Efficient activation of the Co/SBA-15catalyst by high-frequency AC-DBD plasma thermal effects for toluene removal

Dielectric barrier discharge(DBD)plasma excited by a high-frequency alternating-current(AC)power supply is widely employed for the degradation of volatile organic compounds(VOCs).However,the thermal effect generated during the discharge process leads to energy waste and low energy utilization efficiency.In this work,an innovative DBD thermally-conducted catalysis(DBD-TCC)system,integrating high-frequency AC-DBD plasma and its generated thermal effects to activate the Co/SBA-15 catalyst,was employed for toluene removal.Specifically,Co/SBA-15 catalysts are closely positioned to the ground electrode of the plasma zone and can be heated and activated by the thermal effect when the voltage exceeds 10 k V.At12.4 k V,the temperature in the catalyst zone reached 261℃ in the DBD-TCC system,resulting in an increase in toluene degradation efficiency of 17%,CO_(2)selectivity of 21.2%,and energy efficiency of 27%,respectively,compared to the DBD system alone.In contrast,the DBD thermally-unconducted catalysis(DBD-TUC)system fails to enhance toluene degradation due to insufficient heat absorption and catalytic activation,highlighting the crucial role of AC-DBD generated heat in the activation of the catalyst.Furthermore,the degradation pathway and mechanism of toluene in the DBD-TCC system were hypothesized.This work is expected to provide an energy-efficient approach for high-frequency AC-DBD plasma removal of VOCs.

Co_(3)O_(4)/TiO_(2) composite photocatalyst:Preparation and synergistic degradation performance of toluene

TiO_(2) nanobelts and Co_(3)O_(4)/TiO_(2) catalytic materials were prepared using the hydrothermal method.The cat-alyst was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray electron spectroscopy,and fluorescence spectroscopy.At room temperature,with a relative humidity of 50.0%,the total gas flow rate of 1.0 L·min-1,the space velocity of 1.05×10^(4) h^(-1),and toluene volume concentration of 25.0µL·L^(-1),two 6 W vacuum ultraviolet lamps were used as light sources to catalyze,degrade,and mineralize toluene.The results show that the prepared catalyst is in the shape of nano-ribbons.The loading of Co_(3)O_(4) inhibits the recombina-tion of photogenerated electrons and holes and can effectively improve the catalytic performance.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%Co_(3)O_(4) has the best catalytic effect.When N2 was used as a carrier gas,the degradation rate of tol-uene was only 34.7%.The toluene degradation is mainly due to the photolysis of vacuum ultraviolet light.When air was used as a carrier gas,O_(3) was produced.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%and vacuum ultraviolet synergistical-ly promote toluene degradation.The highest degradation rate of toluene was 91.7%and the mineralization rate was 74.6%.The degradation rate of toluene was 2.6 times that of nitrogen as a carrier gas.

Preparation of Corncob-Like WO3 Nanomaterials and Their Photocatalytic Treatment of Toluene

Corn rod-like WO3 nanomaterials were successfully synthesized by a simple hydrothermal method. The morphology, structure and optical absorption properties of the prepared samples were characterized by SEM, XRD, FTIR and UV-Vis-DRS. The WO3 materials were corn rod-like morphology with about 800 nm for length and 150 nm for diameter, especially there were plenty of corn particles (about 20 nm) on the surface of corn rods. The X-ray diffraction peaks of the products corresponded with WO3 standard card, and the characteristic peak of W-O bond was found in the infrared spectrum. The absorption band edge of the products was about 480 nm, indicating their potential visible-light-induced photocatalytic activity. In situ FTIR technology research showed that the prepared WO3 nanomaterials had visible photocatalytic activity to gas-phase toluene. After a photocatalytic reaction for 8 hours toluene was effectively degraded, and carboxylic acid and aldehyde could be regarded as the intermediate products, and CO2 was produced as the final product during the reaction process.

