Oxidation Of O-cresol Research Articles

Chemical composition of secondary organic aerosol particles formed from mixtures of anthropogenic and biogenic precursors

Abstract. A series of experiments was designed and conducted in the Manchester Aerosol Chamber (MAC) to study the photo-oxidation of single and mixed biogenic (isoprene and α-pinene) and anthropogenic (o-cresol) precursors in the presence of NOx and ammonium sulfate seed particles. Several online techniques (HR-ToF-AMS, semi-continuous GC-MS, NOx and O3 analyser) were coupled to the MAC to monitor the gas and particle mass concentrations. Secondary organic aerosol (SOA) particles were collected onto a quartz-fibre filter at the end of each experiment and analysed using liquid chromatography–ultrahigh-resolution mass spectrometry (LC-Orbitrap MS). The SOA particle chemical composition in single and mixed precursor systems was investigated using non-targeted accurate mass analysis of measurements in both negative and positive ionization modes, significantly reducing data complexity and analysis time, thereby providing a more complete assessment of the chemical composition. This non-targeted analysis is not widely used in environmental science and has never been previously used in atmospheric simulation chamber studies. Products from α-pinene were found to dominate the binary mixed α-pinene–isoprene system in terms of signal contributed and the number of particle components detected. Isoprene photo-oxidation was found to generate negligible SOA particle mass under the investigated experimental conditions, and isoprene-derived products made a negligible contribution to particle composition in the α-pinene–isoprene system. No compounds uniquely found in this system sufficiently contributed to be reliably considered a tracer compound for the mixture. Methyl-nitrocatechol isomers (C7H7NO4) and methyl-nitrophenol (C7H7NO3) from o-cresol oxidation made dominant contributions to the SOA particle composition in both the o-cresol–isoprene and o-cresol–α-pinene binary systems in negative ionization mode. In contrast, interactions in the oxidation mechanisms led to the formation of compounds uniquely found in the mixed o-cresol-containing binary systems in positive ionization mode. C9H11NO and C8H8O10 made large signal contributions in the o-cresol–isoprene binary system. The SOA molecular composition in the o-cresol–α-pinene system in positive ionization mode is mainly driven by the high-molecular-weight compounds (e.g. C20H31NO4 and C20H30O3) uniquely found in the mixture. The SOA particle chemical composition formed in the ternary system is more complex. The molecular composition and signal abundance are both markedly similar to those in the single α-pinene system in positive ionization mode, with major contributions from o-cresol products in negative ionization mode.

The effect of mixed sodium dodecyl sulfate–polyethylene glycol systems on kinetic of oxidation of o-Cresol by cerium(IV) in H2SO4 medium

The effect of mixed sodium dodecyl sulfate–polyethylene glycol systems on kinetic of oxidation of o-Cresol by cerium(IV) in H2SO4 medium

Synthesis of salicylaldehyde through oxidation of o-cresol: Evaluation of activity and selectivity of different metals supported on OMS-2 nanorods and kinetics

Octahedral molecular sieve (OMS-2) was synthesized by the hydrothermal method and modified by the impregnation of different metals to give M/OMS-2 catalysts (where M = V, Cr, Fe, Co, and Mo). All these catalysts were tested in the oxidation of o-cresol to 2-hydroxybenzaldehyde (or salicylaldehyde, SAL). Among all M/OMS-2 catalysts, 5% Co/OMS-2 was found to be the most active catalyst for selective oxidation of o-cresol to SAL. Effect of several oxygen sources such as air, hydrogen peroxide (H2O2), molecular oxygen (O2), and tert-butyl hydroperoxide (TBHP) was studied for the oxidation of o-cresol. There was a complete conversion of o-cresol with 98% yield of SAL at 5 atm O2 pressure and 80 °C in 2 h. Additionally, the catalysts (virgin as well as reused forms) were characterized by FESEM, EDS, HR-TEM, XRD, CO2-TPD, TPR, Raman Spectra, BET surface area analysis, XPS, and DSC-TGA. The reaction kinetic model was developed using Mars van Krevelen mechanism. The catalyst was found to be inexpensive, robust, active, and showed very good reusability of 4 cycles, which makes it an attractive choice for o-cresol oxidation to SAL. The atom economy of the oxidation process is 98.15%. Thus, this process is an example of the synthesis of a vital chemical entity, salicylaldehyde, at mild reaction condition by a novel clean and green route.

