (X=0.58) deactivated rapidly due to a higher sensitivity to moisture, causing decomposition. Under various reaction temperature conditions, optimum catalytic activity was observed at 80°C. The result is also attributed to the effect of anion composition. The strong acidic anion increased with temperature. However, at higher reaction temperatures (120°C), the ionic liquid showed a lower activity and TMP selectivity, since the solubility and Bronsted acid sites were reduced by decomposition of imidazolium ions. The selected ionic liquid sample ([C8mim]Br-AlCl3) was compared with one of the standard commercial catalysts, sulfuric acid. Under optimum experimental conditions, it was observed that both catalysts showed comparable catalytic behavior. However, ionic liquid showed higher activity, and lower TMP selectivity due to a more acidic nature and a lower amount of Bronsted acid sites, respectively.
- Yoo, Kyesang,Namboodiri, Vasudevan V.,Varma, Rajender S.,Smirniotis, Panagiotis G.
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p. 511 - 519
(2007/10/03)
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- Isobutane/2-Butene Alkylation on Ultrastable Y Zeolites: Influence of Zeolite Unite Cell Size
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The alkylation reaction of isobutane with trans-2-butene has been carried out on a series of steam-dealuminated Y zeolites with unit cell sizes ranging from 2.450 to 2.426 nm.A fixed-bed reactor connected to an automatized multiloop sampling system allowed us to make differential product analysis from very short (1 min or less) to longer times on stream.A maximum in the initial 2-butene conversion was found on samples with unit cell sizes between 2.435 and 2.450 nm.However, the TMP/DMH ratio, i.e., the alkylation-to-oligomerization ratio, continuously increased withzeolite unit cell size.The concentration of reactants in the pores, the strength distribution of Broensted acid sites, and the extent of hydrogen transfer reactions, which in turn depend on the framework Si/Al ratio of a given zeolite, were seen to affect activity and product distribution of the catalysts.Finally, the influence of these factors on the aging characteristics of the samples was also discussed.
- Corma, A.,Martinez, A.,Martinez, C.
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p. 185 - 192
(2007/10/02)
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- Distinguishing between Polar and Electron-Transfer Mechanisms for Reactions of Anions with Alkyl Halides
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9-Substituted fluorenide carbanions in the series 9-MeFl-, 9-MeO-Fl-, and 9-Me2N-Fl-, which have nearly the same basicities but become progressively easier to oxidize, were selected as a test trio to probe for electron-transfer (eT-) components or radical-pair intermediates in reactions with alkyl halides.The trio members were shown to undergo eT- at progressively faster rates (>102 rate span) with two different types of single-electron acceptors, as expected- On the other hand, with PhCH2Cl, i-BuBr, or i-BuI, SN2 products were formed in a rate order that was the reverse of that established as characteristic of eT-.Reactions of the more sterically hindered 9-i-Pr2N-Fl- ion with PhCH2Cl or i-BuI to give SN2 products were over 1400 times slower than those with 9-MeFl-, whereas the eT- rate with c-C6H10(NO2)Ts was eight times faster.On the other hand, reactions of the test trio with F3CCH2I, which is known to react slowly in SN2 reactions, gave the reactivity order characteristic of eT-, and radical-type products were formed.For this reaction, a plot of log kobsd vs.Eox(A-) for seven 9-G-Fl- ions, wherein the bulk and radical-stabilizing ability of G was varied, was linear.This result shows that Eox(A-) is a good measure of eT- ability and that eT- rates are insensitive to steric effects in either the donor or acceptor that cause larger rate retardations in polar SN2 reactions.
- Bordwell, F. G.,Wilson, Craig A.
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p. 5470 - 5474
(2007/10/02)
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- CONTRIBUTION A L'ETUDE DES REACTIONS DE COMBINAISON DES RADICAUX ALCOYLE TERTIAIRES EN PHASE SOLIDE
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Disproportionation/combination ratios of self-reacting t-alkyl radicals are estimated in solid phase at low temperature.The low temperature solid state limit was estimated to be 7-25, this value is considerably lower than ratios of the literature (100 to 500) and is compatible with the FISCHER limit in liquid state.In the present work, the ratios are determined by product analysis from the gamma radiolysis of isobutane.
- Gourdin-Serveniere, C.,Fontaine, L. M.,Tilquin, B.
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p. 177 - 188
(2007/10/02)
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- HOMOLOGATION OF HEXANE ISOMERS CATALYZED BY PLATINUM
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The homologation of n-hexane, 3-methylpentane, hexadienes and n-heptane were studied over Pt-black (and some supported Pt) and compared to the reactions of C8 hydrocarbons.The composition of C8-aromatics was used to evaluate the possible pathways.The ratio of internal to terminal addition was about 0.25; this way, the C8-composition from n-hexane could be explained.The appearence of branched chain saturated buildup products from 3-methylpentane and methylcyclopentane complicates their homologation and confirms the possibility of addition of C1 units to internal C-atoms, too.The mechanism of O'Donohoe et al. was found to be valid.
- Dobrovolszky, Maria A.,Paal, Zoltan,Tetenyi, Pal
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- COMPETITIVE HYDROGENATION OF UNSATURATED HYDROCARBONS ON PALLADIUM CATALYSTS MODIFIED WITH LEAD AND THALLIUM
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The competitive catalytic hydrogenations of pairs of 2,5-dimethyl-2,4-hexadiene with 1-heptene and 2-octyne with 1-heptene were studied on palladium black modified with lead or thallium to various degrees of coverage.The dissolved and adsorbed hydrogen was determied electrochemically and the selectivities of the competitive hydrogenations were established.The effect of the lead or thallium ad-atoms on the hydrogenation kinetics is discussed.
- Cerveny, Libor,Paseka, Ivo,Surma, Karel,Thanh, Nguyen Thi,Ruzicka, Vlastimil
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- Infrared Spectra of the Isobutyl and Neopentyl Radicals. Characteristic Spectra of Primary, Secondary, and Tertiary Alkyl Radicals
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Infrared spectra are presented for the isobutyl and neopentyl radicals for the first time.Significant differences are observed in the β-Ch stretching and pyramidal bending regions between primary alkyl radicals with straigth chains and those with branched chains like the isobutyl and neopentyl radicals.These are compared with spectra of other alkyl radicals to establish characteristic infrared spectra of primary, secondary, and tertiary alkyl radicals.
- Pacansky, J.,Brown. D. W.,Chang, J. S.
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p. 2562 - 2567
(2007/10/02)
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