Effect of the competitive adsorbates on the catalytic performances of PtSnK/γ-Al2O3 catalyst for isobutane dehydrogenation

The effect of the different competitive adsorbates (acetic acid, hydrochloric acid and nitric acid) on the catalytic performances of PtSnK/gamma-Al2O3 catalyst for isobutane dehydrogenation has been investigated by reaction tests and some physicochemical characterizations such as XRD, nitrogen adsorption, XRF, NH3-TPD, TEM, TPR and H-2 chemisorption. It was found that the presence of hydrochloric acid during the process of catalyst preparation could not only promote the distribution of metallic particles, but also produce the strong interactions between Sn species and support, as well as Pt and tin oxides. Thus, more amounts of tin could exist in oxide states, which was advantageous to the anchoring of Pt active sites and the dehydrogenation reaction. In our experiments, the catalyst prepared in HCl medium exhibited the highest reaction activity and stability. By increasing the reaction temperature (600 degrees C), the use of this adsorbate could also improve the catalytic performance. As compared with this catalyst, relatively poor distribution of metallic particles was found due to the existing steric effect of acetic acid, and the catalyst acidity increased when the used adsorbate was nitric acid. Finally, a model for the influence of hydrochloric add as competitive adsorbate was proposed. (C) 2012 Elsevier B.V. All rights reserved.