Laser synthesis of vanadium-titanium oxide catalysts

Musci, M.; Notaro, M.; Curcio, F.; Casale, C.; Michele, G. De

doi:10.1557/jmr.1992.2846

Cited by 30 publications

(16 citation statements)

References 6 publications

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“…Other researchers have prepared titania-vanadia mixed oxides by a sol-gel process (9), a laser-induced process (23), and a chemical mixing method (24). Similar to our observations, in all these preparations titania crystallizes into the anatase phase upon calcination (9,23,24) and the mixed samples have comparable SCR activity to conventional impregnated titania catalysts (9,24).…”

Section: Effect Of Vanadia In Titania Versus Vanadia On Titania Ratesupporting

confidence: 85%

“…Similar to our observations, in all these preparations titania crystallizes into the anatase phase upon calcination (9,23,24) and the mixed samples have comparable SCR activity to conventional impregnated titania catalysts (9,24). But it is unclear whether there is a structural difference in the active vanadia species in samples that are prepared differently.…”

Section: Effect Of Vanadia In Titania Versus Vanadia On Titania Ratesupporting

confidence: 83%

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Selective Catalytic Reduction of NO by NH₃ over Aerogels of Titania, Silica, and Vanadia

Amiridis

1995

ACS Symposium Series

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Aerogels of titania, titania-silica, and titania-vanadia were prepared with titanium butoxide, silicon ethoxide, and vanadium triisopropoxide as precursors. The titania and titania-silica aerogels were then used as supports for vanadia, introduced by the incipient wetness impregnation of vanadium triisopropoxide and the subsequent calcination at 773 K. The structures of vanadia and titania in these samples were characterized by X-ray diffraction and Raman spectroscopy, and their catalytic properties by the selective catalytic reduction (SCR) of NO with NH 3 . With H 2 O and SO 2 in the feed stream, the SCR activity decreased with increasing vanadia loading. Samples of high activity all contained anatase TiO 2 , but an active vanadia species only needed to be in close proximity and interacting with, and not necessarily deposited on the surface of crystalline titania. Co-gelling was thus an effective way to prepare an active sample in a single step, as demonstrated by the SCR data of the titania-vanadia aerogel. The addition of niobia, up to 10 weight %, did not appreciably change the surface area, structure, or SCR activity of the titania aerogel supported vanadia.Titania-supported vanadia catalysts have been widely used in the selective catalytic reduction (SCR) of nitric oxide by ammonia (1, 2). In an attempt to improve the catalytic performance, many researchers in recent years have used different preparation methods to examine the structure-activity relationship in this system. For example, Ozkan et al (3) used different temperatureprogrammed methods to obtain vanadia particles exposing different crystal planes to study the effect of crystal morphology. Nickl et al (4) deposited vanadia on titania by the vapor deposition of vanadyl alkoxide instead of the conventional impregnation technique. Other workers have focused on the synthesis of titania by alternative methods in attempts to increase the surface area or improve its porosity. Ciambelli et al. (5) used laser-activated pyrolysis to produce non-porous titania powders in the anatase phase with high specific surface area and uniform particle size. Solar et al. have stabilized titania by depositing it onto silica (6). In fact, the new SCR catalyst developed by W. R. Grace & Co.-Conn., SYNOX™, is based on a titania/silica support (7).

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Section: Effect Of Vanadia In Titania Versus Vanadia On Titania Ratesupporting

confidence: 85%

Section: Effect Of Vanadia In Titania Versus Vanadia On Titania Ratesupporting

confidence: 83%

Selective Catalytic Reduction of NO by NH₃ over Aerogels of Titania, Silica, and Vanadia

Amiridis

1995

ACS Symposium Series

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“…% ͑Table I͒, following the procedure described elsewhere. 27 Briefly, a CO 2 laser beam perpendicularly intersects a reactant stream, defining a well-localized reaction zone that enables the growth of nanometric powders with a narrow size distribution. Ti-isopropoxide vapors were used for the synthesis of pure TiO 2 , while controlled amounts of Nb-isopropoxide vapors were added to the reactant stream for the production of Nb-Ti oxides.…”

Section: Methodsmentioning

confidence: 99%

Effects of Nb doping on the TiO2 anatase-to-rutile phase transition

Arbiol

Cerdá

Dezanneau

et al. 2002

Journal of Applied Physics

310

184

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We study the influence of Nb doping on the TiO 2 anatase-to-rutile phase transition, using combined transmission electron microscopy, Raman spectroscopy, x-ray diffraction and selected area electron diffraction analysis. This approach enabled anatase-to-rutile phase transition hindering to be clearly observed for low Nb-doped TiO 2 samples. Moreover, there was clear grain growth inhibition in the samples containing Nb. The use of high resolution transmission electron microscopy with our samples provides an innovative perspective compared with previous research on this issue. Our analysis shows that niobium is segregated from the anatase structure before and during the phase transformation, leading to the formation of NbO nanoclusters on the surface of the TiO 2 rutile nanoparticles.

