LaFeO_3修饰和O_3处理对Au/Al_2O_3催化剂在CO氧化反应中热稳定性的影响

Effect of LaFeO_3 Decoration and Ozone Treatment on the Thermal Stability of Au/Al_2O_3 for CO Oxidation

通过等体积浸渍法并分别经过H2和O3活化制备了系列1·1%Au/LaFeOx/Al2O3催化剂,考察了其在550℃经1·0%CO原料气处理后的CO氧化活性.Fe和La的引入虽然使1·1%Au/Al2O3的初始活性降低,但提高了其高温稳定性.在550℃经1·0%CO原料气预处理2h后,H2活化的1·1%Au/Al2O3在室温完全失活,而同样条件处理的1·1%Au/2%LaFeO3/Al2O3仍能将65%CO转化;这可能是由于LaFeO3以钙钛矿形式单层分散在Al2O3表面而导致的.O3活化能进一步提高催化剂的稳定性,在550℃经原料气预处理后,O3活化的1·1%Au/2%LaFeO3/Al2O3的活性高于1·1%Au/Al2O3和H2活化的1·1%Au/2%LaFeO3/Al2O3.1·0%CO原料气预处理10h后,H2活化的1·1%Au/2%LaFeO3/Al2O3完全失活,而O3活化的催化剂仍具有40%的转化率,这可能是由于O活化使得催化剂中存在部分氧化的金,增强了金属与载体间的相互作用.

1.1% Au/LaFeOx/Al2O3 catalysts were prepared by the iso-volume impregnation method and activated with H2 and O3. The catalytic performance for CO oxidation at room temperature was investigated by accelerated deactivation tests in 1.0 % CO reactant stream at 550 ℃. The introduction of La and Fe enhanced the thermal stability of Au/Al2O3 with a decrease in initial activity, probably due to the formation of LaFeO3 perovskite on Al2O3 surface. The 1.1 % Au/2% LaFeO3/Al2O3 activated by H2 can transform 65% CO into CO2 at room temperature after pretreatment in 1.0 % CO reactant stream at 550 ℃ for 2 h, while 1.1% Au/Al2O3 activated by H2 totally loses its activity. O3 activation can always make 1.1% Au/LaFeO3/Al2O3 more active than that of H2 activation during the pretreatment process in 1.0 % CO. After pretreatment for 10 h, 1.1% Au/2 % LaFeO3 / Al2O3 activated by O3 still shows 40 % conversion of 1.0 % CO at room temperature, whereas those activated by H2 become inactive completely. The better thermal stability of the catalysts activated by O3 may be due to that O3 activation leads to the formation of partially oxidized state of Au in Au/FLA-O3, which may reinforce the interaction between metal and support.