SYNTHESIS OF LAMNO3+DELTA BY FIRING GELS USING CITRIC ACID

摘要

A gel was prepared by adding citric acid to an aqueous solution of lanthanum nitrate and manganese nitrate. From thermal analysis and IR measurement, the gel prepared with 0.0023 mol of citric acid is a mixture of LaMn(C6H5O7) (NO3)(3), La (NO3)(3) . xH(2)O, and Mn(NO3)(2) . xH(2)O; the gel with 0.007 mol of citric acid LaMn(C6H5O7)(NO3)(3); and the gel with 0.015 mol of citric acid is LaMn(C6H5O7)(2). Hexagonal perovskite-type LaMnO3+delta was obtained by firing the gels. The specific surface area, the La/Mn ratio, and the catalytic activity for CO oxidation on LaMnO3+delta were measured. The catalytic activity for CO oxidation on LaMnO3+delta synthesized using citric acid is better than that on LaMnO3+delta synthesized using poly(acrylic acid). For these results, citric acid is inferred to improve the crystallinity (regularity of the ions) of the LaMnO3+delta surface. (C) 1997 Academic Press. [References: 19]