- Probing the pore structure of hierarchical EU-1 zeolites by adsorption of large molecules and through catalytic reaction
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The adsorption of toluene and 1,3,5-trimethylbenzene and the catalytic transformation of 1,3,5-trimethylbenzene are applied as probing approaches to characterize the pore system of hierarchical EU-1 zeolites prepared using organofunctionalized fumed silica as the silicon source. The adsorption and diffusion of toluene and 1,3,5-trimethylbenzene are significantly improved in the hierarchical EU-1 zeolites compared with the conventional microporous EU-1 zeolite. The adsorption kinetics of toluene and 1,3,5-trimethylbenzene suggested that introducing mesopores significantly increases the rate of adsorption and improved the diffusion of large molecules. In the catalytic transformation of 1,3,5-trimethylbenzene, the conversion of 1,3,5-trimethylbenzene on the hierarchical EU-1 zeolites is doubled compared with the conventional microporous EU-1 zeolite, due to the improved diffusion of bulky molecules and enhanced accessibility of active sites in the hierarchical EU-1 structure. Although isomerization is the main reaction, differences are observed in the product ratios of isomerization to disproportionation between the hierarchical EU-1 zeolites and the microporous counterpart with different times on stream. The transformation of 1,3,5-trimethylbenzene over the hierarchical EU-1 zeolites has a higher isomerization to disproportionation ratio than that over the microporous EU-1 zeolite; this is due to the increased mesoporosity.
- Guo, Zaibin,Hao, Wenming,Ma, Jinghong,Li, Ruifeng
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Read Online
- PROCESS FOR CO-PRODUCTION OF MIXED XYLENES AND HIGH OCTANE C9+ AROMATICS
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Disclosed is a process for producing mixed xylenes and C9+ hydrocarbons in which an aromatic hydrocarbon feedstock comprising benzene and/or toluene is contacted with an alkylating agent comprising methanol and/or dimethyl ether under alkylation conditions in the presence of an alkylation catalyst to produce an alkylated aromatic product stream comprising the mixed xylenes and C9+ hydrocarbons. The mixed xylenes are subsequently converted to para-xylene, and the C9+ hydrocarbons and its components may be supplied as motor fuels blending components. The alkylation catalyst comprises a molecular sieve having a Constraint Index in the range from greater than zero up to about 3. The molar ratio of aromatic hydrocarbon to alkylating agent is in the range of greater than 1:1 to less than 4:1.
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Paragraph 0067-0072
(2019/10/23)
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- Selective Production of Renewable para-Xylene by Tungsten Carbide Catalyzed Atom-Economic Cascade Reactions
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Tungsten carbide was employed as the catalyst in an atom-economic and renewable synthesis of para-xylene with excellent selectivity and yield from 4-methyl-3-cyclohexene-1-carbonylaldehyde (4-MCHCA). This intermediate is the product of the Diels–Alder reaction between the two readily available bio-based building blocks acrolein and isoprene. Our results suggest that 4-MCHCA undergoes a novel dehydroaromatization–hydrodeoxygenation cascade process by intramolecular hydrogen transfer that does not involve an external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W2C surface. Notably, this process is readily applicable to the synthesis of various (multi)methylated arenes from bio-based building blocks, thus potentially providing a petroleum-independent solution to valuable aromatic compounds.
- Dai, Tao,Li, Changzhi,Li, Lin,Zhao, Zongbao Kent,Zhang, Bo,Cong, Yu,Wang, Aiqin
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supporting information
p. 1808 - 1812
(2018/02/10)
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- TRI-(ADAMANTYL)PHOSPHINES AND APPLICATIONS THEREOF
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In one aspect, phosphine compounds comprising three adamantyl moieties (PAd3) and associated synthetic routes are described herein. Each adamantyl moiety may be the same or different. For example, each adamantyl moiety (Ad) attached to the phosphorus atom can be independently selected from the group consisting of adamantane, diamantane, triamantane and derivatives thereof. Transition metal complexes comprising PAd3 ligands are also provided for catalytic synthesis including catalytic cross-coupling reactions.
