Silica Cabosil

Ti-ZSM-48 was prepared by the dissolved titanium method using fumed silica (Cabosil), TBOT, H202, and diaminooctane (309-310). Ti-ZSM-48 was also prepared using hexamethonium hydroxide base and by the pre-hydrolysis method (311). 

This tethered ferrocenyl-based Pd complex on MCM-41 (17) was then used for the catalytic amination reaction between cinnamyl acetate and benzylamine (40 °C, THF) [59]. In this case, confinement of the catalyst results in profound changes in regio- and enantioselectivity. When the homogeneous equivalent is used to catalyze the reaction, the straight chained derivative is the sole product. Similar results (only 2% of the branched product) were obtained when the catalyst was tethered to the surface of the non-porous silica Cabosil. When tethered inside the pores of MCM-41 a major change occurred in that now the branched product accounts for about 50% and a change in e.e. from 49% e.e. when anchored to the Cabosil support to +99% when anchored inside the MCM-41 pore could be observed. If the catalyst s chirality was reversed in the MCM-41 immobihzed case, so was the chirality of the product (measured at 93% e.e.) [60]. 

The incorporation of TiIV into a zeolite having the structure of ZSM-48 has resulted from the use of fumed silica (Cabosil), TBOT, H202, and diamino-octane. The titanium alkoxide is transformed into a titanium peroxo compound and added to a suspension of Si02 in diaminooctane. Crystallization for 10 days at 448 K in rotated autoclaves produced Ti-ZSM-48 (Serrano et al., 1992). The synthesis of Ti-ZSM-48 has also been obtained by using the base hexamethon-ium hydroxide [(CH3)3NCH2(CH2)4CH2N(CH3)3(OH)2] (Section III.C). 

Starting materials for the direct synthesis of (Si,B)-ZSM-5 were fumed silica (Cabosil), tetrapropylammonium bromide (TPA-Br), ammonium fluoride and orthoboric acid (16). The source of silica was mixed with TPA-Br and water and then a mixed solution of NH4F and H3BO3 was added under vigorous stirring. The resultant gel was homogenized for 1.5 h and transferred into a Teflon-lined stainless steel autoclave which was then heated at 200°C for 17 days. Zeolite crystals were washed, dried at 60°C and hydrated in a desiccator. 

In these experiments, nickel hydroxide was mixed in a proportion of 12.4% with finely divided silica (Cabosil), pressed in a die and dehydrated at 200°, under vacuum, in the infrared analysis cell. Composition of the sample was therefore different from the composition of the samples used in the gravimetric or calorimetric work [NiO(200°)] and possible effects of the support cannot be, a priori, completely excluded. Calorimetric experiments with the supported samples have shown, however, that their reactivity toward CO is very similar to the reactivity ofNiO(200°). 

This result suggests that, for this family of structures at least, the value of 1.6 mL g 1 provides sufficient weakness to allow total breakdown and full access to all of the catalyst surface. This inference is also supported by a comparison of results obtained with the best commercial silica gels and with a pyrogenic or "fumed silica (Cabosil) formed by flame hydrolysis of SiCl4. The latter has no pore structure, and no such structural limitations. That the two exhibit similar activities indicates that the silica gel had disintegrated to the level at which nearly all of the surface contributed to the polymerization. Furthermore, once friability of the solid is obtained because the pore volume is sufficiently high, activity can still be influenced by the surface area. However, these are only general trends, and some small exceptions are evident in the data in the table as well. It is the structure itself, rather than any porosity measurement, that determines friability. 

The first polyurethane obtained by FP has been derived by the reaction between 1,6-hexamethylene diisocyanate (HDI) and ethylene glycol (EG) in the presence of dibutyltin dilaurate (DBTDL) as a catalyst, and pyrocatechol as an additive necessary for ensuring a sufficiently long pot-life (25). Indeed, if this latter compound is not present, instantaneous SP occurs. Furthermore, fingering was avoided by adding 3 wt.-% fumed silica (Cabosil ) to the above components dissolved in 18 wt.-% dimethylsulfoxide (DMSO). 

When two V/Si02 catalysts of 1 and 10 wt% V205 were tested for butane oxidation, the data in Table IX were obtained. The data show that the lower loading sample was much more selective than the higher loading sample. This difference was not due to the effect of impurities in the support because the data were obtained on an acid-washed Davison 62 silica which contained less than 10 ppm of Na and 200 ppm of Ca. The same effect was observed on catalysts prepared with Cabosil silica, which contained no detectable impurities. 

The details of the sample preparation and studies of the nature of the supported-metal samples have been described in a paper dealing with the effect of surface coverage on the spectra of carbon monoxide chemisorbed on platinum, nickel, and palladium (1). The samples consist of small particles of metal dispersed on a nonporous silica which is produced commercially under the names Cabosil or Aerosil.f This type of silica is suitable as a support because it is relatively inert and has a small particle size (150-200 A.). The small particle size is important because it reduces the amount of radiation which is lost by scattering. A nonporous small particle form of gamma-alumina, known as Alon-C, is also available. This material is not so inert as the silica and will react with gases such as CO and CO2 at elevated temperatures. 

The reactants tin(IV) chloride, alkali-metal base, and colloidal silica (Ludox-HS40) were thoroughly mixed at room temperature, according to the ratios 2-5M20 Sn02 4-10SiO2 8O-IOOH2O, for each synthesis [47], Cabosil (fumed silica) and sodium stannate were also used as reactants. 

The silicas made by this process are commonly known by their trademarks, AerosiT produced by Degussa in Europe, and Cabosil produced by Cabot in America. 

Colloidal silica (Aerosil , Cabosil ) Glidant 0.1-0.2 Excellent glidant... 

A finely divided non-porous silica is produced by the flame hydrolysis of SiCl4. The resulting material, known as Cabosil or Aerosil is produced as 5-40 nm particles with surface areas between 50 and 400 m /g. This method of preparation produces a very pure form of silica that is frequently favored for basic research. ... 

PZC/IEP of Cabosils/Silicas from Cabot (Type Not Specified)... 

Alumina and silica supported MnC>2 catafysts were prepared by inc ient wetness impregnation of supports (Degussa, Atuminoxide C and Cabosil L-90) using manganese acetate (Aldrich) as the precursor and were calcined in air at 773 K for 3 h prior to use. The crystal phases of MnC>2 in the catalysts were identified using X-ray diffraction (XRD) and their surface areas were determined by Nz physisorption u g the BET method. 

Such second-order splitting was also reported for CH on silica gel, PVG, and Cabosil (43). Simulation showed the 1 2 relative intensities predicted when linewldth and separation were considered. It was also shown that the line-width varied considerably with surface coverage by the CH I. (See Table 3). 

The absence of Me on non-porous Cabosil (31) further suggested that a pore structure was responsible for the strongly adsorbed CH I. (2) The high temperature treated silica gel enhances the formation of siloxane bridges which results in electron deficient point defects. Such electron deficient sites are neutralized by radiolysis and accounts for the absence of Me on samples. 

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