Lanthanum based high surface area perovskite-type oxide and application in CO and propane combustion

P R N Silva,A B Soares

doi:10.1590/s0100-46702009000100005

Abstract

The perovskite-type oxides using transition metals present a promising potential as catalysts in total oxidation reaction. The present work investigates the effect of synthesis by oxidant co-precipitation on the catalytic activity of perovskite-type oxides LaBO3 (B= Co, Ni, Mn) in total oxidation of propane and CO. The perovskite-type oxides were characterized by means of X-ray diffraction, nitrogen adsorption (BET method), thermo gravimetric and differential thermal analysis (ATG-DTA) and X-ray photoelectron spectroscopy (XPS). Through a method involving the oxidant co-precipitation it's possible to obtain catalysts with different BET surface areas, of 33-44 m2/g, according the salts of metal used. The characterization results proved that catalysts have a perovskite phase as well as lanthanum oxide, except LaMnO3, that presents a cationic vacancies and generation for known oxygen excess. The results of catalytic test showed that all oxides have a specific catalytic activity for total oxidation of CO and propane even though the temperatures for total conversion change for each transition metal and substance to be oxidized.

Highlights

The removal of CO, unburned hydrocarbons (HC), and NO from automotive exhaust requires catalytic devices in which these pollutants are eliminated
Catalytic combustion offers one of the most efficient means for controlling atmospheric pollution (1). Noble metals, such as palladium, platinum, and Rhodium are well known with higher activity
Base metal catalysts present a lower but still sufficient activity as oxidation catalysts, and have the advantages of lower costs and the potential market in energy generation systems in domestic and small scale industrial applications. For this reason perovskite type compounds have received wide attention, which have been incorporated into the design of the novel combustors (2,3)

Summary

Introduction

The removal of CO, unburned hydrocarbons (HC), and NO from automotive exhaust requires catalytic devices in which these pollutants are eliminated. Lanthanum-based perovskites containing transition metal in B-site, (LaBO3, B = Co, Fe, Ni or Mn), show catalytic activity close to the noble metal, presenting low cost and high thermal stability [8]. The perovskites type oxide LaCoO3, LaMnO3 e LaNiO3 presented specific surface area of the 44, 38 and 33m2/g, respectively. In the catalysts LaCoO3 and LaNiO3 there’s a peak represented by (*), referring to lanthanum oxide (La2O3), indicating a cationic excess.

Results

Conclusion