Pt/Co_3O_4/3DOM Al_2O_3:Highly effective catalysts for toluene combustion

Three-dimensionally ordered macro-/mesoporous alumina（3DOM Al2O3）-supported cobalt oxide and platinum nanocatalysts（xPt/yCo3O4/3DOM Al2O3,Pt mass fraction（x%）= 0-1.4%,Co3O4 mass fraction（y%） = 0-9.2%） were prepared using poly（methyl methacrylate） templating,incipient wetness impregnation and polyvinyl alcohol-protected reduction.The resulting xPt/yCo3O4/3DOM Al2O3 samples displayed a high-quality 3DOM architecture with macropores（180-200 nm in diameter） and mesopores（4-6 nm in diameter） together with surface areas in the range of 94 to 102m^2/g.Using these techniques,Co3O4 nanoparticles（NPs,18.3 nm） were loaded on the 3DOM Al2O3 surface,after which Pt NPs（2.3-2.5 nm） were uniformly dispersed on theyCo3O4/3DOM Al2O3.The1.3Pt/8.9Co3O4/3DOM Al2O3 exhibited the best performance for toluene oxidation,with a T（90%） value（the temperature required to achieve 90%toluene conversion） of 160 ℃ at a space velocity of20000 mL g^（-1） h^（-1）.It is concluded that the excellent catalytic performance of the 1.3Pt/8.9Co3O4/3DOM Al2O3 is owing to well-dispersed Pt NPs,the high concentration of adsorbed oxygen species,good low-temperature reducibility,and strong interaction between the Pt and Co3O4 NPs,as well as the unique bimodal porous structure of the support.

Benzene and Toluene Levels Measured with DOAS During Vehicular Restrictions in Beijing

Measurements of atmospheric benzene and toluene were carried out continuously using dif- ferential optical absorption spectroscopy from August 7 to August 28 in Beijing during the period of vehicular restrictions. The correlations between traffic flows and totals of benzene and toluene were studied during the period of vehicular traffic restrictions from August 17 to August 20 and non-traffic restrictions on August 16 and August 21. The correlation coef- ficient was 0.8 between benzene and toluene. And the calculated daily mean value ratios of benzene to toluene were 0.43-0.50. During the period of vehicular restrictions, traffic flows were reduced about 11.8% and the levels of benzene and toluene were reduced by 11.4% and 12.8%, respectively. The vehicle emissions were recognized as the major sources for atmospheric benzene and toluene in Beijing.

Mass Spectrometry Study of OH-initiated Photooxidation of Toluene

The composition of products formed from photooxidation of the aromatic hydrocarbon toluene was investigated. The OH-initiated photooxidation experiments were conducted by irradiating toluene/CH3ONO/NO/air mixtures in a smog chamber, the gaseous products were detected under the supersonic beam conditions by utilizing vacuum ultraviolet photoionization mass spectrometer using synchrotron radiation in real-time. And an aerosol time-of-flight mass spectrometer was used to provide on-line measurements of the individual secondary organic aerosol particle resulting from irradiating toluene. The experimental results demonstrated that there were some differences between the gaseous products and that of particle-phase, the products of glyoxal, 2-hydroxyl-3-oxo-butanal, nitrotoluene, and methyl-nitrophenol only existed in the particle-phase. However, furane, methylglyoxal, 2-methylfurane, benzaldehyde, cresol, and benzoic acid were the predominant photooxidation products in both the gas phase and particle phase.

Study on ternary polymerization of toluene diisocyanate

For the production of reactive polyurethane cross-linkinger and curing agents, 2, 4-diisocyanate toluene （TDI） terpolymer, which possesses the rigid structures of hexatomic ring and three reactive functional groups, was synthesized and characterized by the Fourier transform infrared （FFIR）, the gel permeation chromatography （GPC） and the chemical analysis methods. The reaction conditions were studied and optimized. A tracking research on the polymerization process of TDI was taken by using the GPC. The formation processes of the terpolymer, oligomers and higher-polymers were also dealt with. Results show that the TDI terpolymer can be prepared in the presence of Cat-3 catalyst and at the reaction temperature of （60 ±2）℃. The reaction time is short, its outcomes have narrow molecular weights distribution, namely molecular weights from 530 to 550, Mw/Mn =1.10, and the mass fraction of NCO is （25. 0 ± 0. 5）%. With the reaction time prolonging, however, TDI can be further higher-polymedzed to form higher-polymers. Benzoyl chloride （0. 4%, mass fraction）, as the stabilizing agent, can effectively inhibit the occurrence of higher-polymerization. The obtained TDI terpolymer can be stable for more than half a year.

