7727-37-9Relevant articles and documents
Can TiO2 promote the reduction of nitrates in water?
Sa, Jacinto,Berger, Thomas,Foettinger, Karin,Riss, Alexander,Anderson, James A.,Vinek, Hannelore
, p. 282 - 291 (2005)
Monometallic palladium catalysts were synthesized using different titanium supports and tested for the reduction of nitrates from aqueous solutions using hydrogen as a reductant. The Pd/TiO2 catalysts were characterized by electron paramagnetic resonance (EPR), low-temperature Fourier transform infrared (FTIR) spectroscopy of adsorbed CO, and X-ray diffraction (XRD). The catalysts studied exhibited a high activity for nitrate removal with a lower tendency for nitrite formation than the conventional bimetallic Pd catalysts. Although ammonium formation was greater than desired, the use of a monometallic catalyst for this two-step reduction process is significant and suggests that a single site may be responsible for both reduction stages. The titanium support (particularly the Ti3+ centers generated during prereduction in the presence of Pd) appear to play an important role in the nitrate degradation process. The potential role of Pd β-hydride in generating these Ti 3+ centers is discussed.
Complexation of nitrous oxide by frustrated lewis pairs
Otten, Edwin,Neu, Rebecca C.,Stephan, Douglas W.
, p. 9918 - 9919 (2009)
(Figure Presented) Frustrated Lewis pairs comprised of a basic yet sterically encumbered phosphine with boron Lewis acids bind nitrous oxide to give intact PNNOB linkages. The synthesis, structure, and bonding of these species are described.
Reaction between NOx and NH3 on Iron Oxide-Titanium Oxide Catalyst
Kato, Akira,Matsuda, Shimpei,Kamo, Tomoichi,Nakajima, Fumito,Kuroda, Hiroshi,Narita, Tsuneo
, p. 4099 - 4102 (1981)
The reduction of NOx (NO2 alone or mixture of NO and NO2) with NH3 on iron oxide-titanium oxide catalyst was studied using a flow reactor.The reaction between NO2 and NH3 proceeds at 3:4 mole ratio in the presence or absence of oxygen.When the reaction gas mixture contain equal amounts of NO and NO2, the reaction consuming equimolal NO and NO2 proceeds preferentially at a NH3/NOx ratio of unity.The rate of the reaction is faster than either the NO-NH3 or NO2-NH3 reaction.The overall reactions between NOx (NO2, NO+NO2) and NH3 are given as 6NO2+8NH3->7N2+12H2O and NO+NO2+2NH3->2N2+3H2O.Reaction mechanisms are proposed to explain the experimental results.
Characterization of vanadium and titanium oxide supported SBA-15
Segura,Cool,Kustrowski,Chmielarz,Dziembaj,Vansant
, p. 12071 - 12079 (2005)
Supported vanadium and titanium oxide catalysts were prepared by adsorption and subsequent calcination of the vanadyl and titanyl acetylacetonate complexes, respectively, on mesoporous SB A-15 by the molecular designed dispersion (MDD) method. Liquid and gas phase depositions at different temperatures were carried out with vanadyl acetylacetonate, and the different results together with those of titanyl acetylacetonate in the liquid phase deposition were discussed. The bonding mechanism, the influence of the metal interaction with the support material, and differences due to the way of deposition and the temperature were investigated by TGA, chemical analysis, FTIR, and Raman spectroscopy. Elevated dissolving temperatures in the liquid phase led to higher final loadings on the SBA-15 without the formation of clusters, even at high loadings. The decomposition of the anchored vanadium and titanium complexes, their thermal stability, and the conversion to the covalently bound VOX and TiOx species on SBA-15 were studied and investigated by in situ transmission IR spectroscopy. In general, the titanium complex is more reactive than the vanadium complex toward the surface of SBA-15 and has a higher thermal stability. The MDD method of the VO(acac)2 and TiO(acac)2 enables to create a dispersed surface of supported VOx and TiOx, respectively. The structure configurations of VOx and TiOx oxide catalysts obtained at different metal loadings were studied by Raman spectroscopy. Pore size distributions, XRD, and N2 sorption confirmed the structural stability of these materials after grafting. VOx/SBA-15 and TiO x/SBA-15 samples, with different metal loadings, were also catalytically tested for the selective catalytic reduction (SCR) of NO with ammonia. ? 2005 American Chemical Society.
