- 2,3-Butanediol dehydration catalyzed by silica-supported alkali phosphates
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Characterization of acid-base centers and catalytic dehydration of 2,3-butanediol (BDO) was performed over a wide range of silica-supported alkali phosphates (M_P/SiO2; M = Na, K, Cs; M:P = 0.5–3 mol:mol). Selectivity to 1,3-butadiene (BD) and 3-butene-2-ol (3B2OL) formed by elimination correlates with the densities of conjugated acid-base pairs and increases in the order Na ??M+ moieties. Isolated Br?nsted acid centers are probably silica grafted phosphoric acid molecules at low M/P and –PO(OH)2 end groups of oligophosphates at M/P > 1.5. Deactivation rate increases with the increase of M/P ratio in order Na K Cs. Deactivation patterns imply that sites responsible for elimination are active in dehydrative epoxidation. Dehydration of 3B2OL smoothly proceeds to BD, but the catalysts deactivate faster compared to BDO dehydration.
- Kim, Wooyoung,Shin, Wookyun,Lee, Kyoung Jun,Cho, YongSeok,Kim, Hyung Soon,Filimonov, Igor N.
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p. 148 - 163
(2018/11/26)
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- Oxidation of lower alkenes by Α-oxygen (FeIII–O??)Α on the FeZSM-5 surface: The epoxidation or the allylic oxidation?
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Reactions of anion-radical α-oxygen (FeIII–O??)α with propylene and 1-butene on sodium-modified FeZSM-5 zeolites were studied in the temperature range from ?60 to 25 °C. Products were extracted from the zeolite surface and identified. It was found that main reaction pathway was the epoxides formation. Selectivity for epoxides at ?60 °C was 59–64%. Other products were formed as a result of secondary transformations of epoxides on the zeolite surface. According to IR spectroscopy, the oxidation of propylene over the entire temperature range and 1-butene at ?60 °C were not accompanied by the formation of (FeIII–OH)α groups, in distinction to methane oxidation. This testifies that hydrogen abstraction does not occur. In case of 1-butene reaction with α-oxygen at 25 °C, hydrogen abstraction occurred but was insignificant, ca 7%. According to DFT calculation ferraoxetane intermediate formation is preferable over hydrogen abstraction. Following decomposition of this intermediate leads to the propylene oxide (PO) formation. The results may be relevant to the low selectivity problem of the silver catalyst in propylene epoxidation and raise doubts about the presently accepted mechanism explaining an adverse effect of allylic hydrogen.
- Starokon, Eugeny V.,Malykhin, Sergei E.,Parfenov, Mikhail V.,Zhidomirov, Georgy M.,Kharitonov, Alexander S.
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- A method for preparing epoxy butane
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The invention relates to a method for preparing epoxy butane, which comprises the following step: in an isopropyl benzene solution containing 25 wt% of cumene hydroperoxide solute, preparing epoxy butane from butylene oxide by using the cumene hydroperoxide solute as an oxidizer and a titanium-silicon molecular sieve with three-dimensional pore canal structure as a catalyst, wherein the fixed bed reaction conditions are as follows: the mole ratio of butylene to the cumene hydroperoxide solute is (5.0-12.0):1, the weight hourly space velocity of the cumene hydroperoxide is 1.0-5.0 h, the reaction pressure is 1.0-6.0 MPa, and the temperature is 60.0-120.0 DEG C. The catalyst is the titanium-silicon molecular sieve with three-dimensional pore canal structure; the molecular sieve has hysteresis loop on the low-temperature nitrogen adsorption and desorption isotherm; the average pore size is 2.0-8.0nm, and the specific area is 650.0-1100.0 m/g; and the catalyst has the advantages of favorable activity and high epoxy butane selectivity, and can be widely popularized and applied to industrial production of epoxy butane by butylene epoxidation.
