An investigation on the utilization of perovskite-type oxides La_(1-x)Sr_xMO_3 (M=Co_0.77Bi_0.20Pd_0.03) ad three-way catalysts

摘要

The perovskite-type oxides La_(1-x)Sr_xMO_3 (M=Co_0.77Bi_0.20Pd_0.03) have been investigated for investigated for three-way catalytic performance and characterized by means of temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalysts exhibited good activity in CO elimination: La_0.8Sr_0.2MO_3 showed ca. 100% CO conversion at 160 deg C, 60 000h~(-1), and #lambda# = 1.00. Under similar reaction conditions, the activity for C_3H_6 elimination decreased in the order of La_0.2Sr_0.8MO_3>La_0.8Sr_0.2MO_3>La_0.4Sr_0.6MO_3>La_0.6Sr_0.4MO_3>LaMO_3, while the activity for NO elimination decreased in the order of La_0.8Sr_0.2MO_3>La_0.2Sr_0.8MO_3>La_0.4Sr_0.6MO_3>La_0.6Sr_0.4MO_3>LaMO_3. With x<0.6, La_(1-x)Sr_xMO_3 were single-phase and hexagonal in structure; at x = 0.6 and 0.8, they were cubic and there was a trace amount of the La_2O_3 phase. The results of TPD, TPR, and XPS studies revealed the coexistence of over-stoichiometric oxygen vacancies in La_0.8Sr_0.2MO_3, a criterion for good three-way catalytic performance.