Abstract: The effect of supports (MSU-1, γ-Al₂O₃, AC (activated carbon), and MgO) on the catalytic activity of Cr-based catalysts was investigated for the dehydrogenation of isobutane with CO₂. The catalytic activity was in the order of CrO_x/MSU-1 > CrO_x/Al₂O₃ > CrO_x/AC > CrO_x/MgO. The catalysts were characterized by N₂ adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD). The XRD results indicate that the active species of Cr are dispersed well on the supports. N₂ adsorption-desorption shows that the support MSU-1 has the largest surface area (804.2 m²/g), which results in excellent dispersion of Cr and highest activity. The XPS results reveal that Cr⁶⁺ is one of the active centers. The results of NH₃-TPD indicate that catalyst activity is proportional to the amount of weak acid adsorption sites. As a result, the best support is the MSU-1 zeolite owing to its high specific area and a large amount of weak acid sites. The 59.2% conversion of isobutane and the 39.5% yield of isobutene are achieved on the CrO_x/MSU-1 catalyst.

Key words: MSU-1 zeolite, chromium oxide, isobutane, carbon dioxide, catalytic dehydrogenation, isobutene