N-BUTANE ISOMERIZATION ON SULFATED ZIRCONIA - DEACTIVATION AND REGENERATION AS STUDIED BY RAMAN, UV-VIS DIFFUSE-REFLECTANCE AND ESR SPECTROSCOPY

n-butane isomerization on sulfated zirconia was studied in the tempera ture range 393-473 K. Rapid deactivation occurs, when the reaction is carried out in He carrier gas. In contrast, stable stationary activity was observed in H-2 carrier gas. In situ Raman and UV-VIS diffuse ref lectance spectroscopy and ESR showed that the deactivation is caused b y the formation of allylic and polyenylic cations and polycyclic aroma tic compounds, the formation of which is largely prevented in the pres ence of H-2. Deactivated catalysts can be fully regenerated by treatme nt at 723-753 K in flowing O-2. The regeneration process was also foll owed by in situ spectroscopies.