Showing papers on "Nitrobenzene published in 2005"
TL;DR: In this article, the effects of solvents and their properties on electro-spinnability of polystyrene (PS) solutions and the morphological appearance of the as-spun PS fibers were investigated qualitatively by means of a scanning electron microscope (SEM).
437 citations
TL;DR: It was found that in MnO(x)/GAC catalytic ozonation, the degradation efficiency of nitrobenzene was higher under low pH conditions than under high pH conditions, and higher pH condition favored ozone decomposition.
228 citations
TL;DR: 1H NMR experiments showed molecular complexation in chloroform between NBZ and model graphene polycyclic aromatic units (naphthalene, phenanthrene, and pyrene) which was absent for BEN and TOL, which is used to support the existence of pi-pi electron donor-acceptor interactions betweenNBZ (electron acceptor) and the poly cyclic aromatic charcoal surface (Electron donor) as the cause of enhanced NBZ sorption.
Abstract: Charcoal, the residue of incomplete biomass burning that is found in many soils and sediments, is considered a high affinity sorbent for organic pollutants However, little is known about the microscopic processes controlling sorption The purpose of this study was to gain molecular-scale insight into the sorption on a charcoal of three weakly soluble aromatic compounds [benzene (BEN), toluene (TOL), and nitrobenzene (NBZ)] by conducting both single-solute and bi-solute experiments The charcoal (420 m2 g-1) was produced from maple wood shavings by oxygen-limited pyrolysis at 673 K Solute affinity for charcoal followed the order NBZ > TOL > BEN Commonly employed sorption models did not adequately describe the single-solute isotherms Competition in both TOL−BEN and the TOL−NBZ bi-solute systems was strong Normalization of the isotherms for the hydrophobic driving force by using an existing free energy correlation between sorption and partitioning to an inert solvent (benzene or n-hexadecane) with a non
192 citations
TL;DR: The Haber mechanism describing the process of hydrogenating nitrobenzene to aniline is shown to be incorrect and a new mechanism is proposed.
182 citations
TL;DR: In this article, carbon nanotube (CNT)-supported Pt catalysts have been prepared by impregnation and reduction-precipitation method using chloroplatinic acid as metal precursor.
Abstract: Carbon nanotube (CNT)-supported Pt catalysts have been prepared by impregnation and reduction–precipitation method using chloroplatinic acid as metal precursor. The structure of the catalysts has been characterised using TEM, BET and XPS. The catalytic performance for nitrobenzene hydrogenation was evaluated under atmospheric pressure and ambient temperature. The results show that the catalysts, both of low and higher Pt loading, show high activity for nitrobenzene directly hydrogenating to aniline under mild conditions. The highly dispersed Pt and mesoporosity structure of acid-oxidized CNT-supported Pt catalyst are responsible for the extraordinary activity.
179 citations
TL;DR: The main photoproducts of photocatalytic degradation of aniline at the pH of maximum adsorption are 2-aminophenol and phenol.
Abstract: Interaction between aromatic amines and TiO 2 takes place preferentially through the amino group when pH > p K a (BH + ) and, as a minor but mechanistically relevant mode, via a π-interaction if pH K a (BH + ). No significant direct photodegradation of aniline or N , N -dimethyl-aniline is detected in acidic medium using λ > 290 nm, but it is enhanced in alkaline medium. 2-Aminophenol and benzoquinone are the main photoproducts of direct irradiation of aniline. The main photoproducts of photocatalytic degradation of aniline at the pH of maximum adsorption are 2-aminophenol and phenol. Scavenging HO • with t -BuOH shows that adsorbed aniline is oxidized by positive holes (h + ), with participation of the anilinium radical cation. In the case of N , N -dimethyl-aniline at the pH of maximum adsorption, N -methyl-aniline is the main photoproduct, formed also via the dimethyl anilinium radical cation. Photocatalytic degradation in acid medium is inhibited due to electrostatic repulsion between the positively charged surface and the protonated amines. Aniline is mainly transformed into phenol and 2-aminophenol, and N , N -dimethyl-aniline into aniline, that undergoes hydroxylation to phenol. In alkaline medium the main photoproduct of degradation of aniline is nitrobenzene, formed with involvement of the anilinyl radical.
124 citations
TL;DR: In this article, a commercial activated carbon (AC) was used as a catalyst for continuous catalytic wet air oxidation (CWAO) in a fixed bed reactor in a trickle flow regime.