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Page/Page column 31
(2017/05/17)
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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 0095-0103
(2016/06/13)
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- Tri(1-adamantyl)phosphine: Expanding the Boundary of Electron-Releasing Character Available to Organophosphorus Compounds
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We report here the remarkable properties of PAd3, a crystalline air-stable solid accessible through a scalable SN1 reaction. Spectroscopic data reveal that PAd3, benefiting from the polarizability inherent to large hydrocarbyl groups, exhibits unexpected electron releasing character that exceeds other alkylphosphines and falls within a range dominated by N-heterocyclic carbenes. Dramatic effects in catalysis are also enabled by PAd3 during Suzuki-Miyaura cross-coupling of chloro(hetero)arenes (40 examples) at low Pd loading, including the late-stage functionalization of commercial drugs. Exceptional space-time yields are demonstrated for the syntheses of industrial precursors to valsartan and boscalid from chloroarenes with ～2 × 104 turnovers in 10 min.
- Chen, Liye,Ren, Peng,Carrow, Brad P.
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supporting information
p. 6392 - 6395
(2016/06/09)
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- Catalytic conversion of isophorone to jet-fuel range aromatic hydrocarbons over a MoOx/SiO2 catalyst
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For the first time, jet fuel range C8-C9 aromatic hydrocarbons were synthesized in high carbon yield (～80%) by the catalytic conversion of isophorone over MoOx/SiO2 at atmospheric pressure. A possible reaction pathway was proposed according to the control experiments and the intermediates generated during the reaction.
- Chen, Fang,Li, Ning,Wang, Wentao,Wang, Aiqin,Cong, Yu,Wang, Xiaodong,Zhang, Tao
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supporting information
p. 11876 - 11879
(2015/07/15)
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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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- Creation of Bronsted acidity by grafting aluminum isopropoxide on silica under controlled conditions: Determination of the number of Bronsted Sites and their turnover frequency for m-xylene isomerization
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There is not a unique Bronsted acid site for aluminosilicates (ASAs). IR spectroscopy following CO adsorption proves the creation of Bronsted acid sites on Al/SiO2 ASAs, which are synthesized by the deposition of aluminum species on hydroxylated silica. These sites are active for ethanol dehydration and m-xylene isomerization. Controlled deposition under anhydrous conditions optimizes the number of sites, whereas the presence of water leads to alumina agglomerates with no Bronsted acidity. The turnover frequency for m-xylene isomerization (4.3×10-4s -1 site-1 at 350°C, atmospheric pressure, and 0.6cm3 h-1 of m-xylene) is approximately 3times lower than that of the Bronsted acid sites of Si/Al2O3 and 75times lower than that of an ultrastable Y-type zeolite without extra-framework aluminum. Ethanol as the acid test: The thermodesorption of ethanol demonstrates the formation of Bronsted acid sites on aluminum-grafted silica. Knowing the number of sites, the turnover frequency (TOF) for m-xylene isomerization is calculated. Bronsted sites of Al/SiO2 are weaker than those of Si/Al2O3 and ultrastable Y-type (USY) zeolites, which is reflected in the ethanol dehydration temperature.
- Caillot, Maxime,Chaumonnot, Alexandra,Digne, Mathieu,Vanbokhoven, Jeroen A.
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p. 832 - 841
(2014/03/21)
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- Cross-coupling reactions through the intramolecular activation of Alkyl(triorgano)silanes
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(Figure Presented) Cross-Si-ing the Jordan: Cross-coupling reactions of 2-(2-hydroxyprop-2-yl)phenylsubstituted alkylsilanes with a variety of aryl halides proceed in the presence of palladium and copper catalysts. The use of K3PO4 base allows for highly chemoselective alkyl coupling with both primary and secondary alkyl groups (Alk).
- Nakao, Yoshiaki,Takeda, Masahide,Matsumoto, Takuya,Hiyama, Tamejiro
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supporting information; scheme or table
p. 4447 - 4450
(2010/08/19)
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- Mesoporous materials with zeolite framework: Remarkable effect of the hierarchical structure for retardation of catalyst deactivation
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Hierarchical MFI zeolite was synthesized following a synthesis route using organic-inorganic hybrid surfactants; the resultant zeolite with mesoporous/microporous hierarchical structure exhibited remarkably high resistance to deactivation in catalytic activity of various reactions such as isomerization of 1,2,4-trimethylbenzene, cumene cracking, and esterification of benzyl alcohol with hexanoic acid, as compared with conventional MFI and mesoporous aluminosilicate MCM-41. The Royal Society of Chemistry 2006.
