Effect of chelating agents on catalytic performance of Cr/γ-Al 2 O 3 dehydrogenation catalysts

Chromia/alumina (Cr 2 O 3 /γ-Al 2 O 3 ) catalysts with addition of chelating agents (citric acid or oxalic acid) were prepared by the incipient impregnation method. The resulting catalysts with different citric acid (CA) or oxalic acid (OA) contents were applied to the dehydrogenation of isobutane to isobutene. The influence of chelating agents on the catalysts was investigated by means of BET, SEM, H 2 -TPR, NH 3 -TPD, and TG-DTG. The results showed that the Cr 2 O 3 /γ-Al 2 O 3 catalysts with addition of CA or OA exerted slightly increase on specific surface area. The addition of the chelating agents as expected, determined a general decrease in the surface acidity. The catalysts with CA or OA have a better anti-coking ability by inhibiting the side reaction of cracking and carbon formation. The addition of CA or OA for preparing these catalysts resulted in a beneficial effect on the reducibility of the Cr species to diminish the reduction temperature. The appropriate content of chelating agents could improve dispersion of metal species in the γ-Al 2 O 3 support. The catalytic activity showed an important enhancement when the metal species was impregnated in the presence of CA or OA.