Dilute Benzene Research Articles

Simulations of 1-Butyl-3-methylimidazolium Tetrafluoroborate + Acetonitrile Mixtures: Force-Field Validation and Frictional Characteristics.

To temper their prohibitively high viscosities, ionic liquids are commonly mixed with polar cosolvents to retain favorable physical properties and make them suitable for industrial applications. Molecular dynamics simulations of 1-butyl-3-methylimidazolium tetrafluoroborate ([Im41][BF4]) mixed with acetonitrile (CH3CN) are conducted primarily to test the accuracy of a composite force field (FF) and also to provide some insights into the solvation and frictional characteristics of this mixture. The FF combines the united-atom model for imidazolium ionic liquids of Zhong et al. [ J. Phys. Chem. B 2011, 115, 10027] with the acetonitrile model of Nikitin and Lyubartsev [ J. Comput. Chem. 2007, 28, 2020]. Comparison of simulated properties such as mixture densities, viscosities, electrical conductivities, and component diffusion coefficients to experimental data at 298 K shows that this combined FF provides reasonable accuracy for both static and dynamic properties. Component rotational dynamics, as well as those of a dilute benzene solute, probed via new 2H NMR T1 measurements, are also reasonably reproduced. Simulated coordination numbers reveal virtually random mixing between the [Im41][BF4] and CH3CN components in this system. Comparison of translational diffusion coefficients and rotation times to simple hydrodynamic predictions indicates that the friction on most motions becomes increasingly decoupled from solution viscosity as the [Im41][BF4] concentration increases.

ChemInform Abstract: AlNbBr8 — Preparation, Crystal Structure, and Vapor Pressure Studies.

AbstractRed crystals of AlNbBr8 are prepared by degradation of Nb2S4Br4 in AlBr3 and [emim]Br under Ar (150 °C, 48 h) followed by dilution in benzene (4 °C, several d).

Selective removal of dilute benzene from water by poly(methyl methacrylate)-graft-poly(dimethylsiloxane) membranes containing hydrophobic ionic liquid by pervaporation

This paper focuses on the addition of hydrophobic ionic liquid, 1-allyl-3-butylimidazilium bis (trifluoromethane sulfonyl) imide ([ABIM]TFSI) to poly(methyl methacrylate)-graft-poly(dimethylsiloxane) (PMMA-g-PDMS) membranes, on the pervaporation characteristics for the removal of dilute benzene from an aqueous solution. When an aqueous solution of 0.05wt% benzene was permeated through [ABIM]TFSI/PMMA-g-PDMS membranes, they showed high benzene permselectivity and permeability. Both the benzene/water selectivity and permeability of the membranes were enhanced with an increase of [ABIM]TFSI, because the affinities of [ABIM]TFSI/PMMA-g-PDMS membranes for benzene were increased by introducing [ABIM]TFSI into the membranes. The [ABIM]TFSI localized in the PMMA layer of the microphase separated PMMA-g-PDMS membrane plays an important role as an absorbent to selectively partition benzene from the aqueous benzene solution.

Removal of Dilute Benzene in Water through Ionic Liquid/Poly(Vinyl Chloride) Membranes by Pervaporation

This paper focuses on the effects of the addition of an ionic liquid, 1-Allyl-3-butylimidazilium bis(trifluoromethane sulfonyl)imide ([ABIM]TFSI), which has a high affinity for benzene, into the poly(vinyl chloride) (PVC) membrane on the pervaporation characteristics of the removal of benzene from aqueous solutions of dilute benzene. When aqueous solutions of 100～500 ppm benzene were permeated through the [ABIM]TFSI)/PVC membranes, they showed a high benzene/water selectivity and permeability of these membranes was enhanced with increasing [ABIM]TFSI content significantly. These pervaporation characteristics are discussed from the viewpoint of chemical and physical structure of [ABIM]TFSI)/PVC membranes in detail. The mechanism of permeation and separation was analyzed by the solution-diffusion model.