- Srivastava, Rajendra,Choi, Minkee,Ryoo, Ryong
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p. 4489 - 4491
(2008/09/19)
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- A novel reduction of polycarboxylic acids into their corresponding alkanes using n-butylsilane or diethylsilane as the reducing agent
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A convenient one-pot reaction has been developed for the reduction of polycarboxylic acids on aliphatic and aromatic systems to their corresponding alkanes. The reduction utilises either diethylsilane or n-butylsilane as the reducing agent in the presence of the Lewis acid catalyst tris(pentafluorophenyl)borane.
- Nimmagadda, Rama D.,McRae, Christopher
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p. 3505 - 3508
(2007/10/03)
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- Process for the production of mesitylene
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A process is described for the synthesis of mesitylene, characterized in that mesitylene is obtained starting exclusively from pseudocumene, without the use of any other chemical compound, operating in continuous, at a temperature ranging from 225 to 400°C, at a pressure ranging from 1 to 50 bar, at a weight space velocity ranging from 0.1 to 10 hours-1, and in the presence of a catalyst containing a zeolite selected from ZSM-5 zeolite having a crystal lattice based on silicon oxide and aluminum oxide, and ZSM-5 zeolite modified by the partial or total substitution of Si with a tetravalent element such as Ti or Ge and/or the partial or total substitution of Al with other trivalent elements, such as Fe, Ga or B.
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- Process for the production of mesitylene and durene
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A process is described for the contemporaneous preparation of mesitylene and durene, characterized in that mesitylene and durene are obtained exclusively starting from pseudo-cumene without the use of any further chemical compound, operating in continuous, at a temperature ranging from 210 to 400° C., at a pressure ranging from 1 to 50 bar, with a weight space velocity ranging from 0.1 to 20 hours?1 and in the presence of a catalyst based on crystalline metal-silicates in acid form. After the recovery of mesitylene and durene from the reaction raw product, some of the remaining components of the raw product itself are recycled and fed to the reactor together with the pseudo-cumene.
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- Process for the production of mesitylene
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A process is described for the synthesis of mesitylene, characterized in that mesitylene is obtained starting exclusively from pseudocumene, without the use of any other chemical compound, operating in continuous, at a temperature ranging from 225 to 400° C., at a pressure ranging from 1 to 50 bar, at a weight space velocity ranging from 0.1 to 10 hours?1, and in the presence of a catalyst containing a zeolite selected from ZSM-5 zeolite having a crystal lattice based on silicon oxide and aluminum oxide, and ZSM-5 zeolite modified by the partial or total substitution of Si with a tetravalent element such as Ti or Ge and/or the partial or total substitution of Al with other trivalent elements, such as Fe, Ga or B.
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- Process for the production of mesitylene and durene
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A process is described for the contemporaneous preparation of mesitylene and durene, characterized in that mesitylene and durene are obtained exclusively starting from pseudo-cumene without the use of any further chemical compound, operating in continuous, at a temperature ranging from 210 to 400°C, at a pressure ranging from 1 to 50 bar, with a weight space velocity ranging from 0.1 to 20 hours-1 and in the presence of a catalyst based on crystalline metal-silicates in acid form. After the recovery of mesitylene and durene from the reaction raw product, some of the remaining components of the raw product itself are recycled and fed to the reactor together with the pseudo-cumene.
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- The acidity and catalytic activity of supported acidic cesium dodecatungstophosphates studied by MAS NMR, FTIR, and catalytic test reactions
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Acidic cesium salts of dodecatungstophosphoric acid (H3PW) supported on silica and MCM-41 were characterized by multinuclear MAS NMR, FTIR, and catalytic test reactions. 31P-NMR data indicate that the supported samples contain salts of various stoichiometries (Cs3PW and Cs2HPW) and even H3PO4. According to 29Si-NMR data, deposition of the Cs salt does not change the relative amount of various SiOH groups in the case of the silica support. In contrast, when the support is MCM-41, the relative amount of the SiOH groups increases significantly, indicating the breaking of the siloxane bonds resulting from their interaction with H3PW. The 133Cs MAS-NMR spectra also suggest that the CsPW salt interacts more strongly with the MCM-41 support than with SiO2. The results of catalytic studies show that cesium salts of dodecatungstophosphoric acid with low Cs content supported on silica or MCM-41 (Cs1.7H1.3[PW12O40]-on-SiO 2 and Cs1.8H1.2[PW12O40]-on-MCM41) are active, selective, and recyclable catalysts in Friedel-Crafts alkylations (isopropylation, transalkylation), the aromatic ortho-Claisen rearrangement, and the dehydration of pinacol. The specific activity of these catalyst preparations are comparable with that of neat Cs2.6H0.4[PW12O40]. This indicates that the active species are in a well-dispersed form.
