Hydrocracking and isomerization of n-octane and 2,2,4-trimethylpentane over a platinum/alumina-pillared clay

The hydrocracking and isomerization of n-octane and 2,2,4-trimethylpentane over an alumina-pillared clay, containing 0.16% Pt was investigated in a microreactor operating at atmospheric pressure with varying temperature (175-325°C) weight hourly space velocity and (0.48-7.5h^-1.The structure of the catalyst changed during the first 30 h of use before becoming stable, as shown by X-ray diffraction. Hydrocracking of n-octane produced significant but diminishing quantities of methane and ethane during the first 30 h on stream. During this time the dominant classical bifunctional reaction mechanism was accompanied by a second reaction mechanism, possibly hydrogenolysis or cleavage by a non-classical pentacoordinated carbonium ion. After the initial period, the catalyst performed as an ideal hydrocracking catalyst, as characterized by high isomerization yields up to medium conversions, and showed product distributions very similar to those found in platinum loaded large pore zeolites.