Synthesis of a porous chromium fluoride catalyst with a large surface area

A novel approach to the preparation of a porous chromium fluoride catalyst with a large surface area is reported. The pores were generated by introduction of a siliceous material into the precursor of the catalyst and then removal of the material by reaction with anhydrous hydrogen fluoride. During the reaction, the formation and escape of a volatile gas (SiF₄) from the precursor enlarged the surface area of the chromium fluoride. This process provided for the first time a porous chromium fluoride with a surface area of 187 m ²/g and a pore volume of 0.58 cm³/g. Furthermore, the porous chromium fluoride exhibited excellent chemical stability in the presence of HCl, HF, and F₂. It was catalytically active for halogen exchange in a fixed-bed fluorination reaction, and it exhibited excellent catalytic performance in mitigating the coke formation on the surface of the catalyst during vapor-phase catalytic fluorination.