Showing papers on "Nitrobenzene published in 1995"

Electrochemical Destruction of Aniline and 4‐Chloroaniline for Wastewater Treatment Using a Carbon‐PTFE O 2 ‐ Fed Cathode

Abstract: The electrochemical degradation of 100 ppm aniline and 4-chloroaniline in basic aqueous solutions of pH ranging between 10.1 and 12.7 has been studied at constant current intensity using a Pb/PbO{sub 2} anode and a carbon-polytetrafluoroethylene O{sub 2}-fed cathode. Under these conditions, hydrogen peroxide was electrogenerated in the cell via a two-electron reduction of oxygen gas fed to the cathode. The current efficiency for H{sub 2}O{sub 2} generation depended on the applied current intensity and the background electrolyte used. The concentration decay for each contaminant with electrolysis time was followed by high pressure liquid chromatography (HPLC). Kinetic analysis of these data showed a pseudo first-order decomposition reaction for both substrates at anodic current densities of 30 mA cm{sup {minus}2} or higher, as well as a decrease, of their half-lifetimes when current intensity increased. A gradual decrease in total organic carbon (TOC) for 0.05 mol/dm{sup 3} NAOH solutions with electrolysis time was always found. Product analysis of these electrolyzed solutions by gas chromatography-mass spectroscopy (GC-MS) and HPLC allowed the detection of nitrobenzene and 1-chloro-4-nitrobenzene proceeding from the anodic decomposition of aniline and 4-chloroaniline, respectively. Maleic acid was also detected as intermediate and ammonia was found as final product. Destruction of initial pollutantsmore » and intermediates is explained by their oxidative reactions with OH and HO{sub 2} radicals at the anode reaction layer. The effect of HO{sub 2} upon decomposition pathways of anilines is discussed.« less

Photodegradation of Water Pollutants

Abstract: Introduction: Advanced Oxidation Processes. Mechanisms: eaq-, 102, .OH and Peroyxy Radicals. Sensitized Excitation. Semiconductor Promoted Photooxidation. Experimental Techniques. Inorganic Ions and Molecules: Water and Hydrogen Peroxide. Halide Ions. Nitrogen Compounds. Phosphorus Oxyanions. Sulfur Oxyanions and Sulfide. Heavy Metal Ions. Organo-Metallic Compounds. Hydrocarbon Derivatives: Aliphatic Compounds. Aromatic and Other Cyclic Compounds. Long-Chain Compounds. Photo-induced Nitrosation and Nitration. Halocarbons: Aliphatic Halocarbons. Aromatic and Other Cyclic Compounds. Organic Nitrogen Compounds: Triazines. Amines, Amides, and Carbamates. Nitrobenzene and Nitrophenols. Bromoxynil and Choroxynil. Thymine. Triclopyr. Fenarimol. Flavins. Catecholamines. Dyes. Polycyclic Aromatic Nitrogen Heterocycles. Organic Phosphorus Compounds: Homogenous Photolysis. Heterogenous Photodegradation. Organic Sulfur Compounds Natural and Waste Waters: Natural Transformations in Freshwater and Oceans. Treatment of Polluted Groundwater. Treatment of Waste Water. Photodynamic Sterilization. Concentrated Sunlight. Evaluation and Future Trends: Photodegradation Compared with Other Methods. Cost estimates, Energetics, and Conclusions. References Index THis TOC has 3 levels: Introduction Advanced Oxidation Processes Mechanisms: eaq-, 102, .OH and Peryoxy Radicals Sensitized Excitation Semiconductor-Promoted Photooxidation Primary Reaction Steps Kinetic Models Role of Oxygen Direct and Indirect Photodegradations Zeta Potentials and Surface Properties Catalyst Preparations Surface Density of OH Groups in TiO2 Particles Quantum Yields and Turnover Numbers Experimental Techniques Reactor Design Laser and Excimer Light Sources Light-Dark Cycling Concentrated Sunlight Photoelectrochemical Reactions Inorganic Ions and Molecules Water and Hydrogen Peroxide Halide Ions Nitrogen Compounds Phosphorus Oxyanions Sulfur Oxyanions and Sulfide Heavy Metal Ions Organo-Metallic Compounds Hydrocarbon Derivatives Aliphatic Compounds Homogenous Photolysis Heterogenous Photodegradation Aromatic and Other Cyclic Compounds Homogenous Photolysis Heterogenous Photodegradation Oil Spills Long-Chain Compounds Surfactants Lignin Sulfonates and Kraft Wastewater Phthalate Esters Polymers Photoinduced Nitrosation and Nitration Halocarbons Aliphatic Halocarbons Aromatic and Other Cyclic Halocarbons Haloaromatics Halogenophenols Polychlorinated Dioxins, Dibenzofurans, and Biphenyls Halocarbon Pesticides Organic Nitrogen Compounds s-Triazines Amines, Amides, and Carbamates Nitrobenzene and Nitrophenols Bromoxynil and Chloroxynil Thymine Triclopyr Fenarimol Flavins Catecholamines Dyes Azo Dyes Tannery Dyes Dyes in Municipal Wastewater Methyl Violet Methyl Viologen Polycyclic Aromatic Nitrogen Heterocycles Organic Phosphorus Compounds Homogenous Photolysis Heterogenous Photodegradation Organic Sulfur Compounds Natural and Waste Waters Natural Transformations in Freshwater and Oceans Treatment of Polluted Groundwater Treatment of Wastewater Photodynamic Sterilization Concentrated Sunlight Evaluation and Future Trends Photodegradation Compared with Other Methods Ozonation Biodegradation Radiolysis Ultrasonics Corona Discharge Electrochemical Oxidation Oxidation in Supercritical Water Cost Estimates, Energetics, and Conclusions Cost Estimates Energy Requirement Evaluation Future Trends References Index

