Showing papers on "Cyclohexene published in 2013"
TL;DR: In this paper, the performance of oxygen and hydrogen peroxide as preferred oxidants for the selective oxidation of cyclohexene and n-hexane to adipic acid is summarized.
238 citations
Journal Article•
TL;DR: In this article, the performance of oxygen and hydrogen peroxide as preferred oxidants for the selective oxidation of cyclohexene and n-hexane to adipic acid is summarized.
Abstract: Research efforts to find more sustainable pathways for the synthesis of adipic acid have led to the introduction of new catalytic processes for producing this commodity chemical from alternative resources. With a focus on the performance of oxygen and hydrogen peroxide as preferred oxidants, this minireview summarizes recent advances made in the selective oxidation of cyclohexene, cyclohexane, cyclohexanone and n-hexane to adipic acid. Special attention is paid to the exploration of catalytic pathways involving lignocellulosic biomass-derived chemicals such as 5-hydroxymethylfurfural, D-glucose, γ-valerolactone and compounds representative of lignin and lignin-derived bio-oils.
199 citations
TL;DR: In this paper, the properties of Fe-MIL-101 and Cr-ML-101 metal-organic frameworks in the solvent-free oxidation of cyclohexene and α-pinene with molecular oxygen have been explored.
188 citations
TL;DR: In this article, the reaction of carbon dioxide (CO2) with cyclohexene oxide, which can lead to the formation of cyclic carbonate and/or polycarbonate products, was studied.
127 citations
TL;DR: In linear domino reactions, the progress of the former step will always affect that of the next steps (Figure 1a) as discussed by the authors, which is a generalization of the notion of a cascade reaction.
Abstract: Traditionally, domino reactions are defined as processes of two or more bond-forming reactions, in which the subsequent transformation takes place at the functionalities obtained in the former transformation under identical reaction conditions. 2] In linear domino reactions, the progress of the former step will always affect that of the next steps (Figure 1a). Among the domino/cascade reactions, organocata-
90 citations
TL;DR: In this article, the effect of the size of gold nanoparticles on their catalytic activity in aerobic oxidation of cyclohexene was established using two triphenylphosphine-stabilized clusters that gradually undergo a change in size during the catalytic reaction.
Abstract: The effect of the size of gold nanoparticles on their catalytic activity in aerobic oxidation of cyclohexene was established using supported gold nanoparticles that gradually undergo a change in size during the catalytic reaction. Two triphenylphosphine-stabilized clusters, Au9(PPh3)8(NO3)3 and Au101(PPh3)21Cl5, were synthesized and deposited on SiO2. The clusters did not retain their structure during the catalytic reaction; larger particles with mean diameters of ∼5–10 nm gradually formed. By combining kinetic experiments with the monitoring of catalyst transformations using transmission electron microscopy, diffuse-reflectance ultraviolet–visible spectroscopy, and X-ray photoelectron spectroscopy, we showed that catalytic activity appeared only after >2 nm Au0 particles had formed, while intact clusters and phosphine-free <2 nm particles were inactive in cyclohexene oxidation under the studied conditions.
73 citations
TL;DR: In this paper, a modified nanoscale SiO2/Al2O3-based Fe nano-catalyst has been covalently anchored on a modified nano-coated SiO 2/Al 2O3.
Abstract: In the present study, heterogeneous Fe-nano-catalyst has been covalently anchored on a modified nanoscale SiO2/Al2O3. The synthesized materials were characterized by FT-IR spectroscopy, DS UV–vis, CHN elemental analysis, BET, EDS, SEM, TEM, TGA and XPS. The catalytic activity of the Fe nano-catalyst (FNC) in the oxidation of ethylbenzene, cyclohexene, and benzylalcohol was studied using tert-butyl hydroperoxide as oxygen source, without the need of any solvent. Oxidation of ethylbenzene, cyclohexene, and benzylalcohol catalyzed by (FNC) gave acetophenone, 2-cyclohexene-1-one and benzaldehyde, respectively, as major products. A suitable reaction condition has been optimized for Fe-nano-catalyst by considering the effect of various parameters such as reaction time and the amount of oxidant, different solvents, concentration of substrate for the maximum conversion of substrates and high selectivity. This catalyst can be easily prepared from inexpensive, commercially available reagent and is stable and reusable for oxidation of ethylbenzene, cyclohexene, and benzylalcohol.
72 citations
TL;DR: This is the first jet-stirred reactor study to report NTC in cyclohexane oxidation andasonable agreement is observed with most of the products observed in the reactor, as well as the literature experimental data considered in this paper.
