Showing papers on "Nitrobenzene published in 2010"
TL;DR: In this paper, the authors investigated the electrochemical degradation of Reactive Red 195 (RR195) in aqueous solution on a Ti/SnO 2 -Sb/PbO 2 electrode.
248 citations
TL;DR: A microporous MOF with two immobilized open metal Zn(2+) sites was obtained by solvothermal reaction, which exhibits highly selective guest sorption and sensing of nitrobenzene.
235 citations
TL;DR: In this article, a correlation between CNT content and the changes in the UV-vis absorption properties is observed especially in the visible spectral range, which may be explained in terms of a strong interphase interaction between carbon nanotubes and TiO 2 in the composite catalysts.
Abstract: Nanostructured composite catalysts produced using multi-walled carbon nanotubes (CNT) and titanium dioxide were prepared by means of a modified acid catalyzed sol–gel method. Materials were extensively characterized by XRD, TG, N 2 adsorption–desorption isotherms, TEM, UV–vis spectroscopy and TPD. Composite catalysts with different CNT contents were tested in the photo-oxidation of phenol under different irradiation wavelengths. A correlation between CNT content and the changes in the UV–vis absorption properties is observed especially in the visible spectral range. The introduction of CNT into the titanium matrix induced a synergic effect when irradiating in the near-UV to visible spectral range. This effect may be explained in terms of a strong interphase interaction between CNT and TiO 2 in the composite catalysts. CNT with different surface chemical groups were used to produce CNT–TiO 2 composites. The presence of mild concentrations of oxygen containing surface groups, mainly carboxylic acids and phenols, appears to produce a beneficial effect in the photocatalytic activity of CNT–TiO 2 composite catalysts. The photocatalytic oxidation of other monosubstituted benzene derivatives such as, aniline, nitrobenzene and benzoic acid, has been investigated under visible irradiation. The primary intermediates of photocatalytic reaction are single substituted hydroxy derivatives. The photoefficiency of the composite catalyst showed to be affected by the aromatic ring reactivity properties of the substrate.
140 citations
TL;DR: Ni nanoparticles embedded in the pores of a mesoporous MOF (MesMOF-1) act as a catalyst for hydrogenolysis of nitrobenzene or hydrogenation of styrene.
134 citations
TL;DR: In this article, the average Ni particle size was 3.7 nm and the selectivity of aniline (AN) reached 99% with a 100% conversion of NB in 5.5 h at 90 °C, 1.0 MPa, and NB:Ni = 305 (mole ratio).
Abstract: Nanosized silica gel supported Ni catalysts that have average Ni particle size of 3.7, 11.4, and 11.8 nm were prepared by facile impregnation of different Ni precursors and used for hydrogenation of nitrobenzene (NB). These catalysts were characterized by N2 adsorption, X-ray diffraction, and transmission electron microscopy. It was found that Ni dispersed highly on the surface of silica gel in the catalyst prepared via Ni(en)3(NO3)2, and the detected average Ni particle size was 3.7 nm. On the 3.7 nm sized Ni catalyst, the selectivity of aniline (AN) reached 99% with a 100% conversion of NB in 5.5 h at 90 °C, 1.0 MPa, and NB:Ni = 305 (mole ratio). But, the activities of 11.8 nm sized Ni catalysts and commercial Raney Ni catalyst are quite lower. The reaction network and mechanism of NB hydrogenation on 3.7 nm sized Ni catalyst were discussed on the basis of products distributions at different temperatures and pressures. The calculated activation energy of NB hydrogenation on Ni-5/SiO2-EN catalyst is 54.5...
132 citations
TL;DR: The results indicated that use of ZVI based permeable reactive barrier technology to remedy nitrobenzene contaminated groundwater was feasible and the observed nitro Benzene reduction rate constant linearly decreased with increase pH and the data fitted on polynomial regression equation for the observations.