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Paragraph 0019; 0020
(2017/03/08)
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- A comprehensive test set of epoxidation rate constants for iron(IV)-oxo porphyrin cation radical complexes
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Cytochrome P450 enzymes are heme based monoxygenases that catalyse a range of oxygen atom transfer reactions with various substrates, including aliphatic and aromatic hydroxylation as well as epoxidation reactions. The active species is short-lived and difficult to trap and characterize experimentally, moreover, it reacts in a regioselective manner with substrates leading to aliphatic hydroxylation and epoxidation products, but the origin of this regioselectivity is poorly understood. We have synthesized a model complex and studied it with low-pressure Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry (MS). A novel approach was devised using the reaction of [FeIII(TPFPP)]+ (TPFPP = meso-tetrakis(pentafluorophenyl)porphinato dianion) with iodosylbenzene as a terminal oxidant which leads to the production of ions corresponding to [FeIV(O)(TPFPP+a?￠)]+. This species was isolated in the gas-phase and studied in its reactivity with a variety of olefins. Product patterns and rate constants under Ideal Gas conditions were determined by FT-ICR MS. All substrates react with [FeIV(O)(TPFPP+a?￠)]+ by a more or less efficient oxygen atom transfer process. In addition, substrates with low ionization energies react by a charge-transfer channel, which enabled us to determine the electron affinity of [FeIV(O)(TPFPP+a?￠)]+ for the first time. Interestingly, no hydrogen atom abstraction pathways are observed for the reaction of [FeIV(O)(TPFPP+a?￠)]+ with prototypical olefins such as propene, cyclohexene and cyclohexadiene and also no kinetic isotope effect in the reaction rate is found, which suggests that the competition between epoxidation and hydroxylation - in the gas-phase - is in favour of substrate epoxidation. This notion further implies that P450 enzymes will need to adapt their substrate binding pocket, in order to enable favourable aliphatic hydroxylation over double bond epoxidation pathways. The MS studies yield a large test-set of experimental reaction rates of iron(iv)-oxo porphyrin cation radical complexes, so far unprecedented in the gas-phase, providing a benchmark for calibration studies using computational techniques. Preliminary computational results presented here confirm the observed trends excellently and rationalize the reactivities within the framework of thermochemical considerations and valence bond schemes.
- Sainna, Mala A.,Kumar, Suresh,Kumar, Devesh,Fornarini, Simonetta,Crestoni, Maria Elisa,De Visser, Sam P.
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p. 1516 - 1529
(2015/03/04)
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- Gas-phase dehydration of vicinal diols to epoxides: Dehydrative epoxidation over a Cs/SiO2 catalyst
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A novel type of dehydration reaction that produces epoxides from vicinal diols (dehydrative epoxidation) using a basic catalyst is reported. Epoxyethane, 1,2-epoxypropane, and 2,3-epoxybutane were produced from the dehydrative epoxidation of ethylene glycol, 1,2-propanediol, and 2,3-butanediol, respectively. Among a number of tested basic catalysts, the Cs/SiO2 catalyst showed outstanding performance for the dehydrative epoxidation of 2,3-butanediol and is considered to be the most promising catalyst for this type of reaction. In order to identify the superiority of the Cs/SiO2 catalyst and a mechanism of the reaction, structure-activity relationships were studied along with density functional theory (DFT) calculations. The following features are found to be responsible for the excellent activity of the Cs/SiO2 catalyst: i) strong basic sites formed by Cs+, ii) low penetration of Cs+ into SiO2 which permits basic sites to be accessible to the reactant, iii) stable basic sites due to the strong interactions between Cs+ and SiO2 surface, and iv) mildly acidic surface of SiO2 which is advantageous for the elimination to H2O. In addition, the dehydrative epoxidation involves an inversion of chirality (e.g. meso-2,3-butanediol (R,S) to trans-2,3-epoxybutane (R,R or S,S)), which is in agreement with DFT results that the reaction follows a stereospecific SN2-like mechanism.
- Kim, Tae Yong,Baek, Jayeon,Song, Chyan Kyung,Yun, Yang Sik,Park, Dae Sung,Kim, Wooyoung,Han, Jeong Woo,Yi, Jongheop
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- Catalytic epoxidation of olefins in the presence of a vanadyl porphyrin complex
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It was found that vanadyl porphyrin complexes synthesized from petroleum metal porphyrin concentrates stimulated epoxidation during the olefin oxygenation process. The yields of obtained oxiranes turned out to be 38-75%, depending on the olefin structure. An epoxidation mechanism that suggests the formation of a protonated dioxygen adduct as an intermediate during oxygenation of olefins in the presence of vanadyl porphyrin complexes was proposed. An analogy is drawn between the epoxide formation reaction upon the catalytic oxygenation of olefins and the Prilezhaev reaction. MAIK "Nauka/Interperiodica".
