Phase cooperation between tin and antimony oxides in selective oxidation of isobutene to methacrolein III. Coprecipitated catalysts

Abstract

A series of Sb-Sn mixed oxides prepared by coprecipitation and calcined at high temperature (900°C) has been studied in the selective oxidation of isobutene to methacrolein. The catalytic properties of these samples depend strongly on the Sb content. The physico-chemical characterization using XRD, BET, electron microscopy (CTEM, SEM, and AEM), and XPS has shown that these samples are composed almost exclusively of a Sb x Sn 1− x O 2 solid solution and pure antimony oxide (Sb 2O 4). A strong catalytic synergy was observed when a Sb-poor coprecipitate was mixed with either a pure α-Sb 2O 4 or a Sb-rich coprecipitate. Physico-chemical characterization did not indicate any mutual contamination or the occurrence of solid state reaction. The catalytic performances of both pure coprecipitates and mechanical mixtures can be explained by a remote control mechanism, i.e., the fact that Sb 2O 4 produces spillover oxygen that can create or regenerate the selective catalytic sites of the Sb x Sn 1− x O 2 solid solution by reacting with its surface.