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“…Detailed descriptions on powder synthesis can be found elsewhere. [13] Commercially available powders were not considered due to too large a grain size and broad distribution of grain dimension, which otherwise would not have allowed one to reach a nanophased film. Previously, preparation of TiO 2 by small-sized powders failed because of the difficulty involved in printing the pastes of such powders and, above all, the appearance of cracks during the drying and firing stages.…”

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confidence: 99%

Preparation and Characterization of Nanostructured Titania Thick Films

Carotta

Ferroni

Guidi³

et al. 1999

Adv. Mater.

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The extraordinary modification of bulk-material properties provided by nanosized materials, due to magnification of surface effects, has encouraged the scientific community to seek novel methodologies of synthesis. Among these, particular emphasis has been given to the techniques that envisage large-scale production and could improve the present-day technology.Nanostructured titania films possess an immense range of applications, e.g. in the field of optics, [1] electrical insulation, [2] photovoltaic solar cells, [3] electrochromic displays, [4] antibacterial coatings, [5] photocatalytic reactors, [6] high-performance anodes in ion batteries, [7] and for gas sensing.[8]Indeed, the production of nanostructured titania thin films has been recently carried out by several methods. [9,10] It was also shown that some applications greatly benefited from a nanostructured phase for TiO 2 .[11]However, production of TiO 2 layers via thick-film technology would allow implementation of high-performance devices at very low cost. It is the purpose of this experimental work to show that a nanostructured titania layer can be achieved via thick-film technology. Also shown is the effect of annealing on the nanophase and the role of doping to prevent coarse-grain growth at relatively high temperature.Furthermore, in order to show a possible application, we produced miniaturized devices, onto which the films were deposited. The devices were tested as gas sensors towards CO and the layers with finer grain size turned out to have better performance than coarse-grained films.Thick-film deposition was carried out using screen-printing apparatus equipped with numerically-controlled settings. Achievement of nanosized titania thick films via this technique was a very important goal due to high-reproducibility of the films that can be produced.Thick-films were manufactured using pure TiO 2 and Nb-doped TiO 2 powders produced through laser-induced pyrolysis. This preparation method allowed us to achieve nanometric-sized particles.[12] Experimentally, we found that the best results in terms of film quality and reproducibility were achieved at 80 m 2 /g for the powder. Pure TiO 2 powders were found in anatase phase while Nb-doped ones were a mixture of anatase (80 %) and rutile (20 %). Rutile appeared due to pyrosynthesis at high temperature, which was necessary in order to add Nb to the powders. Detailed descriptions on powder synthesis can be found elsewhere. [13] Commercially available powders were not considered due to too large a grain size and broad distribution of grain dimension, which otherwise would not have allowed one to reach a nanophased film. Previously, preparation of TiO 2 by small-sized powders failed because of the difficulty involved in printing the pastes of such powders and, above all, the appearance of cracks during the drying and firing stages.Printing of the pastes is complicated by the nanometric size of particles, demanding an unusually large quantity of organic vehicle in order to ensure a suitable viscosity. It w...

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Laser synthesis of vanadium-titanium oxide catalysts

Cited by 30 publications

References 6 publications

Selective Catalytic Reduction of NO by NH₃ over Aerogels of Titania, Silica, and Vanadia

Selective Catalytic Reduction of NO by NH₃ over Aerogels of Titania, Silica, and Vanadia

Effects of Nb doping on the TiO2 anatase-to-rutile phase transition

Preparation and Characterization of Nanostructured Titania Thick Films

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Laser synthesis of vanadium-titanium oxide catalysts

Cited by 30 publications

References 6 publications

Selective Catalytic Reduction of NO by NH3 over Aerogels of Titania, Silica, and Vanadia

Selective Catalytic Reduction of NO by NH3 over Aerogels of Titania, Silica, and Vanadia

Effects of Nb doping on the TiO2 anatase-to-rutile phase transition

Preparation and Characterization of Nanostructured Titania Thick Films

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Selective Catalytic Reduction of NO by NH₃ over Aerogels of Titania, Silica, and Vanadia

Selective Catalytic Reduction of NO by NH₃ over Aerogels of Titania, Silica, and Vanadia