- Molnar,Beregszaszi,Fudala,Lentz,Nagy,Konya,Kiricsi
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p. 379 - 386
(2007/10/03)
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- Evaluation of acute toxicity and genotoxicity of liquid products from pyrolysis of Eucalyptus grandis wood
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Slow pyrolysis of Eucalyptus grandis wood was performed in an oven laboratory, and smoke was trapped and condensed to yield liquid products. Polycyclic aromatic hydrocarbons (PAHs) and phenolic fractions were isolated from the former liquid products using adsorption column chromatography (ACC) and identified by GC/MS. Concentrations of PAH and phenolic fractions in total pyrolysis liquids were respectively 48.9 μg/g and 8.59% (w/w). Acute toxicity of total samples of pyrolysis liquids and the phenolic fraction was evaluated by means of two bioassays, namely, 24-h immobilization bioassay with Daphnia magna and Microtox(TM) bioassays, the latter employing the luminescent bacteria Photobacterium phosphoreum. Total pyrolysis liquids and the PAH fraction were evaluated for genotoxicity by the Microtox(TM) bioassay conducted using rehydrated freeze-dried dark mutant of the luminescent bacteria Vibrio fisheri strain M169. Total pyrolysis liquids and the phenolic fraction, respectively, in concentrations of 170 and 68 mg/L were able to immobilize 50% (EC50) of the D. magna population following 24-h exposure. Concentrations of 19 and 6 mg/L, respectively, for total pyrolysis liquids and phenolic fraction were the effective concentrations that resulted in a 50% (EC50) reduction in light produced by bacteria in the Microtox(TM) bioassay. Accordingly, the Microtox(TM) bioassay was more sensitive to toxic effects of both kind of samples than the D. magna bioassay, particularly for the phenolic fraction. Regarding to the genotoxicity evaluation, the results achieved by Microtox(TM) bioassay showed that total pyrolysis liquids had no genotoxic effects with and without exogenous metabolic activation using rat liver homogenate (S9). However, the PAH fraction showed toxic effects with rat liver activation and had a dose-response number (DRN) equal to 1.6, being in this way suspected genotoxic. The lowest detected concentration (LDC) of the PAH fraction able to cause genotoxic effects was 375 μg/L.
- Pimenta,Bayona,Garcia,Solanas
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p. 169 - 175
(2007/10/03)
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- Characterization of the extra-large-pore zeolite UTD-1
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The molecular sieve UTD-1 is investigated using scanning and transmission electron microscopies (TEM), solid-state NMR spectroscopy, electron (ED) and X-ray diffraction (XRD), adsorption studies, and catalytic test reactions. The results confirm that UTD-1 is the first high-silica zeolite to contain a one;dimensional, extra-large 14-ring pore system. TEM and ED show that UTD-1 is faulted along the (002) planes. Simulations of XRD patterns of faulted structures using DIFFaX indicate that the XRD pattern of a framework containing the so-called double crankshaft chains is in better agreement with the experimental pattern than a framework with the narsarsukite chains previously reported. Thermal/hydrothermal stability studies show that UTD-1 has similar stability to other medium- and large-pore, high-silica zeolites. The ratio of isomerization to disproportionation, and the distribution of trimethylbenzene isomers in the m-xylene isomerization test reaction from UTD-1 are similar to those obtained from other large-pore zeolites (zeolites Y or L). However, UTD-1 shows a p-/o-xylene ratio of products below one.The molecular sieve UTD-1 is investigated using scanning and transmission electron microscopies (TEM), solid-state NMR spectroscopy, electron (ED) and X-ray diffraction (XRD), adsorption studies, and catalytic test reactions. The results confirm that UTD-1 is the first high-silica zeolite to contain a one-dimensional, extra-large 14-ring pore system. TEM and ED show that UTD-1 is faulted along the (002) planes. Simulations of XRD patterns of faulted structures using DIFFaX indicate that the XRD pattern of a framework containing the so-called double crankshaft chains is in better agreement with the experimental pattern than a framework with the narsarsukite chains previously reported. Thermal/hydrothermal stability studies show that UTD-1 has similar stability to other medium-and large-pore, high-silica zeolites. The ratio of isomerization to disproportionation, and the distribution of trimethylbenzene isomers in the m-xylene isomerization test reaction from UTD-1 are similar to those obtained from other large-pore zeolites (zeolites Y or L). However, UTD-1 shows a p-/o-xylene ratio of products below one.
