Vanadium modifier

Fig. 8. EPR spectra of vanadium modified AIPO4- 5 (a) simply calcined at 500°C for 2 hr. (b) successive treatments, (c) VAPO4-5...

Amination of i-butanol to diisobutylamine was investigated on vanadium modified granulated Raney nickel catalyst in a fixed bed reactor. The addition of 0.5 wt.% V to Raney nickel improved the yield of amines and the stability of catalyst. Factorial experimental design was used to describe the conversion of alcohol, the yield and the selectivity of secondary amine as a function of strong parameters, i.e. the reaction temperature, space velocity and NHs/i-butanol molar ratio. Diisobutylamine was obtained with 72% yield at 92% conversion and reaction parameters P=13 bar, T=240°C, WHSV=1 g/g h, and molar ratios NH3/iBuOH= 1.7, H2/NH3= 1.9. 

Reductive Amination of Isohutanol to Diisohutylamine on Vanadium Modified... 

Another typical application is the creation of sensors. Vanadium modified silica, according to reaction (D), yields a very useful compound for the visual control of humidity in gas media.19... 

Periodic mesoporous vanadium modified silicates (V-MCM-41 and V-HMS) were synthesized, characterized and tested in our laboratory [93,141,172-174], V-MCM-41 samples were prepared hydrotheimally at 373 K using Cab-O-Sil fumed silica, vanadyl sulfate and dodecyltrimethylammonium bromide [172]. The preparation of V-HMS was carried out at room temperature in the presence of dodecylamine as template [173,174]. 

The horohydride reduction of a nickel salt solution containing small amounts of other metal salts can lead to co-reduced mixed metal borides that frequently have enhanced catalytic properties when compared to the unmodified nickel boride. The presence of about 2% chromium significantly increased the activity of a P-1 nickel boride toward aldehyde hydrogenation. Molybdenum, tungsten and vanadium modifiers were somewhat less effective than chromium while the presence of a small amount of cobalt had an inhibiting effect on the reaction.22 As the data in Fig. 12.2 show, the amount of chromium responsible for optimum P-1 nickel boride activity depends on the substrate being hydrogenated.39... 

Conversion and selectivity data obtained in the alkylation of ammonia with n-propanol over different Raney nickel catalysts are listed in Table 1. Data given in Table 1 indicate that n-Pr2NH can be obatined on unmodified and vanadium modified Raney nickel catalyst with 70-72 % selectivities at 92-95 % conversions. Upon modifying the Raney nickel catalyst with Mg the selectivity of the secondary amine increased to 74-75 % at 94-97 % conversions. The increase of the reaction temperature from 225 to 245 resulted in slight increase of the conversion and the selectivity to the primary amine both on unmoified and Mg modified catalysts. The introduction of V or Mg modifiers affected both the selectivity of the secondary amine and the ratio of primary to tertiary amines. 

Effect of NH3/n-PrOH molar ratio on the selectivities in the alkylation of ammonia with n-propanol over vanadium modified Raney nickel catalyst (T= 225 °C, WHSV=1.4 h" H2/NH3=3, conversion of n-PrOH=93-95 %). 

It is shown that the addition of vanadium led to a slight enhancement in the selectivity to MAA, both at 260C and at total IBA conversion, with respect to the Ki sample the formation of acetone and propylene decreased, while that of COx increas. However, the improvement in performance obtained by vanadium addition was low, if compared to that reported in literature for vanadium-modified heteropolycompoimds. 

Vanadium. V205-based catalysts have been widely used in industry for many catalytic processes including oxidation reactions under mild conditions. On the other hand, incorporation of metal ions exhibiting redox properties into an alnminophosphate framework with a well-defined system of pores and cavities offers an opportunity for the preparation of novel oxidation catalysts. In this context, vanadium-modified aluminophosphates seem to be promising materials. However, incorporation of vanadium in tetrahedral alnminophosphate frameworks has been for a long time a debatable issue. 

