Ru–CeO2 Nanocatalysts with Weak Metal–Support Interactions for Ethylene Methoxycarbonylation.

In this work, Ru–CeO₂ prepared by a "melting" method and used as a heterogeneous catalyst for ethylene methoxy-carbonylation was investigated, together with two other catalysts prepared by impregnation and aerosol methods. The Ru–CeO₂ (1%-M) catalyst demonstrates activity significantly higher than that of the other catalysts with the same Ru content. The XPS and Raman analysis results suggest that the Ru–CeO₂ (1%-M) oxygen vacancy content is not the highest among the catalysts prepared using the three methods, even though the content oxygen vacancies have been reported to play a crucial role in carbonylation when using a Ru–CeO₂ catalyst. It was discovered that the available Ru⁰ (Ru⁰ in the freshly prepared sample plus that being transformed from Ruⁿ⁺ during reduction) is the other decisive factor in determining the catalyst's performance. We further investigated the high reducibility of the catalyst prepared by using the melting method and discovered that a weak metal–support interaction could be obtained because of the independent formations of Ru and CeO₂ crystals with graphite carbon as the barrier. Removing carbon under the optimal conditions could facilitate the as-formed Ru crystals anchored onto CeO₂; therefore, there is no strong interaction between Ru and CeO₂. [ABSTRACT FROM AUTHOR]