Oxidative Pathway for the Biodegradation of Nitrobenzene by Comamonas sp. Strain JS765.

Abstract: Previous studies have shown that the biodegradation of nitrobenzene by Pseudomonas pseudoalcaligenes JS45 proceeds by the reduction of nitrobenzene through nitrosobenzene and hydroxylaminobenzene, followed by rearrangement to 2-aminophenol, which then undergoes meta ring cleavage. We report here the isolation of a Comamonas sp. that uses an oxidative pathway for the complete mineralization of nitrobenzene. The isolate, designated strain JS765, uses nitrobenzene as a sole source of carbon, nitrogen, and energy. Nitrobenzene-grown cells oxidized nitrobenzene, with the stoichiometric release of nitrite. Extracts of nitrobenzene-grown JS765 showed high levels of catechol 2,3-dioxygenase activity that were not abolished by heating the cell extracts to 60(deg)C for 10 min. The ring cleavage product had an absorbance maximum at 375 nm, consistent with that of 2-hydroxymuconic semialdehyde. Both NAD-dependent dehydrogenase and NAD-independent hydrolase activities towards 2-hydroxymuconic semialdehyde were induced in extracts of nitrobenzene-grown cells. Catechol accumulated in the reaction mixture when cells preincubated with 3-chlorocatechol were incubated with nitrobenzene. Conversion of nitrobenzene to catechol by induced cells in the presence of 3-chlorocatechol and (sup18)O(inf2) demonstrated the simultaneous incorporation of two atoms of oxygen, which indicated that the initial reaction was dioxygenation. The results indicate that the catabolic pathway involves an initial dioxygenase attack on nitrobenzene with the release of nitrite and formation of catechol, which is subsequently degraded by a meta cleavage pathway.

Purification and characterization of nitrobenzene nitroreductase from Pseudomonas pseudoalcaligenes JS45.

Abstract: Pseudomonas pseudoalcaligenes JS45 grows on nitrobenzene as a sole source of carbon, nitrogen, and energy. The catabolic pathway involves reduction to hydroxylaminobenzene followed by rearrangement to o-amino-phenol and ring fission (S. F. Nishino and J. C. Spain, Appl. Environ. Microbiol. 59:2520, 1993). A nitrobenzene-inducible, oxygen-insensitive nitroreductase was purified from extracts of JS45 by ammonium sulfate precipitation followed by anion-exchange and gel filtration chromatography. A single 33-kDa polypeptide was detected by denaturing gel electrophoresis. The size of the native protein was estimated to be 30 kDa by gel filtration. The enzyme is a flavoprotein with a tightly bound flavin mononucleotide cofactor in a ratio of 2 mol of flavin per mol of protein. The Km for nitrobenzene is 5 microM at an initial NADPH concentration of 0.5 mM. The Km for NADPH at an initial nitrobenzene concentration of 0.1 mM is 183 microM. Nitrosobenzene was not detected as an intermediate of nitrobenzene reduction, but nitrosobenzene is a substrate for the enzyme, and the specific activity for nitrosobenzene is higher than that for nitrobenzene. These results suggest that nitrosobenzene is formed but is immediately reduced to hydroxylaminobenzene. Hydroxylaminobenzene was the only product detected after incubation of the purified enzyme with nitrobenzene and NADPH. Hydroxylaminobenzene does not serve as a substrate for further reduction by this enzyme. The products and intermediates are consistent with two two-electron reductions of the parent compound. Furthermore, the low Km and the inducible control of enzyme synthesis suggest that nitrobenzene is the physiological substrate for this enzyme.

