Alumina additives

An enamine was obtained in the synthesis of coronaridine (648) by aluminum hydride reduction of a bridged lactam, followed by dehydration on alumina. Additional examples of enamine formation by reduction of enamides (649) and thioenamides (650) were reported. 

Purification of 1,2-dibromoethane was accomplished by passing a small quantity rapidly through a 5-cm. column of alumina. Addition of 1,2-dibromoethane to the lithium dispersion is accompanied by visible evolution of ethylene (ethene). 

Table V. Pilot Plant Deactivation of Cerium/Alumina Additive...

Silica is known to be volatile in steam (39-40). For instance, the equilibrium concentration of silica in steam at 1 atmosphere from 1200 to 1450 F has been found to range from 0.2 to 0.5 ppm (by weight) showing that the availability of silica in the vapor phase can be substantial under the conditions used in our work. Unfortunately, we cannot predict how much silica will be transferred in our experiments since the rates of either hydrolysis or adsorption on the cerium on alumina additive are unknown. 

Steam Stability. Steam stability of SOx removal agents is strongly affected by temperature. We have seen previously that at 1350 F deactivation of cerium/alumina additive, caused by silica poisoning, was influenced by how long the additive was steamed and whether the additive was steamed in the presence or absence of cracking catalyst. These results were extended to other temperatures. 

Two sets of experiments were made to show the effect of steaming temperature on stability. In the first set, steaming was done non-interactively. Cerium/alumina additive was steamed (100% steam, 1 atm) for 5 hours in a fixed bed from 1200 to 1450 F. SO2 removal ability was then measured on these steamed samples diluted with cracking catalyst. The data in Figure 14 show that, for steamings done separate from cracking catalyst, losses of SO2 removal ability are small but become more pronounced above 1350 F. 

Losses incurred in the non-interactive steamings, however, were lower than those found in the second set of experiments where the cerium/alumina additive was steamed together with a low alumina cracking catalyst at various temperatures. The results from this second set of experiments, shown in Figure 14, indicate that losses are important at temperatures above 1200 F. It should be noted that SO2 removal ability was measured under the same conditions in both sets of experiments. Also, these fixed bed steaming seem to be harsher than fluidized bed steamings because the losses incurred are greater. 

Ellen, Y.S. etal. (1998), Microstructural design of silicon nitride with improved fracture toughness II, Effects of yttria and alumina additives , J. Am. Ceram. Soc., 81(11), 2831-40. 

Powders of undoped y-alumina fired at 1000°C had a specific surface area close to 100 m /g. Addition of 6 mol-% La reduced the surface area with about 20%, while the reduction is about twice as large with a 9 mol-% lanthanum addition. For all these materials the surface area showed an increase after SASRA treatment at 600°C. The increase was largest for 9 mol-% La addition and smallest for pure y-alumina. Addition of MAP reduced the surface area significantly, and opposite to the previous observations, the SASRA treatment gave a further reduction. The remarkable effect of MAP in reduction of surface area is possibly due to the formation of some reaction products of the MAP with the y-alumina. 

The monosubstituted vinylidene complexes are readily deprotonated with a variety of mild bases (e.g., MeO-, C032 ), and this reaction constitutes the most convenient route to ruthenium acetylide complexes. Experimentally the deprotonation is most easily achieved by passing the vinylidene complex through basic alumina. Addition of a noncomplexing acid (e.g., HPF6) to the acetylide results in the reformation of the vinylidene complex [Eq. (66)]. Reaction of 1 and terminal alkynes such as phenylacetylene in methanol followed by the addition of an excess of... 

We believe the effect of alumina additives on catalyst slurry viscosity is associated with the surface reactivity of the additive. OH" is a catalyst for polymerization and Si-O-Si bonding of uncondensed silanols higher pH promotes conversion to a solid phase consisting of discrete silica particles (19). Ostermaier and Elliott (15) suggest that pH be carefully controlled at a value less than 3.5, or thickening occurs in the alumina-free reference formula. 

Figure 6. FCC attrition index vs particle size of CP alumina additive. ...

For a 125,000 ampere cell the metal production capacity is 810-910 kg/day. Normally, alumina additions are made to each cell at about four hourly intervals. However, if the alumina consumption in any one cell exceeds the addition rate and the alumina content of the electrolyte drops to about 2% alumina or less, there is a sudden rise in the cell operating voltage to about 50 V. This is caused by polarization of the anode from the near stationary film of carbon monoxide and carbon dioxide on its surface [1]. This situation, called the anode effect, is detected via a 50-60 V light wired in parallel to each cell in a multicell potline. Normal cell operating voltages are too low to cause bulb incandescence, but when an anode effect occurs the light of the affected pot comes on to alert the operators to correct the situation. 

The Al chemical shift shows a strong evolution upon alumina addition. The chemical shift increases with increasing the amount of alumina dissolved. No significant evolution were observed for the F and Na chemical shifts over the whole range of compositions. 

From these relations and the experimentally measured chemical shifts, it is possible to calculate the fractions of each oxofluoroaluminate species over the whole range of alumina additions. 

The interpretation of evolution of the chemical shift is more complex because of the presence of the different fluoroaluminate species in addition to the oxofluoroalumi-nate. In the simplest approach, it can be assumed that due to the relatively low alumina content, the relative proportions of the AlFx species in cryolite are not affected by alumina additions. The variation in the Al chemical shift, 5(A1), can then be expressed by the relation... 

An alumina addition to silica produces proton-active catalysts for cracking purposes. The selective adsorption of gases with proton affinity can be used to measure the surface area covered with protons 34). The aluminum ions seem to form a unimolecular layer on the surface of the silica 36). 

P. F. Becher, G. S. Painter, M. J. Lance, S. li, Y. Ikuhara, Direct observations of debonding of reinforcing grains in silicon nitride ceramics sintered with yttria plus alumina additives, J. Am. Ceram. Soc., 88, 1222-26 (2005). 

E. Y. Sun, P. F. Becher and K. P. Plucknett, Microstructural Design of Silicon Nitride with Improved Fracture Toughness II, Effects of Yttria and Alumina Additives , J. Am. Ceram. Yoc., 81, 1998,2831-2840. 

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