Effect of oxygen and water on direction of C6-dehydrocyclization of n-octane

Abstract

1. Both oxygen and water change the direction of the C6-dehydrocyclization of n-octane over 0.3% Pt-Al2O3 at 450°, and a pressure of 5 and 20 atm, toward the greater formation of ethylbenzene. 2. A study was made of the electron structure of n-octane in a conformation in which the 1 and 4, and the 5 and 8 C atoms shield each other. The negative charges of all of the C atoms in the molecule increase when going from the transoid to the shielded conformation of n-octane, but the character of their distribution is retained: the maximum negative charges are borne by the C atoms of the methyl groups, while the minimum negative charges are borne by the C atoms attached to them. 3. The observed change in the direction of the reaction is apparently due to two factors: an increase in the electron-donor character of platinum as the result of the adsorption of water by the support of the aluminum-platinum catalyst, and the character of the electron density distribution in the n-octane molecule.