Abstract: Nitrobenzene has been considered as a significant groundwater contaminant due to its wide usage in explosives, insecticides, herbicides, pharmaceuticals and dyes. Nitrobenzene is of environmental concern because of its toxicity. In the presence of zero-valent iron (ZVI), reduction of the nitro group is the dominant transformation process for nitrobenzene. A series of experiments were carried out to investigate the kinetics of nitrobenzene reduction by ZVI and the effects of pH and ZVI particle size on nitrobenzene removal in groundwater. The results indicated that nitrobenzene could be reduced to aniline by ZVI; the reduction of nitrobenzene by ZVI followed a pseudo first-order kinetics; the observed nitrobenzene reduction rate constant (kobs) was 0.0006 min−1 and the half-life of nitrobenzene (t1/2) was 115.5 min; the mass balance achieved 87.5% for nitrobenzene reduction by the 1 mm ZVI particle and the final removal efficiency was 80.98%. In addition, the pH and ZVI particle size were found to exhibit significant influences on the nitrobenzene reduction. The observed nitrobenzene reduction rate constant linearly decreased with increase pH and the data fitted on polynomial regression equation for the observed nitrobenzene reduction rate constant and ZVI particle size. Therefore, use of ZVI based permeable reactive barrier technology to remedy nitrobenzene contaminated groundwater was feasible.
127 citations
TL;DR: In this paper, a facile and efficient route to deposit ultrafine Pt particles onto multi-walled carbon nanotubes (MWNTs) with the aid of tip sonication was developed.
122 citations
TL;DR: In this article, the nanocrystalline hydroxyapatite (HAP) prepared by thermal decomposition of precursors was used as the adsorbent, and the potential of HAP for nitrobenzene removal from aqueous solution was evaluated.
92 citations
TL;DR: In this article, the degradation of nitrobenzene (NB) by modified Fenton reaction at near neutral pH conditions using Fe II -glutamate complex as a source of Fe 2+.
Abstract: We examined the degradation of nitrobenzene (NB) by modified Fenton reaction at near neutral pH conditions using Fe II –glutamate complex as a source of Fe 2+ . The reaction was conducted using 0.04 mM (5 mg L −1 ) of NB in presence of 65 mM H 2 O 2 at room temperature. Complex concentrations of 5, 10, 15 and 20 mM (Fe 2+ = 0.81, 1.62, 2.43 and 3.23 mM) were assayed and showed effective rates of NB degradation with t 1/2 values of 17, 6.2, 4.8 and 1.85 min, respectively. In the pH range 5–7 the complex activity is pH-dependent, and the optimal pH was 6.3. The degradation was monitored by solid-phase microextraction in combination with GC analysis. The rate of degradation recorded at near neutral pH in presence of 20 mM of Fe-complex was equal to that obtained in presence of Fe 2+ (2.5 mM) at pH 2.7. Glutamate complexes formed with Cu 2+ or Co 2+ did not show the improved degradation observed in case of Fe–glutamate. Furthermore, the introduction of the chelating agent as a free ion into the reaction medium containing Fe 2+ did not improve the degradation of NB at neutral pH conditions.
90 citations
TL;DR: It is concluded that NOM-mediated reduction of nitrobenzene was more important than Fe(II)-mediated reduction in systems that contained both NOM and hematite.
Abstract: We examined the reduction of nitrobenzene by Shewanella putrefaciens CN32 in the presence of natural organic matter (NOM) and hematite. Bioreduction experiments were conducted with combinations and varied concentrations of nitrobenzene, soil humic acid, Georgetown NOM, hematite, and CN32. Abiotic experiments were conducted to quantify nitrobenzene reduction by biogenic Fe(II) and by bioreduced NOMs. We show that S. putrefaciens CN32 can directly reduce nitrobenzene. Both NOMs enhanced nitrobenzene reduction and the degree of enhancement depended on properties of the NOMs (aromaticity, organic radical content). Hematite enhanced nitrobenzene reduction by indirect reaction with biogenic-Fe(II), however, enhancement was dependent on the availability of excess electron donor. Under electron donor-limiting conditions, reducing equivalents diverted to hematite were not all transferred to nitrobenzene. In systems that contained both NOM and hematite we conclude that NOM-mediated reduction of nitrobenzene was more important than Fe(II)-mediated reduction.
