Toluene decomposition using a wire-plate dielectric barrier discharge reactor with manganese oxide catalyst in situ

Valence variation of phase-pure M1 MoVNbTe oxide by plasma treatment for improved catalytic performance in oxidative dehydrogenation of ethane

This work presents a new method of catalyst surface modification by using oxygen plasma to change the oxidation state of active sites in metal oxide catalysts.

Enhancement of the non-thermal plasma-catalytic system with different zeolites for toluene removal

Based on the important effect of catalyst on the plasma-catalytic system, various types of zeolites (5A, HZSM-5, Hβ, HY and Ag/HY) were chosen as catalysts to remove toluene under non-thermal plasma conditions in this work.

Ozone catalytic oxidation of adsorbed benzene over AgMn/HZSM-5 catalysts at room temperature

Investigation of ozone catalytic oxidation of adsorbed benzene over AgMn/HZSM-5 to provide insight into plasma catalytic oxidation of adsorbed benzene in the cycled storage–discharge process.

Vehicle exhaust gas clearance by low temperature plasma-driven nano-titanium dioxide film prepared by radiofrequency magnetron sputtering

A novel plasma-driven catalysis (PDC) reactor with special structure was proposed to remove vehicle exhaust gas. The PDC reactor which consisted of three quartz tubes and two copper electrodes was a coaxial dielectric barrier discharge (DBD) reactor. The inner and outer electrodes firmly surrounded the outer surface of the corresponding dielectric barrier layer in a spiral way, respectively. Nano-titanium dioxide (TiO₂) film prepared by radiofrequency (RF) magnetron sputtering was coated on the outer wall of the middle quartz tube, separating the catalyst from the high voltage electrode. The spiral electrodes were designed to avoid overheating of microdischarges inside the PDC reactor. Continuous operation tests indicated that stable performance without deterioration of catalytic activity could last for more than 25 h. To verify the effectiveness of the PDC reactor, a non-thermal plasma(NTP) reactor was employed, which has the same structure as the PDC reactor but without the catalyst. The real vehicle exhaust gas was introduced into the PDC reactor and NTP reactor, respectively. After the treatment, compared with the result from NTP, the concentration of HC in the vehicle exhaust gas treated by PDC reactor reduced far more obviously while that of NO decreased only a little. Moreover, this result was explained through optical emission spectrum. The O emission lines can be observed between 870 nm and 960 nm for wavelength in PDC reactor. Together with previous studies, it could be hypothesized that O derived from catalytically O₃ destruction by catalyst might make a significant contribution to the much higher HC removal efficiency by PDC reactor. A series of complex chemical reactions caused by the multi-components mixture in real vehicle exhaust reduced NO removal efficiency. A controllable system with a real-time feedback module for the PDC reactor was proposed to further improve the ability of removing real vehicle exhaust gas.

Non-thermal plasmas for non-catalytic and catalytic VOC abatement

This paper reviews recent achievements and the current status of non-thermal plasma (NTP) technology for the abatement of volatile organic compounds (VOCs). Many reactor configurations have been developed to generate a NTP at atmospheric pressure. Therefore in this review article, the principles of generating NTPs are outlined. Further on, this paper is divided in two equally important parts: plasma-alone and plasma-catalytic systems. Combination of NTP with heterogeneous catalysis has attracted increased attention in order to overcome the weaknesses of plasma-alone systems. An overview is given of the present understanding of the mechanisms involved in plasma-catalytic processes. In both parts (plasma-alone systems and plasma-catalysis), literature on the abatement of VOCs is reviewed in close detail. Special attention is given to the influence of critical process parameters on the removal process.

Removal of gaseous toluene and submicron aerosol particles using a dielectric barrier discharge reactor

A lab-scale dielectric barrier discharge (DBD) reactor was fabricated, and gaseous and particulate contaminant removal tests were carried out under a range of DBD reactor operating conditions: applied voltage (5.0-8.5 kV), frequency (60-1000 Hz), upstream toluene concentration (50-200 ppm) and gas flow rate (1-5 L min(-1) or 0.48-0.096 s of gas residence time). The results suggested that the toluene removal efficiency (at 1 L min(-1), 100 ppm) increased (up to approximately 46%) either with increasing voltage (at 1000 Hz) or frequency (at 8.5 kV). The overall particle collection efficiency (at 1 L min(-1)) improved (up to approximately 60%) with increasing voltage (at 1000 Hz) whereas the penetration of the particles increased (up to approximately 40%) with increasing frequency (at 8.5 kV). The toluene removal efficiency (at 8.5 kV, 1000 Hz, 100 ppm) decreased (down to approximately 29%) with increasing gas flow rate while the particle collection efficiency decreased slightly (maintaining approximately 60%) regardless of the flow rate. In addition, the toluene removal efficiency (down to approximately 41%) and carbon dioxide selectivity (down to approximately 43%) decreased with increasing upstream toluene concentration (at 5 kV, 1000 Hz, 1 L min(-1)).