71 citations
TL;DR: Rhodium complexes can be homogeneously immobilized on functionalized graphene oxide through coordination interaction and shows enhanced activity in the catalytic hydrogenation of cyclohexene.
Abstract: Rhodium complexes can be homogeneously immobilized on functionalized graphene oxide through coordination interaction. The obtained catalyst can be readily recycled and shows enhanced activity in the catalytic hydrogenation of cyclohexene.
70 citations
TL;DR: In this article, Ru and Ru-Zn catalysts supported on hydroxyapatite (HAP), which is nontoxic and abundant in nature, were prepared via the simple ion-exchange method.
69 citations
TL;DR: In this paper, the synthesis of adipic acid by means of a direct oxidation of cyclohexene by hydrogen peroxide was carried out in a continuous flow packed-bed microreactor.
Abstract: The synthesis of adipic acid by means of a direct oxidation of cyclohexene by hydrogen peroxide was carried out in a continuous-flow packed-bed microreactor. The reaction uses Na2WO4·2H2O as a catalyst and [CH3(n-C8H17)3N]HSO4 as a phase transfer catalyst without additional solvent. A parametric process optimization, such as glass beads size, residence time, concentration of hydrogen peroxide, addition of acid, reaction temperature, and molar ratios of reactants and catalysts, was performed. It is demonstrated that smaller glass beads result in a better yield of adipic acid and that the addition of acid plays an important role in the oxidation of cyclohexene to adipic acid. Based on the concept of Novel Process Windows, the influence of elevated temperatures is investigated.
TL;DR: In this article, a series of alumina and titania-supported Au and dilute Pd-Au catalysts were studied with infrared spectroscopy of CO adsorption, CO oxidation catalysis, and cyclohexene hydrogenation catalysis.
Abstract: Incorporating small amounts of Pd into supported Au catalysts has been shown to have beneficial effects on selective hydrogenation reactions, particularly 1,3-butadiene hydrogenation and the hydrogenation of nitroaromatics, especially p-chloronitrobenzene. Appropriate Pd incorporation enhances hydrogenation activity while maintaining the desirable high selectivity of supported Au catalysts. To better understand this phenomenon, a series of alumina- and titania-supported Au and dilute Pd–Au catalysts were prepared via urea deposition–precipitation. The catalysts were studied with infrared spectroscopy of CO adsorption, CO oxidation catalysis, and cyclohexene hydrogenation catalysis with the goal of understanding how Pd affects the catalytic properties of Au. CO adsorption experiments indicated a substantial amount of surface Pd when the catalyst was under CO. Adsorption experiments at various CO pressures were used to determine CO coverage; application of the Temkin adsorbate interaction model allowed for ...
TL;DR: In this paper, the adsorption experiments showed that the desulfurization performance of NaY decreases with the rise of CHE concentration in MG, whereas that of LaNaY first increases then declines.
TL;DR: In this article, the authors reported the immobilization of different cationic and neutral metalloporphyrins on silica-coated Fe 3 O 4 nanoparticles, obtained by basic hydrolytic sol-gel process.
Abstract: In this paper we report the immobilization of different cationic and neutral metalloporphyrins (MPs) on silica-coated Fe 3 O 4 nanoparticles, obtained by basic hydrolytic sol–gel process. We characterized the MP-immobilized materials by UV–vis spectroscopy (UV–vis), X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). We achieved 100% and 2% immobilization of cationic and neutral MPs, respectively. The strong electrostatic interactions between the hydroxylated surface of the silica and the positive charges of the cationic MPs favored immobilization of the charged MPs; the neutral MP probably established a weak bond with the silica and easily leached from the support. We investigated the catalytic activity of the immobilized MPs in the oxidation of cyclooctene, cyclohexene, and cyclohexane using iodosylbenzene as oxygen donor. We used the immobilized MPs in at least five successive cyclooctene oxidation reactions – the yields did not decrease, confirming that the catalyst can be reused. The synthesized catalysts displayed magnetic properties, which allowed their fast separation from the reaction medium using a simple magnet.
TL;DR: The liquid-phase methodology provides a better dispersion of the metal sites onto the siliceous support than the dry-impregnation approach, and the niobium-silica catalysts were tested in the epoxidation of cyclohexene and 1-methylcyclohexenes, as model substrates.
