Showing papers on "Nitrobenzene published in 2007"
TL;DR: In this paper, nano-TiO 2 particles prepared by the sol-gel method were used as catalyst for the degradation of nitrobenzene by ozone, and the mechanism of catalytic ozonation was also discussed.
Abstract: Nano-TiO 2 particles prepared by the sol–gel method were used as catalyst for the degradation of nitrobenzene by ozone. Catalyst samples were characterized by measuring the specific area ( S BET ), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Removal efficiency of nitrobenzene (NB) was significantly promoted in the presence of catalyst compared with ozone alone. TiO 2 calcined at 500 °C showed the best activity. Different experimental conditions like catalyst dose, ozone dosage, initial nitrobenzene and pH have been examined. The mechanism of catalytic ozonation was also discussed. Both ozonation and catalytic ozonation were significantly influenced by carbonate and tert -butyl alcohol, which confirmed that TiO 2 -catalyzed ozonation follows a radical-type mechanism. And hydroxyl radicals were truly identified by spin-trapping/EPR technique.
195 citations
TL;DR: The electrochemical behaviors of nitrobenzene at a pyrolytic graphite electrode modified with carbon nanotubes (CNTs) were studied using cyclic voltammetry and constant-potential electrolysis technique and the results showed that CNTs exhibited high activity for nitro Benzene reduction to aniline.
175 citations
TL;DR: In this paper, the photocatalytic oxidation of different benzene derivatives has been investigated in order to understand how the substituent group affects the selectivity to hydroxylated compounds.
124 citations
TL;DR: In this paper, the optimum surface conditions for adsorption in aqueous phase were examined for heavy metal ion and aromatic compounds on activated carbons of various amount of surface C-O complexes.
107 citations
01 Nov 2007
TL;DR: Based on the results, it suggests that the adsorption is primarily brought about by hydrophobic interaction between nitrobenzene and MCM-41 surface.
Abstract: Adsorption of nitrobenzene onto mesoporous molecular sieves (MCM-41) from aqueous solution has been investigated systematically using batch experiments in this study. Results indicate that nitrobenzene adsorption is initially rapid and the adsorption process reaches a steady state after 1 min. The adsorption isotherms are well described by the Langmuir and the Freundlich models, the former being found to provide the better fit with the experimental data. The effects of temperature, pH, ionic strength, humic acid, and the presence of solvent on adsorption processes are also examined. According to the experimental results, the amount of nitrobenzene adsorbed decreases with an increase of temperature from 278 to 308 K, pH from 1.0 to 11.0, and ionic strength from 0.001 to 0.1 mol/L. However, the amount of nitrobenzene adsorbed onto MCM-41 does not show notable difference in the presence of humic acid. The presence of organic solvent results in a decrease in nitrobenzene adsorption. The desorption process shows a reversibility of nitrobenzene adsorption onto MCM-41. Thermodynamic parameters such as Gibbs free energy are calculated from the experimental data at different temperatures. Based on the results, it suggests that the adsorption is primarily brought about by hydrophobic interaction between nitrobenzene and MCM-41 surface.
104 citations
TL;DR: Allylic esters of nitrobenzene acetic acids undergo facile palladium-catalyzed decarboxylative coupling and reduction of the product nitroarenes to the corresponding anilines provides access to a variety of heterocycles including quinolines and dihydroquinolones.
Abstract: Allylic esters of nitrobenzene acetic acids undergo facile palladium-catalyzed decarboxylative coupling. Both mono- and dinitroarene substrates give high yields of the coupled products. Moreover, the rates of the reactions suggest that decarboxylation is rate-limiting and substrates that sterically disfavor attainment of the reactive conformation for decarboxylation are not viable. Finally, reduction of the product nitroarenes to the corresponding anilines provides access to a variety of heterocycles including quinolines and dihydroquinolones.
102 citations
TL;DR: In general, activated carbon promotes the reaction of ozonation enhancing the efficiency of this treatment process, and the basic activated carbon presented greater activity in this process leading to higher mineralization rates.
98 citations
TL;DR: In this paper, the photocatalytic reduction of nitrobenzene (ethanol + TiO2 + UV-light) in non-aqueous suspension yielded aniline and acetaldehyde as main products.
Abstract: The photocatalytic reduction of nitrobenzene (ethanol + TiO2 + UV-light) in non-aqueous suspension yielded aniline and acetaldehyde as main products. However, various by-products as intermediates of nitrobenzene photoreduction (i.e. nitrosobenzene and hydroxyaniline) and others (i.e. indoles and quinolines) were also detected. These last results were explained in terms of reactions between aniline and oxidation products of ethanol.
