Adsorption-Induced Active Vanadium Species Facilitate Excellent Performance in Low-Temperature Catalytic NO_x Abatement

Abstract

Vanadia-based catalysts have been widely used for catalyzing various reactions, including their long-standing application in the deNO x process. It has been commonly considered that various vanadium species dispersed on supports with a large surface area act as the catalytically active sites. However, the role of crystalline V 2 O 5 in selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) remains unclear. In this study, a catalyst with low vanadia loading was synthesized, in which crystalline V 2 O 5 was deposited on a TiO 2 support that had been pretreated at a high temperature. Surprisingly, the catalyst, which had a large amount of crystalline V 2 O 5 , showed excellent lowtemperature NH 3 -SCR activity. For the first time, crystalline V 2 O 5 on low-vanadium-loading catalysts was found to be transformed to polymeric vanadyl species by the adsorption of NH 3 . The generated active polymeric vanadyl species played a crucial role in NH 3 -SCR, leading to remarkably enhanced catalytic performance at low temperatures. This new finding provides a fundamental understanding of the metal oxide-catalyzed chemical reaction and has important implications for the development and commercial applications of NH 3 -SCR catalysts.

Hydrothermal Aging Treatment Activates V2O5/TiO2 Catalysts for NOx Abatement

“…X-ray diffraction (XRD), N 2 physisorption, NH 3 -temperature programmed desorption (NH 3 -TPD), H 2 -temperature-programmed reduction (H 2 -TPR), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were performed using the procedures reported in our previous works. , The V/Ti ratio in bulk was analyzed via an inductively coupled plasma instrument (Agilent ICP-OES 730) with a radial view of the plasma. Strong acid solution was applied to dissolve the samples before the test.…”

Structure-Directing Role of Support on Hg0 Oxidation over V2O5/TiO2 Catalyst Revealed for NOx and Hg0 Simultaneous Control in an SCR Reactor

“…The V 2p XPS spectra of V 2 O 5 /TiO 2 catalysts were normalized and deconvoluted into two peaks (Figure d), and the peaks at 517.5 and 516.5 eV could be assigned to the V 5+ and V 4+ of V 2p states, respectively. , Meanwhile, the content of V 5+ and V 4+ were further calculated based on the integral area (Table ) and the V 2 O 5 /TiO 2 -B catalyst also had the highest content of V 5+ , which could promote the Hg 0 oxidation. , In addition, we collected in situ Raman spectroscopies to get a deep insight into the oligomerization of surface vanadyl species on V 2 O 5 /TiO 2 catalysts (Figure S11). It can be seen that a Raman characteristic band located at 1023 cm –1 assigned to the vibration of monomeric vanadyl species was observed over all three catalysts. , …”

Alkali and Heavy Metal Copoisoning Resistant Catalytic Reduction of NOx via Liberating Lewis Acid Sites

“…Nitrogen oxides (NO x ) have been considered one of the most harmful air pollutants. − Selective catalytic reduction with NH 3 (NH 3 -SCR) has been widely used to abate NO x emission from stationary and mobile resources. , However, the alkali and heavy metals contained in the flue gas of coal-fired power plants, waste incinerators, and biomass boilers always severely deactivate the commercial V 2 O 5 –WO 3 (MoO 3 )/TiO 2 catalysts, − reducing the catalyst lifetime and increasing the expense on environmental protection. , Therefore, understanding the SCR catalyst deactivation mechanism is crucial for the development of NH 3 -SCR catalysts with high poisoning resistance and also remains a significant challenge in the field of environmental catalysis.…”