Depolymerization of Poly(bisphenol A carbonate) in Subcritical and Supercritical Toluene

The depolymerization of poly（bisphenol A carbonate）（PC） in subcritical and supercritical toluene was studied. The experimental parameters, which influence the depolymerization reaction such as temperature （570-633 K）, pressure （4.0-7.0 MPa）, reaction time （5-60 min）, and toluene to PC weight ratio （3.0-11.0）, were investigated, and the reaction products were determined by CrC, GC/MS and FT-IR spectrometer. It was found that the main product of the depolymerization reaction was bisphenol A（BPA）. BPA accounted for over 55.7% of the depolymerization products at reaction temperature 613 K, pressure 5.0-6.0 MPa, reaction time 15 min and toluene/PC weight ratio of around 7.0.

PERVAPORATION SEPARATION FOR TOLUENE/n-HEPTANE MIXTURE BY POLYIMIDE MEMBRANES CONTAINING FLUORINE

Five kinds of polyimides were synthesized using five dianhydrides (including 2,2-bis[4-(3,4-dicarboxyphenoxy)- phenyl] propane dianhydride (BPADA),3,3 ,4,4 -diphenylsulfone-tetracarboxylic dianhydride (DSDA),4,4 - (hexafluoroisopropylidene)-diphthalic anhydride (6FDA),1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA), and 4,4 -oxydiphthlic dianhydride (ODPA)) and 2,2-bis[4-(4-aminophenoxy)phenyl] hexafluoropropane (BDAF) via the two- step method that included polyaddition to form the polyamic acid a...

Theoretical Investigation on Photoionization and Dissociative Photoionization of Toluene

The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods. The geometries and frequencies of the reactants, transition states and products have been performed at B3LYP/6-311＋＋G（d,p） level, and single-point energy calculations for all the stationary points were carried out at DFT calculations of the optimized structures with the G3B3 level. The ionization energies of toluene and the ap- pearance energies for major fragment ions, C7H7＋, C6H5＋, C5H6＋, C5H5＋, are determined to be 8.90, 11.15 or 11.03, 12.72, 13.69, 16.28 eV, respectively, which are all in good agree- ment with published experimental data. With the help of available published experimental data and theoretical results, four dissociative photoionization channels have been proposed： CTHT＋＋H, C6Hs＋＋CH3, C5H6＋WC2H2, CsHs＋＋C2H2＋H. Transition structures and intermediates for those isomerization processes are determined in this work. Especially, the structures of C5H6＋ and C5H5＋ produced by dissociative photoionization of toluene have been defined as chain structure in this work with theoretical calculations.

Influences of process parameters on solvent-free toluene oxidation over Au /γ-MnO_2 catalyst

γ-MnO2 nanorobs and Au/γ-MnO2 catalysts were synthesized and characterized by the X-ray powder diffraction XRD the scanning electron microscope SEM and transmission electron microscope TEM . The characterizations show that Au particles are well dispersed on the surface of γ-MnO2 nanorobs with a particle size of about 10 nm.The catalytic performance is evaluated in solvent-free toluene oxidation with oxygen. The influences of several process parameters such as reaction time reaction temperature initial oxygen pressure and catalyst amounts on the catalytic performance are studied.Catalytic results reveal that Au/γ-MnO2 catalyst has a unique selectivity to benzaldehyde and all these factors greatly influence the conversion of toluene and selectivity of bezaldehyde benzoic acid and benzyl benzoate.However these factors have slight influence on the selectivity of benzyl alcohol.

Toluene Sensing Properties of P4VP/Multi-Walled Carbon Nanotubes Multi-Layer Film Sensors

Abstract--Poly4-vinylphenol （P4VP）/multi-wan carbon nanotubes （MWNTs） multi-layer sensitive films were deposited on interdigitated electrodes by airbrush technology to detect toluene vapor at room temperature. The surface and section morphologies of the multi-layer films were observed by a scanning electron microscope （SEM）. It is found that the resistance of the sensor increases when it is exposed to toluene vapor and the response has a good linearity with the concentration of toluene. The results show that the P4VP/MWNTs three-layer film sensors have better sensing properties compared with the two-layer film sensors. The related sensing mechanism is studied in detail.