92 citations
TL;DR: The irradiation-induced reduction of electrochemically grafted nitrobenzene films on Si(111) was monitored by high-resolution photoelectron spectroscopy to follow this process in detail and to determine the constants of growth and decay of the specific components.
Abstract: The irradiation-induced reduction of electrochemically grafted nitrobenzene films on Si(111) was monitored by high-resolution photoelectron spectroscopy. The experiments were performed using synchr...
76 citations
TL;DR: The nano-crystalline sulfated-zirconia catalysts, prepared by one-step as well as two-step sol-gel technique, showed excellent catalytic activity with a high substrate to catalyst weight ratio for the synthesis of 7-substituted 4-methyl coumarins via solvent free Pechmann reaction.
Abstract: The nano-crystalline sulfated-zirconia catalysts, prepared by one-step as well as two-step sol–gel technique, showed excellent catalytic activity with a high substrate to catalyst weight ratio for the synthesis of 7-substituted 4-methyl coumarins via solvent free Pechmann reaction. The m-amino phenol was found to be more reactive than m-hydroxy phenol. The catalyst results 100% conversion of m-amino phenol with ∼100% selectivity of 7-amino 4-methyl coumarin at 110 ◦ C within 2 min. For 7-hydroxy 4-methyl coumarin, 94% yield was obtained after 3 h at 170 ◦ C with phenol to catalyst weight ratio of 80. Slow kinetics was observed in polar nitrobenzene as well as in non-polar toluene for both coumarin derivatives, due to the slow bulk diffusion of reactant molecules in presence of solvent. The solvent free microwave assisted synthesis seems advantageous way to synthesize the hydroxy derivative resulting excellent yield (99%) in much lesser time (15 min) at lower temperature (150 ◦ C) as compared to thermal heating. The use of very small catalytic amount of sulfated-zirconia catalyst for the synthesis of coumarins and the reusability of the catalyst after simple activation for several times with similar catalytic activity are novel properties of the catalyst. © 2007 Elsevier B.V. All rights reserved.
73 citations
TL;DR: The dissociation rates and lifetimes of photodissociation of nitrobenzene and o-nitrotoluene were predicted and compared to experimental results, indicating two dissociation mechanisms involved in the dissociation process.
Abstract: Photodissociation of nitrobenzene at 193, 248, and 266nm and o-nitrotoluene at 193 and 248nm was investigated separately using multimass ion imaging techniques. Fragments corresponding to NO and NO2 elimination from both nitrobenzene and o-nitrotoluene were observed. The translational energy distributions for the NO elimination channel show bimodal distributions, indicating two dissociation mechanisms involved in the dissociation process. The branching ratios between NO and NO2 elimination channels were determined to be NO∕NO2=0.32±0.12(193nm), 0.26±0.12(248nm), and 0.4±0.12(266nm) for nitrobenzene and 0.42±0.12(193nm) and 0.3±0.12(248nm) for o-nitrotoluene. Additional dissociation channels, O atom elimination from nitrobenzene, and OH elimination from o-nitrotoluene, were observed. New dissociation mechanisms were proposed, and the results are compared with potential energy surfaces obtained from ab initio calculations. Observed absorption bands of photodissociation are assigned by the assistance of the ...
TL;DR: In this article, the catalyst activity was studied for vapor phase hydrogenation of nitrobenzene at atmospheric pressure in the temperature range of 498-598 K, and the particle size before and after the reaction was calculated from XRD data.
Abstract: Pd supported on Mg-Al hydrotalcite with different Pd loadings (0.5, 1, 2 and 5 wt.% of Pd) prepared by impregnation method were characterized by XRD, BET Surface area, CO chemisorption and TPR. The catalyst activity was studied for vapor phase hydrogenation of nitrobenzene at atmospheric pressure in the temperature range of 498–598 K. The metallic dispersion, was obtained by CO chemisorption studies. Pd particle size before and after the reaction was calculated from XRD data. From the TPR studies, it was observed that the negative signal due to the decomposition of PdHx in the low temperature region was absent due to the smaller particle size of the Pd. XRD result also indicate the presence of smaller Pd particle size in low Pd loadings which increases with Pd loading. It was observed that very low concentration of Pd supported on hydrotalcite (0.5 wt.% Pd/HT) is sufficient to get high activity towards the hydrogenation of nitrobenzene to aniline (conversion = 97% and selectivity = 98%) at 498 K. The higher activity of this catalyst was attributed to higher dispersion and lower particle size of Pd as observed from CO chemisorption and XRD results. The particle size of Pd before and after reaction is more or less same indicating that the deactivation is not due to Pd agglomeration but due to the poisoning effect of water generated during the course of the reaction. The reconstruction of hydrotalcite structure in the spent catalysts as evidenced by XRD is indication that water is formed during the reaction.
