Amorphous Porous Chromium‐Zirconium Bimetallic Phosphate: Synthesis, Characterization and Application in Liquid Phase Oxidation of Hydrocarbons by Different Oxygen Sources

Abstract

AbstractCr−Zr bimetallic phosphates catalysts were prepared by sol‐gel method and used in the oxidation of cyclohexane, ethylbenzene and cyclohexene, respectively. The catalysts were characterized by a variety of analytical techniques. The results show that chromium ions enter the framework of mesoporous zirconium phosphate, Cr−Zr phosphates catalysts with molar ratio of Cr: Zr=2 (CrZr2P) or Cr: Zr=1 (CrZrP) still retain the mesoporous structure and form composite metal phosphates. Two active centers‐ redox (Cr6+) and acidic sites in these bimetallic phosphates play a synergistic catalytic role in the oxidation of C−H bond. Catalytic activity is closely related to the amount of acid or acid strength, the C=O product selectivity depends on the amount and high dispersion of Cr6+ species. Acidic sites and redox sites are affected by different molar ratios of chromium/ zirconium. Among the Cr−Zr phosphates catalysts, CrZr2P and CrZrP catalysts show excellent activity, just because the formation of mesoporous structure leads to the uniform dispersion of acidic and redox sites.