Temperature dependence of the rate of reaction of OH with some aromatic compounds in aqueous solution. Evidence for the formation of a π-complex intermediate?

Abstract: The rates of reaction of OH with benzene, chlorobenzene, nitrobenzene, ion and benzoic acid have been measured in aqueous solution up to 200 °C using pulse radiolysis to generate OH. The temperature dependence of the observed rate constant, kobs, is essentially the same for each compound and kobs changes by less than three-fold between 20 °C and 200 °C. The kinetic data are consistent with a mechanism whereby OH reversibly forms a π-complex with the aromatic compound, irrespective of the substituent on the ring, which then transforms to a σ-bonded hydroxycyclohexadienyl radical. The values of kobs were determined from the rate of formation of this radical. There is no evidence for dissociation of the σ-bonded radical nor for H atom abstraction from the ring which have been reported for the gas phase. The apparent mechanistic differences between the two phases may be due to the different timescales over which the kinetics measurements were made.

Vapour-phase nitration of benzene over modified mordenite catalysts

Abstract: Active and stable mordenite catalysts have been developed for the selective nitrobenzene production by vapour-phase nitration of benzene with 65 wt.-% HNO 3 at normal pressure and 443 K. The acidic and textural properties of commercial synthetic mordenite have been modified by different combinations of thermal and acid treatments. The physico-chemical properties of the catalysts were investigated by 27 Al and 29 Si MAS-NMR, AAS, XRD, N 2 and low pressure Ar adsorption. The catalytic activity and stability of the modified mordenite catalysts were strongly influenced by the amount and state of aluminium in the zeolite. Extra-framework aluminium species generated by thermal treatment at higher temperatures (≥973 K) induced a severe catalyst deactivation. The deactivation could almost be eliminated by subsequent acid leaching with 6 N HCl, which removed the extra-framework aluminium to a large extent, thus unblocking the pores and/or pore mouths. An optimum mordenite modification procedure was developed, resulting in highly active and selective catalysts, which retained their initial activity for at least 120 h on stream.

Selective reduction of nitrobenzene to nitrosobenzene over different kinds of trimanganese tetroxide catalysts

Abstract: Selective reduction of nitrobenzene has been measured on several kinds of Mn3O4 catalysts obtained by different methods of preparation. Attention is mainly given to the relationship between catalytic performance of different Mn3O4 materials and their redox behaviour. It was found that the catalyst having the most active redox behavior favoured the formation of highly reduced product (e.g. aniline etc) but, the catalyst having the least active redox behaviour showed poor catalytic activity. It seems that the catalytic as well as the redox behavior of Mn3O4 could be related to the Jahn-Teller effect.

Polymer-Coated, Tapered Cylindrical ATR Elements for Sensitive Detection of Organic Solutes in Water

Abstract: Commercially available tapered chalcogenide fibers have been coated with poly(vinyl chloride) (PVC) plasticized with 47% (w/w) chloroparaffin containing 60% Cl by weight. The coating procedure involves applying a drop of a solution containing PVC and the plasticizer in tetrahydrofuran along the fiber while allowing the solvent to evaporate. The coated fibers were exposed to 0.15% (v/v) benzene in water (1479-cm-1 band), 0.40% (v/v) chloroform in water (1216-cm-1), and 0.10% (v/v) nitrobenzene in 1.5% (w/v) methanol/water (1348-cm-1). All three organic solutes gave readily detectable signals with the coated fibers but were not observable when the aqueous solution was sampled with the use of an uncoated, tapered fiber. Detection limits for benzene, chloroform, and nitrobenzene were calculated to be 0.02%, 0.11%, and 0.006% by volume, respectively. These data show that the advantage of using a polymer coating to concentrate the analyte and reduce the water background may be combined with the advantages of using a tapered optical fiber to yield a sensitive method for detecting nonpolar organic solutes in water.

