Quang Hung Trinh

Removal of ethylene from air stream by adsorption and plasma-catalytic oxidation using silver-based bimetallic catalysts supported on zeolite.

Dynamic adsorption of ethylene on 13X zeolite-supported Ag and Ag-M(x)O(y) (M: Co, Cu, Mn, and Fe), and plasma-catalytic oxidation of the adsorbed ethylene were investigated. The experimental results showed that the incorporation of Ag into zeolite afforded a marked enhancement in the adsorptivity for ethylene. The addition of transition metal oxides was found to have a positive influence on the ethylene adsorption, except Fe(x)O(y). The presence of the additional metal oxides, however, appeared to somewhat interrupt the diffusion of ozone into the zeolite micro-pores, leading to a decrease in the plasma-catalytic oxidation efficiency of the ethylene adsorbed there. Among the second additional metal oxides, Fe(x)O(y) was able to reduce the emission of ozone during the plasma-catalytic oxidation stage while keeping a high effectiveness for the oxidative removal of the adsorbed ethylene. The periodical treatment consisting of adsorption followed by plasma-catalytic oxidation may be a promising energy-efficient ethylene abatement method.

Environmental plasma-catalysis for the energy-efficient treatment of volatile organic compounds

Nonthermal plasma (NTP) coupled with catalysis is a promising technique for the abatement of dilute volatile organic compounds (VOCs), because it is operable under mild reaction conditions, i.e., low temperature and atmospheric pressure. This review addresses the mechanistic aspects of catalyst activation by NTP, such as the generation and fixation of reactive species, facilitation of redox cycles, photocatalysis, and local heating, to clarify the combined effects of plasma and catalysis. The plasma-catalytic removal of VOCs preferentially requires the catalyst to have a large specific surface area, high surface oxygen storage capacity, and to be highly reducible. The energy consumption and deactivation of catalysts are considered by comparing continuous and cyclic operations in terms of specific input energy, VOC removal and energy efficiencies, and byproduct formation. Based on the information in the literature, a plasma-catalytic system operating in cyclic adsorption-oxidation mode is recommended for the treatment of air contaminated by dilute VOCs. Finally, the effects of NTP on the regeneration of deactivated catalysts are also discussed.

Adsorption and plasma-catalytic oxidation of acetone over zeolite-supported silver catalyst

The abatement of acetone using a combination of non-thermal plasma, catalysis and adsorption was investigated in a dielectric barrier discharge plasma reactor packed with silver-coated zeolite pellets serving as both adsorbent and catalyst. The removal of acetone in this reactor system was carried out by cyclic operation comprising two repetitive steps, namely, adsorption followed by plasma-catalytic oxidation. The effects of the zeolite-supported silver catalyst on the reduction of unwanted ozone emission and the behavior for the formation of gaseous byproducts were examined. The experimental results showed that the zeolite-supported catalyst had a high acetone adsorption capacity of 1.07 mmol g−1 at 25 °C. Acetone with a concentration of 300 ppm was removed from the gas stream and enriched on the zeolite surface during the adsorption step of the cyclic process (100 min). In the succeeding step, the adsorbed acetone was plasma-catalytically treated under oxygen-flowing atmosphere to recover the adsorption capability of the surface. The plasma-catalytic oxidation of the acetone adsorbed in the previous 100 min adsorption step was completed in 15 min. The abatement of acetone by the cyclic adsorption and plasma-catalytic oxidation process was able to increase the performance of the reactor with respect to the energy efficiency, compared to the case of continuous plasma-catalytic treatment. The use of the zeolite-supported silver catalyst largely decreased the emission of unreacted ozone and increased the amount of gaseous byproducts such as carbon oxides and aldehydes due to the enhanced oxidation of the adsorbed acetone and intermediates.

Tailoring the wettability of glass using a double-dielectric barrier discharge reactor

A double dielectric barrier discharge reactor operated at a low power frequency of 400 Hz and atmospheric pressure was utilized for regulating the wettability of glass surface. The hydrophobic treatment was performed by plasma polymerization of tetramethylsilane (TMS, in argon gas). The obtained results showed that the TMS coatings formed on the glass substrates without oxygen addition were smooth, uniform films with the maximum water contact angle (WCA) of about 106°, which were similar to those obtained by low pressure, high power frequency plasmas reported in the literature. The addition of oxygen into TMS/Ar plasma gas decreased the WCA and induced the formation of SiOSi and/or SiOC linkages, which dominated the existence of Si(CH2)nSi network formed in TMS/Ar (without oxygen) plasma.