The 193 (and 248) nm photolysis of HN3: Formation and internal energy distributions of the NH (a1Δ, b1Σ+, A3Π, and c1Π) states
Rohrer, F.,Stuhl, F.
, p. 4788 - 4799 (1988)
The UV photolysis of HN3 at 193 nm was investigated in detail in the bulk phase at 300 K.NH radicals in the X, a, b, A, and c states were found to be formed with quantum yields 0.0019 , 0.4, 0.017, 0.00015, and 0.000 61, respectively.Relative rotational and vibrational populations were measured for all states except for NH(X).Average translational energies were estimated for NH(a,ν = 0 and 1 ) and NH(b,ν = 0).The 248 nm photolysis of HN3 was reinvestigated with respect to processes forming NH radicals other than NH(a).The observed energy distributions differ for both laser wavelengths and for high and low lying NH states.The distribution can be better described by a simple impulsive than by a statistical model.Some conclusions are drawn concerning the upper HN3 potential surfaces involved.
Photocatalytic reduction of nitrate over chalcopyrite CuFe0.7Cr0.3S2 with high N2 selectivity
Wang, Rong,Yue, Mufei,Cong, Rihong,Gao, Wenliang,Yang, Tao
, p. 731 - 736 (2015)
Photocatalytic reduction of nitrate (NO3-) is a green and potentially inexpensive technique for reducing NO3- pollution in ground water. TiO2-based photocatalysts have been studied extensively for this purpose. In the present study, the semiconducting catalyst CuFe0.7Cr0.3S2 was applied to NO3- reduction. Loading this catalyst with metal co-catalysts (Ru, Au, Cu, Ag, Pt, and Pd) greatly increased the rate of NO3- reduction and the N2 selectivity. In addition, there was a synergistic enhancement of the photocatalytic performance when the catalyst was loaded two co-catalysts. For example, the catalyst loaded with Pd and Au at mass fractions of 0.75% and 3%, respectively, could photocatalyze the complete reduction of NO3- in a 100 ppm N aqueous solution with 100% N2 selectivity in less than 5 h with UV irradiation. However, with an inner irradiation from a full-arc Xe lamp, the NO3- conversion rate reduced to 0.065 mg N/h, probably because of the low density of the photoexcited electrons. The results show the potential of metal sulfides for photocatalytic reduction of NO3-, and the possibility of use of visible light.
Oscillations in the N2O-H2 reaction over Ir(1 1 0). Route to chaos
Carabineiro, Sónia A.C.,Van Noort, Wibo D.,Nieuwenhuys, Bernard E.
, p. 96 - 102 (2003)
The study described in the present paper is focused on the N2O-H2 reaction on the Ir(1 1 0) surface and, in particular, on different kinds of oscillatory behaviour, including the route to chaos. Oscillations in rate were observed in the temperature range between 460 and 464 K, at a N2O pressure of 1 × 10-6 mbar with H2/N2O ratios close to 1. Upon minor changes in the H2/N2O ratio, a series of period doublings is observed, resulting finally in aperiodic behaviour.