Abstract: Continuous catalytic wet air oxidation (CWAO) was investigated as a suitable precursor for the biological treatment of industrial wastewater that contained phenols (phenol, o-cresol, 2-chlorophenol and p-nitrophenol), aniline, sulfolane, nitrobenzene or sodium dodecylbenzene sulfonate (DBS). Seventy-two-hour tests were carried out in a fixed bed reactor in trickle flow regime, using a commercial activated carbon (AC) as catalyst. The temperature and total pressure were 140 8C and 13.1 bar, respectively. The influence of hydroxyl-, methyl-, chloride-, nitro-, sulfo- and sulfonic-substituents on the oxidation mechanism of aromatic compounds, the occurrence of oxidative coupling reactions over the AC, and the catalytic activity (in terms of substrate elimination) were established. The results show that the AC without any supported active metal behaves bifunctionally as adsorbent and catalyst, and is active enough to oxidate phenol, o-cresol, 2-chlorophenol and DBS, giving conversions between 30 and 55% at the conditions tested. The selectivity to the production of carbon dioxide was considerable with total organic carbon (TOC) abatement between 15 and 50%. The chemical oxygen demand (COD) reduction was between 12 and 45%. In turn, aniline, sulfolane, p-nitrophenol and nitrobenzene conversions were below 5% and there was almost no TOC abatement or COD reduction, which shows the refractory nature of these compounds. # 2004 Elsevier B.V. All rights reserved.
122 citations
TL;DR: The structure of NBDO is determined, which has a hetero-hexameric structure similar to that of several other Rieske non-heme iron dioxygenases, and the structures of complexes with substrates nitrobenzene and 3-nitrotoluene reveal the structural basis for its activity with nitroarenes.
111 citations
TL;DR: Using the photodependent cytotoxicity of compound 14 against HCT116 human colon cancer cells, it was demonstrated that 4-substituted-2,6-dimethylnitrobenzene analogues are useful NO donors for the time- and site-controlled NO treatment.
Abstract: A new type of photoinduced nitric oxide (NO) donors was designed from nitrobenzene derivatives. Visible-light irradiation of 2,6-dimethylnitrobenzenes bearing extended π-electron systems at the 4-position revealed efficient NO release using ESR analysis and the Griess assay. Computational study and ultraviolet spectrum analysis suggested that the NO-releasing activity was closely related to the conformation of the nitro group, the absorption intensity, and the length of the conjugated π-electron system. Employing the photodependent cytotoxicity of compound 14 against HCT116 human colon cancer cells, it was demonstrated that 4-substituted-2,6-dimethylnitrobenzene analogues are useful NO donors for the time- and site-controlled NO treatment.
95 citations
TL;DR: In this paper, the placement of the second perforated plate in the fluidized bed reactor inhibits the backmixing of gases and solids and consequently increases the local molar ratio of hydrogen to nitrobenzene in the second stage.
Abstract: Gaseous hydrogenation of nitrobenzene over a Cu/SiO2 catalyst has been studied in a two-stage and in a single-stage fluidized bed reactor, at 513–553 K and atmospheric pressure. The placement of the second perforated plate in the fluidized bed reactor inhibits the backmixing of gases and solids and consequently increases the local molar ratio of hydrogen to nitrobenzene in the second stage. Thus, the conversion of nitrobenzene and the selectivity of aniline production and the stable life of the catalyst are significantly increased in the two-stage fluidized bed reactor, as compared with those in the single-stage one. A comparison of the coke formation and the burning characteristics of cokes in different reactors has also been presented. It suggests the simple catalyst regeneration for the two-stage fluidized bed technology. This work provides an effective method to produce aniline with higher purity.
88 citations
TL;DR: Computer fitting of the cyclic voltammetry of 4-nitroaniline, NA, plus 1,3-diphenylurea in DMF shows essentially no binding between urea and NA in the oxidized state, but very strong binding in the reduced state, along with very rapid rates of hydrogen bond formation, making this system a fast on/off redox switch.
Abstract: Reduction of nitrobenzene derivatives in the presence of arylureas in aprotic solvents results in large positive shifts in potential of the nitrobenzene(0/)(-) cyclic voltammetry wave with little change in wave shape. This behavior is indicative of reversible hydrogen bonding between nitrobenzene radical anions and arylureas. Computer fitting of the cyclic voltammetry of 4-nitroaniline, NA, plus 1,3-diphenylurea in DMF shows essentially no binding between urea and NA in the oxidized state (K(ox) < 1 M(-)(1)), but very strong binding in the reduced state (K(red) = 8 x 10(4) M(-)(1)), along with very rapid rates of hydrogen bond formation (k(f)'s approximately 10(8)-10(10) M(-)(1) s(-)(1)), making this system a fast on/off redox switch.