Investigation of dark condition nitrate radical- and ozone-initiated aging of toluene secondary organic aerosol: Importance of nitrate radical reactions with phenolic products

To investigate the reaction mechanisms during the NO3- and O3-initiated aging of aromatic secondary organic aerosol (SOA), the gases and particles formed from the OH-initiated oxidation of toluene were exposed to NO3 radicals and O3 in a laboratory chamber. Hydroxyl radicals for the oxidation of toluene were produced under light conditions through H2O2 photolysis and dark conditions through tetramethylethylene ozonolysis. Aerodyne aerosol mass spectrometer results demonstrated an increase in SOA and nitrate aerosol concentrations only after N2O5 injection, but no clear change after O3 injection. The results of proton transfer reaction-quadrupole interface-time of flight mass spectrometer showed that the signal of m/z 109.07 decreased and the signals of m/z 123.05 and m/z 154.05 increased after N2O5 injection, suggesting that gaseous cresols formed from toluene oxidation are rapidly degraded and gaseous nitrocresols and methylbenzoquinones are newly formed. The results of liquid chromatography-mass spectrometry analysis showed that nitrocresols and nitrosalicylic alcohols were the major products formed after N2O5 injection in the particle phase. To confirm the contribution of cresols on aging, NO3 oxidation of o-cresol was carried out, which resulted in the formation of similar products, i.e. gaseous nitrocresols and particulate nitrosalicylic alcohols. Yield curve analysis using two product model estimated that cresol accounted for ~62% of the increase in SOA during NO3-initiated aging of toluene SOA.

Catalytic degradation of O-cresol using H2 O2 onto Algerian Clay-Na.

Clay material is used as a catalyst to degrade an organic pollutant. This study focused on the O-cresol oxidative degradation in aqueous solution by adding H2 O2 and Mont-Na. The catalytic tests showed a high catalytic activity of Mont-Na, which made it possible to achieve more than 84.6% conversion after 90min of reaction time at 55°C in 23.2mM H2 O2 . The pH value was found to be negatively correlated with the degradation rate of O-cresol. UV-Vis spectrophotometry revealed that the increase of degradation rate at low pH is related to the formation of 2-methylbenzoquinone as intermediate product. In addition, the content of iron in Mont-Na decreased after the catalytic test, bringing further evidence about the O-cresol catalytic oxidation. The mineralization of O-cresol is also confirmed by the different methods of characterization of Mont-Na after the catalytic oxidation test. The effect of the O-cresol oxidation catalyzed by natural clay is significant. PRACTITIONER POINTS: Algerian Montmorillonite-Na is used as a catalyst to degrade an organic pollutant: O-cresol. It shows a great potential for catalyst properties in the presence of the oxidizing reagent H2 O2 . It proved to be an effective means for the degradation of O-cresol contained in wastewaters.

Formation of highly oxygenated low-volatility products from cresol oxidation

Abstract. Hydroxyl radical (OH) oxidation of toluene produces ring-retaining products: cresol and benzaldehyde, and ring-opening products: bicyclic intermediate compounds and epoxides. Here, first- and later-generation OH oxidation products from cresol and benzaldehyde are identified in laboratory chamber experiments. For benzaldehyde, first-generation ring-retaining products are identified, but later-generation products are not detected. For cresol, low-volatility (saturation mass concentration, C* ∼ 3.5 × 104 − 7.7 × 10−3 µg m−3), first- and later-generation ring-retaining products are identified. Subsequent OH addition to the aromatic ring of o-cresol leads to compounds such as hydroxy, dihydroxy, and trihydroxy methyl benzoquinones and dihydroxy, trihydroxy, tetrahydroxy, and pentahydroxy toluenes. These products are detected in the gas phase by chemical ionization mass spectrometry (CIMS) and in the particle phase using offline direct analysis in real-time mass spectrometry (DART-MS). Our data suggest that the yield of trihydroxy toluene from dihydroxy toluene is substantial. While an exact yield cannot be reported as authentic standards are unavailable, we find that a yield for trihydroxy toluene from dihydroxy toluene of ∼ 0.7 (equal to the reported yield of dihydroxy toluene from o-cresol; Olariu et al., 2002) is consistent with experimental results for o-cresol oxidation under low-NO conditions. These results suggest that even though the cresol pathway accounts for only ∼ 20 % of the oxidation products of toluene, it is the source of a significant fraction (∼ 20–40 %) of toluene secondary organic aerosol (SOA) due to the formation of low-volatility products.

