Interaction Mechanism for Simultaneous Elimination of Nitrogen Oxides and Toluene over the Bifunctional CeO₂–TiO₂ Mixed Oxide Catalyst

Abstract

Simultaneous catalytic elimination of nitrogen oxides (NO x , x = 1 and 2) and volatile organic compounds (VOCs) is of great importance for environmental preservation in China. In this work, the interactions of simultaneous removal of NO x and methylbenzene (PhCH3) were investigated on a CeO2–TiO2 mixed oxide catalyst, which demonstrated excellent bifunctional removal efficiencies for the two pollutants. The results indicated that NO x positively promotes PhCH3 oxidation, while NH3 negatively inhibits through competitive adsorption with PhCH3. The underlying mechanism is that a pseudo PhCH3-SCR reaction happened in this process is parallel to NH3-SCR. Combined with in situ diffuse reflectance infrared Fourier transform spectroscopy and quasi in situ X-ray photoelectron spectroscopy, the interaction mechanism between NO x and PhCH3 is proposed. Specifically, NO x is adsorbed on the catalyst surface to produce nitrate species, which reacts with the carboxylate generated during PhCH3 oxidation to form organic nitrogen intermediates that create N2 and CO2 in the following reactions. In the reaction process, the superoxide (O2 –) generated by O2 activation on the catalyst surface is an important species for the propelling of oxidation reaction. This work could provide guidelines for the design of state-of-the-art catalysts for simultaneous catalytic removal of NO x and VOCs.

Chlorine-Coordinated Pd Single Atom Enhanced the Chlorine Resistance for Volatile Organic Compound Degradation: Mechanism Study

“…Therefore, it is urgent to control the emission of VOCs for the improvement of environment quality and the sustainable development of human society. Among the numerous treatment technologies of VOCs, catalytic oxidation has been proven as the most promising technology for VOC elimination, due to its high removal efficiency, low operating temperature, no secondary pollution, and wide application. − The key of catalytic oxidation depends on the design of high-efficient catalysts. Supported noble metal catalysts have been considered the most promising catalytic materials for VOC elimination because of their high activity and outstanding low-temperature catalytic performance.…”

Chemical Discrimination of Benzene Series and Molecular Recognition of the Sensing Process over Ti-Doped Co3O4

“…The sharp IR peak located at 3068 cm –1 could be identified as the unsaturated CH bond stretching vibration. In Figure b, the IR peaks at 1596, 1519, and 1448 cm –1 were identified as the characteristic stretching vibration of the benzene skeleton . The IR peak at 1467 cm –1 was assigned to the asymmetric bending vibration of methyl.…”

“…In Figure 6b, the IR peaks at 1596, 1519, and 1448 cm −1 were identified as the characteristic stretching vibration of the benzene skeleton. 42 The IR peak at 1467 cm −1 was assigned to the asymmetric bending vibration of methyl. The IR peaks located at 1415, 1303, and 1249 cm −1 were identified as the O−H bending, O−C symmetric, and asymmetric stretching vibration of the carboxyl group, respectively.…”

Catalytic Oxidation of Toluene over Fe-Rich Palygorskite Supported Manganese Oxide: Characterization and Performance

“…In the high wavenumber range, the peak appears at 3068 cm −1 is attributed to the υ(CH-) stretching vibration of methyl group [12]. Additionally, two peaks appear at 1228 cm −1 and 1257 cm −1 may belong to the phenolate (C 6 H 5 -OH) species [44], and the peak located at 1535 cm −1 can correspond to the asymmetric υ(C=O) stretching vibration of a typical carboxylate group [12]. Furthermore, the peak at 1597 cm −1 can be ascribed to the skeleton υ(C=C) vibration of the aromatic ring [47], and the 1405 cm −1 is a C-O symmetric stretching vibration, indicating that the formation of benzoate.…”

“…Figure 6a shows a typical set of temperature dependent DRIFTS spectra during the toluene oxidation process over the 15%Mn-Pal catalyst under 25-275 • C. When toluene was introduced into the reaction system at 25 • C for 30 min, a series of peaks can be observed. The peak at 3029 cm −1 is the signal of C-H stretching vibration on aromatic ring, while two peaks at 2927 cm −1 and 2875 cm −1 represent the methyl and methylene species, respectively [44]. Strong broad band at 1635 cm −1 (δ(H-O-H)) is ascribed to the isolated -OH species on the catalyst surface [45], and it gradually disappeared as the temperature increased.…”