Extraction of cesium and strontium into hydrocarbon solvents using tetra-c-alkyl cobalt dicarbollide

Abstract: Tetra-C-alkyl derivatives of cobalt dicarbollide, CO(C2R2B9H9)2- (CoB2-R4 -R; = CH3, C6H13) are examined as potential cesium and strontium extractants for acidic and alkaline solutions. The mechanism of cobalt dicarbollide extraction is characterized, and extended into new non-toxic solvent systems. Extractions using 0.01 M H+CoB2-hexyl4 - in mesitylene and iethylbenzene are compared to 0.01 M H+CoB2 - in nitrobenzene. H+CoB2-hexyl4 - in diethylbenzene shows improved selectivity (104) forCs over Na in acidic solution. In dilute alkaline solution (0.01 M NaOH), H+CoB2 -hexyl4 - extracts Cs less efficiently, but more effectively removes Sr at higher base concentrations (1.0 M NaOH). Other aspects of the H+CoB2-hexyl4 -/hydrocarbon performace are comparable to the previously known H+CoB2 -/nitrobenzene extractant.

The isomerization of nitrobenzene to phenylnitrite

Abstract: We report ab initio calculations on nitrobenzene (C6H5NO2) and phenylnitrite (C6H5ONO) performed at the MP2(FC) 6-31G∗ level. The results paint a detailed picture of the isomerization pathway between the two species on the ground electronic surface. They show that phenylnitrite is stable with respect to dissociation into phenoxy and nitric radicals by 80.6 kJ mol−1 and lies only 20.2 kJ mol−1 higher in energy than the nitrobenzene global minimum. We estimate the barrier between the two isomers to be less than 108.9 kJ mol−1 (1.13 eV), but we are unable to locate a fully converged transition state. Calculation of the isomerization pathway shows that there is an early barrier close to the initial nitrobenzene geometry. It also provides a clear picture of the extensive rearrangement involving a CN bond being broken, a new CO bond being formed, and further changes in bond lengths, bond angles, and dihedral angles in the C NO2 moiety of the nitrobenzene molecule. The harmonic frequencies of the two isomers and those for the phenoxy and nitric oxide radicals calculated at the same level of theory compare well with previous experimental and theoretical studies. These calculations also bear on our experimental study of the kinetic and internal energy disposal in the photodissociation of nitrobenzene.

Excess Volumes of Substituted Benzenes with N,N-Dimethylformamide

Abstract: Excess volumes of binary liquid mixtures of N,N-dimethylformamide with toluene, ethylbenzene, chlorobenzene, bromobenzene, nitrobenzene, and aniline at 303.15 and 313.15 K have been measured with a dilatometer. Excess volumes are negative for the systems of N,N-dimethylformamide with toluene, ethylbenzene, chlorobenzene, bromobenzene, and aniline. The excess volumes are positive for the system N,N-dimethylformamide with nitrobenzene at 303.15 K and show a change in sign at 313.15 K

Purification of aniline

Abstract: PURPOSE: To readily obtain colorless aniline containing only slight amount of phenol by using a method capable of preventing increase in the viscosity of a waste oil having high boiling point from becoming hardly handleable, or by which corrosion with an alkali is scarcely generated. CONSTITUTION: An aniline solution containing phenols is added with an alkali aqueous solution having a prescribed concentration (e.g. sodium hydroxide or potassium hydroxide), mixed, allowed to stand and separated to oil and water phases, then the oil phase part is distilled under 70-200Torr pressure at 110-140°C to reduce phenol to ≤30ppm. In the process, an alkali concentration in the aqueous phase after adding the alkali aqueous solution is preferably 0.1-0.7wt.% and a molar ratio of the alkali to the phenols is preferably 3-500. This reaction can be performed either by a continuous method or a batch method. The raw aniline solution containing phenols is obtained by a hydrogenating reaction of nitrobenzene. COPYRIGHT: (C)1996,JPO

Biodegradation of nitrobenzene through a hybrid pathway in Pseudomonas putida.

Abstract: The biodegradation of nitrobenzene was attempted by using Pseudomonas putida TB 103 which possesses the hybrid pathway combining the tod and the tol pathways. Analysis of the metabolic flux of nitrobenzene through the hybrid pathway indicated that nitrobenzene was initially oxidized to cis-1,2-dihydroxy-3-nitrocyclohexa-3,5-diene by toluene dioxygenase in the tod pathway and then channeled into the tol pathway, leading to the complete biodegradation of nitrobenzene. A crucial metabolic step redirecting the metabolic flux of nitrobenzene from the tod to the tol pathway was determined from the genetic and biochemical studies on the enzymes involved in the tol pathway. From these results, it was found that toluate-cis-glycol dehydrogenase could convert cis-1,2-dihydroxy-3-nitrocyclohexa-3,5-diene to catechol in the presence of NAD{sup +} with liberation of nitrite and the reduced form of NAD{sup +} (NADH) into the medium.