- Lobo, Raul F.,Tsapatsis, Michael,Freyhardt, Clemens C.,Khodabandeh, Shervin,Wagner, Paul,Chen, Cong-Yan,Balkus Jr., Kenneth J.,Zones, Stacey I.,Davis, Mark E.
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p. 8474 - 8484
(2007/10/03)
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- ORBITAL-CONTROLLED REACTIONS CATALYSED BY ZEOLITES: ELECTROPHILIC ALKYLATION OF AROMATICS
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The role of orbital control in product selectrivity during electrophilic alkylation catalysed by zeolites was studied both theoretically and experimentally.In order to discuss this, the alkylation of toluene and m-xylene by methanol was carried out on a series of large-pore zeolites (HY).The changes in the para to ortho ratio observed on changing the framework Si/Al ratio of the zeolites were related to ab initio molecular orbital calculations of the LUMO energy of structurally alike model clusters but containing different tetrahedral cations around the active site.The observed correlation is discussed in terms of the HSAB principle by taking into account the influence of the catalyst composition on the reactivity of the electrophilic reagent.
- Corma, A.,Zicovich-Wilson, C.,Viruela, P.
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p. 364 - 370
(2007/10/02)
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- Isomerization and Disproportionation of 1,2,4-Trimethylbenzene over HY Zeolite
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The conversion of 1,2,4-trimethylbenzene (1,2,4-TMB) over HY zeolite was studied at atmospheric pressure and 200-300 deg C by using a fixed-bed, integral-flow reactor.The types and initial selectivities of various products were obtained from plots of product selectivity according to the time-on-stream theory.The primarly reaction included the isomerization and the disproportionation: the former led to the simultaneous formation of 1,2,3- and 1,3,5-TMB whereas the latter produced all isomers of xylene and tetramethylbenzene.The relative initial activation energies for the primary reactions were estimated and compared with those in the reaction of 1,2,3-TMB.
- Ko, An-Nan,Kuo, Ching Tung
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p. 145 - 150
(2007/10/02)
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- DETERMINATION OF COMPOSITION OF REACTION MIXTURES FROM ALKYLATION OF TOLUENE ON PHOSPHORUS-MODIFIED H-ZSM-5 ZEOLITE
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Determination of analytical composition of reaction mixtures formed by alkylation of toluene with ethylene on a phosphorus-modified H-ZSM-5 zeolite was made by capillary high resolution gas chromatography.Identification of individual components on these reaction mixtures was performed by GC-MS method, using the samples obtained at 320 and 400 deg C on H-ZSM-5 catalyst (modul 43.6) modified with 3.4 wt.percent phosphorus at toluene to ethylene molar ratio 4.5:1 and the catalyst loading expressed as weight hour space velocity WHSV (for toluene) = 6.9 h-1.The reaction mixtures contained a total 86 hydrocarbons.It was confirmed that in addition to the main alkylation reaction, there proceeds also ethylene oligomerization with subsequent cyclization and aromatization, disproportionation, alkylation and cyclization reactions of alkylaromatic hydrocarbons to give alkylnaphthalines and alkylindanes.
- Mravec, Dusan,Herain, Jiri,Holotik, Stefan
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p. 1832 - 1839
(2007/10/02)
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- Dependence of the Lewis Acid-Induced Reaction of β-Stannyl Ketones upon Substitution Pattern: Cyclopropanation versus 1,2-Alkyl Migration
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3-Stannylcyclohexanones fully substituted at 2 and 3 positions underwent a 1,2-aklyl migration, along with the cyclopropanation.The balance of the reactions depended upon the steric environment and migratory aptitude of the alkyl groups.
- Fujiwara, Jun,Sato, Tadashi
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p. 1258 - 1264
(2007/10/02)
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- Characterization and catalytic properties of USHY zeolite modified with niobium.
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USHY zeolite was exchanged by niobium.Several samples were obtained with various degrees of exchange.Pore volumes and acidity were measured to characterize these exchanged zeolites.Catalytic properties were evaluated with two reaction tests: metaxylene transformation and n-heptane cracking.Key Words: USHY zeolite / niobium exchange / pore volume / acidity / catalysis
- Florentino, A.,Cartraud, P.,Magnoux, P.,Guisnet, M.