Abstract: Niobium-containing silica materials obtained by deposition via liquid-phase grafting or dry impregnation of niobocene(IV) dichloride are active and selective catalysts in the epoxidation of alkenes in the presence of aqueous hydrogen peroxide. The generation of the catalytically-active Nb species was followed step-by-step, and investigated using a combined DR-UV-Vis, NIR, Raman, XRD, XANES and EXAFS analyses. At the end of the grafting procedure, the nature of the surface active species can be described as an oxo-Nb(V) site, tripodally grafted onto the silica surface in close proximity to other Nb(V) centres. The liquid-phase methodology provides a better dispersion of the metal sites onto the siliceous support than the dry-impregnation approach. The niobium–silica catalysts were then tested in the epoxidation of cyclohexene and 1-methylcyclohexene, as model substrates.
TL;DR: In this paper, triclinic WO 3 nanoplates with prominent cyclohexene sensing and photocatalytic properties were fabricated via a facile hydrothermal method assisted with p -aminobenzoic acid.
Abstract: In this paper, triclinic WO 3 nanoplates with prominent cyclohexene sensing and photocatalytic properties were fabricated via a facile hydrothermal method assisted with p -aminobenzoic acid. The as-prepared product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD, SEM and TEM images illustrated that the WO 3 nanoplates have a triclinic phase with the length of 100–200 nm and the thickness of 50–80 nm. The gas sensing properties of the WO 3 nanoplates were measured by detection of methanol, ethanol, cyclohexane, benzene, ethyl acetate and acetone at 160–300 °C, and their photocatalytic activities were investigated by the degradation of methyl blue (MB). The as-prepared product exhibited not only excellent photocatalytic property for the degradation of MB, but also high response (1000 ppm of cyclohexene, R a /R g = 140) and excellent selectivity for the detection of cyclohexene.
TL;DR: The reaction mechanism of olefin hydrogenation catalyzed by the bimetallic gold catalyst was studied by means of density functional theory calculations and suggests that for prochiral substrates the step that determines the enantioselectivity within the ionic mechanism involves a proton transfer.
Abstract: The reaction mechanism of olefin hydrogenation catalyzed by the bimetallic gold catalyst {(AuCl)2[(R,R)-Me-DuPhos]} was studied by means of density functional theory calculations. This catalyst is enantioselective for the homogeneous hydrogenation of olefins and imines. The reaction mechanism involves activation of the H2 molecule. This process takes place heterolytically, generating a metal–hydride complex as the active species and releasing a proton (formally EtOH2+) and a chloride ion to the medium. The hydrogenation reaction proceeds through an ionic mechanism in which the gold catalyst provides a hydride and the proton comes from the solvent. The reaction mechanism ends up with H2 coordination and subsequent heterolytic cleavage, regenerating the gold(I)–hydride active species. Significant differences were found in the reaction mechanism depending on the nature of the substrate (ethene, cyclohexene, or diethyl 2-benzylidenesuccinate) and the character of the catalyst (mono- or bimetallic). Our data s...
TL;DR: In this article, a SiO2/Al2O3-supported cobalt catalyst was used for the selective oxidation of cyclohexene and oximes to the corresponding carbonyl compounds.
Abstract: The selective oxidation of ethylbenzene and cyclohexene to acetophenone and 2-cyclohexene-1-one using N-hydroxyphthalimide (NHPI) under oxygen atmosphere in the presence of an SiO2/Al2O3-supported cobalt catalyst occurs with conversions of 83 and 75% and selectivities of 99%. The supported cobalt is also a suitable and efficient catalyst for the oxidative deprotection of oximes to the corresponding carbonyl compounds. The reaction conditions have been optimized considering the effect of various parameters such as reaction time, amount of catalyst, temperature and reusability of the catalyst after several runs. Moreover, some possible mechanisms for the oxidation of ethylbenzene, cyclohexene and oximes have been proposed.
TL;DR: The synthesis of adipic acid from cyclohexene by tungstic acid-catalyzed oxidation using hydrogen peroxide following the classical Noyori protocol can be accomplished in good yields with residence times as short as 20 min at 140 °C using a safe and scalable microreactor environment.
Abstract: Safe only in a microreactor! The synthesis of adipic acid from cyclohexene by tungstic acid-catalyzed oxidation using hydrogen peroxide following the classical Noyori protocol can be accomplished in good yields with residence times as short as 20 min at 140 °C using a safe and scalable microreactor environment. Under these intensified conditions the use of a phase-transfer catalyst is not required.
TL;DR: In this article, a catechol-functionalized porous organic polymer (POP) was successfully metallated with a TaV trialkyl and remains thermally and structurally robust.