Electrochemical and In Situ FTIR Study of o-Cresol on Platinum Electrode in Acid Medium

The electrochemical behaviour of o-cresol in acidic medium on platinum electrode has been studied by cyclic voltammetry and in situ Fourier transform infrared spectroscopy. The o-cresol suffers hydrolysis during oxidation giving rise to the formation of methyl-p-benzoquinone. In situ FTIR spectroscopic studies also reveal the presence of CO2, formed as a consequence of the rupture of the aromatic ring. Moreover, the oxidation of o-cresol in acidic medium produces a polymeric film on the platinum surface that precludes further oxidation of o-cresol. The reduction of o-cresol at potentials below 0 V produces in the first step the partial reduction of the aromatic ring and when the potential goes to values below 0 V, methyl-cyclohexanone.

Oxidation of p/o-Cresols to p/o-Hydroxybenzaldehydes Catalyzed by Metalloporphyrins with Molecular Oxygen

The two novel green oxidation processes of p/o-cresols to p/o-hydroxybenzaldehydes catalyzed by metalloporphyrins in the presence of molecular oxygen were developed in this work. Among the metalloporphyrins with different central ions and substituents studied, T(p-NO2)PPCoCl and T(p-OCH3)PPFeCl presented the highest activities for p-cresol and o-cresol oxidation reactions respectively. The molar ratio of sodium hydroxide to cresols and different reaction parameters including reaction temperature, reaction time and reaction pressure have been investigated, and 69.8%/50.4% conversions of p/o-cresol and 86.6%/26.6% selectivities for p/o-hydroxybenzaldehydes were reached under optimized conditions.

Theoretical study of mechanism and kinetics for OH-initiated oxidation of o-cresol in the troposphere

Reaction mechanisms for the OH-initiated oxidation of o-cresol in the troposphere were investigated using B3LYP hybrid density functional method with the 6-311++G(2df,2pd) basis set. Single-point energy calculations with the same basis set were performed using the coupled cluster method with single, double, and perturbative triple configurations, CCSD(T). The equilibrium geometries, energies, and thermodynamics properties of all the stationary points along the addition reaction pathway and hydrogen abstraction reaction pathway were calculated. The rate constants and the branching ratios of each pathway were evaluated using classical transition state theory (TST) in the temperature range of 200–360 K, to simulated temperatures in all parts of the troposphere. The ortho (at position ortho- to the hydroxyl group) addition pathway was found dominant, accounting for 95.3–75.0% of the overall products from 200 to 360 K. The calculated rate constants are in good agreement with available experimental values. The addition reaction and hydrogen abstraction reaction are both thermodynamically irreversible.

10.1007/s11494-008-2007-3

The kinetics of o-cresol oxidation with ozone in acetic anhydride was studied. It was shown that o-cresol was acylated in acetic anhydride to give o-cresyl acetate. Ozone attacks the C=C bonds of the aromatic ring of o-cresyl acetate to give unsaturated peroxide compounds. The composition of the oxidation products alters when the ozonation is carried out in the presence of catalytic amounts of sulfuric acid. Along with the products of the destructive oxidation of the aromatic ring, the methyl group oxidation products appeared as the acyl derivatives o-acetoxybenzyl alcohol and o-acetoxybenzaldehyde, a form that is more stable toward the action of ozone (10%). The addition of manganese(II) acetate to the reaction mixture increases the methyl group oxidation selectivity to 75%. The mechanism of the ozone reaction with o-cresol in acetic anhydride that explains the obtained results is discussed.

Reactions of o-cresol with ozone in acetic anhydride

The kinetics of o-cresol oxidation with ozone in acetic anhydride was studied. It was shown that o-cresol was acylated in acetic anhydride to give o-cresyl acetate. Ozone attacks the C=C bonds of the aromatic ring of o-cresyl acetate to give unsaturated peroxide compounds. The composition of the oxidation products alters when the ozonation is carried out in the presence of catalytic amounts of sulfuric acid. Along with the products of the destructive oxidation of the aromatic ring, the methyl group oxidation products appeared as the acyl derivatives o-acetoxybenzyl alcohol and o-acetoxybenzaldehyde, a form that is more stable toward the action of ozone (10%). The addition of manganese(II) acetate to the reaction mixture increases the methyl group oxidation selectivity to 75%. The mechanism of the ozone reaction with o-cresol in acetic anhydride that explains the obtained results is discussed.