Photocatalytic aerobic oxidation of toluene and its derivatives to aldehydes on Pd/Bi_2WO_6

The selective oxidation of toluene and its derivatives is extremely important in the chemical industry.The use of photocatalysis in organic synthesis has attracted considerable attention among synthetic chemists because of its ＂green＂ environmental characteristics.In this study,nanoscale Bi_2WO_6with a flower-like morphology was found to be a highly efficient photocatalyst in the catalytic oxidation of toluene and its derivatives using O_2 as the oxidant.The loading of Pd nanoparticles as a cocatalyst onto the flower-like Bi_2WO_6 was found to produce a significant enhancement in the catalytic activity.Mechanistic investigation showed that the superior performance of Pd/Bi_2WO_6 could be attributed to the improvement of both the reductive and oxidative abilities of Bi_2WO_6 by the loading of the cocatalyst.

Methylation of toluene with methanol over HZSM-5:A periodic density functional theory investigation

Periodic density functional theory was applied to investigate the reaction mechanism for the methylation of toluene with methanol over HZSM-5.The results indicated that toluene could be methylated at its para,meta,ortho and geminal positions via a concerted or stepwise pathway.For the concerted pathway,the calculated free energy barriers for the para,meta,ortho and geminal methylation reactions were 167,138,139 and 183 kJ/mol,respectively.For the stepwise pathway,the dehydration of methanol was found to be the rate-determining step with a free energy barrier of145 kj/mol,whereas the free energy barriers for the methylation of toluene at its para,meta,ortho and geminal positions were 127,105,106 and 114 kj/mol,respectively.Both pathways led to the formation of C8H11^＋ species as important intermediates,which could back-donate a proton to the zeolite framework via a reorientation process or form gaseous products through demethylation.Methane was formed via an intramolecular hydrogen transfer reaction from a ring carbon of the C8H11^＋ species to the carbon of the methyl group,with calculated energy barriers of 136,132 and134 kj/mol for the para,meta and ortho C8H11^＋ species,respectively.The calculated free energy barriers for the formation of para-,meta- and ortho-xylene indicated that the formation of the para-xylene had the highest energy barrier for both pathways.

Multichannel charge separation promoted ZnO /P25 heterojunctions for the photocatalytic oxidation of toluene

The fabrication of multicomponent heterojunctions is an effective strategy to improve the performance of TiO2 based photocatalysts. We provide a new strategy for improving the charge separation and photocatalytic performance of ZnO /TiO2 composites by the formation of multichannel charge separated heterojunctions. ZnO /P25 composites were prepared by an incipient wetness impregnation method, and applied for the photocatalytic destruction of gaseous toluene. The ZnO /P25 composites consist of anatase TiO2（ATiO2）, rutile TiO2（RTiO2） and hexagonal zincite structures. The parasitic phase of ZnO in P25 leads to the formation of ZnO（002）/ATiO2（101）/RTiO2（110） heterojunctions that exhibit enhanced light absorption and improved multichannel electron/hole separation. ZnO /P25 heterojunctions can completely oxidize toluene into CO2 and H2O under ultraviolet light irradiation at room temperature, and show enhanced photocatalytic activity in comparison with P25 owing to the efficient electron-hole separation. Such a multichannel charge separated design strategy may provide new insight into the design of highly effective photocatalysts and their potential technological applications.

Size distribution of the secondary organic aerosol particles from the photooxidation of toluene

In a smog chamber, the photooxidation of toluene was initiated by hydroxyl radical （OH.） under different experimental conditions. The size distribution of secondary organic aerosol（SOA） particles from the above reaction was measured using aerodynamic particle sizer spectrometer. It was found from our experimental results that the number of SOA particles increased with increasing the concentration of toluene. As the reaction time prolonged, the sum of SOA particles was also increased. After a reaction time of 130 min, the concentration of secondary organic aerosol particles would be kept constant at 2300 particles/cm^3. Increasing illumination power of blacklamps could significantly induce a higher concentration of secondary organic aerosol particle. The density of SOA particles would also be increased with increasing concentration of CH30NO, however, it would be decreased as soon as the concentration of CH30NO was larger than 225.2 ppm. Nitrogen oxide with initial concentration higher than 30. 1 ppm was also found to have little effect on the formation of secondary organic aerosol.

