n-Butane isomerization in the gas phase and under supercritical conditions.

Bogdan, V. I.; Khelkovskaya-Sergeeva, E. G.; Vasina, T. V.; Kazanskii, V. B.

The aromatization of n-butane under supercritical conditions on gallium-, zinc-, and platinum-modified high-silica zeolites with a modulus of 30–70 was first studied, and the experimental data were compared to the results of a study of this process in the gas phase. It was found that the operational efficiency of catalysts for n-butane conversion under supercritical conditions was much higher than that for the gas-phase reaction in terms of activity, productivity, and resistance to poisoning by condensation products. The aromatization of gaseous n-butane at 530°C and 1 atm was characterized by rapid catalyst deactivation. The selectivity for the benzene-toluene-xylene (BTX) fraction was higher than 50%. Under supercritical conditions at 430–560°C and 100–200 atm, the selectivity of formation of aromatic compounds decreased by a factor of 2, whereas the yield of C1-C3 cracking products increased by the above factor. On the other hand, it was found that an increase in the productivity of catalysts by a factor of 20–50 with the retention of almost 100% activity for several days of operation is an advantage of the process performed under supercritical conditions. The almost complete conversion of butane under supercritical conditions was found on promoted HZSM-5 zeolite samples. The thermogravimetric analysis of spent samples suggested a higher degree of catalyst carbonization under supercritical conditions, as compared with that in the reaction performed in the gas phase. However, the deposition of 20–30 wt % condensation products on the catalysts had no detectable effect on the high activity of the catalysts in the reaction performed under supercritical conditions.

CHEMICAL inhibitors; ISOMERIZATION; ZEOLITES; CATALYST poisoning; CATALYSTS; CATALYSIS

Kinetics & Catalysis, 2008, Vol 49, Issue 1, p115

0023-1584

Academic Journal

10.1134/S002315840801014X