Active vanadium( iv ) species synthesized at low-temperature facilitate excellent performance in low-temperature NO x -catalytic removal

Vanadium-based catalysts have been extensively used to catalyze various reactions, for example, their long-term application in the de-NO x process. Various vanadium species dispersed on carriers with a large surface area act as catalytic active sites. However, the role of crystal V 2 O 5 in the selective catalytic reduction of NO x by NH 3 remains unclear. In this study, a series of bulk vanadium oxide catalysts were synthesized by varying the synthesis temperature, among which the catalyst with a large amount of crystalline V 2 O 5 synthesized at low temperatures exhibited excellent NH 3 -selective catalytic reduction (NH 3 -SCR) activity at low temperatures. It was found for the first time that V 4+ species in this catalyst play an important role in low-temperature NH 3 -SCR, which significantly improved the catalytic performance at low temperatures. The difference in the NH 3 activation of V 2 O 5 with different ratios of V 4+ /V 5+ was investigated by NH 3 temperature-programmed desorption (TPD) and in situ diffuse reflectance Fourier transform infra-red (IR-DRIFT) tests. The difference in O 2 activation was studied by O 2 -TPD and 18 O 2 isotope exchange experiments. The results show that a higher proportion of V 4+ is more conducive to NH 3 and O 2 activation. This discovery provides a basic understanding of chemical reactions catalyzed by metal oxides and is of great significance for the development and commercial application of NH 3 -SCR catalysts.