Promotion Effect of Ga-Co Spinel Derived from Layered Double Hydroxides for Toluene Oxidation

Considering the radius similarity of Al3+ (0.50 angstrom) and Ga3+ (0.62 angstrom), Al-Co and Ga-Co layered double hydroxides (LDH) was prepared as precursor to improve the synergetic interaction of the transition metals. The Al-Co and Ga-Co spinel catalysts were obtained by the following calcination for the toluene oxidation. The Ga-Co (E-a=79.5 kJ mol(-1)) showed higher activity than the Al-Co (E-a=95.4 kJ mol(-1)), and it exhibited excellent stability and resistance to carbon deposition during a 50 h reaction period at 300 degrees C. Characterization results indicated that the improved activity of Ga-Co spinel could be attributed to the higher reducibility (H-2-TPR), more surface Co3+ and adsorbed oxygen in quantity (XPS) and adsorbed toluene (Toluene-TPD) than Al-Co spinel. Compared with traditional Ga-Co binary catalyst, the spinel structure possessed more B-sites cations outermost of the surface and surface oxygen vacancies for the toluene adsorption and ring-open reaction.