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In this study, the acid sites on the surface of the catalyst were quantitatively analyzed by pyridine adsorption infrared spectroscopy. When the molar ratio of V/P is 5, the molar ratio of HCl/V is 3, and the calcination temperature is 450 °C, the selective catalytic reduction effect of NO over VPO/TiO2 catalyst is the best (up to 99% at 200 °C), and the acidity of the catalyst is the highest, which is 5600 μmol·g−1. The results showed that the SCR activity of VPO/TiO2 catalyst increased with the increase of acidity at low temperature. Furthermore, the correlation between the denitration activity and the surface acid level was established by means of data fitting. The results showed that the low temperature denitrification activities of all VPO/TiO2 catalysts were positively correlated with the content of weak Lewis acid center (correlation coefficient > 0.9). In conclusion, this study provides a new method for analyzing the structure–activity relationship of the catalyst and provides some theoretical basis for the design of NH3-SCR catalyst.

A high moisture content in the flue gas of iron and steel sintering process causes the issue of filter material pasting, which leads to a decrease in the filtration effect and service life of the filter material. Surface modification of the filter materials is a useful strategy for their hydrophobicity enhancement. Therefore, the Sol–gel method was employed to modify the polyethylene glycol terephthalate (PET) filter with tetraethyl orthosilicate(TEOS) as precursor and perfluorodecyl triethoxysilane (PFDTES) as modifier. Field emission scanning electron microscope (FESEM), Fourier transform infrared spectrometer (FT-IR), and contact angle tester were used to characterize the PET filter materials before and after modification, and exhaustive filter efficiency was evaluated by the comprehensive performance test machine. The particle size and distribution of SiO2 nanoparticles were analyzed using a nanometer particle size analyzer, the effects of TEOS/PFDTES loading on the hydrophobic performance and filtration performance of the filter material have been discussed. Based on the results of these studies, superhydrophobic stability of the filter material was evaluated. The results show that the microscopic pore structure of PET filter materials was retained after modification. TEOS modified PET (T-PET) filter materials were completely wetted with static contact angle (WCA) of 0°. The surface energy of PFDTES modified PET (F-PET) filter materials was reduced, the WCA was 144.6 ± 1.6° and WSA was 7.6 ± 4.5°. For TEOS/PFDTES co-modified PET (TF-PET), the SiO2 nanoparticles was modified by the long fluorine chain -CH2CH2(CF2)7CF3 groups, endowing TF-PET with superhydrophobic property. With the increasing of TEOS loading, TF-PET fiber presented significant enhancement of roughness, while average particle size of SiO2 nanoparticles on the fiber surface gradually decreased. The particle size distribution first increased sharply, and then, slowly decreased when TEOS addition was enhanced. TF-PET filter material possessed WCA of 163.2 ± 2.3°, while when TEOS: PFDTES mass ratio was 2.5:2, WSA was 6.2 ± 1.9° with filtration efficiency (0.3 μm) of 68.61%.