Formation of Pcdd/Fs, Pcbs and Hcl During Catalytic Combustion of Chlorobenzene Over Supported Transition Metal (Cr, V and Cu) Oxide Catalysts
SSRN Electronic Journal(2022)
摘要
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 gamma-Al2O3supported 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 (T90) were 331, 353 and 386 degrees 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 Bronsted 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 n-ary sumation PCDD/Fs and n-ary sumation PCBs were the largest on 10V-Al at T10, 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.
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关键词
Chlorobenzene, Catalytic combustion, Supported transition metal oxide catalysts, HCl production rate, Polychlorinated by-products
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