DBD Plasma Assisted CO2 Decomposition: Influence of Diluent Gases

arbon dioxide (CO2) partial reduction to carbon monoxide (CO) and oxygen has been conducted in a dielectric barrier discharge reactor (DBD) operating a packed bed configuration and the results are compared with that of no packing condition. The effect of diluent gas is studied to understand the influence on dielectric strength of the plasma gas on CO2 splitting, with the objective of obtaining the best CO selectivity and high energy efficiency. Typical results indicated that among N-2, He and Ar gases, Ar showed the best decomposition efficiency. Glass beads packing has a strong influence on the performance, probably due to the enhanced field strength due to dielectric nature of the packed material. In a similar manner, Ar mole ratio in the gas mixture also played a significant role, where the maximum CO2 conversion of 19.5% was obtained with packed DBD at CO2: Ar ratio 1: 2. The best CO yield (16.8%) was also obtained under the same conditions. The highest energy efficiency was found to be 0.945 mmol/kJ. The activated species formed inside the CO2 plasma were identified by optical emission spectroscopy

Esterification of methacrylic acid with ethylene glycol over heteropolyacid supported on ZSM-5

Esterification of methacrylic acid with ethylene glycol was carried out over Heteropolyacids [HPA: H4SiW12O40 (STA) and H3PW12O40 (PTA)] supported on ZSM-5. For comparison, the same reaction was carried out over unsupported HPA, H 2SO4, BF3 and PTSA. Among the catalysts studied, HPA showed better activity compared to H2SO4, BF3 and PTSA. Catalytic activity was compared with HPA supported ZSM-5 catalysts. Typical results indicated that 30 wt% PTA supported on ZSM-5 showed nearly the same activity as that of bulk PTA. It was found that the reaction follows first order kinetics with respect to methacrylic acid. The reaction products were identified by 1H-NMR and FT-IR

Enhanced photocatalytic and antibacterial activity of plasma-reduced silver nanoparticles

A non-thermal atmospheric pressure plasma jet has been used for the green synthesis of highly dispersed colloidal silver nanoparticles. The reducing species such as hydrogen radicals and hydrated electrons are identified, and the change in the solution pH is studied during AgNP formation. The structural properties and size of the plasma-reduced silver nanoparticles are characterized via X-ray diffraction, ultraviolet-visible spectroscopy, fluorescence spectroscopy and transmission electron microscopy. The size of the colloidal AgNPs is tuned by adjusting the initial concentration of AgNO3. The effect of terephthalic acid, a hydroxyl radical scavenger, on the reduction of Ag+ ion is studied. The typical catalytic activity data indicate the better performance of the plasma-reduced colloidal Ag nanoparticles than that obtained from the chemical reduction method. The antibacterial activity of the plasma-reduced Ag nanoparticles also shows a better performance than that of the chemically reduced AgNPs, highlighting the potential of the plasma reduction approach for the synthesis of metal nanoparticles, which are stable even after 30 days without a stabilizing agent. Additionally, the effects of hydroxyl scavengers (isopropyl alcohol) and Fenton's reagent (Fe2+ salt) on CV degradation are studied

Novel Catalytic Dielectric Barrier Discharge Reactor for Gas-Phase Abatement of Isopropanol

Catalytic gas-phase abatement of air containing 250ppm of isopropanol (IPA) was carried out with a novel dielectric barrier discharge (DBD) reactor with the inner catalytic electrode made of sintered metal fibers (SMF). The optimization of the reactor performance was carried out by varying the voltage from 12.5 to 22.5kV and the frequency in the range 200-275Hz. The performance was significantly improved by modifying SMF with Mn and Co oxide. Under the experimental conditions used, the MnO x /SMF showed a higher activity towards total oxidation of IPA as compared to CoO x /SMF and SMF electrodes. The complete destruction of 250ppm of IPA was attained with a specific input energy of ∼235J/L using the MnO x /SMF catalytic electrode, whereas, the total oxidation was achieved at 760J/L. The better performance of the MnO x /SMF compared to other catalytic electrodes suggests the formation of short-lived active species on its surface by the in-situ decomposition of ozon

Kinetics of hydrogen sulfide decomposition in a DBD plasma reactor operated at high temperature

The present study investigates the kinetics of hydrogen sulfide (H 2 S) decomposition into hydrogen and sulfur carried out in a nonthermal plasma dielectric barrier discharge (NTP-DBD) reactor operated at ∼ 430 K for in situ removal of sulfur condensed inside the reactor walls. The dissociation of H 2 S was primarily initiated by the excitation of carrier gas (Ar) through electron collisions which appeared to be the rate determining step. The experiments were carried out with initial concentration of H 2 S varied between 5 and 25 vol% at 150 mL/min (at standard temperature and pressure) flow rate in the input power range of 0.5 to 2 W. The reaction rate model based on continuous stirred tank reactor (CSTR) model failed to explain the global kinetics of H 2 S decomposition, probably due to the multiple complex reactions involved in H 2 S decomposition, whereas Michaelis-Menten model was satisfactory. Typical results indicated that the reaction order approached zero with increasing inlet concentration