Effects of seed aerosols on the growth of secondary organic aerosols from the photooxidation of toluene

Hydroxyl radical （.OH）-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium chloride, were introduced into the chamber to assess their influence on the growth of secondary organic aerosols （SOA）. It was found that the low concentration of seed aerosols might lead to high concentration of SOA particles. Seed aerosols would promote rates of SOA formation at the start of the reaction and inhibit its formation rate with prolonging the reaction time. In the case of ca. 9000 pt/cm^3 seed aerosol load, the addition of sodium silicate induced a same effect on the SOA formation as ammonium nitrate. The influence of the four individual seed aerosols on the generation of SOA decreased in the order of calcium chloride〉sodium silicate and ammonium nitrate〉ammonium sulfate.

Disproportionation of Toluene by Modified ZSM-5 Zeolite Catalysts with High Shape-selectivity Prepared Using Chemical Liquid Deposition with Tetraethyl Orthosilicate

Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS （tetraethyl orthosilicate）.Various parameters for preparing catalysts were changed to investigate the suitable conditions.The resulting cata-lysts were tested in a pressured fixed bed reactor and characterized by SEM （scanning electron microscopy）.The conversion of toluene and para-xylene selectivity were influenced remarkably by the n（SiO2）/n（Al2O3） ratio of ZSM-5 zeolite,the type and amount of deposition agent,acid and solvent used,and the time and cycle of deposition treatment.TEOS was proved to be a more efficient agent than the conventional polysiloxanes when the deposition amount was low.The catalyst prepared at the suitable conditions exhibited a high para-xylene selectivity of 91.1% with considerable high conversion of 25.6%.SEM analyses confirmed the formation of a layer of amorphous silica on the external surface of ZSM-5 zeolie crystals,which was responsible for the highly enhanced shape-selectivity.

Phase behavior of TXs/toluene/water microemulsion systems for solubilization absorption of toluene

Triton Xs （TXs） surfactants/cosurfactant/water/oil （toluene） microemulsion systems for enhancing toluene solubilization were proposed and its potential was investigated for toluene removal from gas stream. The results indicated that TX-100 was superior to other TXs surfactants in removing toluene without cosurfactant. The efficiency of cosurfactants for improving toluene solubilization capacity follows the order： amine 〉 alcohol 〉 acid. According to the factor analysis, the linear cosurfactants are better than the branched ones. The effects of hydrophile-lipophile balance （HLB）, salt （NaCl） concentration and temperature on the formation of microemulsion system were also discussed. The results suggested that the optimum value of HLB was 15, the effect of NaCl concentration on the system was inconspicuous and the lower temperature enhanced the solubilization capacity. Nonionic surfactant-based microemulsions had a significant absorption enhancement for toluene, indicated by as much as 82.72% of toluene in phase composition diagram, which will have a great prospect in air pollution treatment.

Toluene Oxyfunctionalization with Air over Metalloporphyrins and Reaction Condition Optimization

Catalytic activities of a series of metalloporphyrin complexes in selective aerobic oxidation of toluene were investigated.The effects of different central metal ions in metalloporphyrins[T(p-Cl)PPMCl(M=Fe,Co,Mn,Cu)] on the reaction course had been examined and it was found that T(p-Cl)PPCu presented the highest catalytic activ- ity in the reaction.The reaction conditions of toluene oxidation were optimized by using orthogonal experiment de- sign.Five relevant factors were investigated:temperature,air pressure,catalyst loading,air flow rate and reaction time.The effects of the five factors on both toluene conversion and total yield of benzaldehyde and benzyl alcohol were discussed.The research results showed that the reaction temperature was the most significant factor influenc- ing toluene oxidation.On the basis of the margin analysis,the optimum conditions for the toluene conversion and the total yield of benzaldehyde and benzyl alcohol respectively were achieved,under which the toluene conversion was up to 14.67%and the total yield of benzaldehyde and benzyl alcohol reached 5.89%.