Synthesis and structure screening of nanostructured chromium oxide powders (original) (raw)

The evolution with calcinations of chromium oxide (Cr 2 O 3 ) nanocrystals of catalytic interest, prepared from reduction of K 2 Cr 2 O 7 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), N 2 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 K 2 Cr 2 O 7 /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 Cr 2 O 3 of the pore diameter distribution in the range of 2-6 nm and specific surface area of 123 m 2 /g. The particle size and phases of chromium oxide were affected by the ratio of K 2 Cr 2 O 7 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.