Nature and catalytic role of active silver species in the lean NO x reduction with C3H6 in the presence of water
Iglesias-Juez,Hungria,Martinez-Arias,Fuerte,Fernandez-Garcia,Anderson,Conesa,Soria
, p. 310 - 323 (2003)
A study of the lean NOx reduction activity with propene in the presence of water over Ag/Al2O3 catalysts with different silver loadings (1.5-6 wt%) has been done using X-ray diffraction, ultraviolet-visible spectroscopy, transmission electron microscopy, and in situ diffuse reflectance infrared and X-ray absorption spectroscopies under reaction conditions. The catalysts were prepared by an impregnation method employing EDTA complexes that allow highly dispersed silver phases to be obtained, which are stabilized under reaction conditions by strong interactions with the support. It is shown that the active species corresponds to silver aluminate-like phases with tetrahedral local symmetry. The role of silver in the reaction mechanism is shown to be mainly in the activation of NO x and propene species. In particular, the silver entities have been found to offer a new reaction path for propene activation which involves generation of acrylate species as a partially oxidized active intermediate. Differences between two active catalysts containing 1.5 and 4.5 wt% of Ag suggest that optimization of the SCR activity can be related to the oxygen lability of the tetrahedral silver aluminate-like phase present in the catalyst. As postulated previously, the high nonselective propene oxidation activity of the highest loaded sample (with 6 wt% Ag) appears to be related to formation of metallic silver surface states at low reaction temperatures which are active for NO dissociation.
Nano-spatially confined Pd-Cu bimetals in porous N-doped carbon as an electrocatalyst for selective denitrification
Bai, Nan,Chen, Zehan,Fan, Jianwei,Gu, Tianhang,Teng, Wei,Zhang, Wei-Xian,Zhao, Dongyuan
, p. 9545 - 9553 (2020)
Bimetals have attracted considerable attention as electrocatalysts towards selective reduction of nitrate to benign dinitrogen. Design of highly efficient and stable bimetallic catalysts by taking the effects of both active sites increasing and synergistic composition into account is of paramount importance but still a grand challenge. Herein we report novel bimetallic Pd-Cu nanoparticles (NPs) incorporated in porous N-doped carbon octahedra prepared by a spatial confinement strategy ofin situpyrolysis of metal-organic frameworks with the assistance of polyvinyl pyrrolidone (PVP) as electrocatalysts achieving targeted denitrification. Pd-Cu NPs exhibit superior dispersity with a N-doped matrix and are strongly dependent on the variation of PVP, Pd precursor and pyrolysis temperature. The material shows high efficiency (~97.1%) for the reduction of nitrate from 100 to 2.9 mg NO3--N L-1(well below drinking water standards of 10 mg NO3--N L-1), and especially the selectivity over 83% for benign N2at neutral pH within 24 h. Encapsulated and well-dispersed Pd-Cu NPs and doped N in the carbonaceous matrix synergistically enhance the interfacial electron transfer for transformation of NO3--N(v). Porous structures endow the catalyst with outstanding stability after eight cycles and over a wide pH of 4-10. More importantly, the nanocatalyst performs well with real contaminated water (selectivity of 91% for nitrogen) in laboratory batch reactors. This nanocatalyst shows promise in wastewater treatment and environmental remediation due to the spatial confinement strategy and introduction of heterogeneous atoms.
Promotional effects of Zr on K+-poisoning resistance of CeTiOx catalyst for selective catalytic reductionof NOx with NH3
Xu, Baoqiang,Xu, Haidi,Lin, Tao,Cao, Yi,Lan, Li,Li, Yuanshan,Feng, Xi,Gong, Maochu,Chen, Yaoqiang
, p. 1354 - 1361 (2016)
CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 (NH3-SCR). Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K+-poisoning resistance of the CeTiOx catalyst. The NH3-SCR performance of the catalysts showed that the NOx removal activity of the Zr-modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunauer-Emmett-Teller data indicated that the Zr-containing catalyst had a larger specific surface area and pore volume both before and after K+ poisoning. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X-ray photoelectron spectra showed that the Ce3+/Ce4+ ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K+ loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3-SCR performance; the temperature-programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K+-poisoning resistance of the CeTiOx catalyst.
