Low temperature removal of toluene over Ag/CeO₂/Al₂O₃ nanocatalyst in an atmospheric plasma catalytic system

Abstract

The efficient removal of toluene by plasma catalytic system (PCS) requires catalysts that can generate strong synergetic effect with discharge to oxidize toluene while promoting CO 2 selectivity and suppressing the formation of harmful byproducts. We report that application of an Ag/CeO 2 /Al 2 O 3 catalyst into PCS enables high conversion of toluene to CO 2 and H 2 O with the low concentration of ozone and nitrogen oxides. The Ag nanoparticles dispersed on CeO 2 surface transforms the filamentary discharge to a relatively uniform discharge with high-efficiency, facilitates surface oxygen activation and organic intermediates oxidation, thus, enhances toluene removal efficiency. At 1800 J L −1 , toluene conversion and CO 2 selectivity reached maximum at 93% and 71%, respectively, whereas the removal process exhibited a good stability during a 5-h test.

Enhancing toluene removal in a plasma photocatalytic system through a black TiO2 photocatalyst

“…According to our results, modulating the discharge atmosphere (such as increasing humidity) or constructing composite photocatalysts (such as the hybrid between TiO 2 and MnO x ) could greatly suppress the formation of O 3 and NO x , which might be promising approaches for tackling the environmental effect of the PPS in future studies. Figure 7(a) also shows that IR bands of CO 2 (2360 cm −1 ), CO (2180 cm −1 ), formic acid (1124 cm −1 ) and benzaldehyde (1735 cm −1 ) can be detected for both the DBD alone and PPS (B-TiO 2 ) due to the oxidation of toluene [26,28] benzene (m/z=77 and 78) are also identified by MS for the DBD alone (figure 7(c)). These organic intermediates are generated from partial oxidation of toluene and could be further oxidized to CO 2 and H 2 O.…”

“…These results suggest that the secondary pollution originating from air discharge could be remarkably suppressed by applying the PPS (B-TiO 2 ). The secondary pollutants are closely related to the excited O atoms generated in the discharge [26,27], which suggests that the accelerated plasma photocatalytic reactions between reactive organic intermediates and excited O atoms over B-TiO 2 could effectively suppress the formation of excited O atoms, and thus O 3 and NO x . It is worth noting that the concentrations of O 3 and NO x are still higher than the limitation concentration.…”

“…Secondly, integrating B-TiO 2 with the DBD makes the discharge transform from the filamentary mode into a relatively uniform mode and leads to the increased discharge power. This benefits the generation of active species, and also alleviates the production of NO x due to the suppressed formation of NO under undermined current pulses [24,26]. Lastly, and most significantly, B-TiO 2 possesses abundant surface oxygen vacancies and strong absorption ability for UV-visible light, which makes the PPS (B-TiO 2 ) utilize light emitted from the discharge to efficiently catalyze surface reactions between active species, such as O, •OH, + N , 2 O 3 and -O , 2 and absorbed toluene molecules, thus enabling the acceleration of deep oxidation of organic intermediates to CO 2 .…”

Plasma catalytic removal of VOCs using cycled storage‐discharge (CSD) mode: Tandem effect of zeolite adsorbents and Au catalysts on complete oxidation of toluene

“…Interestingly, at t dis = 5 min, the toluene conversion attains ~100%, but CO 2 , CO, and CO x selectivities are only 26%, 22%, and 48%, respectively (Figure 1b). It implies that, at a discharge time of 5 min, half of the surface intermediates (e.g., formic acid, oxalic acid [6,[17][18][19][20][21] ), formed from the adsorbed C 7 H 8 , is converted into CO x , and the other half remains on the HZ. When the discharge time increases to 20 min, CO 2 and CO selectivities climb to 58% and 32%, respectively.…”

Effect of megapore particles packing on dielectric barrier discharge, O3 generation and benzene degradation

“…Therefore, the packed bed discharge reactor is beneficial to produce reactive species including O 3 , O, e, etc for degradation of VOCs. However, because microporous and mesoporous materials are usually used in plasma catalytic systems for supporting catalytic components such as Cu doped MnO 2 , Co-Mn, Ag/Au-CeO 2 , CeO 2 -MnO x [14][15][16][17][18], the deposition of intermediate products from the degradation of VOCs on the surface of the catalyst and the inside of pores easily causes the deactivation of catalyst and leads to low treatment efficiency of VOCs [17,19,20] because the reactive species is difficult to transfer into the pores of catalysts to react with the VOCs adsorbed in the pores [21].…”