Zirconium-containing compositions with a component ratio characteristic ofthe garnet structure: Physicochemical and catalytic properties

The possibility for the formation of garnet structures in the Mn-Fe-Zr-O an d Ca-Sm-Zr-O systems obtained by the precipitation of the corresponding sal ts is studied. It is shown that, in the Mn-Fe-Zr-O system, garnet is crysta llized at 860-920 degreesC, for which probable cation distribution is estim ated to be {Zr-2.5(4+) Mn-0.5(2+)}[Mn-2(2+)](Fe-2.5(3+) Mn-0.5(3+))O-12. In the Ca-Sm-Zr-O system, the perovskite CaZrO3, pyrochlore Sm2Zr2O7, and CaO are formed at 900-1200 degreesC, but compounds with garnet structures are not found. The reported systems are characterized by surface areas of 300-4 50 m(2)/g at less than or equal to 450 degreesC, and they have the polydisp erse distribution of pores over sizes. The introduction of surfactants at t he stage of component mixing enables an increase in the overall pore volume and mechanical strength of these systems. The Mn-Fe-Zr and Ca-Sm-Zr compos itions are active catalysts for the complete oxidation of hydrocarbons.