Low-temperature synthesis of MgxCo1-xCo2O4 spinel catalysts for N2O decomposition

Low-temperature synthesis of spinels MgxCo1-xCo2O4 (x = 0.0-0.9) has been investigated with two important synthetic parameters and XRD/FTIR/DSC/BET/ICP/CHN methods. It; is found that with an increase in hydrothermal treatment temperature, precursor compounds change from the hydrotalcite-like to brucite-like and then to cubic spinel phase when the initial metal concentration ratio [Mg2+]:[Co2+] greater than or equal to 1, while from the turbostratic to hydrotalcite-like and then to cubic spinel phase when the [Mg2+]:[Co2+] < 1. The MgxCo1-xCo2O4 (x less than or equal to 1/3) spinels were formed at temperatures as low as 50-100 degrees C. In the postsynthesis thermal treatment, various thermal events have been observed, and in all cases the spinel phase can be prepared at temperatures below 300 degrees C. On the basis of FTIR results, a topotactic mechanism for the formation of the spinel phase has been confirmed. Specific surface area as high as 210 m(2)/g has been attained in 400 degrees C calcined MgxCo1-xCo2O4 with x = 0.9. Causes for the formation of the spinel phase at low temperatures have been addressed. Excellent catalytic activity for N2O decomposition (30.6-38.9 mmol (N2O)/g.h at GHSV = 21200 h(-1) and 380-400 degrees C; N2O = 10 mol % balanced with He) has been observed and discussed for these Mg-Co spinels.