Investigation of the effects of CeO 2 addition to MCM ‐41 supported CrO x catalysts on catalytic performance in isobutane dehydrogenation

Abstract This study aimed to investigate the effects of the addition of CeO 2 to the chromium‐based catalyst on the activity and selectivity of the isobutane dehydrogenation. MCM‐41 supported catalysts without Ce and with Ce/Cr mass ratios of 1 and 5 were first prepared hydrothermally (Cr:10%, by mass). As the Ce/Cr ratio increased, the formation of inactive α ‐Cr 2 O 3 decreased and almost disappeared when the Ce/Cr ratio was 5; thus, it was decided to use this ratio in further catalyst preparation. Then, catalysts with and without Ce were prepared by the impregnation method. X‐ray diffraction (XRD) and scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) analyses showed that CeO 2 distribution was better in the hydrothermally prepared catalyst. IR analyses of pyridine adsorbed catalysts showed that the number of Bronsted acid centres increased when CeO 2 was not well dispersed in the catalyst structure prepared by the impregnation method. Since high Bronsted acidity caused more α ‐hydrogen displacement, the formation of deep oxidation product CO x increased and lower isobutene selectivities were observed. When Ce was added to the chromium‐based catalyst, the total number of acid centres decreased by approximately 50% and the oxygen capacity increased approximately twofold. The decrease in acidity with the addition of Ce also reduced the formation of deep oxidation product CO x . Ce addition prevented the rapid decrease in conversion and selectivity in the CrO x catalyst synthesized hydrothermally. Isobutane conversion and isobutene selectivity were maintained at approximately 85% during 2 h reaction period. This was explained by the fact that CeO 2 successfully transferred the oxygen required for the reaction to the neighbouring.