Synthesis and structure screening of nanostructured chromium oxide powders

The evolution with calcinations of chromium oxide (Cr2O3) nanocrystals of catalytic interest, prepared from reduction of K2Cr2O7 with maleic acid has been studied. The characterization of the materials was confirmed by X-ray diffraction (XRD), Fourier transformation infrared (FT-IR), transmission electron microscope (TEM), N2 adsorption–desorption isotherms, and thermo-analytical methods. The influence of the operating variables such as molar ratio, pH, gelation time and specific surface area was investigated and discussed. The results showed that the K2Cr2O7/maleic acid of 1:1.7 molar ratio at pH 7 and 15 days gelation time were considered to be the best conditions for producing Cr2O3 of the pore diameter distribution in the range of 2–6 nm and specific surface area of 123 m2/g. The particle size and phases of chromium oxide were affected by the ratio of K2Cr2O7 to maleic acid, temperature, and time of calcination. The amorphous phase appeared at room temperature, whereas it turned to crystalline phase when the calcination temperature increased to about 400 °C.