Alumina: also

Hydrogenation of Acetylenes. Complete hydrogenation of acetylenes to the corresponding alkanes, which maybe requited to remove acetylenic species from a mixture, or as a part of a multistep synthesis, may be accompHshed using <5 wt % palladium or platinum on alumina in a nonreactive solvent under very mild conditions, ie, <100°C, <1 MPa (10 atm). Platinum is preferred in those cases where it is desired to avoid isomeri2ation of the intermediate olefin. Silver on alumina also can be used in this appHcation as can unsupported platinum metal. 

Purified by careful fractional distn, followed by passage through neutral activated alumina. Also by shaking with mercury, drying with K2CO3 and distn. from CaS04. 

One important factor to consider in the preparation of the organic phase is the presence of inhibitors in the monomers. Some formulae call for the removal of inhibitors, primarily TCB, from the monomers. The TCB inhibitor forms highly colored complexes with metallic salts rendering the final product colored. Styrene has about 50 ppm of TCB. DVB, being more reactive, contains about 1000 ppm of TCB. There are several options for the removal of inhibitors. Columns packed with DOWEX MSA-1 or DOWEX 11 ion-exchange resins (Dow Chemical Company) can be used. White drierite or activated alumina also works well. 

From an acid chloride t-BuOH, AgCN, benzene, 20-80°, 60-100% yield.Alumina also promotes the conversion of an acid chloride to a t-Bu ester in 79-96% yield. ... 

In figure 5 spectra are presented for a Pt-Re catalyst that has just been dried at 120°C (curve 1) and the same catalyst after reducing at 400°C for 18 hours (curve 2). The potassium containing alumina also shows the weak, interferring peak (curve 3, noisy because of a limited number of scans). 

Further dehydration of boehmite at 600 0 produces y-alumina, whose spectrum is shown in Figure 3b. There is a loss in surface area in going from boehmite to y-alumina. The sample shown here has a surface area of 234 m /g (this sample was obtained from Harshaw A23945 the calcined Kaiser substrate gave an identical infrared spectrum). The y-alumina sample shows two major differences from o-alumina. First, there is a more intense broad absorption band at 3400 cm" due to adsorbed water on the y-alumina. Second, the y-alumina does not show splitting of the phonon bands between 400 and 500 cm" as was observed for o-alumina. The y-alumina is a more amorphous structure and has much smaller crystallites so the phonon band is broader. The y-alumina also shows three features at 1648, 1516 and 1392 cm" due to adsorbed water and carbonate. 

While the most reactive Mg was produced using the lithium reduction procedure in the presence of alumina, the presently preferred method is entry 11. Though not as reactive as 10, it is more reproducible. The procedures which do not employ alumina also extend equipment life and are thus safer. 

The Lewis base sites of the aluminas also participate in the dehydration of primary and secondary alcohols by the removal of a proton from either the j8- or y-carbon atom in relation to the a carbon containing the hydroxyl group. 

The efficient and selective catalysis of some Diels-Alder reactions by lanthanide P-diketonate complexes has been known since 1975 [226, 227]. The fluorinated p-diketonate complexes Ln(fod)3 (cf. Scheme 12.5) selectively catalyze the Danishefsky transformation (Scheme 12.23) as a consequence of their mild Lewis acidity. Importantly, zeolites and Lewis acid modified silica or alumina also catalyze Diels-Alder reactions [228-232]. 

Also for this reaction, namely esterification plus transesterification, mixed oxides, this time acidic in nature, appear to be the most promising alternative. Tungstated zirconia-alumina (WZA), sulfated zirconia-alumina and sulfated tin oxide were shown to be active in the transesterification of soybean oil with methanol at 200-300 °C and in the esterification of n-octanoic acid with methanol at 175-200 °C. Although the order of activities is different for the two reactions, WZA gives high conversions in both readions and it is stable under the reaction conditions [31]. Titania on zirconia, alumina on zirconia and zirconia on alumina also showed good performances [32, 6]. 

Alumina also has been used as a support for tri-n-butylammonium and tri-n-butylphosphonium ion catalysts 32 and 33, prepared by the same method used with silica gel U8>. 

Both alumina and silica gel are more stable physically than the common polystyrene supports. The alumina-bound catalysts are particularly promising because of their higher activity and higher selectivity compared with the silica gel-bound catalysts. Alumina also is stable in alkali. The alumina-bound catalysts 32 and 33 worked well for reaction of 1-bromooctane with concentrated aqueous sodium cyanide 118). 

Uydrate of potassa is a most valuable agent to the chemist, and especially in the estimation of the carbon of organic bodies. It is also used to displace metallic oxides from their combinations, ae a solvent for oxides or zino and alumina, also for the decomposition of silicioua minerals by fusion, for drying certain gases, and a variety of ether purposes. In surgery, it is used in the solid stata, cost into sticks, as a most powerful caustie. In medicine, its solution is also frequently employed, especially os an antacid. 

The alumina also serves the function of making the catalyst less expensive by diluting the metal. Because of the enormous commercial success of these catalysts, for over 50 years much of the scientific effort in understanding these catalysts was directed at the supported versions. This resulted in a... 

The Peri model of alumina also demonstrates that basic sites of various strength, consisting of oxygen atoms in various arrangements (isolated... 

Consider the battery in Fig. 7.18. The sodium beta alumina barrier allows sodium ions formed at the anode to Row across to the sulfur compartment, where, together with the reduction products of the sulfur, U forms a solution of sodium trisulfide in the sulfur. The latter is held at 300 CC to keep it molten. The sodium beta alumina also acts like an electronic insulator to prevent short circuits, and it is inert toward both sodium and sulfur. The reaction is reversible. At the present state of development, when compared with lead storage cells, batteries of this sort develop twice the power on a volume basis or four times the power on a weight basis. 

For the intermolecular version, strained alkenes such as norbomene give satisfactory results. Cyclopentenones are obtained in good yields by the reaction of alkyne Co complex with alkene in the presence of silica. Wet alumina also gives good... 

Silica-aluminas also develop reducing activity the reducing power of the corresponding donor sites increases with increasing A1 content (332). The OH ions are responsible for the reducing activity of HY zeolites after activation at around 250°C (555), whereas electronegative and electropositive sites are created at higher activation temperatures of around 650°C. 

Figure 2 shows the effectiveness of this procedure as a function of the preoxidation temperature. At 500°C preoxidation no difference is observed between either a He or H reduction. After a 600°C calcination the He reduction was less effective, especially for higher temperature peaks, and this difference was more pronounced after a 700°C calcination temperature. It is important to note that more than oxidation occurs at high temperatures, sintering of the Pt and dehydration of alumina also occur. However, it is not surprising that hard to reduce Pt occurs at the highest temperature of preoxidation. All these factors contribute to the change in the... 

Alumina also serves as the support for reagents effecting the epoxidation of alkenes efficiently under mild conditions. This is the case with triphenylsilyl hydroperoxide even aryl-substituted alkenes are eas-... 

Alumina also absorbs iron pentacarbonyl vapour to the extent of about 25% by weight. If the alumina containing the absorbed pentacarbonyl is exposed to sunlight, it becomes red in colour and the theoretical quantity of carbon monoxide in the absorbed iron pentacarbonyl is evolved (Dewar). 

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