Enthalpies of Vaporization and Sublimation of the Halogen-Substituted Aromatic Hydrocarbons at 298.15 K: Application of Solution Calorimetry Approach

Recently, the solution calorimetry has been shown to be a valuable tool for the indirect determination of vaporization or sublimation enthalpies of low volatile organic compounds. In this work we studied 16 halogen-substituted derivatives of benzene, naphthalene, biphenyl, and anthracene using a new solution calorimetry based approach. Enthalpies of solution at infinite dilution in benzene as well as molar refractions for the chlorine-, bromine-, and iodine-substituted aromatics were measured at 298.15 K. Vaporization and sublimation enthalpies of these compounds at 298.15 K were indirectly derived from the solution calorimetry data. In order to verify results obtained by using solution calorimetry, vaporization/sublimation enthalpies for 1,2-, 1,3-, 1,4-dibromobenzenes, 4-bromobiphenyl, and 4,4′-dibromobiphenyl were additionally measured by using the well established transpiration method. Experimental data available in the literature were collected and evaluated in this work for the sake of comparison wi...

Solution calorimetry as a complementary tool for the determination of enthalpies of vaporization and sublimation of low volatile compounds at 298.15 K

Abstract In this work a new solution-based calorimetry approach for determination of the sublimation and vaporization enthalpies of low volatile compounds was proposed. The approach is based on the measurement of solution enthalpy of a molecule of interest in benzene and as well as the measurement of molar refraction index for this molecule. Enthalpies of solution at infinite dilution in benzene for a set of 18 aromatic and polyaromatic hydrocarbons were measured at 298.15 K. Experimental data on vaporization/sublimation enthalpies for this set were collected from the literature. For validation of the literature data additional sublimation experiments were performed for phenanthrene, 1-phenylnaphthalene, 1,2-diphenylbenzene, 1,2,3,4-tetraphenylnaphthalene, hexaphenylbenzene, and rubrene using transpiration, quartz crystal microbalance, and thermogravimetry. Vaporization/sublimation enthalpies derived from the solution calorimetry approach were in good agreement (within experimental uncertainties) with those measured by conventional methods. The solution-based calorimetry approach gives a reliable and quick appraisal of vaporization/sublimation enthalpies. This approach constitutes a complementary additional thermochemical option for vaporization/sublimation enthalpies data evaluation as well as for rapid data gathering for low volatile and/or thermally unstable organic compounds.

Synthesis and properties of axially BODIPY conjugated subphthalocyanine dyads

The treatment of boron(III) subphthalocyanine chloride with borondipyrromethene derivatives containing either one or two [4-(N,N-dimethylamino)phenyl]ethenyl groups in toluene gave the corresponding axially substituted boron(III) subphthalocyanine dyes. The novel borondipyrromethene–subphthalocyanine dyes were fully characterized by mass spectrometry, UV–Vis, 1H and 13C NMR spectroscopy as well as elemental analysis. The photophysical properties of title compounds were investigated by means of absorption and fluorescence spectroscopy in dilute benzene solutions. The new dyads exhibited a highly efficient energy transfer process from the excited subphthalocyanine unit to the borondipyrromethene unit. The singlet oxygen generation ability of these dyads was also investigated in dimethylsulfoxide for determination of possibility of these compounds for photodynamic therapy of cancer.

Catalytic nonthermal plasma reactor for the abatement of low concentrations of benzene

Oxidative decomposition of dilute benzene in air was carried out in a dielectric barrier discharge reactor with inner metal fiber electrode that was later modified with transition metal oxides. Typical results indicated the best performance of the designed reactor for the removal of dilute benzene, where conventional techniques may not be efficient. The introduction of transition metal oxides in the discharge zone increased the conversion of benzene and shifted the product distribution to total oxidation. The performance of the reactor was further improved on humidification of air stream. The better performance of MnOx/SMF over CoOx and SMF may be due to in situ decomposition of ozone that may lead to the formation of strong oxidant atomic oxygen, whereas the best performance with TiO2/MnOx/SMF may be assigned due to the synergy between ozone decomposition on MnOx surface and photocatalytic action on TiO2.

