Effects of preparation parameters on structures and properties of mesoporous La-Co-Zr-O catalysts with high specific surface area

A series of mesoporous La-Co-Zr-O mixed oxide catalysts with various (n(1a)+n(Co))/(n(1a) +n(Co)+n(Zr)) ratios and different calcination temperatures were prepared by decomposition of dual-organic templates of cetyltrimethylammonium bromide (CTAB) and p-octyl polyethylene glycol phenyl ether (OP). The catalysts were characterized by XRD, XPS, N-2 adsorption/desorption and H-2-TPR. The effects of component ratios and calcination temperatures on the catalytic properties were investigated using CO and C3H8 oxidation as model reactions. The results of N-2 adsorption/de sorption and pore size distribution measurements show that the samples possess very large specific surface area (108 similar to 266 m(2) center dot g(-1)) and narrow pore size distribution (3.4 similar to 3.9 nm). The catalyst containing higher content of Zr shows larger specific surface area. The results of XRD indicate that the active component cobalt species in samples mainly exist as Co3O4. The results of H2-TPR and XPS indicate that the amount and mobility of the reducible lattice oxygen in samples and the concentration of surface cobalt atoms are closely relevant to the activities of the catalysts. There are more reducible lattice oxygen species for the sample with atomic ratio of 0.5 at low temperature than in other samples, and there are more surface cobalt atoms for the sample with atomic ratio of 0.7, thus making the two samples exhibited excellent catalytic oxidation activity. After calcination at 650 degrees C, the sample still keeps high specific surface areas (108 m(2)center dot g(-1)) and very narrow pore diameter distribution (the most probable pore size similar to 3.83 nm) with a slightly decreased activity, indicating a very good ability of of mesoporous structures for this series of catalysts sintering resistance and high thermal stability mesoporous structures for this series of catalysts.