Fumed titania

Certain APIs are susceptible to oxidation, e.g., atorvastatin and cytidine nucleoside analogues. Fumed metal oxides (e.g., fumed silica, fumed titania, and fumed zirconia) can promote such oxidation reactions. These reactions are more complex in some ways, and less easy to predict. 

Fumed Titania from Chlorovinyl Another sample studied by the same research group in described in Section 3.1.39.1.1.20. 

Gunko, V.M. et al.. Structure of fumed titania and silica/titania and influence of the nature of surface sites on interaction with water, J. Colloid Interf. Sci., 188, 39, 1997. 

In addition to the reaction pathways of the previously discussed substrates, 4-chlorobenzaldehyde 1c can be hydrodehalogenated. Indeed, the main product obtained using the Pd catalysts on fumed titania was toluene 6c which is the hydrogenolysis product of 4-chlorotoluene 3c. No benzyl alcohol 2c was formed. Apart from about 50-60% of toluene, 4-chlorotoluene 3c, ether 4b and saturated aromatic ring product 5c are present in the range of between 5 and 30%. In this case, the different acidic properties of the Pd catalysts on fumed titania are of minor importance. The release of hydrogen chloride from the hydrodechlorination reaction compensates for the initial differences of the catalyst acidity. 

FIGURE 37.1 OPTPD spectra of water desorbed from (a) fumed silica A-300 and fumed titania (b) fumed silica/titania and CVD-Ti02/fumed Si02 and (c) fumed silica/alumina re-hydration (R) time is 0.5 h. 

These processes are very rapid and allow the preparation of inorganic supports in one step. This technique allows large-scale manufacturing of supports such as titania, fumed silica, and aluminas. Sometimes the properties of the material differ from the conventional preparation routes and make this approach unique. Multicomponent systems can be also prepared, either by multimetallic solutions or by using a two-nozzle system fed with monometallic solutions [22]. The as-prepared powder can be directly deposited onto substrates, and the process is termed combustion chemical vapor deposition [23]. 

Figure 9. Surface content of (a) A1 in fumed silica/alumina and (b) Ti in titania/silica and the maximum adsorption of (a) Pb(II) and (b) Ni(II) as a function of the total (a) alumina or (b) titania content in mixed oxides.

Figure 2. Optical spectra of (dimethylamino) azobenzene, DMAAB, adsorbed onto individual fumed alumina, silica A-300, and titania, and mixed oxides Si02/Ti02 (37 wt% Ti02), Al203/Si02 (30 wt% A1203) and Al203/Si02/Ti02 (22, 28, and 50 wt% res-pecttively).

Keywords fumed silica alumina/silica, titania/silica alumina/silica/titania Ni(II) Cd(II) Pb(II) polyethylene glycol) poly(vinyl alcohol) adsorption potentiometric titration surface charge density... 

Nanooxides such as fumed silica, titania, alumina, etc. (with spherical primary nanoparticles) are used as fillers for complex drugs, enterosorbents, vaccine adjuvants, food additives, etc.1,2 In general nonporous spherical nanoparticles can adsorb solutes in low amounts because the desolvation effect causes an... 

V. M. Gun ko, V. M. Bogatyrev, V. V. Turov, R. Leboda, J. Skubiszewska-Ziqba, L. V. Petrus, G. R. Yurchenko, O. I. Oranska, and V. A. Pokrovsky, Composite powders with titania grafted onto modified fumed silica, Powder Technology, submitted for publication. 

Abrasive particles are a key component in CMP slurry. The most commonly used abrasive particles include silica, alumina, ceria, zirconia, titania, and diamond. Table 21.1 listed a set of information on each type of abrasive particles such as density, microhardness, and isoelectric points (lEP). It is important to point out that the specific values for these properties depend highly on the preparation techniques and the specific states of the samples. The values listed in the table represent an average of the most commonly reported data. For example, the isoelectric point for silica is a function of the number of hydroxyl groups, type and level of adsorbed species, metal impurity in the solid matrix, and the treatment history of the materials [1]. There are three major types of silica according to their preparation methods fumed, colloidal, and precipitated. The common sources for obtaining these abrasive particles are listed in Table 21.2. As examples, some of the more specific information on... 

Periodic nanoporous silicates have been prepared in a wide variety of conditions. Different sources of molecular, and non molecular silica have been used. This includes TEOS, TMOS, fumed, colloidal and precipitated silicas. Depending on the synthesis conditions, particularly on the nature of the silica source, crystallization may take place in seconds at subambient temperatures [82], or at room temperature [60,61,69,72,83]. However, in most cases the crystallization temperature was set in the 80 - 120 °C range. Liu et al. [84,85] found that the use of small amounts of colloidal particles (silica or titania) promotes the formation of ordered structures by providing nucleation seeds. The pH conditions varied from extremely acidic [60,61], to neutral [69,72] to very basic [48,49]. Ryoo and Kim [86]... 

A process called flame combustion synthesis is widely used to manufacture catalysts containing carbon black, fumed silica, or titania [277-279]. 

Thus, the addition of small amount (0.5-2 wt.%) of highly disperse (fumed) modified titania, Ti02/Si02 or silica allows us to improve the adhesion properties... 

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