TL;DR: In this paper, two active carbons from Algerian date pits were prepared by chemical activation at moderate temperature (500-600 degrees C) with H3PO4 and ZnCl2 and one commercial active carbon (from Darco) was oxidized with air at different temperatures (300-450 degrees C).
Abstract: Two active carbons from Algerian date pits prepared by chemical activation at moderate temperature (500-600 degrees C) with H3PO4 and ZnCl2 and one commercial active carbon (from Darco) have been oxidized with air at different temperatures (300-450 degrees C) and with nitric acid in severe conditions during a short time. It has been demonstrated that air treatment generates surface oxygenated groups (XPS) that have an acidic character (simplified Boehm titration), without degrading the specific surface area (BET). Each active carbon has an optimal oxidation temperature depending on its activation procedure and corresponding to 20% in weight loss during the oxidation process. This optimal temperature achieves the highest surface oxygen content, which is directly correlated to the global acidity. It also means that when the support is loaded with 5% Pd by incipient wetness method, the catalyst exhibits the best activity for the liquid phase hydrogenation of nitrobenzene to aniline. In general, the metallic dispersion of the catalysts (CO chemisorption) remained appreciable even after oxidizing treatments. Exception is noted when nitric acid is used as oxidant while the active carbon has been prepared using zinc chloride. (c) 2005 Elsevier B.V. All rights reserved.
TL;DR: Use of labeled 18O2, H218O, a competitive kinetic isotope experiment, and use of phenyl-tert-butylnitrone as a spin-trap and identification by EPR provided evidence for formation of a radical intermediate involving a selective intramolecular interaction at the ortho position due to formation of an H5PV2Mo10O40-nitrobenzene complex.
Abstract: Nitrobenzene was regioselectively oxidized to 2-nitrophenol with oxygen in a reaction catalyzed by the H5PV2Mo10O40 polyoxometalate. The reaction was first order in oxygen and catalyst. 15N NMR showed the interaction between nitrobenzene and the polyoxometalate. Use of labeled 18O2, H218O, a competitive kinetic isotope experiment, and use of phenyl-tert-butylnitrone as a spin-trap and identification by EPR provided evidence for formation of a radical intermediate involving a selective intramolecular interaction at the ortho position due to formation of a H5PV2Mo10O40−nitrobenzene complex.
TL;DR: The nitration of naphthalene was studied in aqueous solution to gain insight into the processes leading to theNitration of aromatic compounds in atmospheric hydrometeors and nitrite photochemistry (and nitrite-induced photonitration) is expected to be relevant in fog and cloudwater in polluted areas.
Abstract: The nitration of naphthalene was studied in aqueous solution to gain insight into the processes leading to the nitration of aromatic compounds in atmospheric hydrometeors. Reactants used were nitric acid, nitrogen dioxide and peroxynitrous acid in the dark, nitrate, and nitrite/nitrous acid under illumination. Naphthalene nitration can lead to two possible isomers, 1- and 2-nitronaphthalene. The former nitrocompound preferentially forms upon electrophilic processes and in the presence of nitrogen dioxide. Electrophilic nitration of naphthalene takes place in the presence of concentrated nitric acid, but nitration with nitric acid and oxidants (charge-transfer nitration) occurs under much milder conditions than with nitric acid alone. Charge-transfer nitration may have some environmental significance in particular cases, e.g. in acidic aerosols in the presence of HNO3 and oxidants. Nitrogen dioxide is thought to have a role in PAH nitration in the Antarctic particulate matter. In previous papers we have found that nitration induced by peroxynitrous acid, HOONO, can follow two pathways, the former electrophilic (leading for instance to the formation of nitrophenols from phenol) and the latter probably involving HOONO itself (accounting for the formation of nitrobenzene from benzene). In the case of naphthalene and HOONO the electrophilic pathway mainly leads to 1-nitronaphthalene, while the other one preferentially yields 2-nitronaphthalene. The nitration of naphthalene in the presence of nitrite/nitrous acid under irradiation leads to both nitroisomers in similar ratios, and the process is not inhibited by hydroxyl scavengers. This excludes nitrogen dioxide as reactive species for nitration and marks a difference with phenol photonitration and a similarity with the behavior of benzene under comparable conditions. Nitrite photochemistry (and nitrite-induced photonitration as well) is expected to be relevant in fog and cloudwater in polluted areas. An important difference with the gas-phase nitration is that the radicals OH and NO3 are unlikely to play a relevant role in the nitration of naphthalene in aqueous solution.
TL;DR: A new methodology for the trace detection of organic explosives containing nitro functionalities is described, both easy to implement and could be built as a compact, low-power device.