Effect of Pt/TiO 2 characteristics on temporal behavior of o-cresol decomposition by visible light-induced photocatalysis

Platinum deposited TiO 2 films were prepared on quartz substrates by dip-coating process for the photodecomposition of o-cresol. The characteristics of Pt/TiO 2 and the temporal behavior of o-cresol decomposition by Pt/TiO 2 photocatalysis under visible light irradiation were investigated. Platinum deposited on TiO 2 photocatalysts was characterized by Brunauer–Emmett–Teller (BET) surface area measurement, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), diffuse reflectance UV–Vis spectra (DRS) and photoluminescence (PL) emission spectra. The results indicated that the deposition of platinum on TiO 2 promoted the optical absorption in the visible region and made it possible to be excited by visible light. The decomposition rate of o-cresol under visible light irradiation from a fluorescent lamp was enhanced to noticeably extents for experiments conducted with Pt/TiO 2 containing platinum up to 0.50 wt% platinum because of the presence of Ti 3+ resulted from the platinum deposited on the TiO 2 surface; and the formation of Schottky Barrier between platinum and TiO 2 preventing the recombination of electric holes and electrons. Specifically, the reaction rate of o-cresol photodegradation at pH 9 using the 0.50 wt% Pt/TiO 2 was 4.8 times than that of using pure TiO 2. The intermediates identified by GC/MS spectroscopy during the photocatalytic oxidation of o-cresol. The proposed kinetic model could be adequately applied to describe the temporal behavior of the o-cresol decomposition with and without the dosage of Pt on TiO 2 in aqueous solution by UV/TiO 2 process.

Elimination of phenol and aromatic compounds by zero valent iron and EDTA at low temperature and atmospheric pressure

This work deals with a new abiotic oxidation process designed as a suitable pre-treatment step within a biological depuration of wastewater containing phenol or its derivatives (o-cresol, 2-chlorophenol and p-nitrophenol) or aniline. The reaction was carried out in a stirred tank reactor at 20 degrees C and atmospheric pressure in presence of the organic compound, 150mgl(-1), zero valent iron particles (10g), ethylenediamine tetraacetic acid (EDTA, 101mgl(-1)) and air. The experimental results show that 85% of phenol conversion can be achieved after 360min. 2-Chlorophenol was found to be more easily degradable and it is completely eliminated after 300min. The oxidation of o-cresol and aniline behaved more closely to phenol obtaining after 360min 70% and 68% of conversion respectively. p-Nitrophenol was a very refractory compound, giving only 28% of conversion after 360min. Moreover, the influence of some operating variables was studied over the following ranges: temperature from 20 to 50 degrees C, initial phenol concentration from 150 to 1000mgl(-1), EDTA concentration from 50 to 200mgl(-1) and iron particles from 5 to 20g. As expected, temperature strongly enhances phenol conversion. Also, an increase of the catalyst to phenol ratio or the iron or EDTA to phenol ratio improves the reaction rate. A preliminary kinetic analysis of the data shown that the rate of phenol disappearance is not first order with respect to the phenol.

Electrochemical incineration of p-cresol and o-cresol in the filter-press-type FM01-LC electrochemical cell using BDD electrodes in sulfate media at pH 0

This work shows a comparative study of the incineration of 2-mM p-cresol and o-cresol in 1 M-H 2SO 4 in aqueous media. Microelectrolysis studies indicated that both the p-cresol and o-cresol oxidation were carried out via hydroxyl radicals (OH ) formed by water oxidation in the boron-doped diamonds (BDD)-H 2O-H 2SO 4- p-cresol and o-cresol interface. In both cases, the potential and current density ranges, where great amounts of OH are formed, were between 2.3 V ≤ E ≤ 2.75 V versus SHE and J = 10 mA cm −2. Electrolyses in an undivided FM01-LC reactor were performed at different Reynolds values 27,129 ≤ Re ≤ 42,631, and at J = 10 mA cm −2. For p-cresol and o-cresol, the rate of degradation was slow, however it increases slightly as a function of the Re, indicating that the oxidation involves a complex pathway; current efficiency also rises as a function of the Re. For p-cresol, the mineralization at Re = 42,631 reached 90%, with 71% current efficiency and an energy consumption of 7.84 kWh m −3; whereas o-cresol was mineralized to 84%, with 67% current efficiency and an energy consumption of 6.56 kWh m −3. The results obtained in this work demonstrated that o-cresol is more recalcitrant than p-cresol.

One-step heterogeneously catalytic oxidation of o-cresol by oxygen to salicylaldehyde.

Salicylaldehyde (selectivity = 57.3% at a conversion = 73.8%) was prepared for the first time by the oxidation of o-cresol in a single step using impregnated CuCo/C catalysts.

