Decomposition Of Benzene Research Articles

Effect of Ag/TiO2 catalyst preparation on gas-phase benzene decomposition using non-thermal plasma driven catalysis under oxygen plasma

Non-thermal plasma (NTP) driven catalytic decomposition of gas-phase benzene under oxygen plasma was carried out at room temperature over silver on titanium dioxide catalysts. Three preparation methods were investigated as well as the effect of silver loading amount. The catalysts were prepared using impregnation method (IP), deposition–precipitation method with NaOH (DPN), and deposition–precipitation method with H2O2 (DPH) with 1, 3 and 5 % silver loading by weight. The catalysts were characterized using XRD, XPS, SEM–EDS and N2 adsorption, and the catalytic activity was tested on 200 ppm benzene. Low energy treatment by NTP alone only showed insignificant change in benzene concentration but upon the addition of catalysts, IP catalysts were able to decompose the pollutant up to 20 % and with DPN and DPH catalysts up to 100 %. DPN catalysts were also able to decompose the ozone produced in the reactor. The 3 % Ag/TiO2 prepared by DPN method showed the highest energy efficiency capable of decomposing benzene at 392 g/kWh.

Simplified sonochemical preparation of titania embedded with selected metals for purification of benzene and toluene

Titania (TiO2) photocatalysts, each embedded with one of six metals (Ag, Ce, Co, Fe, Mg, and Mn), were prepared using a simplified ultrasonic process. The characteristics of the prepared metal-embedded TiO2 (metal–TiO2) were determined using transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, photoluminescence emission spectroscopy, UV–visible spectroscopy, and nitrogen adsorption–desorption. Except for Co–TiO2, the metal–TiO2 photocatalysts showed improved performance for the decomposition of gaseous benzene and toluene, which are two of the most problematic indoor air pollutants that can cause a variety of adverse health symptoms, under daylight lamp irradiation. Photocatalytic activity was greatest for the Mg–TiO2 sample, followed by, in order, the Ag–TiO2, Ce–TiO2, Fe–TiO2, Mn–TiO2, unmodified TiO2, and Co–TiO2 samples. Although Mg–TiO2 showed the least redshift in its light absorption and the highest electron–hole recombination rate among the metal–TiO2 photocatalysts, it yielded the highest photocatalytic activity, likely because of its increased adsorption capacity and anatase composition. The degradation of benzene and toluene over Mg–TiO2 improved as ultrasound treatment amplitude increased from 20 to 37μm, then decreased gradually as amplitude was further increased to 49μm. Degradation efficiency also improved as ultrasound operation time increased from 30 to 60min, then decreased gradually as amplitude was further increased to 90min. Overall, this process could be utilized to prepare metal–TiO2 photocatalysts with improved performance for the decomposition of gas phase pollutants under daylight lamp irradiation.

Optimizing the packing density of TiO2 nanorod arrays for enhanced light harvesting by a light trapping effect and its photocatalytic decomposition of gaseous benzene

A single-crystalline TiO2 nanorod array with a preferred [002] axial orientation was grown on transparent conductive fluorine-doped tin oxide substrates by a hydrothermal process.

Enhanced Decomposition of Benzene by Non-thermal Atmospheric Pressure Plasma with Oxidized Titanium Electrode

Enhanced Decomposition of Benzene by Non-thermal Atmospheric Pressure Plasma with Oxidized Titanium Electrode

Benzene Removal Using Non-thermal Plasma with CuO/AC Catalyst: Reaction Condition Optimization and Decomposition Mechanism

Non-thermal plasma (NTP) technology in synergy with adsorption catalysts was used to decompose volatile organic compounds. The obtained results indicated that the non-thermal plasma-assisted catalytic system (NTP-C) resulted in higher benzene removal capability and system energy efficiency. The CuO/AC (AC: active carbon) catalysts were prepared by incipient-wetness impregnation method, and effect of CuO loading on benzene destruction was tested. The effect of reaction conditions such as inlet benzene concentration, reaction space velocity, reaction humidity and energy density were also studied. Additionally, the reaction conditions were optimized by the multi-factor orthogonal experiment, and the highest benzene removal efficiency achieved 96.5 %. The influence degree of various factors for benzene elimination was: reaction space velocity ≫ CuO loading > energy density > inlet benzene concentration ≫ reaction humidity. Furthermore, the benzene decomposition mechanism was discussed by analyses of the reaction exhaust, the coke substance inside the reactor, and the surface property of the used catalyst. The oxidation byproducts primarily consisted of phenol and substitutions of phenol. We propose that the radical reactions play a significant role in benzene removal on the surface of catalysts.