Combustion synthesized TiO2 for enhanced photocatalytic activity under the direct sunlight-optimization of titanylnitrate synthesis

Optimized synthesis of Ti-precursor ‘titanylnitrate’ for one step combustion synthesis of N- and C-doped TiO2 catalysts were reported and characterized by using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), diffused reflectance UV–vis spectroscopy, N2 adsorption and X-ray photoelectron spectroscopy (XPS). XRD confirmed the formation of TiO2 anatase and nano-crystallite size which was further confirmed by TEM. UV-DRS confirmed the decrease in the band gap to less than 3.0 eV, which was assigned due to the presence of C and N in the framework of TiO2 as confirmed by X-ray photoelectron spectroscopy. Degradation of methylene blue in aqueous solution under the direct sunlight was carried out and typical results indicated the better performance of the synthesized catalysts than Degussa P-25

Catalytic decomposition of N2O over CeO2 supported Co3O4 catalysts

This work was aimed to design efficient catalysts for N2O decomposition at low temperatures. Cobalt oxide (Co3O4) was prepared by hydrothermal, precipitation and combustion methods and tested for N2O decomposition. It was found that the catalysts prepared by solution combustion synthesis were most active for this reaction. Subsequently, a series of ceria (CeO2) supported Co3O4 catalysts (xCeCo) were prepared by solution combustion method and used them for N2O decomposition. All the catalysts were characterized by analytical methods like XRD, TEM, BET, XPS, UV-Vis, Raman and H (2)-TPR. It was found that 10 and 20 wt..% loading of CeO2 on Co3O4 promoted the activity of Co3O4 towards N2O decomposition, whereas, higher loading of CeO2 reduced the activity. Typical results indicated that addition of CeO2 increases the surface area of Co3O4, and improves the reduction of Co3+ to Co2+ by facilitating the desorption of adsorbed oxygen species, which is the rate-determining step for the N2O decomposition over Co3O4 spinel catalysts. Optimal CeO2 loading can increase both dispersion and surface area of Co3O4 catalysts and weaken the Co-O bond strength to promote N2O decomposition

Catalytic non-thermal plasma reactor for decomposition of dilute chlorobenzene

Oxidative decomposition of low concentrations of chlorobenzene (CB) in air was carried out in a NTP reactor. Typical results indicated the better performance on addition of metal oxide catalysts in plasma zone. It may be concluded that catalytic plasma approach has promise, especially for the removal of low concentraions of CB, where conventional techniques are not energetically feasible. Among the metal oxides studied, AgOx/MnOx showed the better performance than MnOx and CoOx. During the removal of 50 ppm of CB, AgOx/MnOx under humid conditions showed 100% selectivity to total oxidadtion at 260 J L-1, which may be assigned due to the formation of hydroxyl radical and/or due to in situ ozone decomposition on the catalyst surface that may lead to the formation of a powerful oxidant atomic oxygen. Oxidative decomposition of low concentrations of chlorobenzene in air was carried out in a NTP reactor. Results indicated the improved performance on addition of catalysts in plasma zone. It has been observed that the integration of metal oxides, promoted the total oxidation, whose activity was further enhanced on addition of water vapor. During the abatement of 50 ppm of CB, selectivity to CO2 was 100% at 260 J L-1 with AgOx/MnOx/SMF catalytic electrode

Nonthermal plasma assisted photocatalytic oxidation of dilute benzene

Oxidative decomposition of low concentrations (50-1000 ppm) of diluted benzene in air was carried out in a nonthermal plasma (NTP) dielectric barrier discharge (DBD) reactor with the inner electrode made up of stainless steel fibres (SMF) modified with transition metal oxides in such a way to integrate the catalyst in discharge zone. Typical results indicate the better performance of MnOx and TiO2/MnOx modified systems, which may be attributed to the in situ decomposition of ozone on the surface of MnOx that may lead to the formation of atomic oxygen; whereas ultraviolet light induced photocatalytic oxidation may be taking place with TiO2 modified systems. Water vapour improved the selectivity to total oxidatio

Combustion synthesis of cadmium sulphide nanomaterials for efficient visible light driven hydrogen production from water

Anion-doped cadmium sulphide nanomaterials have been synthesized by using combustion method at normal atmospheric conditions. Oxidant/fuel ratios have been optimized in order to obtain CdS with best characteristics. Formation of CdS and size of crystallite were identified by X-ray diffraction and confirmed by transmission electron microscopy. X-ray photoelectron spectroscopy confirmed the presence of C and N in the CdS matrix. The observed enhanced photocatalytic activity of the CdS nanomaterials for the hydrogen production from water (2120 μmol/h) can be attributed to high crystallinity, low band gap and less exciton recombination due to the C and N doping