Alkane Adsorption on Silica, Alumina and Silica-Alumina Catalysts

Abstract

A study has been made of the adsorption of some lower molecular weight alkanes by silica-alumina cracking catalysts and related materials. The adsorption measurements were carried out using both a volumetric procedure and a radiotracer technique. The latter was capable of measuring isobutane adsorptions as low as 10~5 6 cc.(STP)/g. The adsorptions on silica-alumina of propane and «-butane at 760 mm. and of isobutane at 760 and 4 mm. were investigated by use of the volumetric technique. Over the temperature range from 100 to 350°, the adsorptions were found to decrease continuously with increasing temperature up to the point at which incipient adsorbate decomposition occurred. In general, no traces of chemisorption could be detected by the use of this method. By application of the more sensitive radiotracer technique, it was found that silica-alumina, dried at 500°, chemisorbed about 0.003 cc.(STP)/g. of isobutane at 10 mm. and at 25 and 150°. Also, it appeared that both a reversible and irreversible chemisorption were involved. The former constituted about 80% of the total and was capable of exchanging with the gas phase isobutane. The latter required a combustion process to effect its removal from the surface. Both water, added back to the dried catalyst, and metal ions partially poisoned the silica-alumina with respect to isobutane chemisorption. Pure silica gel and pure alumina were found to chemisorb only about Vio as much isobutane as silica-alumina. Further, the adsorption on the silica was entirely reversible, while with alumina it was for the most part irreversible.

Reactivity screening of silica

“…However, measurements about the kinetics and dynamics of alkane adsorption on SiO 2 surfaces are mostly limited to early measurements of thermodynamic properties (e.g. compressibility, liquid-gas transitions critical parameters) at large pressures on microporous silica gels [14][15][16][17] and powders, [18] as well as recent studies on the liquid-silica interface [19]. Single-crystal silica surfaces are conveniently used as supports to grow a variety of nanostructures such as nanotubes, [20,21] model array catalysts, [22,23] and metal-on-support model catalysts [24,25].…”

Adsorption and separation of linear and branched alkanes on carbon nanotube bundles from configurational-bias Monte Carlo simulation

“…[4][5][6] Over years, numerous experimental studies have been carried out on the adsorption and separation of alkanes on various types of adsorbents. Maciver et al 7 measured the adsorption of lower molecular weight alkanes ͑C 3 , nC 4 and iC 4 ͒ on silica, alumina, and silica-alumina cracking catalysts over the temperature range from 25°to 350°C, and observed physisorption accompanied by chemisorption. Bruce et al 8 determined the gas-solid second virial coefficients for the normal C 3 ,C 4 ,C 5 , and C 6 alkanes on Carbopack C and C-HT in the temperature range of 323 to 471 K, and found that the gassolid adsorption energy has a linear correlation with the boiling point and with the ratio of critical temperature to the square root of the critical pressure.…”

Contact angles and transition regions in soap films

“…The difference between yt and 2 0 can be interpreted as the free energy of interaction per square centimeter of the equilibrium film, i.e., the nongravitational work done in bringing the surfaces from infinity to their equilibrium separation. Hence -AF = 2 0 -yt = 2 0(1 -cos 0) (5) The values of AF for 0.2% NaCi0SO4 + NaCl are given in the last column of Table I. It thus appears that contact angle measurements can give important new information on thin liquid films, A few observations that were made in the course of these experiments are worth mentioning, although they were not studied in any detail.…”