Synthesis of a novel N[sbnd]H[sbnd]TiO2 photocatalyst by annealing in NH3 and H2 for complete decomposition of high concentration benzene under visible light irradiation

A novel NHTiO2 photocatalyst was prepared via hydrothermal synthesis followed by a thermal treatment in NH3 and H2 atmospheres. The results showed that benzene with the initial concentration of 150ppm (±5ppm) could be thoroughly removed by NHTiO2 under visible light irradiation. The influences of doping and hydrogenation on properties of TiO2 samples were investigated. It is suggested that the disordered surface layer introduced by hydrogenation contributes to the excellent photocatalytic activity of NHTiO2. The synergistic effect of N doping and surface oxygen vacancies was also confirmed by ultraviolet–visible diffuse reflectance spectra and photoluminescence. Moreover, the diverse role of oxygen vacancies in different positions of TiO2 has been focused on.

Selective photocatalytic oxidation of benzene for the synthesis of phenol using engineered Au-Pd alloy nanoparticles supported on titanium dioxide.

The selectivity of photocatalytic phenol production from the direct oxidation of benzene can be enhanced by fine adjustment of the morphology and composition of Au-Pd metal nanoparticles supported on titanium dioxide thereby suppressing the decomposition of benzene and evolution of phenolic compounds.

Experimental and kinetic modeling investigation on laminar premixed benzene flames with various equivalence ratios

Chemical structures of six laminar premixed benzene/oxygen/argon flames with equivalence ratios from 0.75 to 2.0 were investigated at 30Torr. Dozens of flame species, especially radicals and large aromatics, were qualitatively identified and quantitatively measured using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). A kinetic model was developed from our previous models of aromatic fuels to simulate the decomposition of benzene and formation of large aromatics, and was validated against the measured mole fraction profiles of flame species. Based on the rate of production analysis in the leanest and richest flames, the decomposition processes of benzene and the fate of C6 and smaller products were discussed in detail. Benzene, phenyl radical and cyclopentadienyl radical are concluded as key precursors of large aromatics, and the low formation of PAHs in rich benzene flames compared with rich alkylbenzene flames mainly derives from the low production of benzyl radical, which is consistent with the observed trends of the sooting tendencies of benzene and alkylbenzenes in previous studies.

Effect of Reduction Treatment on Structural Properties of TiO2 Supported Pt Nanoparticles and Their Catalytic Activity for Benzene Oxidation

A series of highly active Pt-TiO2 catalysts have been prepared by impregnation methods via different reduction processes and used for catalytic decomposition of benzene. The oxidized and reduced Pt-TiO2 catalysts exhibit apparent differences in physical/chemical features (e.g. particle size, chemical state, and electronic property of Pt nanoparticles, and surface oxygen) and catalytic activities for benzene oxidation. Nearly 100 % benzene conversion is achieved on Pt-TiO2 catalysts obtained by the sodium citrate (C6H5Na3O7 center dot 2H(2)O, Na(3)Ct) reduction at approximate 160 A degrees C. Metallic Pt nanoparticles have strong capacity for oxygen activation, and the negative charges and rich chemisorbed oxygen on the surface of metallic Pt nanoparticles are probably responsible for their high catalytic activities for benzene oxidation. 1 wt% Pt-TiO2 catalysts have been prepared by impregnation methods via different reduction processes and used for catalytic decomposition of benzene. The oxidized and reduced catalysts exhibit apparent differences in physical/chemical features and catalytic activities for benzene oxidation. Metallic Pt nanoparticles have strong capacity for oxygen activation, and the negative charges and rich chemisorbed oxygen on the surface of metallic Pt nanoparticles are probably responsible for their high catalytic activities for benzene oxidation.