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p. 496 - 500
(2007/10/02)
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- Catalytic Isomerization of Trimethylbenzenes over a Graphite-Sulfuric Acid
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The isomerization of 1,2,3- and 1,2,4-trimethylbenzene took place over a graphite-sulfuric acid to form 1,2,4- and 1,2,3-trimethylbenzene, respectively, but that of 1,3,5-trimethylbenzene was not observed.
- Tsuchiya, Susumu,Fujii, Kenji,Mitsuno, Tadashi,Sakata, Yoshihisa,Imamura, Hayao
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p. 1011 - 1012
(2007/10/02)
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- Kinetics of the thermolysis of [n.2.2]propellanes and related compounds. Mechanism of the thermolysis of bicyclo[2.2.0] hexanes
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The thermolyses of a series of 1,4-bridged bicyclo[2.2.0]hexanes have been studied. With bridges having three or more carbons, the compounds have higher activation energies than for bicyclo[2.2.0]hexane, indicating that the bridge prevents the formation of a chair cyclohexane-1,4-diyl, forcing the reaction to proceed via an orbital symmetry disallowed process. It appears likely that [2.2.2]propellane and its derivatives react via the same mechanism, and the driving force from strain relief appears to be the major factor in reducing its activation energy. The thermolysis of the relatively unstrained [3.3.2]propellane occurs at a significantly higher temperature and leads to a mixture of products which also were found in the thermolysis of 1,5-dimethylenecyclooctane. The thermolysis of the latter at 420°C formed the propellane. The strain relief in the cleavage of the central bond in this group of propellanes were estimated via a combination of ab initio and molecular mechanics calculations and was found to be correlated with the changes in activation energy. The thermolyses of [3.2.1]- and [4.2.1]propellanes also are reported and were found to be less reactive than expected on the basis of strain energy relief.
- Wiberg, Kenneth B.,Caringi, Joseph J.,Matturro, Michael G.
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p. 5854 - 5861
(2007/10/02)
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- Shape Selective Property of Alumina-pillared Montmorillonite with Different Lateral Distances in m-Xylene Conversion
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In m-xylene conversion on alumina-pillared montmorillonite, the selectivity of disproportionation increased with increasing lateral distance, while isomerization was predominant for the small lateral distance.The observed results suggest that the shape selectivity operates in the reaction.
- Mori, Toshiaki,Suzuki, Kenzi
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p. 2165 - 2168
(2007/10/02)
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- FORMATION DE COKE ET DESACTIVATION DE ZEOLITHES PROTONIQUES AU COURS DE LA TRANSFORMATION DU m-XYLENE
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A kinetic study of coke formation during the transformation of m-xylene was carried out on 4 protonic zeolites: HY, H-mordenite (HM), H-offretite (HO) and HZSM-5.Whatever the zeolite, strong acid sites (on which the heat adsorption of ammonia is over 100 kjoules per mole) are capable of isomerizing about 100 m-xylene molecules per hour.However their activities for coke formation depend on the type of zeolite: similar on HM and on HY, 7 times smaller on HO and 50 times on HZSM-5.On the two latter, coke formation is inhibited because of steric constraints in the vicinity of the acid centers.The coke deposit causes disproportionation to decrease more than isomerization.The toxicity of coke also depends very much on the zeolite used: low on tridimensional zeolites (HY, HZSM-5), very high on monodimensional ones (HM and HO) and this especially since the channels are narrower.This very rapid deactivation of the monodimensional zeolites can be easily explained by the blockage of their channels: a coke deposit corresponding to an occupation of about 20 percent of the channel volume in the case of HM and of about 5 percent in the case of HO is sufficient to suppress all their activity.
- Gnep, Ngi Suor,Tejada, Jorge,Guisnet, Michel
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- Hydrocarbures arylaliphatiques. Partie VIII. Etude cinetique de la protodesilylation de benzocyclenes tricycliques
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A kinetic study of the protodesilylation of silylated derivatives of hemimellitene, 2a,3,4,5 tetrahydro acenaphthene and 1H 2,2a,3,4,5,6 hexahydro benzo(c,d)azulene is described.These results complete those published previously and which are related to the influence of the ring size of alicyclic systems pericondensed to a benzene nucleus on the reactivity of the nucleus to acetylation or bromination.The silylated derivatives were prepared from the corresponding bromo compounds.The synthesis of the bromo compounds, some of which were described in an earlier study, is completed here by using a synthetic pathway which allows the preparation of the β isomers starting from the ortho bromo derivatives.The kinetic results show a deactivation of the β position of the hemimellitene.A little deactivation of ortho α position of the five membered ring in the tricyclic compounds is also observed.This last result, significant in the case of bromination, seems to be related to the Mills-Nixon effect and can be explained by using Streitwieser's hybridization for the ? skeleton.