82 citations
TL;DR: The biocatalytic activity of nitroreductase from Salmonella typhimurium (NRSal) was investigated for the reduction of alpha,beta-unsaturated carbonyl compounds, nitroalkenes, and nitroaromatics, and demonstrated the first single isolated enzyme-catalyzed reduction of nitrobenzene to aniline through the formation ofNitrosobenZene and phenylhydroxylamine as intermediates.
Abstract: The biocatalytic activity of nitroreductase from Salmonella typhimurium (NRSal) was investigated for the reduction of α,β-unsaturated carbonyl compounds, nitroalkenes, and nitroaromatics. The synthesized gene was subcloned into a pET28 overexpression system in E.coli BL21 strain, and the corresponding expressed protein was purified to homogeneity with 15% protein mass yield and 41% of total activity recovery. NRSal showed broad substrate acceptance for various nitro compounds such as 1-nitrocyclohexene and aliphatic nitroalkenes (alkene reductase activity), as well as nitrobenzene (nitroreductase activity), with substrate conversion efficiency of > 95%. However, the reduction of enones was generally low, proceeding albeit with high stereoselectivity. The efficient biocatalytic reduction of substituted nitroalkenes provides a route for the preparation of the corresponding nitroalkanes. NRSal also demonstrated the first single isolated enzyme-catalyzed reduction of nitrobenzene to aniline through the formation of nitrosobenzene and phenylhydroxylamine as intermediates. However, chemical condensation of the two intermediates to produce azoxybenzene currently limits the yield of aniline.
TL;DR: Chars were generated by pyrolyzing pine wood and calculated that chars may be considered to consist of the partition domain, the high-energy micropores domain and the low-energy large pores domain.
TL;DR: In this article, the activation of α-Fe 2 O 3 in a water bath under air atmosphere at room temperature followed by heating at 200 °C, dramatically increase the activity of activated hematite, and a wide variety of benzene derivatives were easily converted into the corresponding acylated products in a clean and high yielding acylation reaction.
Abstract: Catalytic Friedel-Crafts acylation of benzene and unactivated benzenes such as chlorobenzene and nitrobenzene have been successfully carried out using activated hematite (α-Fe 2 O 3 ) as a new, heterogeneous and green catalyst. Sonication of neat α-Fe 2 O 3 in a water bath under air atmosphere at room temperature followed by heating at 200 °C, dramatically increase the activity of α-Fe 2 O 3 . With the catalyst loading as low as 5.0 mol%, a wide variety of benzene derivatives were easily converted into the corresponding acylated products in a clean and high-yielding acylation reaction. It was found that the activated α-Fe 2 O 3 could be efficiently recycled and reused several times by simple washing with ethyl acetate, this cannot be attained with most of the traditional catalysts.
TL;DR: MAS presents to be a good adsorbent to remove nitrobenzene from water, and CB is a successful modifier, implying the adsorption occurrence tends to be on a homogeneous surface by monolayer adsorptions other than multi-layer adsorptive which accounts for the adsorship onto UMAS.
TL;DR: The photochemistry of anthraquinone-2-sulfonate was studied as a function of pH, combining laser flash photolysis and steady-state irradiation experiments, with the additional help of a computational study of energy levels.
Abstract: The photochemistry of anthraquinone-2-sulfonate (AQ2S) was studied as a function of pH, combining laser flash photolysis and steady-state irradiation experiments, with the additional help of a computational study of energy levels. Two out of the three transient species produced upon irradiation of AQ2S can be involved into the degradation of dissolved molecules, and also AQ2S in its ground state is degraded. The reactive transients are less stable but often more reactive under acidic conditions, which modulates the pH trend of the photodegradation of the adopted organic substrates (furfuryl alcohol, benzene, nitrobenzene). The ability of the excited states of irradiated AQ2S to simulate the reactivity of singlet oxygen upon degradation of furfuryl alcohol, and that of the hydroxyl radical by producing phenol from benzene, can have important consequences. Furfuryl alcohol and benzene are widely adopted probe molecules for the respective quantification of singlet oxygen and the hydroxyl radical in many systems, among which are natural waters under irradiation. This study shows that the interference of AQ2S on singlet oxygen determination would be higher in acidic or basic than in ~neutral conditions, while in the case of the hydroxyl radical the interference would increase with pH. Processes analogous to those studied could account for the interference of coloured dissolved organic matter on the quantification of singlet oxygen, observed in previous studies.
