Vanadium pentoxide gel

Stizza, S., 1. Davoli, and M. Benfatto (1987). X-ray absorption spectroscopy in compressed vitreous silica and vanadium pentoxide gel. J. Noncryst. Solids 95 96, 327-34. 

J. J. Legendre and J. Livage, Vanadium pentoxide gels I. Structural study by electron diffraction, J. Colloid Interface Set, 94, 75-83 (1983). 

Livage J (1991) Vanadium pentoxide gels. Chem Mater 3 578-593... 

The active phase, which is soHd at room temperature, is comprised of mixed potassium and sodium vanadates and pyrosulfates, whereas the support is macroporous siUca, usually in the form of 6—12 mm diameter rings or pellets. The patent Hterature describes a number of ways to prepare the catalyst a typical example contains 7 wt % vanadium pentoxide, 8% potassium added as potassium hydroxide or carbonate, 1% sodium, and 78 wt % siUca, added as diatomaceous earth or siUca gel, formed into rings, and calcined in the presence of sulfur dioxide or sulfur trioxide to convert a portion of the alkah metal salts into various pyrosulfates (81,82). 

Through the years, several catalyst formulations have been employed, but one of the traditional catalytic agents has been vanadium pentoxide. Calderbank (114) has indicated that for a catalyst consisting of V205 supported on silica gel, the kinetic data are represented by a rate expression of the form... 

A colloidal suspension of conductive vanadium pentoxide [130] can be used to perform intercalation, adsorption or encapsulation of electroactive molecules or biomolecules for electrodes or biosensor realization [131]. Encapsulation of glucose oxidase in nanocomposite films made with polyvinyl alcohol and V205 sol-gel matrix or in ferrocene intercalated V2Os sol-gel [132] were envisaged to prepare glucose biosensors. 

The process. A typical process for phthalic anhydride starts with mixing hor q-xylene vapor with excess preheated air in a ratio of 20 1 air to o-xylene by weight. The gaseous mixture is then fed to a reactor consisting of tubes packed with vanadium pentoxide catalyst on a silica gel. The reaction takes place at 800—1000°F. Like most oxidation reactions, this one is exothermic, and the heat of reaction must be removed from the tubes to maintain the reaction temperature. 

Spectroelectrochemical analysis of charge-insertion nanostructured materials already offers important insight into these systems. These methods were recently exploited to characterize the electrochemical processes of nanostructured manganese oxide ambi-gel and xerogel films. " 6-229 Spectroelectrochemical measurements were used to corroborate electronic state changes with the observed electrochemical response for the insertion of small cations (Li+, Mg2+) and the unexpected insertion of a bulky organic cation (tetrabutylammonium). Vanadium pentoxide exhibits two distinct electrochromic features that can be assigned to the transition at either sto-... 

AIPO4-5 molecular sieve (BET surface area, 299 m g ) used in this study was prepared by the method of Wilson et al. [1j. VjOg/AIPO -S samples were prepared by impregnating with aqueous solutions of ammonium vanadate after removing templating agent in the AIPO -S by calcining at 530°C. The samples were dried at 110 C for 24 h then calcined in air at 550°C for 2 h. VAPO -S was prepared from gel mixture of phosphoric acid, pseudoboehmite, vanadium pentoxide, tri-propylamine and water (1.3 PrjN x AljOj PjOj 40 HjO) by crystallization at 165°C for 3 - 7 days [7. ... 

Colloidal Vanadium Pentoxide.11—When a soluble vanadate is treated with mineral acids, a red, curdy form of vanadium pentoxide is precipitated, which, on being shaken with water, appears to dissolve to a red liquid. This reaction gives rise to the following usual method for making a colloidal solution Ammonium metavanadate, NH4V03, is made into a paste with 10 per cent, hydrochloric acid of 10 per cent, concentration, and the resulting gel of vanadium pentoxide is washed repeatedly on the filter with distilled water until it assumes the colloidal form, i.e. until it is peptised, and in consequence passes through the... 

As in the case of hydrated niobium and vanadium pentoxides, it is a difficult matter to remove traces of mineral acids from the precipitate. Treatment with water gives rise to a cloudy hydrosol which passes through an ordinary filter. This can be prevented by addition to the wash-water of a small quantity of ammonia or acetic acid.4 In the preparation of anhydrous tantalum pentoxide, traces of adds can be removed by igniting the gel in admixture with a small quantity of ammonium carbonate. 

Although the forward reaction is favored by increase in pressure, this is not employed in practice since 97 to 99% conversion of sulfur dioxide to sulfur trioxide can be accomplished at the temperature specified here, provided suitable catalysts are used. The first catalyst used for this reaction consisted of finely divided platinum dispersed in asbestos, anhydrous magnesium sulfate, or silica gel. Other catalysts were later discovered. Mixtures of ferric and cupric oxides are useful, but these are less efficient than platinum. Certain mixtures containing vanadium pentoxide (V205) and other compounds of vanadium appear to be as good as or better than platinum. There has been much controversy over the relative merits of platinum and vanadium catalysts, and only time will provide the answer as to which is best. 

Design a multitube fixed-bed reactor system to accomplish the reaction of naphthalene (N) with air to produce phthalic anhydride over a catalyst of vanadium pentoxide on silica gel at a temperature of about 610-673 K. 

In the German phthalic anhydride process naphthalene is passed over a vanadium pentoxide (on silica gel) catalyst at a temperature of about 350°C. Analysis of the available data indicates that the rate of reaction (pound moles of naphthalene reacted to phthalic anhydride per hour per pound of catalyst) can be represented empirically by the expression... 

Vanadium pentoxide Silica gel 380-460 Toluene Benzaldehyde Maleic acid (40)... 

Vanadium pentoxide Alundum Silica gel 400-500 Naphthalene Naphthaquinone Phthalic anhydride, CO and H.O (42)... 

Rojas E, Valverde M, Herrera LA, Altamirano-Lozano M and Ostrosky-Wegman P (1996) Genotoxicity of vanadium pentoxide evaluate by the single cell gel electrophoresis assay in human lymphocytes. Mutat Res 359 77-84. 

Vanadium pentoxide, on silica gel carriers, is used as a catalyst in the fluidized-bed process. Potassium hydrogen sulfate is added as a modifier, especially to pre-... 

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