Hyun-Ha Kim

Effect of different catalysts on the decomposition of VOCs using flow-type plasma-driven catalysis

This paper presents the effect of different catalysts on the decomposition of benzene and toluene using flow-type plasma-driven catalyst (PDC) system. Three representative materials of titanium dioxide, two types of gamma-alumina and two zeolites were tested. Several types of metal catalysts (Ag, Ni, Pt, Pd) and their loading amount were also investigated for the optimization of the PDC system. Three key factors of energy consumption, carbon balance and safety of products were emphasized in evaluating the performance of different catalysts. The type of catalysts greatly influenced on the carbon balance, CO₂ selectivity, ozone formation, while no much difference was observed in the degree of enhancement in energy efficiency. Pt/gamma-Al₂O₃ catalyst was found to be effective in enhancing the CO₂ selectivity. The CO₂ selectivity increased as Ag-loading amount on TiO₂ catalyst increased. The 4.0 wt% Ag/TiO₂ catalyst was effective in suppressing the formation of NO₂ and N₂O. Zeolites showed comparable decomposition efficiency and good carbon balance, while the CO₂ selectivity was poor compared to the other catalysts. Mechanical mixing of 2.0 wt% Ag/H-Y zeolite with Pt/gamma-Al₂O₃ was effective in enhancing the CO ₂ selectivity without changing other performance

Effective combination of nonthermal plasma and catalysts for decomposition of benzene in air

Abstract The effective combination of plasma energy and solid surface properties, such as catalysis and adsorption, was investigated using packed-bed type catalyst–hybrid and adsorbent–hybrid reactors that were packed with a mixture of BaTiO 3 pellets and other ceramic pellets (catalyst or adsorbent). The plasma reactor that employed catalysts indicated improvement in CO 2 selectivity and suppression of N 2 O formation compared with the reactor that was packed with BaTiO 3 alone. It was also found that the catalysts and adsorbents in the plasma reactor were useful in enhancing energy efficiency. Furthermore, the catalyst and adsorbent positions in the plasma reactor were very important for induction of surface reactions on the packed materials.

Atmospheric plasma-driven catalysis for the low temperature decomposition of dilute aromatic compounds

The decomposition of volatile organic compounds (VOCs)—six aromatic compounds of benzene derivatives and formic acid—was investigated using a plasma-driven catalysis (PDC) system at atmospheric pressure. In the PDC reactor, the decomposition efficiency of VOCs was mostly determined by the specific input energy (SIE) and insensitivity to the gas hourly space velocity from 11 000 to 55 000 h−1. Formic acid (HCOOH) was formed as a common intermediate from the decomposition of the tested aromatic compounds. Formic acid was also found to be an important intermediate for CO2 formation. Except for styrene, all the tested VOCs indicated zero-order kinetics, which confirm the dominant role of the catalytic reaction in the decomposition of VOCs using the PDC reactor. A simple kinetic model represents well the observed zero-order kinetics with respect to the SIE. Unlike conventional plasma reactors, no correlation between the ionization potential and the decomposition was found with the PDC reactor. Continuous operation tests indicated stable performance without deterioration of catalytic activity over 150 h.

Comparative assessment of different nonthermal plasma reactors on energy efficiency and aerosol formation from the decomposition of gas-phase benzene

This work presents a comparative assessment of five different types of plasma reactors (pulsed corona, dielectric-barrier discharge (DBD), surface discharge (SD), BaTiO/sub 3/ packed-bed reactor, and plasma-driven catalyst (PDC) reactor) using the decomposition of gas-phase benzene. The parameters used in the assessment include energy constant, carbon balance, product selectivity, and nanometer-sized aerosol formation. The DBD reactor, the pulsed corona reactor, and the SD reactor, where the gas-phase chemical reactions prevail, showed similar performance both in the decomposition efficiency and in the aerosol formation. Size distribution and number concentration of the aerosol formed in the SD and the pulsed corona were 10-80 nm and /spl sim/10/sup 5/ particles/cm/sup 3/, respectively. The PDC reactor showed the highest removal efficiency as well as the highest CO/sub 2/ yield. Carbon balances were strongly related to the nanometer-sized aerosol formation. Negligible amounts of aerosol were formed in the BaTiO/sub 3/ packed-bed reactor and the PDC reactor packed with Ag/TiO/sub 2/ catalyst.

