Effect of the synthesis method on the properties of lanthanum oxide-stabilized aluminum oxide

Aluminum oxide is widely used in industry, including as a support for precious metals in three-way catalysts. For this application, the material should have a well-developed surface and high porosity and should withstand three-way catalyst operating temperatures of up to 1100 °C, i.e., it should be thermally stable. An effective way to improve these properties is to introduce lanthanum oxide as a modifying additive. This article compares the surface characteristics and thermal stability of aluminum oxide samples containing 3 wt. % lanthanum oxide, calculated relative to the final mixed oxide. The samples were prepared by different methods: mechanical mixing of aluminum and lanthanum oxides; direct, reverse, and so-called fast precipitation of aluminum and lanthanum hydroxides; incipient wetness impregnation and impregnation in excess solvent of aluminum hydroxide with lanthanum nitrate; by capacity and, and controlled double-jet coprecipitation of aluminum and lanthanum hydroxides. The article examines how the synthesis method affects the characteristics of the resulting material. The samples differed already at the synthesis stage in particle shapes and size , which ultimately led to differences in surface characteristics and porosity. Among the selected precipitation methods, the sample obtained by controlled double-jet coprecipitation had the highest specific surface area. This material can be used in three-way catalysts.

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