Electro-optical Properties, Polarity and Chain Rigidity of Poly(dialkoxyphosphazene)s with Variable Side-Chain Length

Molecular properties of poly(dialkoxyphosphazene) (PDAOP) series with the aliphatic side-chains contained 3, 4, 6, and 7 carbon atoms were investigated in dilute benzene solutions by techniques of electro-optical Kerr effect and dynamo-optical Maxwell effect, and by dielectric spectroscopy. The sign inversion of Kerr effect and Maxwell effect in PDAOP solutions from positive to negative was detected at the side-chain length range of 5–6 carbon atoms. These phenomena were explained by the strong dependence of anisotropy of optical polarizability of PDAOP monomeric unit on chemical structure and change of its sign at the indicated side-chain lengths. It was demonstrated that PDAOPs possess a critical side-chain-length interval at which their physical properties, depending on the intramolecular ordering, display a singularity. It was also shown that the studied PDAOP samples are not flexible-chain polymers. They are characterized by Kuhn segment 47–65 A, the value of which increases with the elongation of aliphatic side-chain. Dielectric properties of PDAOP were correlated to the properties of the macromolecules with manifestation of kinetic rigidity under a treatment of electric field.

Nonthermal plasma assisted photocatalytic oxidation of dilute benzene

Oxidative decomposition of low concentrations (50–1000 ppm) of diluted benzene in air was carried out in a nonthermal plasma (NTP) dielectric barrier discharge (DBD) reactor with the inner electrode made up of stainless steel fibres (SMF) modified with transition metal oxides in such a way to integrate the catalyst in discharge zone. Typical results indicate the better performance of MnOx and TiO2/MnOx modified systems, which may be attributed to the in situ decomposition of ozone on the surface of MnOx that may lead to the formation of atomic oxygen; whereas ultraviolet light induced photocatalytic oxidation may be taking place with TiO2 modified systems. Water vapour improved the selectivity to total oxidation. Oxidative decomposition of low concentrations of (50–1000 ppm) of diluted benzene in air was carried out in a nonthermal plasma (NTP) dielectric barrier discharge (DBD) reactor at ambient conditions with the inner electrode modified with transition metal oxides (TiO2, MnOx and TiO2/MnOx). The results indicated that TiO2/MnOx integrated system showed the best performance.

The mechanism of oxidative addition of iodine to a dimethylplatinum(II) complex

The oxidative addition of iodine to [PtMe2(bipy)], 1, occurs easily with trans stereochemistry to give trans-[PtI2Me2(bipy)], 2a, which then equilibrates slowly with cis-[PtI2Me2(bipy)], 2b. The structures of 2a and 2b were determined in a crystal containing both isomers and an additional iodine molecule. Low temperature NMR studies show that an intermediate charge transfer complex [PtMe2(I2)(bipy)], 3, or solvated iodine complex [PtMe2(I2)(S)(bipy)], S = solvent, may be formed in dichloromethane or acetone solution before formation of 2a. In dilute benzene solution, as monitored by UV–visible spectroscopy, the rearrangement of the intermediate complex to 2a followed first order kinetics, and exhibited a large negative entropy of activation, as expected if cleavage of the I–I bond to give an ionic intermediate [PtIMe2(bipy)]+I−, is rate determining. The overall reaction is slower in more polar solvents because, although the I–I bond is more easily cleaved to give [PtIMe2(bipy)(S)]+I−, the subsequent displacement of solvent, S, by iodide to give 2a is slow.

Pervaporation Characteristics in Removal of Benzene from Water through Polystyrene-Poly (Dimethylsiloxane) IPN Membranes

This paper focuses on the effects of the PSt content of polystyrene (PSt)-poly (dimethylsiloxane) (PDMS) interpenetrateing network (IPN) polymer membranes, on the pervaporation (PV) characteristics during the removal of benzene from an aqueous solution of dilute benzene. When an aqueous solution of 0.05wt% benzene was permeated through the PSt-PDMS IPN membranes, they showed high benzene/water selectivity. Both the permeability and the benzene/water selectivity of the membranes were enhanced with increasing PSt content in the PSt-PDMS IPN membrane. The physicochemical mechanism of permeation and separation through the PSt-PDMS IPN membranes during PV is also discussed. The best normalized permeation rate, separation factor for benzene selectivity, and PV separation index of the PSt-PDMS IPN membrane were 1.27 × 10-6 kgm (m2hr)-1, 3293, and 41821, respectively. These PV characteristics are discussed from the viewpoint of the chemical and physical structure of the PSt-PDMS IPN membranes.

