Intrazeolite ruthenium carbonyls. Applications to the conversion of carbon dioxide to methane and to other catalytic processes

In this study attempts were made to synthesize Ru{dollar}sb3{dollar}(CO){dollar}sb{lcub}12{rcub}{dollar} inside the 13A supercages of NaY zeolite and to evaluate the encapsulated product as a catalyst for the hydrogenation of CO{dollar}sb2{dollar} to CH{dollar}sb4{dollar}. Characterization by IR and size-selective phosphine reactions indicates that the trimer carbonyl was successfully placed inside the zeolite structure. Evaluation of this new material as a catalyst for CO{dollar}sb2{dollar} methanation revealed that no advantage is gained by placing Ru{dollar}sb3{dollar}(CO){dollar}sb{lcub}12{rcub}{dollar} inside the structure over using a Ru{dollar}sb3{dollar}(CO){dollar}sb{lcub}12{rcub}{dollar}/NaY catalyst in which the metal cluster is known to reside on the outer surface of the zeolite support. Indeed, there are indications that the metal in the activated catalyst which begins in the interior of the zeolite prefers to come to the surface when reactant H{dollar}sb2{dollar} is depleted. This migration to the outside of the support is accompanied by a rise in catalytic activity. The encapsulated Ru{dollar}sb3{dollar}(CO){dollar}sb{lcub}12{rcub}{dollar}/NaY complex was also evaluated as a pseudo-homogeneous catalyst for the water-gas shift reaction and the carbonylation of methanol to methyl formate. While some of the reaction chemistry of the complex mimicked well-established solution chemistry, the complex offered no significant advantage over homogeneous catalysts.