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Selective catalytic reduction
About: Selective catalytic reduction is a research topic. Over the lifetime, 10502 publications have been published within this topic receiving 226291 citations.
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TL;DR: In this article, the catalytic properties of the as-prepared MnM2O4 microspheres were comparatively investigated by the selective catalytic reduction (SCR) of NO with NH3, and their reaction mechanisms were studied by in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFT).
89 citations
TL;DR: In this paper, the chemical changes that occurred in two copper-based catalysts (Cu-ZSM-5 and Cu-Al2O3) during the selective reduction of NO with propene in the presence of oxygen were studied using in situ X-ray absorption near edge structure (XANES).
Abstract: The chemical changes that occurred in two copper-based catalysts (Cu-ZSM-5 and Cu-Al2O3) during the selective reduction of NO with propene in the presence of oxygen were studied using in situ X-ray absorption near edge structure (XANES). For the quantitative analysis of the XANES spectra, a mathematical procedure based on evolving factor analysis (EFA) has been applied. Correlation with catalytic data shows that copper is fully oxidized in both systems when the conversion of propene is complete and the conversion of NO to N2 reaches its maximum value. The XANES analysis together with comparison of the catalytic behavior of Cu-ZSM-5 with Cu-Al2O3 and Cu-SiO2 systems indicates that the rate limiting step of the reaction takes place on cupic oxides (although other species may also participate). This conclusion is of general significance because it establishes the physical basis for the role of Cu in selective catalytic reduction of NO by hydrocarbons; this explains the recently recognized fact that zeolitic ...
89 citations
TL;DR: In this paper, the catalytic activities of Fe/Beta catalysts with various Fe loadings were investigated for the selective catalytic reduction (SCR) of nitric oxide by ammonia.
Abstract: The catalytic activities of Fe/Beta (i.e., by incipient wetness impregnation) zeolite catalysts with various Fe loadings were investigated for the selective catalytic reduction (SCR) of nitric oxide by ammonia. Their stabilities and deactivation behavior were studied via hydrothermal aging and hydrocarbon coking. The results showed that NO conversion over 2.5 wt% Fe/Beta catalyst could reach 97.0% in the temperature range of 300–500 °C at a high space velocity (1.9 × 10 5 h −1 ). The Fe/Beta catalyst showed stability up to a hydrothermal aging temperature of 750 °C. XRD results showed that the structure of Fe/Beta was altered by hydrothermal aging over 750 °C, with significant de-alumination as well as a decrease of lattice constants at 900 °C. The catalysts after deactivation by the presence of propylene could be fully regenerated by burning off the coke in the reactants over 450 °C or in air at 550 °C. It was found that the deposition of carbon species on Fe/Beta decreased its activity for forming NO 2 as evidenced by FTIR. XPS results showed that the introduction of C 3 H 6 in the reactants resulted in partial reduction of Fe 2+ thereby decreased the activity of Fe/Beta for NO SCR.
89 citations
TL;DR: In this article, the effect of doping SnO2 into TiO2 for selective catalytic reduction of NO by NH3 was investigated, and the results of catalytic tests suggested that the catalyst with the optimal molar ratio exhibited the best catalytic performance.
88 citations
TL;DR: A quaternary catalyst library of 56 samples comprising all combinations of four elements, viz. Ag, Co, Cu, In, with six equally spaced atomic fraction increments from 0 to 1 was prepared by impregnation of a proprietary mesoporous alumina support as discussed by the authors.
Abstract: A quaternary catalyst library of 56 samples comprising all combinations of four elements, viz. Ag, Co, Cu, In, with six equally spaced atomic fraction increments from 0 to 1 was prepared by impregnation of a proprietary mesoporous alumina support. Catalytic properties of the library were tested in the selective catalytic reduction (SCR) of NO x by propane under lean conditions in the temperature range 400–500 °C. The catalytic data acquired by a parallel 64-channel microreactor system with automated time-of-flight mass spectrometric analysis have been evaluated regarding selectivity–compositional relationships, synergistic effects for NO x conversion, and efficiency of propane utilization. Full conversion of NO x is achieved over Ag–Co combinations at 450 °C with N 2 selectivities of more than 90% and reductant utilization of 20% in a feed of 1500 ppm NO, 1500 ppm propane and 5 vol.% O 2 (space velocity of 36,000 cm 3 g cat −1 h −1 ). For the single-component catalysts Ag/Al 2 O 3 , Co/Al 2 O 3 , Cu/Al 2 O 3 , and In/Al 2 O 3 , the state of the elements on the mesoporous alumina was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Cobalt forms a spinel-like cobalt aluminate phase whereas copper and indium are present as oxides with small sizes not detectable by XRD. Silver occurs in both metallic state and as Ag 2 O, and forms Ag n clusters of at least two different sizes, predominantly with diameters of about 30 nm. The conclusions are consistent with the reducibility of the single-component catalysts samples by H 2 . Surface area measurements and pore size distributions revealed reasonable modifications of the textural properties. The main pore size of the alumina support is decreased from 7 to ca. 5 nm after loading of the active components.
88 citations