Kinetics analysis of phenol and benzene decomposition in supercritical water

Decomposition of phenol and benzene was studied in supercritical water (SCW) at 370–450°C and 25MPa over very short residence times (0.5–100s). The study of simple model compounds such as phenol and benzene is an essential preliminary step to elucidate the primary mechanism of char and gas formation from lignin compounds. A quantitative detailed chemical kinetics model for the primary pathways of phenol and benzene decomposition in SCW was determined using the reaction pathways for its decomposition under supercritical conditions. The activation energy of benzene decomposition (91.16kJmol−1) in SCW is much higher than that of phenol (54.17kJmol−1) under similar experimental conditions. This emphasized the importance of the substituent group (hydroxyl group) in the benzene ring to enhance its decomposition rate. In addition, the reaction rate parameters, which are deduced for the overall reaction network of its decomposition under similar conditions, show good agreement with each another. Hence, the reaction rates of these reaction pathways are successfully described in this study.

Visible light-driven decomposition of gaseous benzene on robust Sn2+-doped anatase TiO2 nanoparticles

The Sn2+-doped TiO2 nanoparticles are excellent and promising visible-light photocatalysts for the decomposition of benzene with robust photostability.

Catalytic Oxidation of Benzene Using Mesoporous <I>α</I>-Mn<SUB>2</SUB>O<SUB>3</SUB>

The catalytic oxidation of benzene was carried out over mesoporous alpha-Mn2O3, MnOx/KIT-6, and bulk commercial Mn oxides (Mn2O3, MnO2, and MnO). The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller analysis, and temperature-programmed reduction analysis. MnOx/KIT-6, prepared by impregnating MnOx on KIT-6, exhibited a low activity for the oxidation of benzene, whereas mesoporous alpha-Mn2O3, manufactured using KIT-6 as the template, showed a high activity. The order of the activities of bulk Mn oxides for benzene decomposition was shown to be Mn2O3 > MnO2 > MnO. Therefore, the high activity of mesoporous alpha-Mn2O3 is attributed to the uniform distribution of highly active Mn2O3 in the mesoporous structure.

PVP-assisted synthesis of porous strontium tantalate hydrate nanosphere and enhanced photocatalytic properties

Porous Sr0.25H1.5Ta2O6·H2O (HST) nanosphere with high surface area has been prepared by a PVP-assisted hydrothermal method for the first time. In the synthesis, PVP played an important role in formation of porous nanosphere. This approach could also be used to prepare other nanostructured tantalate efficiently without rigorous reaction conditions. The photocatalytic activities were evaluated by the decomposition of benzene in gaseous phase. Results showed that benzene could be effectively degraded and mineralized over the HST samples. Due to the unique porous structure, larger surface area, and stronger oxidizing ability of the photogenerated holes, HST nanosphere exhibited a superior photocatalytic activity for the degradation of benzene compared with HST nanopolydera and TiO2 (Degussa P25). The effect of the crystallinity of the samples on the photocatalytic activities was also discussed.

Study on the decomposition of trace benzene over V2O5–WO3/TiO2-based catalysts in simulated flue gas

