Silica gel, Davison

In Fig. 16 is shown an experimental resonance absorption recorder curve of the above-mentioned protons. This signal is from a Davison silica gel (SG) with a BET surface area of 687 meterVgram, dehydrated in vacuum at 500°. The width between points of maximum slope of this resonance is 310 milligauss and the corresponding spin-spin relaxation time is 1.8 X 10 ... 

Davison silica gel grade 22, impregnated with Ni(NOs)2 solution. 

Figure 1. Adsorption isotherms at 0 and 25 C. for ozone in oxygen on Davison silica gel...

W.R. Grace Co., Davison Silica Gels, Davison Chemical Division, Baltimore, MD, 1996. 

Figure 1 also shows the pure water vapour adsorption isotherms on UOP 13X zeolite and a sample of Davison silica gel at 30°C. These data were measured at Air Products laboratories. They are, respectively, type I and IV in shape. The zeolite adsorbs water very strongly (very high capacity at low x). The water adsorption capacities of the silica gel is comparable to those of the aluminas at low x but it exhibits higher water adsorption... 

Syloid . [Wit. Grace/Davison] Silica gels bonding agent for adhesives. 

The hydrocarbons were extracted by passing 100 mL diethyl ether through the columns over a period of about 15 min. The ether extracts were dried with anhydrous sodium sulfate overnight, and then they were evaporated in a conical tube under a stream of dry nitrogen to 2 mL without external heating. One mL hexane was added, and the sample evaporated to 1 mL. The extracted hydrocarbons were separated into saturate and aromatic types using a modification of a procedure described by Warner (19) and employed in these laboratories for sediment analysis (20). Fifteen grams of Davison silica gel (100-200 mesh) in a Chroma-flex column were washed with 30 mL methylene chloride, then 40 mL hexane. The 1-mL sample was first eluted with 40 mL hexane to obtain the saturate fraction, and then with 86 mL 20% methylene chloride in hexane to obtain the aromatic fraction. Each fraction was evaporated to 1 mL then 1 mL of internal standard was added and the sample reevaporated to 1 mL and analyzed by GC. A 20-/i,g/mL solution of 2,6,10-trimethyldodecane in hexane was used for the saturate internal standard and a solution of 20/ig/mL hexamethyl-benzene was used for the aromatics analysis. 

The high area small pore silica xerogel used in these studies is manufactured by the Davison Chemical Corporation and is labeled Davison Silica Gel 12966-120. It has a silica content of 99.7% on the dry basis. 

The silica-magnesia catalysts, DA-5 and Nalco, in the virgin state, along with Davison silica gel have practically their entire area and pore volume contributed by the very smallest of pores that are encountered in catalyst structures that is, pores in the 10 to 15 A. radius range. It is apparent in Fig. 2 that for these materials there is no appreciable adsorption at the high relative pressures. This indicates the absence of large pores. One and one-half monolayers according to the BET theory effectively fill the pore volume of the DA-5 and the Davison silica gel, and only two monolayers are required for Nalco. Very little hysteresis is observed for any of these three materials. 

Davison silica gel is an excellent example of a high area small pore xerogel structure. Its adsorption isotherm is a Type I curve according... 

In preliminary steam sintering experiments with Davison silica gel it appears that sintering is accelerated considerably by the presence of steam at atmospheric pressure. Furthermore, there is a small but significant increase in pore radius. The small hysteresis loop that almost disappears on vacuum sintering is apparently maintained or perhaps slightly broadened on sintering in steam. Detailed data must await the completion of the steam series. 

These flow rates give a hydrogen-to-hydrocarbon mole ratio of 4 1. The reactant is Philhps Pure Grade cyclohexane. It is purified by passing 1 vol. of cyclohexane through 3 vol. of Davison silica gel at a rate of approximately 5 cc./min. to remove polar compounds which inhibit the catalytic reactions. The liquid product is collected by three successive condensers at 20°, ice, and hquid-N2 temperatures. The accumulated condensate from 20 min. of operation is pooled and the resulting samples analyzed for benzene by mass spectrometer. 

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