Reactions of Iron Atoms with Benzene

The reaction of iron atoms with benzene has been studied for nearly 40 years. Despite this, there is no agreement as to the nature of the products. With the aid of density functional theory calculations of the energetics and the infrared spectra of the various species, the present work provides a rationalization of the conflicting reports regarding the nature of the products of the reaction of iron atoms with benzene in low-temperature matrices. At low temperature in dilute benzene matrices, Fe(eta(6)-C(6)H(6)) and Fe(eta(6)-C(6)H(6))(2) are the major products. At high iron concentrations, Fe(2)(eta(2)-C(6)H(6)) is also formed. In pure benzene at low temperature, Fe(eta(6)-C(6)H(6))(2) and Fe(eta(6)-C(6)H(6))(eta(4)-C(6)H(6)) are formed. None of the species undergo photoexcitation to give insertion products HFe(C(6)H(5)). In pure benzene at 77 K, Fe(eta(6)-C(6)H(6))(eta(4)-C(6)H(6)) is the major product, together with small amounts of Fe(eta(6)-C(6)H(6))(2) and iron clusters. The infrared spectra of pure benzene are complicated by the activation of infrared forbidden modes by the presence of the metal atom.

High-efficiency plasma catalytic removal of dilute benzene from air

Achieving complete oxidation, good humidity tolerance and low energy cost is the key issue that needs to be addressed in plasma catalytic volatile organic compounds removal from air. For this purpose, Ag/HZSM-5 catalyst-packed dielectric barrier discharge using a cycled system composed of a storage stage and a discharge stage was studied. For dilute benzene removal from simulated air, Ag/HZSM-5 catalysts exhibit not only preferential adsorption of benzene in humid air at the storage stage but also almost complete oxidation of adsorbed benzene at the discharge stage. Five ‘storage–discharge’ cycles were examined, which suggests that Ag/HZSM-5 catalysts are very stable during the cycled ‘storage–discharge’ (CSD) plasma catalytic process. High oxidation rate of absorbed benzene as well as low energy cost can be achieved at a moderate discharge power. In an example of the CSD plasma catalytic remedy of simulated air containing 4.7 ppm benzene with 50% RH and 600 ml min−1 flow rate, the energy cost was as low as 3.7 × 10−3 kWh m−3 air. This extremely low energy cost to remove low-concentration pollutants from air undoubtedly makes the environmental applications of the plasma catalytic technique practical.

CuO–CeO 2 binary oxide nanoplates: Synthesis, characterization, and catalytic performance for benzene oxidation

This work reports the first synthesis of CuO–CeO 2 binary oxides with a plate-like morphology by a solvothermal method. The as-prepared CuO–CeO 2 nanoplates calcined at 400 °C were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectrum, and tested for catalytic oxidation of dilute benzene in air. Various structural characterizations showed that large amounts of copper species were exposed on the CuO–CeO 2 nanoplate surface. The effect of the synthesis conditions on the structure of the product, as well as the growth process of the nanoplates, has been studied and discussed. The CuO–CeO 2 nanoplates exhibited an excellent catalytic activity for benzene oxidation despite its relatively low surface area and could catalyze the complete oxidation of benzene at a temperature as low as 240 °C.

Highly efficient complete oxidation of dilute benzene over ultrafine Cu0.1Ce0.5Zr0.4O2− catalyst in a fluidized bed reactor

Ultrafine Cu0.1Ce0.5Zr0.4O2-delta catalyst operated in a fluidized bed reactor was found to be very effective for complete oxidation of dilute benzene in air. The complete conversion of benzene could be achieved at reaction temperature as low as 220 degrees C. The mechanism of benzene oxidation over the Cu0.1Ce0.5Zr0.4O2-delta catalyst was investigated by conducting pulse reaction of pure benzene in the absence of O-2 over the catalyst and the results indicated the involvement of lattice oxygen from the catalyst in benzene oxidation. (C) 2009 Elsevier B.V. All rights reserved.