Abstract: We describe a new methodology for the trace detection of organic explosives containing nitro functionalities. Conventional gas chromatography separates the components of an explosive mixture. Effluent from the gas chromatograph is pyrolyzed by passage over a heated Nichrome wire. Nitric oxide produced on pyrolysis of a nitroorganic compound is then detected by ultraviolet absorption spectroscopy between 180 and 240 nm, using a deuterium lamp as the light source. Nitric oxide exhibits a sharply banded, characteristic spectrum in this region, enabling detection of nitroorganics. The system is tested using the explosive simulants nitrobenzene and 2,4-dinitrotoluene, and with the nitramine explosive tetryl. Detection limits are 25 ng for nitrobenzene and 50 ng for 2,4-dinitrotoluene. Tetryl is detected with a detection limit of 50 ng. The system is both easy to implement and could be built as a compact, low-power device.
TL;DR: The high activity and selectivity in the present Ag/TiO2-photocatalyzed reduction are rationalized in terms of the charge separation efficiency, the selective adsorption of the reactants on the catalyst surfaces, and the restriction of the product readsorption.
Abstract: TiO2 particles loaded with silver nanoparticles with a mean diameter of 1.5 nm exhibit a high photocatalytic activity (84 % conversion after 1 h irradiation) for the reduction of nitrobenzene to aniline with 100 % selectivity in the presence of CH3OH (concentration=100 mM). High-resolution transmission electron microscopic studies of Pt-photodeposited Ag/TiO2 demonstrate that the Ag nanoparticles act as reduction sites in the photocatalytic reaction. Both spectroscopic measurements and density functional theory (DFT) calculations reveal that nitrobenzene is selectively adsorbed onto the Ag surfaces of Ag/TiO2 via partial electron transfer from Ag to nitrobenzene, whereas the interaction between aniline and Ag/TiO2 is weak. The kinetic analysis indicates that the recombination between the electrons flowing into the Ag nanoparticle and the holes left in the TiO2 valence band is significantly suppressed, particularly in the presence of CH3OH. The high activity and selectivity in the present Ag/TiO2-photocatalyzed reduction are rationalized in terms of the charge separation efficiency, the selective adsorption of the reactants on the catalyst surfaces, and the restriction of the product readsorption.
TL;DR: In this paper, the formation of transition metal complexes between dichlorocopper and a poly(4-vinylpyridine)/divinylbenzene(2%) polymeric matrix is described.
TL;DR: In this paper, the acylation with acetic anhydride of six aromatic substrates with different features (degree of activation of the aromatic ring towards electrophilic substitution, number of rings, i.e., 1 or 2) was carried out in a batch reactor at 373 K over a H-BEA zeolite (Si/Al = 15) with nitrobenzene as a solvent.
TL;DR: The polarization behavior of the couple Fe/Cu in 100 mg/L nitrobenzene aqueous solution was studied, and it was indicated that the iron corrosion was limited by both anodic and cathodic half-cell reactions under the neutral conditions, and cathodically controlled under the alkaline conditions.
TL;DR: In this article, the application of the palladium-phenanthroline catalytic system to the carbonylation of nitrobenzene in the presence of aniline to afford diphenylurea has been investigated.
TL;DR: Using lutetium bis(tetra-tert-butylphthalocyaninato) as a redox probe for the three-phase electrode, the transfer of both anions and cations across the water/nitrobenzene interface can be studied in a single experiment.
Abstract: The redox properties of lutetium bis(tetra-tert-butylphthalocyaninato) (LBPC) have been studied in nitrobenzene that is deposited as a microfilm on the surface of highly oriented pyrolytic graphite electrodes. The behavior of the modified electrode, which is immersed in an aqueous electrolyte solution, is typical for the three-phase electrode (Scholz, F.; Komorsky-Lovric, S.; Lovric, M. Electrochem. Comm. 2000, 2, 112−118). LBPC can be both oxidized and reduced in one electron reversible processes. The oxidation and the reduction of LBPC at the graphite|nitrobenzene interface is accompanied by the transfer of anion or cation, respectively, from the aqueous phase into the organic layer. Thus, using LBPC as a redox probe for the three-phase electrode, the transfer of both anions and cations across the water|nitrobenzene interface can be studied in a single experiment. The hydrophobicity of LBPC is so high that it enables inspection of cations and anions with ≤ 43 kJ/mol and ≤ 50 kJ/mol, respectively. The di...
TL;DR: In this article, the experimental values of density, viscosity, and ultrasonic velocity for the binary mixtures of cyclohexane + nitrobenzene, cycloxidehexane+nibenzene and cyclonehexane-nibene were determined at (298.15, 303.15 and 308.15) K over the entire composition range.
