Abstract
A series of poisoned catalysts with various forms and contents of sodium salts (Na2SO4 and Na2S2O7) were prepared using the wet impregnation method. The influence of sodium salts poisoned catalysts on SO2 oxidation and NO reduction was investigated. The chemical and physical features of the catalysts were characterized via NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). The results showed that sodium salts poisoned catalysts led to a decrease in the denitration efficiency. The 3.6% Na2SO4 poisoned catalyst was the most severely deactivated with denitration efficiency of only 50.97% at 350 °C. The introduction of SO42− and S2O72− created new Brønsted acid sites, which facilitated the adsorption of NH3 and NO reduction. The sodium salts poisoned catalysts significantly increased the conversion of SO2–SO3. 3.6%Na2S2O7 poisoned catalyst had the strongest effect on SO2 oxidation and the catalyst achieved a maximum SO2–SO3-conversion of 1.44% at 410 °C. Characterization results showed sodium salts poisoned catalysts consumed the active ingredient and lowered the V4+/V5+ ratio, which suppressed catalytic performance. However, they increased the content of chemically adsorbed oxygen and the strength of V5+=O bonds, which promoted SO2 oxidation.
Highlights
Nitrogen oxides (NOx ) are recognized as a major air pollutant
The sodium salts poisoned catalysts significantly increased the conversion of SO2 –SO3 . 3.6%Na2 S2 O7 poisoned catalyst had the strongest effect on SO2 oxidation and the catalyst achieved a maximum SO2 –SO3 -conversion of 1.44% at 410 ◦ C
The results indicate that the SO2 –SO3 -conversion of different catalysts increases gradually with increasing temperature
Summary
Nitrogen oxides (NOx ) are recognized as a major air pollutant. They destroy the ozone layer, form acid rain, affect the ecological environment, and endanger human health. The presence of large amounts of fly ash and alkali metals in the flue gas can cause catalyst clogging and poisoning The former is generally reversible and belongs to physical function. Peng et al [11,12] studied the mechanism of alkali metals poisoning catalysts They concluded that after the alkali metals were added they would interact with the V species, causing a reduction in the surface acidity and inhibition of the adsorption of NH3. This is thought to have resulted in the decreased activity of the catalysts. The influence of sulfur-containing sodium salts poisoned catalysts on SO2 oxidation and NO removal was investigated experimentally
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