The catalytic activity measurements were effected on samples treated at 380 (300 C for sample VNaTiP) and 600°C in He or air flow, at different reaction temperatures. The results are reported in Fig. 4-6. The parent material a-TiP exhibits low activity, NO conversions being lower than 5% up to 300°C either for sample treated at 380 C or at 600°C, and reaching 15% at 400°C for sample treated at 600°C. By contrast high activity is shown by vanadium modified phosphates even with low vanadium content. NO conversion increases with vanadium loading whatever the atmosphere and temperature of pretreatment. All samples, after treatment either at 380 or 600°C were found very selective towards the N2 formation. The conversion to N2O was negligible at low temperature, and reached values of about 1-3% at 300-400 C, suggesting the occurrence of ammonia oxidation reactions (3, 10) in low extent. 

A. A. Teixeira-Neto, L. Marchese and H. O. Pastore, Vanadium-Modified Molecular Sieves Preparation, Characterization and Catalysis , Quim. Nova, 2009, 32, 463. 

Todorova, S., Parvulescu, V., Kadinov, G., Tenchev, K., Somacescu, S., and Su, B.L. (2008) Metal states in cobalt- and cobalt-vanadium-modified MCM-41 mesoporous silica catalysts and their activity in selective hydrocarbons oxidation. Microporous Mesoporous Mater., 113 (1-3), 22-30. 

Escanddn, L., Ordonez, S., Diez, E, et al. (2003). Methane Oxidation over Vanadium-modified Pd/Al203 Catalysts, Catal. Today, 78, pp. 191-196. 

Carbon content is usually about 0.15% but may be higher in bolting steels and hot-work die steels. Molybdenum content is usually between 0.5 and 1.5% it increases creep—mpture strength and prevents temper embrittlement at the higher chromium contents. In the modified steels, siUcon is added to improve oxidation resistance, titanium and vanadium to stabilize the carbides to higher temperatures, and nickel to reduce notch sensitivity. Most of the chromium—molybdenum steels are used in the aimealed or in the normalized and tempered condition some of the modified grades have better properties in the quench and tempered condition. 

Benzene-Based Catalyst Technology. The catalyst used for the conversion of ben2ene to maleic anhydride consists of supported vanadium oxide [11099-11-9]. The support is an inert oxide such as kieselguhr, alumina [1344-28-17, or sUica, and is of low surface area (142). Supports with higher surface area adversely affect conversion of benzene to maleic anhydride. The conversion of benzene to maleic anhydride is a less complex oxidation than the conversion of butane, so higher catalyst selectivities are obtained. The vanadium oxide on the surface of the support is often modified with molybdenum oxides. There is approximately 70% vanadium oxide and 30% molybdenum oxide [11098-99-0] in the active phase for these fixed-bed catalysts (143). The molybdenum oxide is thought to form either a soUd solution or compound oxide with the vanadium oxide and result in a more active catalyst (142). 

The anhydride of 1,8-naphthalenedicarboxyHc acid is obtained in ca 95—116 wt % yield by the vapor-phase air-oxidation of acenaphthene at ca 330—450°C, using unsupported or supported vanadium oxide catalysts, with or without modifiers (96). 

Most catalysts for solution processes are either completely soluble or pseudo-homogeneous all their catalyst components are introduced into the reactor as Hquids but produce soHd catalysts when combined. The early Du Pont process employed a three-component catalyst consisting of titanium tetrachloride, vanadium oxytrichloride, and triisobutjlalurninum (80,81), whereas Dow used a mixture of titanium tetrachloride and triisobutylalurninum modified with ammonia (86,87). Because processes are intrinsically suitable for the use of soluble catalysts, they were the first to accommodate highly active metallocene catalysts. Other suitable catalyst systems include heterogeneous catalysts (such as chromium-based catalysts) as well as supported and unsupported Ziegler catalysts (88—90). 

In the calciaation process, a mixture of corresponding oxides and an optional modifier, eg, molybdic acid, are milled together to achieve a homogenous mixture. The mixture is calciaed at 750—950°C and milled to a desired particle size. Wet milling ia an alkaline medium is recommended to remove any unreacted vanadium salts that ate beheved to degrade the pigmentary properties of bismuth vanadate (39). 

