1. Formation of PCDD/Fs, PCBs and HCl during catalytic combustion of chlorobenzene over supported transition metal (Cr, V and Cu) oxide catalysts.
- Author
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Xing, Defeng, Wang, Sheng, Fan, Yun, Zhang, Haijun, Wang, Ting, Wang, Mingzhe, Wang, Shudong, Wang, Jiancheng, Pan, Dahai, and Song, Xueding
- Subjects
POLYCHLORINATED dibenzodioxins ,TRANSITION metal oxides ,COPPER ,TRANSITION metals ,CATALYST selectivity ,CHLOROBENZENE ,CATALYSTS - Abstract
As an efficient scheme, catalytic combustion can be used to eliminate chlorinated volatile organic compounds (CVOCs). To avoid the formation of more toxic by-products, it is essential to reveal the relationship between the chlorine-containing products and redox properties of catalyst. In the present study, the activity for chlorobenzene (CB) oxidation, HCl production, and formation of by-products polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs)were investigated over γ-Al 2 O 3 -supported transition metal (Cr, V and Cu) oxide catalysts. The results showed that the 10Cr-Al catalyst with relatively high specific surface areaand more oxygen absorbed than other catalysts exhibited higher catalytic oxidation activity for CB. The temperatures needed for 90% conversion of CB (T 90) were 331, 353 and 386 °C for 10Cr-Al, 10V-Al and 10Cu-Al, respectively. The amount and type of acid sites on the surface of catalysts play an important role in the distribution of products and by-products. It was found that the increase of acid sites and the presence of Brønsted acid (B-acid) significantly improve the HCl selectivity of catalysts. More HCl was formed on the 10V-Al catalyst with B-acid sites. Meanwhile PCDD/Fs and PCBs detected in the by-products had a tight relationship with the acidity sites and redox performance of the catalyst. The yields of ∑PCDD/Fs and ∑PCBs were the largest on 10V-Al at T 10 , reaching 25.60, 66.93 mmol/mol CB, respectively. The obtained results provided theoretical support for the subsequent development of CVOCs catalytic oxidation catalysts and the control of toxic by-products. [Display omitted] • Superior catalytic activity for chlorobenzene oxidation was achieved over 10Cr-Al. • The highest HCl selectivity over 10 V-Al was attributed to its strong acidity and abundant Brønsted acid sites. • Formation of PCDD/Fs was promoted by Brønsted acid and moderate oxidation capacity. • Production of PCBs was enhanced over 10Cu-Al owing to its high Deacon reaction activity and reduction ability. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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