Abstract: A catechol-functionalized porous organic polymer (POP) has been successfully metallated with a TaV trialkyl and remains thermally and structurally robust. The resulting POP-supported (catecholato)TaV trialkyl sites remain accessible to small molecules and can undergo reactions to yield stable, monomeric complexes that are quite different from those observed with the homogeneous analogues. Using a combination of reactivity studies, high-resolution solid-state NMR spectroscopy, and X-ray absorption spectroscopy (XAS), we are able to precisely determine the functionality and coordination environment of the active (catecholato)TaV trialkyl site and its products in reactions with Bronsted acids. Additionally, the Ta-metallated POP was found to have enhanced catalytic activity in the hydrogenation of cyclohexene and toluene relative to a homogeneous analogue.
TL;DR: In this article, a new manganese(III) complex, [Mn(saldien)(N3)], has been anchored on mesoporous SBA-15 to produce a stable, active, and selective heterogeneous catalyst.
Abstract: A new manganese(III) complex, [Mn(saldien)(N3)], has been anchored on mesoporous SBA-15 to produce a stable, active, and selective heterogeneous catalyst SBA15-[Mn(saldien)(N3)] (saldien = N,N′-bis(salicylidene)diethylenetriamine). Complex [Mn(saldien)(N3)] was characterized by spectroscopic methods and its structure determined by single crystal X-ray diffraction. SBA15-[Mn(saldien)(N3)] was characterized by small angle X-ray diffraction (SAX), scanning electron microscopy (SEM), nitrogen sorption measurement and Fourier transform infrared spectroscopy. Both [Mn(saldien)(N3)] anchored on mesoporous SBA-15 through a covalent bond and the “free” complex catalyze the oxidation of cycloalkanes and cyclohexene in acetonitrile, with H2O2 as terminal oxidant. A remarkable result for these systems is their capability of catalyzing efficient oxidation of the hydrocarbons with 1.2 equiv. of hydrogen peroxide. Compared to homogeneous catalyst, the heterogenized catalyst is more stable and can be recycled four times without any significant loss of activity. Immobilization of complex [Mn(saldien)(N3)] onto SBA-15 increased the selectivity toward cyclohexanone in the oxidation of cyclohexane. In general, metallosalen-catalyzed reactions have been carried out in the presence of an excess of a donor ligand; however, the present reactions do not need the addition of any extra donor ligand.
TL;DR: In this paper, a series of four PdO/SBA-15 catalysts with 1, 2, 4, 5% (by weight) loading was prepared by a conventional impregnation method and are characterized by N2-adsorption, low-angle and wide-angle XRD, XPS and TEM techniques.
TL;DR: Zwitterionic micelles can be used to catalyze a variety of simple reactions, as the attraction of ions to the micelle brings the reactants together as discussed by the authors.
Abstract: Zwitterionic surfactants are relatively overlooked and some of their properties resemble those of ionic and non-ionic surfactants, but others are unique. There is unimpeachable evidence that aqueous solutions of zwitterionic micelles interact specifically with anions, forming “anionoid” micelles, which concentrate cations in the surfaces. Thus, unlike ionic micelles, both the cation and anion of the electrolyte solution can be concentrated at zwitterionic interfaces. This unique effect, known as the “Chameleon Effect”, can be used to catalyze a variety of simple reactions, as the attraction of ions to the micelle brings the reactants together. Furthermore, zwitterionic surfactants stabilize metallic nanoparticles and the magnetically stirred two-phase system could be reused 3 more times in the hydrogenation of cyclohexene (Pd:cyclohexene ratio of 1:18300), with very little loss in activity, and an average turn-over frequency of 1000 h − 1 .
TL;DR: In this paper, the mesoporous carbon nitride (UF-MCN) was characterized as a graphitic structure with hexagonal pores of 3-4nm and short channels in the submicron range.
TL;DR: The ratio of heterolysis to homolysis increased gradually in all solvent systems, suggesting that [(TMP)Mn-OOC(O)R] species 2a is the major active species, and a Mn(V)=O intermediate generated from the heterolytic cleavage of 2b becomes a major reactive species.