TL;DR: An increment of approximately 64% of aniline reduction and 110% of TOC reduction were observed with respect to the addition of the separated O3 and US systems, proving US/O3 technology had significant synergetic effects.
TL;DR: In this article, the photooxidation rates of an OH-radical probe compound, nitrobenzene, were compared in aqueous solutions of free chlorine, and H 2 O 2, exposed to monochromatic UV irradiation (254 nm).
Abstract: Hydroxyl radicals (•OH) are a direct photolysis product of both aqueous free chlorine and hydrogen peroxide under UV irradiation. The photooxidation rates of an OH-radical probe compound, nitrobenzene, were compared in aqueous solutions of free chlorine, and H 2 O 2 , exposed to monochromatic UV irradiation (254 nm). Acidic ( 2 (pH 7) 2 O 2 2 (pH 6) 2 (pH 5). However, water quality had a significant impact; background photon and radical scavengers led to reduced rates of nitrobenzene decay in natural waters. Analysis of the necessary energy input required to achieve 90% nitrobenzene degradation showed UV-Cl 2 at pH 5 to be the most efficient oxidation process whereas at neutral pH, process efficiency was a function of the initial concentration of the oxidant; at 0.05 or 0.06 mM initial oxidant, UV-Cl 2 was the most efficient oxidation process, while at >0.15 mM initial oxidant, UV-H 2 O 2 was most efficient.
TL;DR: Photoirradiation of a deaerated 2-propanol aqueous solution containing nitrobenzenes and rhodium-loaded silica-coated cadmium sulfide nanoparticles produced azoxybenzene with relatively high selectivity, the photocatalytic activity being enhanced with a decrease in the size of the semiconductor particle core.
TL;DR: In this paper, the removal of nitrobenzene (NB) from water by combining adsorption onto zeolites and regeneration with ozone was investigated, and NB was completely removed from water and the initial adorption capacity of the zeolite was totally restored.
Abstract: This work investigates the removal of nitrobenzene (NB), a model pollutant from water, by combining adsorption onto zeolites and regeneration with ozone. The adsorption equilibrium isotherms of NB onto zeolites enabled the best adsorbent to be selected and zeolites with a high Si/Al ratio were the most efficient. The adsorption capacity depended on the Si/Al ratio and on the pore size. In a sequential process coupling adsorption and oxidation by ozone, NB was completely removed from water and the initial adsorption capacity of the zeolite was totally restored. Although no catalytic effect was noticed, the adsorption produced locally high concentrations, thus enhancing the oxidation rate for NB.
TL;DR: The electrophilic monofluoromethylation of carbon-nucleophiles was attempted with CH2ClF, CH2FI, or FCH2OTs, but with no success as mentioned in this paper.
TL;DR: The PANI-SPME-GC method offers high accuracy and precision, high sensitivity and low detection limits, and could be used as a new way to monitor the trace levels of chloro- and nitrobenzene compounds in real water bodies.
TL;DR: In this paper, the post crosslinking reaction parameters were systematically studied for the investigation on formation mechanism of oxygen containing groups on the surface of hypercrosslinked polymers, and the FT-IR spectra and the Boehm titration were employed to characterize the surface chemistry of the synthesized polymers.
TL;DR: In this paper, an ionic liquid (i.e., 1-butyl-3-methylimidazolium hexafluorophosphate, BMIMPF6)-single-walled carbon nanotube (SWNT) gel modified glassy carbon electrode (BMIMPF 6-SWNT/GCE) is fabricated.
