TURNOVER RATES FOR HEPTANE REFORMING OVER PT/L ZEOLITES WITH DIFFERENT ALKALI CATIONS

A series of 0.6 wt% Pt/BaL catalysts with different alkali cations have been tested for heptane reforming at 440-degrees-C, 0.16 atm heptane, 0.95 atm H-2, 6.7 atm He, 3 to 5 h of reaction, and conversions between 2 and 10%. As the cations in the zeolite are progressively changed from lithium to cesium, the turnover rates for hydrogenolysis and dehydrocyclization increase by about 5-10 times, while the turnover rate for isomerization remains unchanged. Since the turnover rates for hydrogenolysis and dehydrocyclization are similarly affected, exchanging lighter alkali cations for heavier ones increases the aromatics selectivity by a small amount, from 72 to 82%. These results indicate that metal-support interactions have a moderate effect on the heptane reforming activity, but only a weak effect on the selectivity.