- Miralamov,Mamedov
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- Surface-modified mixed oxides containing noble metal and titanium for the selective oxidation of hydrocarbons
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This invention relates to a process for the production of a composition containing gold and/or silver particles, mixed oxides containing titanium and silicon which have been surface-modified, to the compositions producible in this process and to the use thereof in processes for the selective oxidation of hydrocarbons in the presence of oxygen and a reducing agent. The catalytically active compositions exhibit constantly high selectivities and productivities.
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- Sol-gel hybrid materials containing precious metals as catalysts for partial oxidation of hydrocarbons
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The present invention relates to a process for preparing a composition containing gold and/or silver particles and an amorphous, organic/inorganic titanium/silicon mixed oxide, the compositions which can be prepared by this process and their use as catalysts for the selective oxidation of hydrocarbons.
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- Catalyst for use in production of epoxide, method for producing the catalyst, and method for producing epoxide
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To provide an epoxide-production-use catalyst that is suitably used for producing an epoxide by partial oxidation of an unsaturated hydrocarbon, a catalyst in accordance with the present invention is obtained by fixing gold fine particles to a carrier containing an oxide containing at least one of titanium and zirconium, and has an acid quantity of not more than 0.1 mmol/g determined by the NH3-TPD method. Such a catalyst for epoxide producing use can be produced by, for instance, fixing gold fine particles to a carrier having an acid quantity of not more than 0.15 mmol/g. The catalyst for epoxide producing use arranged as above is preferably used as a catalyst in partial oxidation of an unsaturated hydrocarbon to produce a corresponding epoxide.
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- 8-HYDROXY-SUBSTITUTED ISOCOUMARINS BY LITHIATION OF BENZENE DERIVATIVES PROMOTED BY β-FUNCTIONALISED ALKYL GROUPS. A REGIOSELECTIVE AND SIMPLE SYNTHESIS OF OOSPOLACTONE
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3-(3-hydroxyphenyl)-2-butanone (obtained in 3 steps from 3-bromophenol and 3-chloro-2-butanone) was ketalised with ethylene glycol and protected at the phenolic OH as the methoxymethyl ether.The intermediate diacetal thus obtained underwent hydrogen-metal exchange with n-butyllithium; the metallated intermediate, after carbonation, methanolysis of acetal groups and elimination of methanol, regioselectively afforded the title compound (8-hydroxy-3,4-dimethylisocoumarin).
- Ramacciotti, Alessio,Fiaschi, Rita,Napolitano, Elio
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p. 111 - 114
(2007/10/02)
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- Reactions Involving Hot O(3P) Atoms and Isomeric 2-Butene
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The low-pressure gas-phase investigation is reported on the reactions involving high-energy O(3P) atoms with cis- and trans-butene.Gas chromatographic analysis of stable hydrocarbon end products revealed a complex spectrum of compounds containing carbonyl, epoxide, and alcohol groups.The large distribution of alcohol products was a distinct feature in these hot atom systems, indicating that OH radical formation was important.These analyses revealed differences in the internal energy levels of the reaction intermediates formed through the greater pressure dependence exhibited by the degree of stereospecific addition of oxygen atoms to trans-butene then reaction with cis-butene and through the greater degree of internal rearrangement and carbon-carbon bond scission exhibited by the trans intermediate.Direct measurements using on-line mass spectrometry also revealed that CO product signals were 14.6 times higher from reactions with cis-butene than with trans-butene, indicating greater reactivity of the cis ?-bond toward oxygen atom attack.Similarly, these direct analyses revealed that OH product signals were 1.7 times higher from reactions with cis-butene, suggesting that in addition to direct H abstraction an indirect pathway involving mutual interaction with the substrate's ?-bond may have contributed, in part, to those OH products observed in these studies.Kinetic energy moderator studies supported this hypothesis through the different moderator dependencies exhibited by the OH product signals seen to arise from high-energy oxygen atom reactions with the two stereoisomers.
- Ferrieri, Richard A.,Wolf, Alfred P.