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

Minor uses of vanadium chemicals are preparation of vanadium metal from refined pentoxide or vanadium tetrachloride Hquid-phase organic oxidation reactions, eg, production of aniline black dyes for textile use and printing inks color modifiers in mercury-vapor lamps vanadyl fatty acids as driers in paints and varnish and ammonium or sodium vanadates as corrosion inhibitors in flue-gas scmbbers. 

CHARACTERISTICS OF SORPTION OF MOFYBDENUM, TUNGSTEN AND VANADIUM ON CHEMICAEEY MODIFIED... 

Other catalyst systems such as iron V2O5-P2O5 over silica alumina are used for the oxidation. In the Monsanto process (Figure 6-4), n-butane and air are fed to a multitube fixed-bed reactor, which is cooled with molten salt. The catalyst used is a proprietary modified vanadium oxide. The exit gas stream is cooled, and crude maleic anhydride is absorbed then recovered from the solvent in the stripper. Maleic anhydride is further purified using a proprietary solvent purification system. ... 

A thin layer deposited between the electrode and the charge transport material can be used to modify the injection process. Some of these arc (relatively poor) conductors and should be viewed as electrode materials in their own right, for example the polymers polyaniline (PAni) [81-83] and polyethylenedioxythiophene (PEDT or PEDOT) [83, 841 heavily doped with anions to be intrinsically conducting. They have work functions of approximately 5.0 cV [75] and therefore are used as anode materials, typically on top of 1TO, which is present to provide lateral conductivity. Thin layers of transition metal oxide on ITO have also been shown [74J to have better injection properties than ITO itself. Again these materials (oxides of ruthenium, molybdenum or vanadium) have high work functions, but because of their low conductivity cannot be used alone as the electrode. 

Reducing the amount of vanadium and sodium deposits formed through the use of slag modifiers can also effect good control of acid corrosion by S03. Vanadium and sodium deposits form low-melting-point slags and are a major contributor to the formation of S03. 

By modifying the catalyst with a so-called promoter (in this case vanadium oxide) it is possible to largely eliminate the intermediate. As Fig. 2.6 shows, the rate constant of the reaction from the hydroxylamine to the amine is much larger when the promoted catalyst is used, and thus the intermediate reacts instantaneously, resulting in a safer and environmentally friendlier process. 

The process has been commercially implemented in Japan since 1977 [1] and a decade later in the U.S., Germany and Austria. The catalysts are based on a support material (titanium oxide in the anatase form), the active components (oxides of vanadium, tungsten and, in some cases, of molybdenum) and modifiers, dopants and additives to improve the performance, especially stability. The catalyst is then deposited over a structured support based on a ceramic or metallic honeycomb and plate-type structure on which a washcoat is then deposited. The honeycomb form usually is an extruded ceramic with the catalyst either incorporated throughout the stmcture (homogeneous) or coated on the substrate. In the plate geometry, the support material is generally coated with the catalyst. 

Orvig, C. Thompson, K. Cam, M. McNeil, J. Vanadium Compounds as Possible Insulin Modifiers In Uses of... 

Three preparations are described using the molybdenum complexes as representative examples. These can be modified as noted below to give the vanadium, chromium, and tungsten analogs.5... 

In the NO-SCR by NH3, we note the highest reduction activity and selectivity on catalyst containing both vanadium and molybdenum than catalysts issued containing Mo or V, only. Furthermore, it should be underlined that a higher efficiency is obtained with ZSM-5 as host structure than samples issued from USY and MOR. Where a higher loss of porous volume were observed. On the basis of characterization data it has been suggested that the observed synergism in the SCR reaction is related to the existence of electronic interaction between the V and Mo species. In particular, it has been proposed that the presence of such electronic interactions modifies the catalysts redox properties, which have been claimed an essential property in the NO-SCR by NH3 reaction. 

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