Catalytic decomposition of benzene was studied by using oxides of vanadium and tungsten supported on titanium oxide (TiO2) catalysts for effective reduction of emissions of toxic organic compounds from waste incineration. Experiments were conducted to evaluate the effects of the catalyst's composition, and operating conditions on benzene decomposition, and the relationship between molecular structures of catalysts and their activity was also investigated through replacing the conventional TiO2 catalyst support by nano-sized TiO2. Trace levels (1 and 10ppm) of gaseous benzene were catalytically decomposed in a fixed-bed catalytic reactor with monolithic oxides of vanadium and tungsten supported on titanium oxide (V2O5–WO3/TiO2) catalysts under conditions simulating the cooling of waste incineration flue gas. On-line monitoring of trace benzene concentrations before and after the catalyst was achieved by means of resonance enhanced multiphoton ionization-time of flight mass spectrometry (REMPI-TOFMS). Catalysts were characterized by nitrogen adsorption, X-ray diffraction, energy dispersive X-ray spectroscopy, temperature-programmed reduction, and Raman spectroscopy. The effects of several parameters, including catalyst operating temperature, space velocity (SV) and initial benzene concentration, on catalytic oxidation of benzene were investigated. Experimental results indicate that reduction of the initial benzene concentration from 10 to 1ppm either enhances or decreases the catalytic removal efficiency depending on the adsorption capability as well as the oxidation ability of the catalyst tested. The catalytic activity for benzene oxidation not simply relies on the vanadium content of the catalyst; the molecular structure of vanadium oxide, which is known to be influenced by both vanadium oxide loading and the type of support, is very important. Nano-sized TiO2 supported vanadium oxide catalyst (VWNT) with lowest V loading (0.75wt.%) provides higher catalytic activity than those of the catalysts with higher V contents (1.31 and 2.92wt.%) but supported by conventional TiO2 (VWT1 and VWT2). The relatively higher catalytic activity of VWNT may be attributed to: (a) the presence of monomeric VOx species, with one terminal VO bond as indicated by Raman spectra; (b) fewer impurities confounding active catalytic constituents (V, W and Ti); (c) pure anatase phase of TiO2 rather than a mixture phase of anatase and rutile servicing as catalyst support besides its nano-scale particle size; (d) larger specific surface area, smaller average pore diameter, and narrower pore size distribution contribute higher adsorption ability for benzene. No obvious competition effect between NOx removal and benzene oxidation was observed in this study. Reaction rate constants and activation energies for benzene catalytic oxidation tested by the catalysts were calculated. Lower activation energy obtained from VWNT than those of the two catalysts further confirming the higher catalytic activity of VWNT.

Synthesis and characterization of Pt–ZnO-hydroxyapatite nanoparticles for photocatalytic degradation of benzene under visible light

Abstract Hydroxyapatite modified Pt–ZnO nanoparticles (Pt–ZnO –HAP) were synthesized by a template-ultrasonic assisted method. The nanoparticles were characterized by X-ray diffraction, UV–Vis absorption spectroscopy, N2 adsorption–desorption measurement (Brunauer, Emmett and Teller [BET]), photoluminescence spectroscopy, etc. The photocatalytic activities were evaluated by a photocatalytic oxidation decomposition of benzene under a visible-light irradiation. The results showed that the coupled system (Pt–ZnO –HAP) indicated a maximum photocatalytic activity and photochemical stability under a visible-light irradiation than all the other catalysts. The intensively improved visible-light-induced photocatalytic activity of the Pt–ZnO –HAP hybrids could be attributed to its strong absorption in the visible-light region, low recombination rate of the electron–hole pair, and large BET specific surface area.

Fabrication and Photocatalytic Performance of Titanium Dioxide Nanoparticle/Polymethylmethacrylate

t has been found that the photocatalytic activity of TiOB2B toward the decomposition of gaseous benzene in a batch reactor can be greatly improved by modifying TiOB2 Bin the presence of 3-(trimethoxysilyl) propylmethacrylate (MPS). The prepared photocatalyst (PMMA-TiOB2B) was characterized by FTIR, UV/Vis diffuse reflectance spectroscopy and XPS. PMMA-TiOB2 Bdemonstrates 2.3 times the photocatalytic activity of that of TiOB2B.

Template-free synthesis of a CdSnO3⋅3H2O hollow-nanocuboid photocatalyst via a facile microwave hydrothermal method

A CdSnO3⋅3H2O hollow-nanocuboid photocatalyst was successfully synthesized via a facile template-free microwave hydrothermal method for the first time. The as-prepared samples were characterized by x-ray diffraction, UV–vis diffuse reflectance spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis and x-ray photoelectron spectroscopy. Moreover, samples prepared under different reaction times were analyzed by transmission electron microscopy to investigate the formation process of the CdSnO3⋅3H2O hollow-nanocuboids. Based on this result, a possible mechanism for the formation process was proposed. The sample prepared at 160 ° C for 2 h at pH 11 exhibited the best photocatalytic activity and stability for the degradation of gaseous benzene under UV irradiation (λ = 254 nm) as compared with the other samples. The conversion and mineralization rates of benzene were about 12.5% and 67%, respectively. The mineralization rate was twice as high as that of commercial TiO2 (Degussa Co.). Furthermore, the excellent stability for the benzene decomposition was attributed to the positive charge on the catalyst surface, which was analyzed both by electron spin resonance and Zeta-potentials.

