Condensation of Olefins on Clays. Gas-Solid Systems. Part I: Gravimetric Methods

Abstract

Abstract--The adsorption-condensation of olefins was studied on 7 adsorbents: 2 commercial clays, a natural clay and its protonated form, ~-alumina and porous and nonporous silicas. These adsorbents were characterized by X-ray diffraction (XRD), chemical analysis, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and determination of specific surface area measurement by the BET method. The experiments were carried out gravimetrically, in gas-or vapor-solid systems, at 25 ~ and on adsorbents dried at 120 ~ Adsorption-condensation of olefins are fast processes, diffusion controlled. Alumina and silicas adsorb olefins and paraffins only reversibly, but are unable to condense olefins. The water polarized by the countercations is the source of BrCnsted acid sites. When the gas phase is evacuated or swept with inert gas, the condensation terminates. On clays, paraffins are reversibly adsorbed but no condensation was observed.

Condensation of Olefins on Clays. Gas-Solid Systems. Part II: Spectroscopic Methods

“…The preliminary remarks formulated in Choren et al (1997) are now complemented with infrared evidence. CONCLUSIONS 1) Adsorption-condensations of olefins onto clays are fast processes, diffusion-controlled.…”

“…In Choren et al (1997), a gravimetric study of adsorption and condensation of light olefins in the gasor vapor-phase on 7 adsorbents, some preliminary remarks were drawn. Although gravimetry allows the visualization of some aspects of the whole process, spectroscopic methods are valuable for understanding aspects that do not depend upon mass or mass changes.…”