Silica acidity

Figure 1. IR spectra of a silica acid substrate before and after silylation with CH3Si(OC2H5)3...

Aliphatic alcohols silica acids water chloroform-CCLt... 

Steroids silica acids methanol/water benzene-chloroform... 

These rate differences show that, over platinum on silica-alumina, two cyclization reactions occur simultaneously. One is catalyzed by the platinum metal it is the mechanism observed over platinum on silica. Acid catalyzed self-alkylation is the second reaction. The following steps are involved. 

The acid-base properties of polymers, fillers and silane additives, as described by Fowkes [14] can be used to predict the effect of silanes on the dispersion of fillers in polymer, and viscosity of the mix. In general, opposites attract (give good dispersion) while like materials repel (poor dispersion) [15]. The effect of cationic silane (Z-6032) on the dispersion of silica (acidic filler) in this particular unsaturated polyester resin (acidic polymer) is shown in Table 6. Addition of Z-6032 in increments to a silica-filled polyester resin lowered the viscosity of the mixture to a minimum at about 0.4% silane based on the filler. 

Octadecyl -silica Acidic potassium phosphate Fluores- cence Recovery 93.9 7.6%... 

Ammonia solution Gelatinous precipitate of silica acid... 

Drinking water (CDDs) Addition of 13C-labeled CDD internal standards extraction with organic solvent volume reduction clean-up on multiple columns of silica gel/basic silica/acidic silica, AgN03-siiica/basic alumina, and HPLC HRGC/LRMS (SIM) HRGC/MS/MS (SIM) No data No data McCurvin et al. 1989... 

Wipe and liquid samples from pyrolized transformer oil (CDDs) Extraction with organic solvent clean-up on neutral silica/basic silica/acidic silica column clean-up and fractionation by sequential chromatography on basic alumina, carbon/silica gel, and Sepralyte columns HRGC/HRMS No data 58-151 (wipe) 51-136 (liquid) Hardin et al. 1989 (ASME method)... 

As an example of a unimolecular decomposition reaction, we study the monomolecular catalytic cracking reaction of //-paraffins in high-silica acid zeolites or other crystalline or ordered acid porous materials, in this section [97-102],... 

Capsuies/tablets HPLC Grind,ultrasonicate Silica acid-P04 5 mA/P04, pH 254 nm [204] Resolved aspirin. [178... 

The hydrolysis can be acid- or base-catalyzed. In the case of silica, acid-catalyzed hydrolysis results in sols with weakly-branched polymers that lead to final products having smaller pores while base-catalyzed hydrolysis produces particulate sols and final porous bodies showing larger pores [Brinker ct al.. 1982 Shafer ct al.. 1987]. 

Sample preparation. Sulfabromomethazine added to tissue as an internal standard, extraction with water, centrifugation, and cleanup and concentration by a series of solid phase extractions using C-18 bonded silica, acidic alumina, and AG MP-1 anion exchange microcolumns. 

Giesche, H. and Matijevic, E., Well-defined pigments I. Monodispersed silica-acid dyes systems. Dyes Pigm., 17, 323, 1991. 

The corrosion resistance of enamel is generally attributed to a surface layer of silica. Acid first dissolves the surface alkali oxide leaving a hydrated porous layer which is mainly silica, that acts as a barrier through which corrosive agents must difiltse for further attack to occur. As the affected layer deepens, the diffusion process slows down so that the enamel becomes protected by a skin of acid resisting silica. 

That dechlorinations w re accelerated by the ZV-metal particles was demonstrated by replacing the metal particles with silica (acid washed sea sand). For the silica column operated under dechlorinating conditions that had been optimal for ZV metal (400 C, 31.0 MPa), the recovery of organically bound chlorine from the eluate was virtually quantitative. In further trials, acetone-hexane extract of a sandy loam soil (spiked with 600 ppm Aroclor 1254) was fed to the reactor at 0.1 mLymin and dechlorinated efficiently. Chlorinated residues were not detected in the reactor effluent by GC-MS. More importantly, soil co-extractives in the PCB solution did not seem to affect the course or the efficiency of the reaction perceptibly. 

Chem. Descrip. Blend of liq. hydrocarbons, hydrophobic silica acid, syn. 

Silica acid. See Silica, hydrated Silica aerogel. See Silica gel... 

CAS 1343-98-2 EINECS/ELINCS 215-683-2 Synonyms Hydrated silica (INCI) Hydrosilicic acid Polyorthosilicic acid Polysilicic acid Precipitated silica Silica acid Silic acid (polyortho) Silica hydrate Silica, precipitated Silicic acid Silicic acid hydrate Si-... 

Note from these tables that all pretreatments significantly reduce the ash content of the raw biomass on a weight percentage basis (12 to 37%). The ash that remains is insoluble in acid and is assumed to be mainly silica. Acid hydrolysis shows the smallest reduction in ash content of the three pretreatments. In fact, acid hydrolysis is probably very efficient in removing alkali but it also removes carbohydrate from the feedstock in the form of pentose sugar hydrolyzed from hemicellulose. In this case, the percentage change in ash... 

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