TL;DR: In this article, the results showed that with increasing dielectric constant of the diluent, the extraction percent decreased while the separation factors did not change considerably while the values of the equilibrium constants and the separation factor were calculated.
TL;DR: In this article, TFPP@MCM-41 was used as a photocatalyst for the photodegradation of 2,4,6-trimethylphenol.
Abstract: MCM-41 immobilized ( ship-in-a-bottle ) meso -tetrakis(2-fluorophenyl)porphyrin, TFPP@MCM-41, and meso -tetrakis(2,6-dichlorophenyl)porphyrin, TDCPP@MCM-41, and the corresponding copper metal complexes, CuTFPP@MCM-41 and CuTDCPP@MCM-41, were successfully synthesized by the condensation of pyrrole with the desired benzaldehydes, using the nitrobenzene method, in the absence or presence of copper salt, respectively. Their characterization was performed by DRS-UV–vis, luminescence, EPR, ATR-FTIR spectroscopies, PXRD, TG/DTA, nitrogen adsorption analysis and elemental analysis. All the immobilized porphyrins TFPP@MCM-41, TDCPP@MCM-41, CuTFPP@MCM-41 and CuTDCPP@MCM-41 were tested in the photodegradation of 2,4,6-trimethylphenol and TFPP@MCM-41 showed the best performance. The studies were extended to the photodegradation of pesticides fenamiphos and diuron using TFPP@MCM-41 as photocatalyst and the photoproducts were identified by LC–MS. Mechanistic studies, using furfuryl alcohol as singlet oxygen trap revealed that there was no involvement of this species in the photodegradation of the above mentioned pesticides and the identified photoproducts are consistent with a radical mechanism. An efficient photolysis of the pesticides after 5 h, in aerated aqueous solutions, was observed with TFPP@MCM-41 with no loss of the photocatalytic activity over recycling. These heterogeneous photocatalysts with no significant decomposition of the porphyrin make them promising candidates for water treatment.
TL;DR: In this paper, a fixed-bed heterogeneous catalytic transfer hydrogenation (CTH) of styrene and nitrobenzene over Pd-based catalyst using methanol as hydrogen donor was investigated.
Abstract: The heterogeneous catalytic transfer hydrogenation (CTH) of styrene and nitrobenzene over Pd-based catalyst using methanol as hydrogen donor was investigated in a fixed-bed reactor. With the increase of the molar ratio of water to methanol from 0 to 1, the conversions of styrene and nitrobenzene are increased from 26.3% and 7.1% to 100% and 31.9%, respectively, and the selectivity of aniline is increased from 22.0 to 94.5 mol%. The presence of water improves the hydrogen transfer from methanol to styrene or nitrobenzene through the quick reaction of water with formaldehyde, formed from the dehydrogenation of methanol, into formic acid, which is an excellent hydrogen donor for the CTH of unsaturated organics. In the presence of water, methanol is a better hydrogen donor than isopropanol, n-propanol and ethanol, because water cannot easily react with acetone, propionaldehyde, and acetaldehyde formed from isopropanol, n-propanol, and ethanol, respectively. Additionally, the hydrogen atom utilization of the methanol donor in the presence of water is higher than the other donors, hydrogen atom in a part of water can also be utilized for the reduction of unsaturated organics.
TL;DR: In this article, the feasibility of photocatalytic reduction of nitrobenzene using titanium dioxide powder as photocatalyst, under the protection of nitrogen and presence of hole scavenger conditions, was studied.
Abstract: The feasibility of photocatalytic reduction of nitrobenzene using titanium dioxide powder as photocatalyst, under the protection of nitrogen and presence of hole scavenger conditions, was studied. Effects of the illumination time, amount of catalyst and sorts of solvent on the photocatalytic reduction of nitrobenzene were investigated, respectively. The results showed that, for the photocatalytic reduction of nitrobenzene, aniline was the main product. When the illumination time was 6 h, 8.15×10−4 mol/L of nitrobenzene could be photocatalytically reduced completely, with the yield of aniline being 88.5%. The optimum amount of TiO2 used was 4.0 g/L, the optimum initial pH value of reaction solution was 4.0 and the best solvent was methanol. The kinetics and mechanisms of the photocatalytic reduction of nitrobenzene were also discussed.
