HYDROISOMERIZATION AND HYDROCRACKING OF NORMAL-HEPTANE AND NORMAL-HEXADECANE ON SOLID SUPERACIDS

Formation of highly branched long-chain paraffins and highly isomerized shorter chain paraffins from conversion of heavier n-paraffinic fractions is of interest for the production of high-octane gasoline, jet fuel, and lubricants. In this study, n-hexadecane was hydroisomerized and hydrocracked on a platinum-doped solid superacid, Pt/ZrO2/SO42−, in a batch horizontal shaking microreactor system at rather mild conditions: 130–170 °C, 300 psig initial hydrogen pressure, and 15–75-min reaction time. A moderate conversion level, over 65 wt %, was achieved at temperatures above 140 °C, which is significantly lower than Pt-doped acid catalysts in similar studies. Up to 70% of the hydroisomerized products are multibranched isohexadecanes. For the hydrocracked products, a very high selectivity, more than 90%, to isoparaffins resulted. Less than 1 wt % of platinum on the surface was very effective in preventing catalyst deactivation under low hydrogen pressure. The presence of small amounts of moisture in the reaction system enhanced catalyst reactivity, probably due to transformation of Lewis acid sites to Bronsted acid sites. Product distribution studies indicated that n-hexadecane was first transformed to monobranched isohexadecanes through skeletal isomerization, with consecutive reactions to multibranched isomers. Cracking products were obtained from cleavage of multibranched isohexadecanes; cracking of monobranched isohexadecanes appeared unlikely to occur under the reaction conditions studied. © 1990, American Chemical Society. All rights reserved.