Kinetics and Products from o-Cresol Oxidation in Supercritical Water

Dilute aqueous solutions of o-cresol (2-methylphenol) were oxidized in a tubular flow reactor at near-critical and supercritical conditions. The power-law rate expression that best correlates the kinetics of o-cresol disappearance is rate = 10{sup 5.7} exp({minus}29,700/RT)[o-cresol]{sup 0.57}[O{sub 2}]{sup 0.22}[H{sub 2}O]{sup 1.44}. The power-law rate expression that best correlates the experimental results for the conversion of organic carbon to CO{sub 2} is rate = 10{sup 6.8} exp({minus}34,000/RT)[TOC]{sup 0.34}[O{sub 2}]{sup 0.73}[H{sub 2}O]{sup 1.18}. All concentrations are in moles per liter, the activation energy is in calories per mole, and the rate is in moles per liter per second. The most abundant products from o-cresol oxidation were typically phenol, 2-hydroxybenzaldehyde, 1,3-benzodioxole, indanone, CO, and CO{sub 2}. 2-Hydroxybenzaldehyde was the major primary product. A reanalysis of published kinetics data for the oxidation of two other ring-containing compounds (pyridine and 4-chlorophenol) in supercritical water revealed that the rate laws previously reported for these two compounds do not provide the best correlation of the experimental data. The authors report the new rate laws, which are similar to those for o-cresol, 2-chlorophenol, and phenol in that the global reaction orders are between 0.55 and 0.9 for the organic compounds and between 0.2 and 0.5 for oxygen.

Kinetics of Oxidation of o-Cresol by Cerium(IV) in Acidic Medium

Kinetics of Oxidation of o-Cresol by Cerium(IV) in Acidic Medium

Metabolism of phenol and cresols by Bacillus stearothermophilus.

An obligate thermophilic strain of Bacillus stearothermophilus, strain PH24, isolated from industrial sediment by elective culture, grew readily at 55 C on phenol or on one of the isomers of cresol as the major carbon source. Intact cells grown in the presence of phenol, o-cresol, m-cresol, or p-cresol were induced to oxidize, without lag, these substrates together with catechol, 3-methylcatechol, and 4-methylcatechol. Cell extracts prepared from B. stearothermophilus PH24 after growth in the presence of phenol converted phenol to catechol with a concomitant uptake of 1 mol of oxygen per mol of substrate in reaction mixtures supplemented with reduced nicotinamide adenine dinucleotide. These preparations also catalyzed the oxidation of o-cresol to 3-methylcatechol and of m-cresol and p-cresol to 4-methylcatechol. Enzyme activity was inhibited by 1 mM p-chloromercuribenzoate and by 0.1 mM 0-phenanthroline. Catechol and the corresponding methylcatechol intermediates were further dissimilated by cell extracts of phenol-grown cells via the meta-cleavage route to yield 2-hydroxymuconic semialdehyde and the respective methylated derivatives.

METABOLISM OF CRESOLS BY THE PHENOL-ADAPTED CELLS OF Candida tropicalis ISOLATED FROM ACTIVATED SLUDGE

An yeast strain that utilizes phenol as sole carbon source was isolated from activated sludge, and identified as Candida tropicalis. The cells utilized catechol and methylcatechol for growth as a sole carbon source, but not cresols, hydroxybenzoates and protocatechuate. The yeast cells could rapidly oxidize cresols after the cells were adapted to phenol. The cells oxidized m-cresol and accumulated metabolite in the reaction mixture. Chemical structure of the m-cresol metabolite was identified as 5-formyl-2-hydroxy-4-methyl-2, 4-pentadienoic acid by the UV and IR absorptions, and by the Rf value of paperchromatography. The cells hydroxylate m-cresol to form 4-methylcatechol, and the benzene ring is oxidized by the meta-type fission. The metabolite of o-cresol oxidation suggests that the oxidation may occur through catechol and the benzene ring is cleaved. These results suggest that the yeast strain has catechol oxygenase, but not protocatechuate oxygenase. The pathway of cresol oxidation in the cells is probably initiated by the formation of phenol hydroxylase and catechol oxygenase induced by phenol.

Metabolism of omicron-cresol by Pseudomonas aeruginosa strain T1.

SUMMARY: There is evidence that oxidation of o-cresol by Pseudomonas aeruginosa proceeds through 3-methylcatechol and 2-hydroxy-6-oxohepta-2,4-dienoic acid. 3-Methylcatechol has been characterized as a metabolite in growing cultures, and is oxidized by cells or cell extracts obtained from cultures grown on o-cresol but not by those grown on glucose. The rates of dissimilation of 2-hydroxy-6-oxohepta-2,4-dienoic acid are in excess of its rates of formation from 3-methylcatechol by extracts of cells. The catechol 2,3-oxygenase is formed in response to a variety of inducers and will cleave the ring of catechol and 4-methylcatechol also. The low specificity of the 2,3-oxygenase and earlier enzymic activities (hydroxylases), to both inducers and substrates, is discussed.