Aluminum activity

The reaction conditions of example 1 were repeated using a different hydrocarbyl aluminum activator in a 4 1 molar ratio to chromium(III) tris(bis(trimethylsilyl)-amide). Reactions were conducted at an ethylene pressure of 100 psi at 70°C for 60 minutes. Neither 1-butene nor 1-decene was detected in the product mixture. A summary of reaction scooping is provided in Table 1. 

As for the fate of butyl bromide, 1.1 mmole of a gaseous product was evolved for the reaction of the starting material (4.6 mmole) after 12 min of milling. The main component of that gas was butane. Butene was a minor product. The residue was a viscous and dark brown material. Bromide ion (4.6 equivalents) was detected in the residue. The residue was a mixture of aluminum bromide and a polymerized matter. The reaction with aluminum activated by vibromilling may be described with these equations ... 

Vacuum Activated carbon Aluminum Activated carbon Separator Activated carbon Aluminum Activated carbon Separator... 

Munns, D.N., Helyar, K.R., and Conyers, M., Determination of aluminum activity from measurements of fluoride in acid soil solutions, J. Soil Sci., 43, 441, 1992. 

To date, low volumes of materials have been produced commercially from norbomene and cyclo-octene. Numerous products are expected to result from the materitd produced by the ROMP of dicyclopentadiene in a RIM (reaction injection molding) process. In a RIM process, two streams of a monomer are mixed in the mold where it is polymerized to the final part. In this case, one of the monomer streams contains a tungsten complex while the second contains an alkyl aluminum activator. When the two streams of dicyclopentadiene are mixed, the metathesis catalyst is formed and the monomer is ROMP polymerized (equation 12). 

Here, M — iAl, is an aluminum-filled Si-O-Si-linked surface site, s equals the number of aluminum ions exchanged to create a surface precursor site, and A,- stands for the rth aqueous species involved in the formation of the precursor. The rate model described in Equation (21) predicts two types of behavior (Oelkers and Schott, 1995a) at low aluminum activity, rates are at a maximum and are independent of aqueous aluminum activity (or concentration), and at higher aluminum activity, fewer precursors are found on the mineral surface and the rate is slower and dependent on dissolved aluminum activity (or concentrations). As discussed later, these authors further argue that a region exists in which the rate is dependent also on an affinity term (Equation (66)). 

The alkali feldspar model of Equation (21) (Oelkers et al., 1994) differs from the anorthite model of Equation (24) (Oelkers and Schott, 1995b) in the assumed chemistry of the precursor for alkali feldspars, the precursor contains no aluminum (and thus dissolution depends on aluminum activity in solution) while for anorthite, the precursor contains aluminum (and therefore exhibits no dependence on aluminum activity in solution). In the first model, Al-H exchange occurs at the mineral surface, while in the second model H adsorption is the precursor to dissolution. These models have also been compared to glass dissolution for compositions ranging from albite to nepheline (Hamilton et al., 2001). 

Oelkers et al. (1994) and Schott and Oelkers (1995) suggested that dissolution rate of an aluminosilicate dissolving at low pH is best modeled using a modified version of Equations (21) or (25) that incorporates both aqueous aluminum activity and chemical affinity ... 

C-SiC has several potential shallow-level acceptors (p-type dopant) with aluminum (activation energy of 0.26 eV), gallium (activation energy of 0.344 eV), and boron (activation energy 0.735 eV). 

Figure 11. Predominant form of complex and ratio of free aluminum activity to total dissolved aluminum as a function of pH and fluoride activity...

Incompatibilities and Reactivities Ammonia, acetylene, acetaldehyde, powdered aluminum, active metals, liquid chlorine ... 

Multicomponent alloys of nickel and aluminum activated by Ti, Mo are most widespread and wide by used materials for hydrogen electrodes of low temperature alkaline fuel cells. To make hydrogen electrodes skeletal nickel prepared by alkali-soluble of alloy with composition 50 %Ni -i- 47 % A1 -i-3 % Ti is used. Raney catalyst is processed by 20 % suspense of Fluoroplast F-4 D with following drying in vacuum at 50 °C that permits pyrophoric catalyst to protect against self combustion and serves hydrophobic binder to form electrodes [5]. 

The pAl vs. pH curves at varying pSi developed from this empirical K value clearly showed the attenuating influence of silica on aluminum activity in acidic solutions. One becomes aware of the fact that nonideal solid solutions control the activity of A1 and Si in natural water. 

The synthesis of polystyrene with a liighly syndiotactic microstructure (Scheme 22.7) was achieved for the first time by Ishihara in 1986 with a catalyst consisting of a titanium precursor and aluminum activator. Roughly 98% of the polymer was insoluble in 2-butanone, and this material had an rrrr-pentad content greater that 98%. Many simple titanium catalysts activated by MAO were later shown to generate syndiotactic polystryrene. Tetrabenzyltitanium, when activated by MAO, catalyzes the polymerization of styrene to form a syndiotactic material with greater than 98% rr triads. Tetrahalo and tetraalkoxo titanium compounds also form syndiotactic polystryene when activated by MAO, but the activity of these catalysts was relatively low. 

Tactic PS. Isotactic (iPS) and syndiotactic (sPS) PSs can be obtained by the polymerization of styrene with stereospecific catalysts of the Ziegler-Natta-type. Aluminum-activated TiCls yields iPS while soluble Ti complexes [eg, ( j -CsHslTiCls] in combination with a partially hydrolyzed alkylaluminum [eg, methylalumoxane] yield sPS. The discovery of the sPS catalyst system was first reported in 1986 (33). As a result of the regular tactic structure, both iPS (phenyl groups cis) and sPS (phenyl groups alternating trans) are highly crystalline. Samples of iPS quenched from the melt are amorphous, but become... 

Ti(0-n-Bu)4 systems, the tacticity of the obtained polystyrene strongly depends on the support material (i.e., the presence of Cl in the carrier). When MgCh-supported Ti(0-n-Bu)4 is activated with MAO, the soluble part of the catalyst in toluene can afford sPS, whereas the insoluble part of the catalyst gives iPS. This is also true for the Ti(0- -Bu)4/Mg(0H)Cl system when activated with MAO. For Ti(0-n-Bu)4/Mg(OH)2/MAO, which has no Cl in the carrier, the insoluble part gives syndiotactic polystyrene, and the soluble part is almost inactive for styrene polymerization. For the TiCls (AA)/MAO-system (AA = aluminum-activated), iPS (95% mmmm pentad, melting point 221 °C) and sPS are obtained from the insoluble and soluble part of the catalyst respectively. ... 

The alkyl-aluminum activator is representative of a common choice, methyl aluminoxane, MAO, which is an ill-defined oligomer formed by... 

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