Study on the Preparation of Cr‐based Catalysts Doped by Zn using Sol–Gel Auto‐Combustion Method and Its Application for Synthesis of 1‐Chloro‐2,3,3,4,4,5,5‐heptafluorocyclopentene

Abstract

High‐surface‐area chromium‐based catalysts in the presence of a small amount of zinc were prepared via a sol–gel auto‐combustion method using chromic nitrate, zinc nitrate, and citric acid. First, the auto‐combustion behavior of the dried gel was investigated by derivative thermogravimetry and (DTG)‐TG and infrared (IR) techniques. The results revealed that the dried gel exhibited self‐propagating combustion properties. Second, the as‐burnt powders were characterized by IR, X‐ray diffraction (XRD), Brunauer–Emmett–Teller analysis (BET), and scanning electron microscopy (SEM). The findings showed that the gels were directly converted into CrZn‐O nanoparticles with high surface area during the auto‐combustion process. Third, the pre‐fluorination Cr‐Zn catalysts were characterized by XRD, BET, SEM, X‐ray photoelectron spectroscopy (XPS), and Fourier transform (FT)‐IR spectroscopy of pyridine adsorption techniques. It was found that the presence of zinc led to significant structural changes in the catalyst, the particle size was smaller, the surface area became larger, and more active sites appeared. Finally, the catalytic activities of the samples were tested for the fluorination of 1,2‐dichlorohexafluorocyclopentene (1,2‐F6) with anhydrous hydrogen fluoride. The obtained results indicated that the pre‐fluorination activated Cr‐Zn catalysts prepared by this sol–gel auto‐combustion method exhibited high efficiency in the synthesis of cyclic hydrofluorocarbons.