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p. 4747 - 4752
(2007/10/02)
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- Oxidation Chemistry of Propene in the Autoignition Region: Arrhenius Parameters for the Allyl + O2 Reaction Pathways and Kinetic Data for Initiation Reactions
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The oxidation of propene has been studied at a total pressure of 60 Torr between 400 and 520 deg C, and a detailed product analysis made in the initial stages of reaction over a wide range of mixture composition.Mechanisms for the formation of the products are discussed.The initial rates of formation of hexa-1,5-diene (HDE) and carbon monoxide are used to obtain A8 = 109.66 +/- 0.35 dm3 mol-1 s-1 and E8 = 78.6 +/- 4.5 kJ mol-1, the former giving from the known value of k1 CH2=CHCH2* + CH2=CHCH2* -> CH2=CHCH2CH2CH=CH2 (1).CH2=CHCH2* + O2 -> CO + products.Arrhenius parameters are also given for alternative pathways of the allyl + O2 reaction.All involve high energy barriers.From measurements of the accelerating effect of small amounts of additives CH3CHO, HCHO, HDE and propene oxide, rate constants at 480 deg C are obtained (for the first three) for the initiation reaction (21) RH + O2 -> R + HO2.Very few independent data for this type of reaction are available.The accelerating effect of propene oxide is ascribed to an exothermic isomerisation product which is not thermally stabilised at 60 Torr and undergoes homolysis to radical fragments.HDE is shown to have a spectacular accelerating effect on propene oxidation and values of k21n/k10 = 1050 +/- 200 at 480 deg C is obtained.C3H6 + O2 -> CH2=CHCH2* + H2O.HDE + O2 -> *CH2CH=CHCH2CH=CH2 + H2O.
- Stothard, Nigel D.,Walker, Raymond W.
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p. 2621 - 2630
(2007/10/02)
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- Oxirane Formation in the Reaction of NO3 Radicals with Alkenes
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Chemical Kinetics / Mass Spectrometry / Radicals.Mass spectra of products formed in the reaction between NO3 and cis-2-butene, isobutene, 2-methyl-2-butene and 2,3-dimethyl-2-butene at 298 K and p = 3-10 mbar were obtained, using a fast flow system with molecular beam sampling.The spectra indicate formation of an oxirane in each reaction.Within experimental error the oxirane yields in the reaction of cis-2 butene and of 2,3-dimethyl-2-butene were identical (90+/-10)percent.The rate of oxirane formation was found to obey the rate equation for the reaction: NO3 + alkene oxirane + NO2. (1) Good agreement was obtained for the rate constants of reaction (1) determined from the rate of oxirane formation and those determined in earlier works from the consumption of reactants.
- Wille, U.,Rahman, M. M.,Schindler, R. N.
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p. 833 - 835
(2007/10/02)
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- Arrhenius Parameter for the Addition of HO2 Radicals to (E)-But-2-ene over the Range 400 - 520 deg C
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Studies have been made of the addition of HO2 radicals to (E)-but-2-ene in the temperature range 400 - 520 deg C, by use of the co-oxidation of (E)-but-2-ene and propene in the presence of tetramethylbutane as a source of HO2 radicals.From measurements of the relative yields of 2,3-dimethyloxirane and methyloxirane and the known Arrhenius parameters for reaction (6), values of A7 = 108.61 +/- 0.30 dm3 mol-1 s-1 and E7 = 50.0 +/- 4 kJ mol-1 have been obtained. .The values are compared with data for HO2 addition to other alkenes.The excellent correlation between the activation energy for addition and the ionisation energy of the alkene is used to provide a kinetic data base for HO2 addition to alkenes over the range 600-1000 K, where the reactions are of major importance.From studies of the relative yields of 2,3-dimethyloxirane and (Z)-but-2-ene from (E)-but-2-ene + H2 + O2 mixtures, further evidence is presented to show that the decomposition of hydroperoxyalkyl radicals, such as CH3CH(OOH)CHCH3, into alkene + HO2 is at most a minor process compared with formation of an oxirane + OH radical.
- Stothard, Nigel D.,Walker, Raymond W.