Influence of balance gas mixture on decomposition of dimethyl sulfide in a wire-cylinder pulse corona reactor

The influence of balance gas mixture on decomposition of dimethyl sulfide was investigated experimentally by a wire-cylinder pulse corona reactor at room temperature. A new type of high voltage pulse generator with a thyratron switch and a Blumlein pulse-forming network was used in the experiments. The experiments were conducted at a fixed pulse frequency of 100pps. The DMS decomposition efficiency as well as energy yield was investigated using varying oxygen concentration (0.6-21.0%), humidity (0-1.0%) and different balance gas (air, N(2), Ar). Breakdown voltage of DMS in Ar is lower than that of DMS in N(2), both of which are proportional to the gas pressures. The conversion of DMS in Ar is more efficient than that in N(2) and air at a fixed peak voltage. In addition, it is found that 5% oxygen is the optimum concentration in decomposition of DMS, due to higher conversion of DMS and relatively fewer yields of by products, such as O(3), NO(x) and SO(2). The highest DMS removal efficiency where the energy yield was 1.24mgkJ(-1) was achieved with the gas stream containing 0.3% H(2)O in air.

Removal of volatile organic compounds by single-stage and two-stage plasma catalysis systems: a review of the performance enhancement mechanisms, current status, and suitable applications

This paper provides a comprehensive review regarding the application of plasma catalysis, the integration of nonthermal plasma and catalysis, on VOC removal. This novel technique combinesthe advantages of fast ignition/response from nonthermal plasma and high selectivity from catalysis. It has been successfully demonstrated that plasma catalysis could serve as an effective solution to the major bottlenecks encountered by nonthermal plasma, i.e., the reduction of energy consumption and unwanted/hazardous byproducts. Instead of working independently, the combination could induce extra performance enhancement mechanisms either in a single-stage or a two-stage configuration, in which the catalyst is located inside and downstream from the nonthermal plasma reactor, respectively. These mechanisms are believed to be responsible for the higher energy efficiency and better CO2 selectivity achieved with plasma catalysis. A comprehensive discussion on the performance enhancement mechanisms is provided in this review paper. Moreover, the current status of the applications of two different plasma catalysis systems on VOC abatement are also given and compared. The catalyst plays an important role in both configurations. Especially for the single-stage type, depositing an inappropriate active component on catalytic support would decrease the VOC removal efficiency instead. To date, no definite conclusion on catalyst selection forthe single-stage plasma catalysis is available. However, MnO2 seems to be the best catalyst for two-stage configuration because it could effectively decompose ozone and generate active species toward VOC destruction. On the other hand, although the single-stage plasma catalysis has been proved to be superior to the two-stage configuration, it does not mean that the former is always the best choice. Considering the typical VOC concentrations from different sources and the characteristics of different plasma catalysis systems, the single-stage and two-stage configurations are suggested to be more suitable for industrial and indoor air applications, respectively.

Detection of hydroxyl radical in plasma reaction on toluene removal

A new method was introduced to detect the concentration of OH radical in dielectric barrier discharge (DBD) reaction. A film, which was impregnated with salicylic acid, was used to detect OH radical in plasma reaction at room temperature and atmospheric pressure. Salicylic acid reacts with OH radical and produces 2,5-dihydroxybenzoic acid (2,5-DHBA). Then, a high performance liquid chromatography (HPLC) was carried out to detect the concentration of 2,5-DHBA. Therefore, OH radical in nonthermal plasma reaction could be calculated. In this plasma reaction, the applied voltage was controlled at 10 kV, the initial concentration of toluene was 400 mg/m3, and the gas flow rate was 300 ml/min. It was observed that when the film was placed away from the plasma area, 2,5-DHBA could not be detected by HPLC, although the sampling time lasted for 48 h. On the other hand, when the film was placed in the plasma area and the sampling time being too long (> 4 h), the concentration of 2,5-DHBA was also below detection limit, and it could not be detected by HPLC. However, when the film was placed in the plasma reaction field with the sampling time being 3 h, the concentration of OH radical was calculated to be 10.54 x 10(12) cm(-3). In addition, concentration of OH radical was investigated under different humidity, such as 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%. The results showed that the amount of OH radical stayed at order of magnitude of 10(12) cm(-3) and increased with the increase of humidity.