Comparative Investigation of Benzene Steam Reforming over Spinel Supported Rh and Ir Catalysts

In a combined experimental and first-principles density functional theory (DFT) study, benzene steam reforming (BSR) over MgAl2O4-supported Rh and Ir catalysts was investigated. Experimentally, it has been found that both highly dispersed Rh and Ir clusters (1–2 nm) on the spinel (e.g., MgAl2O4) support are stable during the BSR in the temperature range of 700–850 °C. Compared to the Ir/MgAl2O4 catalyst, the Rh/MgAl2O4 catalyst is more active with higher benzene turnover frequency and conversion. At steam conditions with the molar steam-to-carbon ratio >12, the benzene conversion is only a weak function of the H2O concentration in the feed. This suggests that the initial benzene decomposition step, rather than the benzene adsorption, is most likely the rate-determining step in BSR over supported Rh and Ir catalysts. To understand the differences between the two catalysts, we followed with a comparative DFT study of initial benzene decomposition pathways over two representative model systems for each supported metal (Rh and Ir) catalysts. A periodic terrace (111) surface and an amorphous 50-atom metal cluster with a diameter of 1.0 nm were used to represent the two supported model catalysts under low and high dispersion conditions. Our DFT results show that the decreasing catalyst particle size enhances the benzene decomposition on supported Rh catalysts by lowering both C–C and C–H bond scission. The activation barriers of the C–C and the C–H bond scission decrease from 1.60 and 1.61 eV on the Rh(111) surface to 1.34 and 1.26 eV on the Rh50 cluster. For supported Ir catalysts, the decreasing particle size only affects the C–C scission. The activation barrier of the C–C scission of benzene decreases from 1.60 eV on the Ir(111) surface to 1.35 eV on the Ir50 cluster while the barriers of the C–H scission are practically the same. The experimentally measured higher BSR activity on the supported highly dispersed Rh catalyst can be rationalized by the thermodynamic limitation for the very first C–C bond scission of benzene on the small Ir50 catalyst. The C–C bond scission of benzene on the small Ir50 catalyst is highly endothermic although the barrier is competitive with those of both the C–C and the C–H bond-breaking on the small Rh50 catalyst. The calculations also imply that, for the supported Rh catalysts, the C–C and C–H bond scissions are competitive, independent of the Rh cluster sizes. After the initial dissociation step via either the C–C or the C–H bond scission, the C–H bond breaking seems to be more favorable rather than the C–C bond breaking on the larger Rh terrace surface.

Highly stable FeCo/carbon composites: Magnetic properties and microwave response

Highly steady composites of FeCo alloy and carbon nanotubes have been synthesized by in situ catalytic decomposition of benzene over FeCo alloy nanoparticles generated through procedures of sol–gel fabrication and hydrogen reduction. Magnetic measurement indicates that the coercivity (HC) increases with the rise of Co concentration and the saturation magnetization (MS) rises in the order of FeCo13@C<FeCo31@C<FeCo22@C. The complex permittivity and permeability of the composites indicates that the maximum reflection loss (RL) is −6.7dB at 11.1GHz at thickness of 1.5mm for FeCo13@C, and as well as the electromagnetic wave absorption properties can be tuned by adjusting the composition of FeCo alloy and the absorption layer thickness.

Catalytic nonthermal plasma reactor for the abatement of low concentrations of benzene

Oxidative decomposition of dilute benzene in air was carried out in a dielectric barrier discharge reactor with inner metal fiber electrode that was later modified with transition metal oxides. Typical results indicated the best performance of the designed reactor for the removal of dilute benzene, where conventional techniques may not be efficient. The introduction of transition metal oxides in the discharge zone increased the conversion of benzene and shifted the product distribution to total oxidation. The performance of the reactor was further improved on humidification of air stream. The better performance of MnOx/SMF over CoOx and SMF may be due to in situ decomposition of ozone that may lead to the formation of strong oxidant atomic oxygen, whereas the best performance with TiO2/MnOx/SMF may be assigned due to the synergy between ozone decomposition on MnOx surface and photocatalytic action on TiO2.