Abstract: An ionic liquid (i.e., 1-butyl-3-methylimidazolium hexafluorophosphate, BMIMPF6)-single-walled carbon nanotube (SWNT) gel modified glassy carbon electrode (BMIMPF6-SWNT/GCE) is fabricated. At it the voltammetric behavior and determination of p-nitroaniline (PNA) is explored. PNA can exhibit a sensitive cathodic peak at −0.70 V (vs. SCE) in pH 7.0 phosphate buffer solution on the electrode, resulting from the irreversible reduction of PNA. Under the optimized conditions, the peak current is linear to PNA concentration over the range of 1.0×10−8–7.0×10−6 M, and the detection limit is 8.0×10−9 M. The electrode can be regenerated by successive potential scan in a blank solution for about 5 times and exhibits good reproducibility. Meanwhile, the feasibility to determine other nitroaromatic compounds (NACs) with the modified electrode is also tested. It is found that the NACs studied (i.e., p-nitroaniline, p-nitrophenol, o-nitrophenol, m-nitrophenol, p-nitrobenzoic acid, and nitrobenzene) can all cause sensitive cathodic peaks under the conditions, but their peak potentials and peak currents are different to some extent. Their peak currents and concentrations show linear relationships in concentration ranges with about 3 orders of magnitude. The detection limits are 8.0×10−9 M for p-nitroaniline, 2.0×10−9 M for p-nitrophenol, 5.0×10−9 M for o-nitrophenol, 5.0×10−9 M for m-nitrophenol, 2.0×10−8 M for p-nitrobenzoic acid and 8.0×10−9 M for nitrobenzene respectively. The BMIMPF6-SWNT/GCE is applied to the determination of NACs in lake water.
TL;DR: In this paper, seventeen commercially available ketones were selected as representatives of alkyl ketones, and their extraction behavior was fully investigated with these extractants the partitioning of Pd(II) to the organic phase was significant at a ligand concentration of 30 m and acidity above 20 m.
Abstract: Solvent extraction of Pd(II) with various ketones in nitrobenzene from nitric acid medium was investigated In this study, seventeen commercially available ketones were selected as representatives of alkyl ketones It was found that several ketones effectively extracted Pd(II) from nitric acid medium Methylalkylketones, such as 2‐octanone, 2‐nonanone, 2‐undecanone, 2‐tridecanone, and ketones containing symmetrical alkyl configuration, such as 5‐nonanone, 5‐decanone, 5‐undecanone, and 6‐undecanone exhibited significant extraction of Pd(II) from nitric acid Particularly, 2‐tridecanone and 2‐nonanone showed efficient extractability for Pd(II) and their extraction behavior was fully investigated With these extractants the partitioning of Pd(II) to the organic phase was significant at a ligand concentration of 30 M and acidity above 20 M
TL;DR: In this article, the surface properties of activated carbons were studied by means of N2 adsorption experiments, elemental analysis, XPS, and TPD spectra, which indicated the presence of aromatic rings and oxygenated functional groups in the surface material.
Abstract: The adsorption processes of several aromatic chemicals onto activated carbons (ACs) from aqueous solutions have been studied. The activated carbons were prepared from eucalyptus kraft lignin with CO2 at 1073 K activation temperature. The surface properties of the ACs play a significant role when these materials are used for adsorption from liquid phases. The physicochemical properties and the surface chemical structure of the ACs were studied by means of N2 adsorption experiments, elemental analysis, XPS, and TPD. The XPS and TPD spectra of ACs suggest the presence of aromatic rings and oxygenated functional groups in the surface material. Benzene, nitrobenzene, aniline, p-nitroaniline, toluene, and p-nitrotoluene as aromatic adsorbates have been used in the present study. Adsorption isotherms data were fitted to the Freundlich and Fritz−Schlunder equations. We have developed the thermodynamic study from the equilibrium data. The values of ΔH, ΔG, and ΔS were calculated, and these indicate that the proces...
TL;DR: In this paper, the authors investigated the micro amounts of strontium and barium extracted by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−1) in the presence of benzo-18-crown-6 (B18C6, L) with the equilibrium data been explained assuming that the complexes HL+, ML2+, ML22+ and MHL23+ (M2+ = Sr2+, Ba2+) are extracted into the organic phase.
Abstract: Extraction of microamounts of strontium and barium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−1) in the presence of benzo-18-crown-6 (B18C6, L) has been investigated. The equilibrium data been explained assuming that the complexes HL+, ML2+, ML22+ and MHL23+ (M2+ = Sr2+, Ba2+) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.
TL;DR: The photoreactivity results indicate that two reaction pathways occur in parallel with both substrates from the start of irradiation: partial oxidation to monohydroxy derivatives and mineralization as discussed by the authors.