TL;DR: In this paper, the influence of bicarbonate on degradation efficiency of nitrobenzene in aqueous solution by ceramic honeycomb supported manganese catalytic ozonation has been investigated.
Abstract: The influence of bicarbonate on degradation efficiency of nitrobenzene in aqueous solution by ceramic honeycomb supported manganese catalytic ozonation has been investigated. Under the lower concentration condition (25 and 50 mg L −1 ), bicarbonate enhances the degradation efficiency of nitrobenzene, while bicarbonate presents the inhibition effect at the higher concentration (100–250 mg L −1 ). The modification of ceramic honeycomb with Mn improves its resistibility to the negative effect of bicarbonate, and the inhibition effect of bicarbonate also can be decreased, respectively by increasing total applied ozone or amount of catalyst. The utilization efficiency of ozone increases with the increasing bicarbonate concentration (0–100 mg L −1 ). The formation of H 2 O 2 and the initiation of hydroxyl radical ( OH) reach a maximum at the bicarbonate concentration 75 and 50 mg L −1 , respectively. The mechanism investigation suggests that bicarbonate plays an important role as a promoter of radical chain reactions accelerating the ozone mass transformation, causing the increases in the utilization efficiency of ozone, the formation of H 2 O 2 and the initiation of OH at the lower concentration. Bicarbonate with the higher concentration exerts a negative effect on the degradation efficiency of nitrobenzene due to the predominance derived from its scavenging capacity of OH.
TL;DR: In this article, the Pt-Pd bi-metal nanoparticles were captured and stabilized by imine groups inside a periodic mesoporous organosilica of SBA-15 and their catalytic performances in the hydrogenation of nitrobenzene were investigated.
TL;DR: The result indicates that modification of TiO(2) with electron-donating groups is an effective way to enhance photoreduction of nitroaromatic compounds.
TL;DR: In this article, the results of solvent extraction of europium and cerium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of polyethylene glycol PEG 600 (L) has been investigated.
Abstract: Solvent extraction of microamounts of europium and cerium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B−) in the presence of polyethylene glycol PEG 600 (L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, H2L2+ and ML3+ (M3+ = Eu3+, Ce3+; L = PEG 600) are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined. It was found that the stability constants of the EuL3+ and CeL3+ cationic complex species (L = PEG 600) in water-saturated nitrobenzene are the same.
TL;DR: In this paper, the effects of inorganic ions including chloride ions, dihydrogen phosphate ions and nitrate ions on the oxidation of nitrobenzene by the fluidized-bed Fenton process were investigated.
Abstract: This study investigated the effects of inorganic ions including chloride ions, dihydrogen phosphate ions and nitrate ions on the oxidation of nitrobenzene by the fluidized-bed Fenton process. The nitrobenzene degradation decreased with increasing chloride, dihydrogen phosphate and nitrate concentrations. Dihydrogen phosphate and chloride ions significantly inhibited nitrobenzene degradation. However, the inhibition caused by chloride ions could be overcome by extending the reaction time if the concentration of chloride ions was low. Nitrate did not have significant effect on nitrobenzene removal. The inhibition effect of each inorganic ion on the nitrobenzene degradation was in the order: H2PO4− ≫ Cl− > NO3−. In addition, the results also show that the removal efficiency of nitrobenzene by fluidized-bed Fenton process was higher than traditional Fenton process.
TL;DR: The results indicate that, in the experimental domain tested, the prevailing NB nitration pathway involves the reaction between the .OH-NB adduct and .NO(2) radicals.
TL;DR: The above results demonstrated that the catalytic performance of Fe3O4-CoO/Al2O3 in ozonation of studied organic substance was universal to a certain degree.
