Abstract: Modification of activated carbon (AC) with different acid solution might result in various surface oxygen groups, which can enhance the anchoring interaction between AC support and metal precursor and change the dispersion and basicity of the catalyst. The influence of HCl, HNO₃, and HF treatment on RbNO₃-KF/AC catalyst in the gas-phase synthesis of C₂F₅I by reaction of C₂HF₅ with I₂ and O₂ was studied. The pore structure and the surface chemical properties of the AC support were investigated by N₂ adsorption-desorption and Boehm titration. The dispersion and basicity of the catalyst before and after acid treatment were investigated by CO₂ temperature-programmed desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectrometry. It was found that after the HCl treatment, the RbNO₃-KF/AC(HCl) catalyst has high dispersion and moderately basicity, which is helpful for the enhancement of catalytic activity for C₂F₅I synthesis. The catalyst dispersion is in the order: RbNO₃-KF/AC(HNO₃) > RbNO₃-KF/AC(HF) > RbNO₃-KF/AC(HCl) > RbNO₃-KF/AC. The same sequence is also observed for the amount of acid surface oxygen groups on AC, but not for the weak basicity of the catalyst. The key role of acid treatment on the AC surface chemistry and moderate basic sites, which are closely related to catalyst dispersion and basicity, is examined to rationalize these findings.

Key words: activated carbon, acidic treatment, surface oxygen group, rubidium nitrate, potassium fluoride, pentafluoroethyl iodide