Abstract: The experimental values of density, viscosity, and ultrasonic velocity for the binary mixtures of cyclohexane + nitrobenzene, cyclohexanone + nitrobenzene, and cyclohexane + cyclohexanone are determined at (298.15, 303.15, and 308.15) K over the entire composition range. The excess molar volume (VE), deviation in viscosity (Δη), and excess isentropic compressibility ( ) have been calculated.
TL;DR: In this article, aniline was selectively converted into the corresponding nitrosobenzene and nitrobenzenes by oxidation with 30% aqueous hydrogen peroxide.
Abstract: Aniline was selectively converted into the corresponding nitrosobenzene and nitrobenzene by oxidation with 30% aqueous hydrogen peroxide. The reaction was catalyzed by various heteropolyoxometalates, at room temperature, in dichloromethane under two-phase conditions. Findings show that H3PW12O40 is the best catalyst in the oxidation of aniline. Na3PW9Mo3O40 and K4SiW9Mo2O39 also displayed high reactivity in the oxygenation system. Phase transfer agents and temperature increase also contribute to the efficiency of the oxidation.
TL;DR: In this article, a new kind of silica gel confined ionic liquid containing a metal complex as heterogenized catalysts was prepared for the carbonylation of amines and nitrobenzene without molecular oxygen to afford the corresponding ureas with greatly enhanced catalytic activity.
Abstract: A new kind of silica gel confined ionic liquid containing a metal complex as heterogenized catalysts was prepared for the carbonylation of amines and nitrobenzene without molecular oxygen to afford the corresponding ureaswith greatly enhanced catalytic activity (TOF exceeded 11000 mol.mol - 1 . h - 1 ), with a much lower amount of ionic liquids being needed, with easy catalyst separation and possible reusability, and avoidance of the using of explosive CO + O 2 gas mixtures. Such an enhancement in catalytic activity may be derived from the effect of a high concentration of ionic liquid containing a metal complex due to the confinement into the nanopores or cavities of the silica gel matrix.
TL;DR: In this paper, the dissolution of C60 in these aromatic organic solvents was observed to be exothermic, with exception of benzene and nitrobenzene, in which the enthalpy is close to zero.
TL;DR: In this paper, the catalytic behavior of the catalysts supported on purified activated carbon felt (ACF) and powder carbon (C) has been studied in the nitrobenzene (NBZ) hydrogenation reaction in liquid phase after activation under a H 2 atmosphere between 298 and 623 K.
TL;DR: Simultaneous nitrobenzene and phenol wet air oxidation was investigated in a stainless autoclave and the presence of phenol in the reaction media greatly improved the removal efficiency of nitro Benzene.
TL;DR: DFT calculations suggest formation of a superelectrophilic polyprotonated species that can transfer Cl + to the aromatic ring more efficiently than TICA due to charge-charge repulsion relief.
Abstract: +ao anel aromatico mais eficientemente do que o TICA devido ao alivio da repulsao carga-carga. Trichloroisocyanuric acid (TICA) in H 2 SO 4 is an efficient reagent for regioselective chlorination of isatin at the 5-position and deactivated aromatic compounds, such as nitrobenzene. DFT calculations suggest formation of a superelectrophilic polyprotonated species that can transfer Cl + to the aromatic ring more efficiently than TICA due to charge-charge repulsion relief.
TL;DR: In this paper, various chemical wet oxidation techniques to remove toxic non-biodegradable pollutants from wastewater were compared in a Trickle Bed Reactor and a tubular coil reactor at 25-550°C and 10-150 bar.
TL;DR: Time-resolved optical Kerr effect spectroscopy has been used to probe the molecular environment afforded by the hydrophobic core of oil-in-water microemulsions and suggests stabilization of the polar dispersed phase in polar regions of the micelle.
Abstract: Time-resolved optical Kerr effect spectroscopy has been used to probe the molecular environment afforded by the hydrophobic core of oil-in-water microemulsions. This was achieved by measuring the ultrafast dynamics of a series of benzene derivatives (benzonitrile, nitrobenzene, fluorobenzene, styrene, and toluene) incorporated as the oil phase within oil-in-water microemulsions and comparing them to the dynamics in neat liquid and the liquid diluted in nonpolar solvent. Polar and strongly interacting liquids (benzonitrile and nitrobenzene) showed dynamics in the microemulsion that are similar to those in the solution phase, while weakly interacting and mildly polar liquids (fluorobenzene, styrene and toluene) reveal dynamics more similar to those of the neat liquid. This suggests stabilization of the polar dispersed phase in polar regions of the micelle.