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p. 2115 - 2119
(2007/10/02)
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- Stopped-Flow Studies of the Mechanisms of Ozone-Alkene Reactions in the Gas Phase: trans-2-Butene
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The reaction of ozone with trans-2-butene has been studied in the gas phase at 294 K and 530 Pa (4 Torr) by using a stopped-flow reactor coupled to a photoionization mass spectrometer.The concentrations of reactants and products were determined as a function of reaction time.A mechanism is proposed to account for the observed products: CH3CHO, H2CO, CO2, CH4, CF3C(O)C(H)(OH)CH3, H2C=C=O, H2O, 2-butanone, 2,3-epoxybutane, CH3C(O)C(O)CH3, and HC(O)C(O)H.This work again indicates that simple "hot" ester hypothesis needs to be critically reconsidered for gas-phase ozonolysis.
- Martinez, Richard I.,Herron, John T.
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p. 4644 - 4648
(2007/10/02)
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- USING THE COMPARISON OF STERIC VERSUS ELECTRONIC EFFECTS TO INFER MECHANISTIC INFORMATION IN STEPWISE ELECTROPHILIC ADDITION REACTIONS INVOLVING THREE-MEMBERED CYCLIC INTERMEDIATES
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Correlations of IP's versus relative reactivities or formation constants of reactions of alkenes with ArSCl, MeCO3H, Ag(1+), or HgCl2 reveal that complexation reactions show steric dependence, that additions with the first step rate-determining are sterically independent, and that those with the second step rate-determining are sterically dependent.
- Nelson, Donna J.,Soundararajan, Raman
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p. 6207 - 6210
(2007/10/02)
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- CHIMIE ORGANOMETALLIQUE SOUS HAUTE PRESSION: REACTION DES CHLOROCETONES AVEC L'HYDRURE DE TRIBUTYLETAIN
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High-pressure reaction of tributyltin hydride with several chloroketones (3-chloro-2-butanone, 4-chloro-2-butanone, 5-chloro-2-pentanone, 6-chloro-2-hexanone and 7-chloro-2-heptanone) led to the formation of chloroalkoxytins or cyclic ethers.An ionic mechanism, starting with nucleophilic attack at the carbonyl group, is proposed to explain the formation of the reaction products.
- Degueil-Castaing, M.,Maillard, B.,Rahm, A.
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- EPOXIDATION OF 2-BUTENE BY ORGANIC HYDROPEROXIDES.
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The authors report the results of a study of epoxidation of 2-butene by organic hydroperoxides ( alpha -methylbenzyl, alpha , alpha -dimethylbenzyl, and tert-butyl) in presence of hydrocarbon-soluble molybdenum compounds. Alkylbenzenes (toluene, ethylbenzene, and isopropylbenzene) were used as solvents. It is shown that a comparison of the reactions of 2-butene epoxidation by various organic hydroperoxides ( alpha -methylbenzyl, alpha , alpha -dimethylbenzyl, and tert-butyl) shows that under the given conditions approximately equal degrees of conversion of these hydroperoxides are attained, i. e. , they are virtually equal in activity, while selectivity for 2-butene oxide formation is somewhat lower when alpha , alpha -dimethylbenzyl hydroperoxide is used.
- Farberov,Bondarenko,Obukhov,Srednev,Vasil'eva
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p. 134 - 138
(2007/10/02)
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- RATE CONSTANTS FOR THE FORMATION OF OXIRANES BY γ-SCISSION IN SECONDARY β-t-BUTYLPEROXYALKYL RADICALS
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Rate constants for the title reactions have been determined from the ratios of oxirane to peroxide obtained in the reductons of β-bromoalkyl t-butyl peroxides with tributyltin hydride.At ca. 298 K the rate constants are 0.32, 1.12, 1.96, 2.0 and 6.2E6 s-1 for β-t-butylperoxy derivatives of trinorbornan-2-yl (exo) cyclohexyl, 1-methylpropyl , cyclopentyl and 1-ethylbutyl, respectively.The results are discussed in terms of steric and electronic effects in the transition state leading to ring closure of the radicals.
- Bloodworth A. J.,Courtneidge, J. L.,Davies, Alwyn G.