Abstract: The oxidation of nitrobenzene and phenylamine has been carried out by heterogeneous photocatalysis in aqueous suspensions of commercial TiO2. The photoreactivity results indicate that two reaction pathways occur in parallel with both substrates from the start of irradiation: partial oxidation to monohydroxy derivatives and mineralization. The first pathway involves the entering of radical HO• into the aromatic ring giving rise to monohydroxy derivatives, and the second one involves the total oxidation of the substrates to CO2. The partial oxidation of nitrobenzene produces all the three possible monohydroxy derivatives, while that of phenylamine only produces the ortho- and para-isomers. The extent of adsorption in the dark was found to be about 8% mol for nitrobenzene, while the amounts were not detectable for phenylamine. The Langmuir-Hinshelwood approach has been satisfactorily applied for modeling the photoreactivity results, and the values of the kinetic model parameters have been determined. © 2007 American Institute of Chemical Engineers AIChE J, 2007
TL;DR: The proposed method provided fast, sensitive and sometimes real time detection of nitrobenzene and offered low limit of determination, easy operation, the use of simple instrumentation, high sensitivity and good reproducibility.
Abstract: The determination of trace amount nitrobenzene in wastewater on a hanging mercury drop electrode was studied. The determination conditions of pH, supporting electrolyte, accumulation potential, accumulation time, and voltammetric response were optimized. The sharp peak of the nitrobenzene was appeared at 0.05 V. The peak electric current was proportional to the concentration of nitrobenzene in the range of 1.47 × 10−5 ∼ 1.0 × 10−3 mol/l with relative standard deviations of 3.99 ∼ 8.94%. The detection limit of the nitrobenzene in water was 5 × 10−6 mol/l. The proposed method offered low limit of determination, easy operation, the use of simple instrumentation, high sensitivity and good reproducibility. It was applied to the determination of nitrobenzene in wastewater with an average recovery of 94.0% ∼ 105%. The proposed method provided fast, sensitive and sometimes real time detection of nitrobenzene.
TL;DR: In this paper, the oxidative degradation of nitrobenzene (NB) induced by gaseous glow discharge plasma in contact with aqueous solution was investigated, and the experimental results indicated that NB removal obeyed first-order kinetics under certain applied currents.
Abstract: The oxidative degradation of nitrobenzene (NB) induced by gaseous glow discharge plasma in contact with aqueous solution was investigated. The experimental results indicated that NB removal obeyed first-order kinetics under certain applied currents. The major degradation byproducts such as nitrophenols, phenol, 1,3-dinitrobenzene and carboxylic acids have been detected. The distribution of nitrophenols follows the order o- > p- > m- and oxalic, formic and acetic acids are major carboxylic intermediates. The eventual products were nitrate ion and carbon dioxide. During the treatment, a large amount of hydrogen peroxide was produced. Addition of ferrous or ferric ions into the solution greatly enhanced the degradation rate due to Fenton’s reaction. The energy efficiencies of NB removal and hydrogen peroxide formation were compared with those of other discharges. Hydroxyl radicals were shown to be the most likely species responsible for NB degradation
TL;DR: In this article, a fluorescent film was prepared by chemically immobilizing 5-dimethylamino-1-naphthalenesulfonyl (dansyl) onto an epoxide-terminated self-assembled monolayer on glass.
TL;DR: In this paper, the effects of ligating topologies and hydrogen bonding backbone of the ligands and counter anions on the supramolecular structural diversities in the resulting metal-organic frameworks are discussed.
Abstract: Six metal–organic frameworks (MOFs) namely [{(CH3COO)(μ–OOCH3)Zn}2(μ–L1)2]n1, [{(H2O)2Zn}(μ–L1)4}BF4]n2, [{(Cl)2Zn}(μ–L1)]n3, [{(NO3)2Cd(μ–L1)2}·nitrobenzene]n 4, [{Cl2Zn(μ–L2)}]n5 and [{(NO3)2Cd}(μ–L2)4]n6
(where L1
= N-(3-pyridyl)nicotinamide and L2
= N-(3-pyridyl)isonicotinamide) have been synthesized and crystallographically characterized. The main aim of this work is to study the effects of ligating topologies and hydrogen bonding backbone of the ligands and counter anions on the supramolecular structural diversities in the resulting MOFs. The structures of these MOFs are discussed in this context.
TL;DR: In this article, the authors examined the effect of a number of reaction parameters such as hydrogen pressure, reaction temperature, stirring rate, and the amounts of NB, the catalyst and the surfactant present in the reaction mixture had on the rate and selectivity of the hydrogenation.
Journal Article•
TL;DR: In this paper, the authors investigated the performance of strontium extraction in the presence of Slovafol 909 (p-nonylphenylnonaethylene glycol, L) as a synergic agent.
Abstract: The extraction of microamounts of strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H + B) in the presence of Slovafol 909 (p-nonylphenylnonaethylene glycol, L) as a synergic agent has been investigated. The equilibrium data have been explained assuming that the complexes HL + , HL 2 + , SrL 2+ and SrL 2+ 2 are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.