Decomposition of Benzene Using Ag/TiO2 Packed Plasma-Driven Catalyst Reactor: Influence of Electrode Configuration and Ag-Loading Amount

This paper describes the effects of electrode configuration and the loading amount of Ag catalyst on the decomposition of gas-phase benzene using plasma-driven catalyst (PDC) reactors. Modification of ground electrode brought out a great enhancement in the energy efficiency for benzene decomposition by reducing abnormal discharges outside the reactor tube. The data of carbon balance and the selectivity of CO2 indicated that the Ag catalyst played an important role in the decomposition of benzene, especially for the intermediates. The larger the Ag-loading amounts on the TiO2, the better the performance of benzene decomposition in terms of the carbon balance and the selectivity of CO2. Formation of NO2 and N2O indicated that the maximum specific input energy applicable to the PDC reactor should be determined not only by the decomposition efficiency but also by the formation of nitrogen oxides.

Microscopic observation of discharge plasma on the surface of zeolites supported metal nanoparticles

The physical role of nanometre-sized metal particles (Ag, Zr, Cu) in the generation of discharge plasma over the surface of zeolites is presented. The optical observation system, consisting of a microscope–ICCD camera, was applied to observe the generation of discharge plasma on zeolites supported metal nanoparticle. The zeolite supported metal nanoparticles assisted the discharge plasma to expand over a wide surface area. Among the tested active metals in this study, silver exhibited the most prominent influence in the discharge plasmas on the surface of zeolites. On the other hand, plasma generation was limited to the edges of the zeolites when the bare zeolites were used. The difference in the shape and the area of the discharge plasma was also found to be correlated with the performance of plasma–catalyst reactor for the decomposition of volatile organic compounds. The microscopic observation method can also be used for the rough-but-rapid evaluation of catalyst for a plasma-driven catalyst process.

Plasma Catalysis for Environmental Treatment and Energy Applications

The current status of plasma-catalysis research and the associated possible applications are outlined. A basic explanation of plasma chemistry is given, which is then used as a foundation to indicate the research vector for the ongoing development of various applications. As an example of an environmental application, volatile organic compound decomposition using plasma-catalysis is discussed in depth, from the fundamental concept to the current industrial application status. As a potential application of plasma-catalysis towards the realization of a future “hydrogen society”, ammonia synthesis is discussed in terms of current social attitudes and regulations, along with historical developments. Additionally, up-to-date information on the fundamentals of the nonthermal plasma interaction with a catalyst is provided.

Charged nanoparticle formation from humidified gases with and without dilute benzene under electron beam irradiation

Abstract The nucleation of aerosols in a field of high-density free radicals, ions, and secondary thermalized electrons was studied by irradiating air, N 2 , O 2 , and Ar containing different water contents with electron beams. The charged nanoparticles in the irradiating gases were analyzed by a cluster differential mobility analyzer equipped with a Faraday cup electrometer. All experiments with humidified gases formed both positively and negatively charged particles with mean mobil. equiv. diameters ( D m ) range of 7–10 nm and with the same number concentration ( N ) as well as water ion clusters with D m range of 1.0– 1.1 nm . The N of these large particles increased with water content and absorbed dose. The experimental result showed that hydrogen peroxide was contained in these large charged particles as its part. In the presence of ppbv-level benzene, the D m and N of large charged particles increased with benzene concentration, although their D m were constant at different doses.

Decomposition of Gas-Phase Benzene Using Plasma – Driven Catalyst Reactor: Complete Oxidation of Adsorbed Benzene Using Oxygen Plasma

Abstract In this work, we report the decomposition of gas-phase benzene using plasma-driven catalyst (PDC) system of a single-stage configuration. The decomposition of benzene was affected by the reactor diameter of the surface discharge type PDC reactor. The smaller the reactor diameter, the higher the decomposition efficiency. Long-term test over 150 h demonstrated the stable operation of the PDC reactor without any deterioration of catalytic activity. The PDC reactor with Ag/TiO2 catalysts showed highly oxygen-dependent characteristics for benzene decomposition. Increase of oxygen partial pressure in the gas mixture enhanced deep oxidation to CO2 resulting in higher CO2 yield even at fixed specific input energy. This highly oxygendependent property was further extended the PDC system to a complete oxidation of adsorbed benzene using oxygen plasma. This new volatile organic compounds treatment method showed 100% of CO2 selectivity as well as no formation of CO and nitrogen oxides.

Study of Plasma-Induced Surface Active Oxygen on Zeolite-Supported Silver Nanoparticles

Surface oxygen induced by non-thermal plasma at atmospheric pressure on silver nanoparticle-loaded zeolite was determined by a chemical probe based on the oxidation of NO. The amount of active oxygen fixed onto the catalyst surface by O2 plasma was approximately proportional to the square of the amount of supported silver. In dry air, its extraordinary long lifetime was confirmed for the first time.Graphical Abstract