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p. 523 - 528
(2007/10/02)
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- A FACILE METHOD FOR OXYTELLURATION OF OLEFINS
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Treatment of olefins with phenyltellurium(II) or (IV) species in alcohol at room to reflux temperature for 1-24 h produces the corresponding (2-alkoxyalkyl)phenyltellurium dihalides in good yields, the reaction being trans-stereoselective and highly regioselective.
- Uemura, Sakae,Fukuzawa, Shin-ichi,Toshimitsu, Akio,Okano, Masaya
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p. 1177 - 1180
(2007/10/02)
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- The Mechanism of Ozone-Alkene Reactions in the Gas Phase. A Mass Spectrometric Study of the Reactions of Eight Linear and Branched-Chain Alkenes
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The stable products of the low-pressure (4 - 8 torr (1 torr = 133.33 Pa)) gas-phase reactions of ozone with ethene, propene, 2-methylpropene, cis-2-butene, trans-2-butene, trans-2-pentene, 2,3-dimethyl-2-butene, and 2-ethyl-1-butene have been identified by using a photoionization mass spectrometer coupled to a stirred-flow reactor.The products observed are characteristic of (i) a primary Criegee split to an oxoalkane (aldehyde or ketone) and a Criegee intermediate, (ii) reactions of the Criegee intermediates such as unimolecular decomposition, secondary ozonide formation, etc., and (iii) secondary alkene chemistry involving OH and other free-radical products formed by the unimolecular decomposition of the Criegee intermediates.The secondary OH - alkene - O2 reactions account for a significant fraction of the alkene (CnH2n) consumed and lead to characteristic products such as Cn dioxoalkanes nH2n + 30)>, Cn acyloins nH2n + 32)>, and Cn alkanediols nH2n + 34)>.Cn oxoalkanes and Cn epoxyalkanes observed at m/e (CnH2n + 16) are probably formed primarily via epoxidation of the alkene by O3.A general mechanism has been proposed to account for the observations.
- Martinez, Richard I.,Herron, John T.,Huie, Robert E.
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p. 3807 - 3820
(2007/10/02)
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- Oxygenation with Molecular Oxygen. Thermal and Photochemical Epoxidation of Propylene in the Presence of Sulfur Dioxide in Acetonitrile at Ambient Temperature
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Irradiation of a mixture of propylene and sulfur dioxide in acetonitrile at ice-cold temperature causes absorption of molecular oxygen and gives propylene oxide as the sole volatile product.Also, in the absence of light, the addition of nitrile or nitrate salts to a mixture of sulfur dioxide and propylene in acetonitrile under oxygen at room temperature leads to the smooth formation of propylene oxide as the only volatile product.Both reactions show quite similar solvent dependence and are retarded by the additives with ionization potentials lower than ca. 9.5 eV.The main byproduct is poly(propylenesulfonate).The mechanisms of the epoxidation reactions are discussed.
- Sasaki, Tadahiro
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p. 3882 - 3886
(2007/10/02)
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- ETUDE ANALYTIQUE DE LA REACTION D'OXYDATION DE BASSE TEMPERATURE DU BUTANE EN PRESENCE DE METHYLAMINES
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Studied by static method the reaction is followed by measuring the derivative of the pressure variations as a function of time and by analysis of methanol, ethanol, acetone, nitromethane, 2,3 epoxy butane, 1,2 epoxy butane, butanone, 2-butanol and carbon oxide and dioxide by gas-chromatography.The methylamines are analysed by colorimetry through pH measurements.The analyses are mainly performed in the slow branched-chains reaction zone and followed as a function of the butane concentration and for increasing amounts of each of the three additives.A relevant explanation of the nitromethane formation in presence of methylamines enable us to enlighten some interesting features of the reaction mechanism.
- Lemahieu Joseph,Antonic, Stanislas
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p. 337 - 342
(2007/10/02)
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- Process for preparing aldehydes from oxirane compounds
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Aldehydes are prepared by reacting an oxirane compound with hydrogen peroxide in the presence of a boron compound.
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2-Halogenoalkoxytributyltin compounds have been prepared from tributylethoxytin and 1,2-halohydrins. The thermal degradation and its mechanism are investigated. These reactions offer a convenient way to prepare epoxides.
- Delmond, Bernard,Pommier, Jean-Claude,Valade, Jacques
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