A synthetic approach to C-nor-D-homosteroids based on a cascade of radical cyclisations from a vinylcyclopropane-substituted acyl radical precursor

Treatment of the arylvinylcyclopropane-substituted seleno ester 5 with Bu 3SnH–AIBN, under high dilution in benzene at 80 °C, led to a 1:1 mixture of C10 methyl epimers of the C-nor-D-homosteroid ring system 24/ 25. The homosteroid was formed from 5 via a cascade of sequential acyl 13- endo trig radical macrocyclisation, benzyl radical 5- exo trig transannulation and alkyl radical transannulation reactions ( Scheme 1). The macrocyclic dienone 23 was also isolated as an intermediate in the radical cascade between 5 and 24/ 25, and the dioxolanes 29 were interesting by-products. The cascade of radical cyclisations leading to the homosteroid 24/ 25 from the acyl radical precursor 5 is compared and contrasted with similar radical cascades from arylvinylcyclopropane-substituted alkyl radical precursors, i.e, 30→ 31 and 32b→ 38.

Unusual Luminescence Enhancement of Metallogels of Alkynylplatinum(II) 2,6-Bis(N-alkylbenzimidazol-2′-yl)pyridine Complexes upon a Gel-to-Sol Phase Transition at Elevated Temperatures

A series of alkynylplatinum(II) complexes of 2,6-bis(N-alkylbenzimidazol-2'-yl)pyridine has been synthesized and characterized by (1)H NMR, IR, FAB mass spectrometry, and elemental analysis; the photophysical properties have also been investigated. All the complexes have been shown to exhibit interesting gelation properties. Scanning electron microscopy (SEM) of the xerogels showed a network of fibrous structures, typical of morphologies of organogels/metallogels. Interestingly, two of the complexes were found to show strong luminescence enhancement upon a gel-to-sol phase transition upon increasing the temperature. This unusual behavior is rarely encountered, as it represents a sharp contrast to that exhibited by other typical thermotropic organogels and metallogels reported so far. Variable-temperature UV-vis and luminescence spectroscopies were performed to probe the gel-to-sol phase transition. Concentration-dependent, variable-temperature, and time-resolved emission studies in dilute benzene solution have also been made to provide further insights into the spectroscopic origin in the sol forms. A quantitative treatment of the system based on the Birks scheme has been performed.

Water and alcohol(s): what's the difference? A proton NMR and DFT study of hetero‐association with pyridine

AbstractHetero‐association of water and some simple aliphatic alcohols with pyridine in benzene has been studied by 1H nuclear magnetic resonance (NMR) spectroscopy at very low donor concentration, where self‐association is negligible. Association constants for the formation of 1:1 and 2:1 pyridine:water complexes can then be determined without recourse to ad hoc computer programmes. That for association of a second pyridine with water is about 10 times lower than for the first. Reaction parameters for the first association with water are very similar to those for the alcohols, whereas the reaction enthalpy for the second association is somewhat smaller. The chemical shift of the OH protons and the HCOH coupling constants for alcohols at high dilution in benzene are almost identical with gas‐phase data. The change in chemical shift upon association with pyridine correlates with the free energy of the reaction. Quantum mechanical calculations [BPE0 functional, 6‐311+G(d,p) basis set and a polarized continuum model of the solvent (IEFPCM)] have been run on complexes of pyridine with water, both 1:1 and 2:1, and with four alcohols. Calculated reaction enthalpies are in qualitative and, in some cases, almost quantitative agreement with the experimental data. The association constants for 1:1 complexation of pyridine with alcohols follow a rough Taft correlation in terms of polar substituent constants. Substituent size, even in the case of very bulky groups, seems to be unimportant. Copyright © 2008 John Wiley & Sons, Ltd.

Gas-sensing properties of well-crystalline ZnO nanorods grown by a simple route

Well-crystalline ZnO nanorods were synthesized by a simple solution route employing dodecyl benzene sulfonic acid sodium salt (DBS) as a modifying agent. ZnO gas sensors were fabricated from ZnO nanorods with an average diameter of around 95nm and their gas-sensing properties were investigated. It was found that the sensors based on ZnO nanorods exhibit high responses and good selectivities to benzene and ethanol gas. Our results indicate that ZnO sensors will be promising candidates for practical detectors for dilute benzene and ethanol, respectively.