Abstract: The participation of multiple active oxidants generated from the reactions of two manganese(III) porphyrin complexes containing electron-withdrawing and -donating substituents with peroxyphenylacetic acid (PPAA) as a mechanistic probe was studied by carrying out catalytic oxidations of cyclohexene, 1-octene, and ethylbenzene in various solvent systems, namely, toluene, CH(2) Cl(2) , CH(3) CN, and H(2) O/CH(3) CN (1:4). With an increase in the concentration of the easy-to-oxidize substrate cyclohexene in the presence of [(TMP)MnCl] (1a) with electron-donating substituents, the ratio of heterolysis to homolysis increased gradually in all solvent systems, suggesting that [(TMP)Mn-OOC(O)R] species 2a is the major active species. When the substrate was changed from the easy-to-oxidize one (cyclohexene) to difficult-to-oxidize ones (1-octene and ethylbenzene), the ratio of heterolysis to homolysis increased a little or did not change. [(F(20) TPP)Mn-OOC(O)R] species 2b generated from the reaction of [(F(20) TPP)MnCl] (1b) with electron-withdrawing substituents and PPAA also gradually becomes involved in olefin epoxidation (although to a much lesser degree than with [(TMP)Mn-OOR] 2a) depending on the concentration of the easy-to-oxidize substrate cyclohexene in all aprotic solvent systems except for CH(3) CN, whereas Mn(V)=O species is the major active oxidant in the protic solvent system. With difficult-to-oxidize substrates, the ratio of heterolysis to homolysis did not vary except for 1-octene in toluene, indicating that a Mn(V)=O intermediate generated from the heterolytic cleavage of 2b becomes a major reactive species. We also studied the competitive epoxidations of cis-2-octene and trans-2-octene with two manganese(III) porphyrin complexes by meta-chloroperbenzoic acid (MCPBA) in various solvents under catalytic reaction conditions. The ratios of cis- to trans-2-octene oxide formed in the reactions of MCPBA varied depending on the substrate concentration, further supporting the contention that the reactions of manganese porphyrin complexes with peracids generate multiple reactive oxidizing intermediates.
TL;DR: In this paper, an iron-II and cobalt-II phthalocyanine complexes were obtained by the reaction of the phthalonitrile derivative 3 with n-pentanol in a standard Schlenk tube in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU).
TL;DR: In this article, a surface modified niobium oxyhydroxide (NbO 2 OH) catalyst was utilized for the selective liquid-phase oxidation of cyclohexene to epoxide in the presence of hydrogen peroxide.
Abstract: A surface modified niobium oxyhydroxide catalyst was utilized for the selective liquid-phase oxidation of cyclohexene to epoxide in the presence of hydrogen peroxide. After surface modification with a surfactant (cetiltrimetilamonium bromide -CTAB), the very active niobium oxyhydroxide (NbO 2 OH), presented hydrophobic characteristics and good activity for the oxidation of cyclohexene over the heterogeneous catalyst. Furthermore, the hydrophobic material presented a high selectivity toward the formation of the epoxide species. The mass spectrometry analysis of the reaction showed that epoxide species was produced with a selectivity of 60% using 0.2 mL of hydrogen peroxide, with 65% of conversion. The results strongly suggest that the reaction involves oxidizing species generated after the reaction with H 2 O 2 . The surfactant anchored over the niobium catalyst promotes a better interaction with the nonpolar substrate.
TL;DR: In this paper, the structure and chemical state of supported Pd nanoparticles in contact with H2 in the aqueous phase have been explored by X-ray absorption spectroscopy to better understand their surface reactivity in polar condensed media.
Abstract: The structure and chemical state of supported Pd nanoparticles in contact with H2 in the aqueous phase have been explored by X-ray absorption spectroscopy to better understand their surface reactivity in polar condensed media. The Pd–Pd distances at substantial H2 pressures indicate the presence of sorbed hydrogen and point to the presence of Pd hydrides, proving that such nanoparticles are hardly influenced by the presence of water. During the hydrogenation of the reactants (phenol, cyclohexanone, and cyclohexene), the Pd–Pd bond length decreased, indicating a drastically lower concentration of sorbed H compared to Pd in the absence of the reactants. This steady state concentration of sorbed hydrogen is established by all reactions involving H2, i.e., the sorption/desorption into the bulk, the adsorption at the surface, and the reaction with unsaturated reactants, but not by reaction with water. This demonstrates that neither the Pd particles nor the H/Pd ratio is influenced by water, but dynamically ada...
TL;DR: In this paper, the metal-organic framework IRMOF-3 has been synthesized and functionalized with supported rhodium species and it has been catalytic tested in the hydroformylation of olefins to the corresponding aldehydes.
TL;DR: In this paper, a dual task-specific ionic liquid was used for oxidation of cyclohexene to adipic acid using 30% hydrogen peroxide, and the catalyst showed desirable activity toward oxidation of some cyclic olefins to produce their corresponding dicarboxylic acids.