- Gruber, Rene,Kirsch, Gilbert,Cagniant, Denise
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p. 498 - 504
(2007/10/02)
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- Composition and process for augmenting, enhancing or imparting a leather aroma to consumable materials
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Described is the process for augmenting, enhancing or imparting leather aromas to consumable materials including perfume compositions, colognes, perfumed polymers and perfumed articles including solid or liquid anionic, cationic, nonionic or zwitterionic detergents, fabric softener compositions, fabric softener articles, hair preparations, cosmetic powders and the like, by adding thereto a composition of matter consisting of the following ingredients: "A": At least one substance having the structure: STR1 in an amount of from about 1% up to about 5% wherein R9 represents C9 -C11 straight-chain alkyl and wherein R10 represents methyl and X is a moiety selected from the group consisting of: STR2 "B": At least one compound having the structure: STR3 in an amount of from about 3 up to about 7% wherein each of R12 -R15 represents hydrogen or C1 -C4 alkyl with the proviso that at least two of R12 -R15 represents hydrogen; "C": At least one compound having the structure: STR4 in an amount of from about 2% up to about 6% wherein R1, R2, R3, R4 and R5 each represents hydrogen or C1 -C4 alkyl with the proviso that one, two or three of R1, R2, R3, R4 and R5 represents C1 -C4 alkyl; "D": Optionally, at least one compound having the structure: STR5 in an amount of from 0% up to about 1.2% wherein R6 represents hydrogen or methyl and R11 represents hydrogen or methyl with the proviso that at least one of R6 or R11 is hydrogen; "E": At least one compound defined according to the structure: STR6 in an amount of from about 30% up to about 70% wherein R7 represents C11, C13, or C15 straight-chain alkyl and R8 represents C1 -C3 lower alkyl; "F": At least one compound having the structure: STR7 in an amount of from about 20% up to about 60% wherein n represents an integer of from 8 up to 28; "G": Optionally, the compound having the structure: STR8 in an amount of from 0 up to about 6%; and "H": Optionally, the compound having the structure: STR9 in an amount of from 0 up to about 6% with the requirement that: STR10 equal 100%.
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- Alkylation Reactions over Ion-exchanged Molecular Sieve Zeolite Catalysts. Part 1. Alkylation of Toluene with Methanol: Consideration of the Effects of Reaction Parameters on Catalyst Deactivation and the Extent of Polysubstitution
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The alkylation of toluene with methanol under non-isomerizing conditions has been studied over a range of ion-exchanged zeolite catalysts.Rapid deactivation with increasing time on stream was observed in the case of LaY and NH4Y catalysts, whereas a NiY and a range of Ni,SnY samples manifested a high steady-state activity; the catalytic activity at the steady state could be related to the chemical composition of these latter samples.Catalyst deactivation was always associated with the formation of polysubstituted products.From a detailed study of the systems at the steady state it was concluded that (i) methylation of toluene is always a ssociated with the formation of tri- or tetra-methylbenzenes to a greater or lesser extent over the partially deactived catlysts; (ii) the origin of the polymethylated products is a weakly adsorbed o-xylene species: (iii) the selectivity towards polysubstitution varies with time on stream.This results from a change in the strength of interaction between the xylenes and the catalyst surface as shown by studies of the heats of immersion of the catalysts.