Contribution of Lignin Sub-Structures to Nitrobenzene Oxidation Products

Abstract: Nitrobenzene oxidation of a series of lignin model compounds with varying aromatic nuclei and sidechain structures, including diphenylmethane compounds, gave benzaldehydes and benzoic acids in a range of yields. The yields were dependent on the structure of the aromatic nucleus, and were in the order syringyl > guaiacyl > 4-hydroxyphenyl. The yields were also dependent on the benzylic group, in the order C=O > CHOH > CH2. Veratryl compounds afforded low yields of oxidation products. Lignin model 1-1′-, 1,5′-and 5,5′-diphenylmethanes gave rise to moderate yields of nitrobenzene oxidation products. However, 1,6′-diphenylmethanes gave only low yields of oxidation products, and no oxidation products were obtained from a nonphenolic 1,1′-diphenylmethane. This suggests that the assumption in the nucleus exchange-nitrobenzene oxidation method for determining lignin structures, that diphenylmethanes do not give rise to oxidation products, should be reappraised. It is proposed that a key influence on the ...

Individual extraction constants of some dicarbollylcobaltate anions in the water-nitrobenzene system

Abstract: Individual extraction constants of nine dicarbollylcobaltate anions in the two-phase water-nitrobenzene system were determined radiometrically assuming that the changes of Gibbs energy of the transfer of the tetraphenylarsonium cation, Ph4As+, and of the tetraphenylborate anion, BPh 4 − , from the aqueous into the nitrobenzene phase are equal. The constants obtained by this method were correlated with Hansch's constants of hydrophobity.

Distribution Study on Electroneutral and Protonated Amino Acids between Water and Nitrobenzene. Determination of the Standard Ion-Transfer Potentials of Protonated Amino Acids.

Abstract: In order to determine the standard ion-transfer potentials () of protonated amino acids (HA+) from water to an organic solvent of moderate dielectric constant, new theoretical equations were derived. Various theoretical predictions were verified experimentally by the solvent extraction of D- and L-amino acids with perchloric and nitric acid from water to nitrobenzene at 25 °C. Furthermore, the distribution constants (KD,A) of the electroneutral D- and L-amino acids (A) between water and nitrobenzene were determined at 25 °C. The amino acids were Ala, Val, Ile, Leu, Met, Phe, Thr, Asn, and Gln. The KD,A values of the D- and L-form of the same amino acid are equal. The same is true for the values. The hydrophilicity of A decreases in the following order: Asn > Thr > Gln > Ala > Val > Met > Ile ≥ Leu > Phe. The same order of decreasing hydrophilicity was also observed for HA+. All of the A and HA+ are much more soluble in water than in nitrobenzene. The A is more lipophilic than the corresponding HA+. Contri...

Catalytic Ability of Octopus-Type Calixarene in the Formation of Ethers from Phenols and Alkyl Halides or 1-Chloro-4-nitrobenzene

Abstract: The formation of ethers was catalyzed by 5,11,17,23,29,35-hexa-p-t-butyl-37,38,39,40,41,42-hexakis(3,6,9-trioxadecyloxy)calix[6]arene (1). It was found that the calixarene-catalyzed reaction of phe...

Role of Interfacial Reaction in Heterogeneous Aromatic Nitration

Abstract: The previously established mechanism of two-phase nitration has been revised by proposing an additional mode of reaction, viz., interfacial nitration. The interfacial mechanism involves adsorption of the nitronium ion at the interface, followed by its reaction with the aromatic substrate present in the interfacial monolayer. The evidence for the proposed mechanism is provided by the results of the experiments, conducted in this work, on nitration of nitrobenzene. Relative magnitudes of the bulk and the interfacial rates during the nitration of nitrobenzene have been determined. The effects of interfacial area, concentrations of sulfuric and nitric acids, and addition of surfactant and inert diluent in the organic phase on the rate of interfacial nitration are studied. On the basis of the proposed mechanism, plausible explanations have been provided to the anomalies in the rates of nitration, observed under the industrially relevant operating conditions.

Reduction of nitrobenzene to aniline with carbon monoxide and water

Abstract: Modified catalyst systems composed of palladium or its chloride and co-catalysts such as FeCl3, Fe2O3, metallic Fe-powder, metallic Fe-wire net, iodine, pyridine or aniline, applied in the reduction of nitrobenzene to aniline in the presence of carbon monoxide and water are described. The reaction proceeds at 150–180 °C and 2.5–7 MPa gauge pressure. After 1–7 h the reaction was complete, reaching nitrobenzene conversions of 98–100%. Selectivity of the reaction with respect to aniline was also 100%.