Temperature Dependence of Plasma−Catalysis Using a Nonthermal, Atmospheric Pressure Packed Bed; the Destruction of Benzene and Toluene

Abstract

A nonthermal, atmospheric pressure, packed-bed plasma reactor has been used to study the effect of temperature on the plasma−catalytic destruction of toluene and benzene in air. The plasma reactor was packed with BaTiO3 beads to which TiO2, γ-Al2O3, and Ag, Pt, or Pd impregnated catalysts were added. The reactor can be heated up to ∼500 °C, and the destruction efficiencies for toluene and benzene were determined for plasma alone, catalyst alone, and the combined plasma−catalyst configuration. Comparisons have been made to determine the relative contributions of the catalyst and plasma and to discover any synergistic effects. Plasma−catalysis shows greater destruction than catalysis alone with increasing temperature for both benzene and toluene. Catalysis alone has a threshold temperature of ∼300 °C for the destruction of toluene and benzene, but plasma−catalysis with Pd- and Pt-impregnated alumina achieves >95% destruction at this temperature and has a threshold of ∼100 °C. Toluene is more easily destroyed than benzene at all temperatures, by all catalysts.

The Effect of Temperature on the Plasma-Catalytic Destruction of Propane and Propene: A Comparison with Thermal Catalysis

“…3 shows that plasma-catalysis using Pt/c-Al 2 O 3 improves the destruction of propane from 54 to 61% at 200°C and from 58 to *85% at 250°C. Improvements in pollutant removal from air streams using plasma-catalytic processing compared to thermal-catalysis and plasma-alone operation have been reported by many other groups [7,16,17]. A study into the removal of 200 ppm of toluene from air by Kirkpatrick et al [7] using metal-coated electrodes showed that plasma-catalysis can improve conversions by *25% compared to thermal catalysis at low temperatures (*130°C).…”

Influence of Temperature on Gas-Phase Toluene Decomposition in Plasma-Catalytic System

“…The experimental setup was based upon that used previously [14] modified for the introduction of a catalyst and supplied with heating [15][16][17]. The experiments were carried out using a non-thermal, atmospheric pressure plasma, consisting of a BaTiO 3 dielectric packed-bed reactor: a quartz tube of 24 mm internal diameter with two electrodes apart through which the gas passes.…”

Plasma Reactivity and Plasma-Surface Interactions During Treatment of Toluene by a Dielectric Barrier Discharge

“…Therefore, this suggests that electron collisions remain effective in toluene removal when O 2 is added to N 2 : (i) toluene is dissociated through reaction (20) (direct formation of C 2 H 2 ) or through other processes to produce bi-radicals, (ii) stable compounds obtained from bi-radicals are also dissociated to produce CH and CH 2 which recombine, reactions (23) and (24) (possible processes for indirect formation of C 2 H 2 ). When oxygen is added to the mixture, the decrease of HCN and CH 4 concentrations could be a consequence of numerous loss reactions of the methyl group which hinder reactions (25) and (28). Losses due directly to oxygen are:…”

“…Since the first work by Yamamoto et al [11], electron beams as well as several types of discharge such as dielectric barrier (DBD) or corona discharges, capillary discharge, DC glow discharge, multi hollow needle discharge, and also various types of packed-bed reactors, have been studied for the treatment of toluene in air [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. Some results were published concerning the efficiency of the nitrogen plasma to remove toluene and about the influence of the oxygen percentage added to N 2 [15,19,23,24,29].…”