Abstract: Fe3O4-CoO/Al2O3 catalyst was prepared by incipient wetness impregnation using Fe(NO3)3-9H2O and Co(NO3)2-6H2O as the precursors, and its catalytic performance was investigated in ozonation of 2-(2,4-dichlorophenoxy)propionic acid (2,4-DP), nitrobenzene and oxalic acid. The experimental results indicated that Fe3O4-CoO/Al2O3 catalyst enabled an interesting improvement of ozonation efficiency during the degradation of each organic pollutant, and the Fe3O4-CoO/Al2O3 catalytic ozonation system followed a radical-type mechanism. The kinetics of ozonation alone and Fe3O4-CoO/Al2O3 catalytic ozonation of three organic pollutants in aqueous solution were discussed under the mere consideration of direct ozone reaction and OH radical reaction to well investigate its performance. In the catalytic ozonation of 2,4-DP, the apparent reaction rate constants (k) were determined to be 1.456 x 10−2 min-1 for ozonation alone and 4.740 x 10−2 min −1 for O3/Fe3O4-CoO/Al2O3. And O3/Fe3O4-CoO/Al2O3 had a larger Rct (6.614 x 10−9) calculated by the relative method than O3 did (1.800 x 10-9), showing O3/Fe3O4-CoO/Al2O3 generated more hydroxyl radical. Similar results were also obtained in the catalytic ozonation of nitrobenzene and oxalic acid. The above results demonstrated that the catalytic performance of Fe3O4-CoO/Al2O3 in ozonation of studied organic substance was universal to a certain degree.
TL;DR: In this article, metal-exchanged microporous titanium silicate M−ETS-10 (M = Fe, Co, Ni, Cu, and Ag) samples were prepared by ion exchange with respective metal salt solutions.
Abstract: Engelhard titanosilicate ETS-10 was synthesized using Degussa P25 as the titanium source. Metal-exchanged microporous titanium silicate M−ETS-10 (M = Fe, Co, Ni, Cu, and Ag) samples were prepared by ion exchange with respective metal salt solutions. The synthesized samples were characterized by powder X-ray diffraction, BET surface area, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and UV−vis diffuse reflectance measurements (DRS). The photocatalytic activity of these samples was investigated for the decomposition of nitrobenzene (NB). The pristine ETS-10 and transition-metal-ion-exchanged ETS-10 samples were found to be active photocatalysts that can decompose nitrobenzene under UV irradiation. Results demonstrated that silver-ion-exchanged ETS-10 shows the highest photocatalytic activity for degradation and mineralization of nitrobenzene.
TL;DR: In this article, the exchange extraction constants corresponding to the general equilibrium M(aq)? Sr(nb) ¢ M(nb ) ¢ Mn(nb), ¢ Ni(Ni), Ni, Ni, Cu, Cd \ Co \ Mg \ Ca \ Mn, Fe \ Sr \ Pb \ Ba, Pb, UO2þ 2, Mn, Fe, Co, Ni; aq = aqueous phase, nb = nitrobenzene phase.
Abstract: From extraction experiments and c-activity measurements, the exchange extraction constants corresponding to the general equilibrium M(aq) ? Sr(nb) ¢ M(nb) ? Sr(aq) taking part in the two-phase water– nitrobenzene system (M = Mg, Ca, Ba, Cu, Zn, Cd, Pb, UO2þ 2 , Mn , Fe, Co, Ni; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the individual extraction constants of the M cations in the mentioned two-phase system were calculated; they were found to increase in the following cation order: UO2þ 2 \ Zn , Ni \ Cu, Cd \ Co \ Mg \ Ca \ Mn, Fe \ Sr \ Pb \ Ba.
TL;DR: In the catalytic hydrogenation of nitrobenzene, the calcined Pt-MCM-41 meso-materials, like the corresponding reduced samples, exhibit high catalytic activities with an excellent selectivity to aniline, which are much better than those of the reduced Pt/MCm-41 prepared by the incipient wetness method.
TL;DR: In this paper, a bi-functional Pt catalyst was used to convert nitrobenzene to phenylhydroxylamine, which requires only minute amounts of Pt. This process does not require sulphuric acid or additives such as DMSO or alkylsulphides, thereby simplifying the downstream processing.