CONDENSATION OF OLEFINS ON CLAYS - GAS-SOLID SYSTEMS .2. SPECTROSCOPIC METHODS

The adsorption of olefins at 25 degrees C in gas- or vapor-solid syste ms on 4 clays dried at 120 degrees C, was studied by infrared spectros copy. Products of condensation have the spectra of paraffinic oligomer s. Paraffins are adsorbed onto the same structural surface hydroxyls t hat adsorb olefins, confirming the physical unspecific character of th is adsorption. These hydroxyls do not participate in the condensation reaction. The reappearance of these hydroxyl bands after evacuation su ggests that product molecules are not adsorbed onto the surface but re main on it because of its low vapor pressure. The reversible adsorptio n sites participate in feeding the condensation sites. Double-bond iso merization of olefins was not observed, at room temperature, on clays, alumina and silicas dried at 120 degrees C. When the gas-phase is eva cuated or swept with inert gas, reaction does not proceed with a new m onomer. Paraffins are only physically adsorbed.