Time filter

Source Type

Glen Burnie, MD, United States

In order to meet impending regulations for soot and NOx reduction from mobile diesel engines, advanced emission control systems may require SCR catalysts with substantially improved thermal durability. State of the art vanadia-based SCR catalysts are composed of vanadia, tungsta, and possibly silica, present at relatively low mass fraction and supported on high-surface-area titania. Concern over the possible emission of metals such as vanadia from diesel vehicles fitted with vanadia-based catalysts limits their potential utility. Vanadia and tungsta oxide and hydroxide vapor pressures over the bulk oxides under conditions relevant for the simulated lifetime exposure of catalysts in the mobile SCR application were estimated on the basis of literature data, and the vapor pressures can be consequential. For the bulk tungsta and vanadia, the most volatile component is WO2(OH) 2, formed from the reaction of tungsta with water, followed by V 4O10 and then VO(OH)3, also a reaction product. An experimental method was developed to measure the vapor-phase transport (a manifestation of vapor pressure) of such inorganic components over real catalysts in representative gas streams by collection on high-surface-area alumina at exposure temperature. In the absence of water at 750 °C, only V4O10 was anticipated as the volatile species. However, no V was observed downstream of the catalyst, so that the vapor pressure of titania-supported vanadia was strongly suppressed relative to the bulk oxide. In the presence of water, the results depended on the support. In the case of a support that underwent substantial loss of surface area during exposure, amounts of W were collected consistent with equilibrium vaporization as WO 2(OH)2. However, the amounts of V collected were below the amount expected based on equilibrium vaporization as either V4O 10 or VO(OH)3. Thus, the reaction of titania-supported vanadia with water at high temperatures was also suppressed. The vapor pressures of the vanadia and tungsta, and the extent of their reaction with water, can be reduced by varying degrees by reducing loss of the surface area of the titania support during exposure and by minimizing the mass fractions of the surficial oxides. New, highly stable titania supports with optimized compositions were found to virtually eliminate the loss of vanadia and tungsta. © 2010 Elsevier B.V. All rights reserved. Source

Pickett B.,Cristal Global
PPCJ Polymers Paint Colour Journal | Year: 2012

Cristal Global has developed CristalACTiV, an environmentally friendly ultra-fine TiO2 photocatalytic technology that can be added to paint, coatings and building materials or simply sprayed on surfaces on its own given its active non-pigmenting and odorless properties. UltrafineTiO2 CristalACTiV particles use UV energy from the sun or artificial lighting to break down pollution. The photocatalytic chemical reaction happens at the molecular level when polluting substances come into contact with a treated surface. The combination of a tiny amount of water, sunlight and CristalACTiV breaks the molecular bonds of sulphur oxides, nitrogen oxides, VOCs and other substances produced during combustion or that are released in the atmosphere. CristalACTiV surfaces will draw dramatic volumes of NOx out of the air, effectively eliminating pollution. It has anti-bacterial properties and enough durability. Source

Mills A.,Queens University of Belfast | Hill C.,Cristal Global | Robertson P.K.J.,Robert Gordon University
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2012

The current eight published ISO standards associated with semiconductor photocatalysis are considered. These standards cover: (1) air purification (specifically, the removal of NO, acetaldehyde and toluene), (2) water purification (the photobleaching of methylene blue and oxidation of DMSO) (3) self-cleaning surfaces (the removal of oleic acid and subsequent change in water droplet contact angle), (4) photosterilisation (specifically probing the antibacterial action of semiconductor photocatalyst films) and (5) UV light sources for semiconductor photocatalytic ISO work. For each standard, the background is first considered, followed by a brief discussion of the standard particulars and concluding in a discussion of the pros and cons of the standard, with often recommendations for their improvement. Other possible standards for the future which would either compliment or enhance the current ones are discussed briefly. © 2012 Elsevier B.V. All rights reserved. Source

Snider D.,Cpfd Software, Llc | Banerjee S.,Cristal Global
Powder Technology | Year: 2010

Heterogeneous catalytic chemistry is used throughout the chemical and petro-chemical industry. In predicting the performance of a reactor, knowing the gases and solids flow dynamics is as important as having good chemical rate expressions. This paper gives the solution of ozone decomposition in a bubbling bed using the CPFD numerical scheme which is a Eulerian-Lagrangian solution method for fluid-solid flows. The ozone decomposition can be described by a single stoichiometric equation and has a first order reaction rate. The ozone decomposition is a standard problem for chemical analysis and has been used to characterize gas-solid contacts in fluidized beds. The accuracy of predicting the ozone decomposition comes from correctly predicting the bed dynamics. The solution in this study is three-dimensional and predicts the coupled motion of both solids and gas. The chemical rate equation uses solids volume fraction, but the numerical method could calculate chemistry on the discrete catalyst, including a variation in size (surface area) if such a rate equation was available. The numerical results compare well with an analytic solution of the decomposition rate, and calculated results compare well with the experiment by Fryer and Potter [Fryer, C. and Potter, O.E, (1976), "Experimental investigation of models for fluidized bed catalytic reactors," AIChE J., 22.]. © 2009 Elsevier B.V. All rights reserved. Source

News Article
Site: http://www.materialstoday.com/news/

Cristal Global, a producer of titanium metal powder, announced that prices on all its TiONA and Tikon titanium dioxide (TiO ) products will increase in all regions. In North America prices for the products will increase by US $0.07 per pound, while in Latin America, the prices will increase by US$150 per metric ton. In Eastern and Western Europe, including Turkey, prices for all TiONA and Tikon titanium dioxide products will increase by €150 per metric ton and in Russia and CIS region by US$160 per metric ton. In the Middle East, Asia Pacific and Africa prices will increase by US$150 per metric ton and in North Africa by €150 per metric ton. In China, prices for all TiONA and Tikon titanium dioxide products will increase by US$150 or RMB 1000 per metric ton. This story uses material from Cristal Global, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.

Discover hidden collaborations