Synergistic Elimination of NO_x and Chloroaromatics on a Commercial V₂O₅–WO₃/TiO₂ Catalyst: Byproduct Analyses and the SO₂ Effect

Abstract

The synergistic control of multipollutants is the frontier of environmental catalysis. This research is in the infancy stage, and many uncertainties still remain. Herein, we investigated the reaction characteristics of synergistic elimination of NO x and chloroaromatics on a commercial V2O5–WO3/TiO2 catalyst. The reaction byproducts were qualitatively and quantitatively analyzed, and their origins were clarified. In particular, the origins of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the synergistic reaction with or without SO2 were first explored; this is crucial for assessing the environmental risk by applying such a synergistic system. Experimental results indicate that during the synergistic reaction, the V2O5–WO3/TiO2 catalyst was deactivated at 200 and 250 °C, whereas the 300 °C was sufficient to durably convert the NO and chlorobenzene at the turnover frequency (TOF) of 7.23 × 10–4 and 1.32 × 10–4 s–1, respectively. A range of aromatics, alkenes, and alkanes, particularly their chlorinated congeners, were observed in the off-gases and on the catalyst surface, where those of 3-chlorobenzonitrile, 4-chloro-2-nitrophenol, and inorganic CS2 were first discovered. In the time-on-stream test at 250 °C, the PCDD/Fs collected from the off-gases was measured at 0.0514 ng I-TEQ Nm–3, but the most toxic dioxins congener, 2,3,7,8-TCDD, was not observed. The alkalinity of selective catalytic reduction reaction likely facilitated the chlorophenol formation, which eventually promoted PCDD/F generation. The SO2 was found to benefit polychlorinated byproduct generation, but the addition of which distinctly inhibited PCDD/F formation.

Selective catalytic reduction of NO over W–Zr-Ox/TiO2: performance study of hierarchical pore structure

“…The broad peak at 400-700 C should correspond to the reduction of Ti 4+ to Ti 3+ . 39,40 As shown in Fig. 8(a), although the WZ/T catalyst had the highest hydrogen consumption (3.21 mmol g À1 ), the hydrogen reduction peak temperature was also the highest (640 C).…”

Interaction Mechanism Study on Simultaneous Removal of 1,2-Dichlorobenzene and NO over MnOx–CeO2/TiO2 Catalysts at Low Temperatures

“…Incineration has become the preferred waste treatment method for municipal solid waste (MSW) and medical waste (MW) in China. However, multiple pollutants including chlorinated aromatic compounds (e.g., chlorobenzenes, chlorophenol, and dioxins), heavy metals (e.g., Hg and Pb), particulate matter, and acid gases (e.g., NO x and SO 2 ) coexist in waste incineration flue gases. , Due to their adverse health and environmental effects, a stringent emission standard (GB18485-2014) has been promulgated by the Chinese Government to limit the emissions of these pollutants. The selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) has been proven to be an efficient post-combustion technique to minimize NO x emissions from stationary sources, and as a consequence, the NH 3 -SCR technique is also applied for NO x removal in some waste incinerators.…”

Remarkable Enhancement In The N2- Selectivity of NH3-SCR Over The CeNb3Fe0.3/TiO2 Catalyst In The Presence of Chlorobenzene

“…V 2 O 5 -WO 3 and/or V 2 O 5 -MoO 3 supported on TiO 2 are the most widely used industrial catalysts for SCR (Gan et al 2018b). However, they still exhibit some major shortcomings, such as a narrow working temperature range (300-400°C), toxic effects of vanadium on the ecological environment and human health, high toxicity of active vanadium substances, and low N 2 selectivity at higher temperatures (Jiang et al 2019). Cerium is frequently utilized due to its excellent oxygen-storage capacity and high redox capacity via the reduction of Ce 4+ to Ce 3+ (Lee et al 2019, Lei et al 2020).…”