- Coughlan, Brendan,Carroll, William M.,Nunan, John
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p. 281 - 296
(2007/10/02)
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- Generation of Acidic Sites in Metal Salts of Heteropolyacids
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The effects of water and hydrogen on the generation of acid sites in the metal salts of dodecatungstophosphoric acid (H3PW12O40, HTP) are studied by means of catalysis amd infrared spectroscopy.The silver salt has no activity for o-xylene isomerization and pyridinium ion was not formed by adsorption of pyridine.By the reaction of the salt with hydrogen at 300 deg C, the activity for xylene isomerization appeared and the development of acid sites is confirmed by infrared spectroscopy.The scheme of the generation of acid sites is expressed as Ag+ + 1/2 H2 --> Ago H+.The features of the copper(II) salt are similar to those of the silver salts.The high acidity of the copper(II) salt is demonstrated by the inhibition of the catalytic activity for dehydration of 1-butanol by the sorption of pyridine.For the aluminium salt, hydrogen has no effect on the isomerization activity.But the activity and the capacity for pyridinium ion formation are enhanced by treatment with water.A plausible scheme for acid-site formation in aluminium salt is expressed as Al3+ + H2O --> 2+ + H+.
- Baba, T.,Watanabe, H.,Ono, Y.
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p. 2406 - 2411
(2007/10/02)
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- Mise au point d'une reaction simple de caracterisation du reseau poreux des zeolithes de taille de pore intermediaire
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Over three protonic zeolithes : HY, HZSM-5 and H mordenite, the initial selectivities of the transformations of xylenes and 1,2,4-trimethylbenzene have been compared.The ratio of disproportionation to isomerization rates which is close to 1 on Y zeolite, is 3 to 20 times lower on mordenite and equal to zero on ZSM-5 zeolite.The ratio of the amount of hydrocarbon transformed into coke to the amount isomerized is 2 times greater for Y zeolite than for mordenite and 30 to 90 times greater than for ZSM-5 zeolite.The distribution of the primary products of isomerization depends very much on the zeolite : the smaller the pore size, the more favoured will be the smallest isomer.Thus by m-xylene isomerization over Y zeolite, ortho and para-xylenes are obtained in equal quantities, whereas over mordenite and above all over ZSM-5 zeolite, the smallest para isomer is definitely favoured.The distribution of the disproportionation primary products is also quite different over mordenite and over Y zeolite.For example, over Y zeolite, the 1,3,5- and 1,2,4-trimethylbenzenes are formed in their equilibrium mixture, whereas over mordenite, the 1,3,5-trimethylbenzene is practically not formed.These observations can be explained by the three types of shape selectivity defined by Csicsery (Zeolite chemistry and catalysis, Ed.J.A.Rabo, ACS monograph, 171, Washington, 1976, p. 680) : selectivity due to i) the difficulty of access of the reactant to active sites; ii) the difficulty of product desorption; iii) the difficulty of formation of bulky intermediates.The reactions of these aromatic hydrocarbons are therefore of great interest for characterizing the pore structure of intermediate pore size zeolites such as mordenite and ZSM-5 zeolite.The m-xylene transformations are shown to be model reactions the best adapted for this characterization.The selectivity of m-xylene isomerization is related to the pore size : the smaller the pores, the more favoured p-xylene will be.The distribution of the disproportionation products (trimethylbenzenes) as well as the ratio of the rate of disproportionation (a bimolecular reaction) to the rate of isomerization (an intramolecular reaction) are directly related to the maximum space available for the formation of intermediates or of transition states, and are therefore directly related to the cavity size or to the size of the channel intersections.This model reaction which is easy to use leads to more detail information than the constraint index (as defined by Mobil investigators) which is related only to the pore size.
- Gnep, Ngi Suor,Tejada, Jorge,Guisnet, Michel
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- Photoinduced Decomposition of Peracetic Acid in Xylenes. Orientation in Aromatic Substitution of Methyl and Hydroxyl Radicals
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The photolysis of peracetic acid (1) in o-,m- or p-xylenes (2) has been carried out using 2537-Angstroem or >2900-Angstroem light at 20-22 deg C.The yields of ethyltoluenes (3), trimethylbenzenes (4), and dimethylphenols (6) are higher at 2537-Angstroem than those at >2900-Angstroem photolysis, but the reverse is true with the yield of methylbenzyl alcohol (5).The isomer distribution of trimethylbenzenes (4) formed from o- (2a) or m-xylene (2b) suggests that an attack of methyl radical at the position meta to the methyl group is favored with 2537-Angstroem light, while an attack at the ortho position is preferential with >2900-Angstroem light.On the other hand, the isomer distribution of dimethylphenols (6) at 2537 Angstroem suggests that an attack of hydroxyl radical is favored at positions ortho and para to the methyl group.These orientations of radical attack are briefly discussed.
- Ogata, Yoshiro,Tomizawa, Kohtaro
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p. 785 - 788
(2007/10/02)
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