Fundamental origins of different activity and time-on-stream stability of supported Mo-, W-, and Re-based materials in metathesis of ethylene and 2-butene to propene

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An attractive alternative for on-purpose propene production is the metathesis of ethyleneand 2-butene over supported WOx-, MoOx-, and ReOx-based catalysts. These catalysts operateat different reaction temperatures (300°C, 10 0°C, and room temperature, respectively)and possess different propene selectivity and time-on-stream stability. It is still unclear whichfundamental catalyst features determine their different performance although the reactionover WOx-based catalysts is in practice in industry since several years. Previous mechanisticknowledge obtained for the reverse reaction starting from propene can be applied only toa limited extend, because the metathesis of ethylene and 2-butene is complicated by in paralleloccurring cis-/trans and 2-/1-isomerisation reactions of 2-butene. This project is proposedto close these gaps. It aims at understanding (i) structure-reactivity/selectivity relationshipsand (ii) elucidating mechanistic and kinetic aspects of ethylene and 2-butene metathesisto propene as well as the role of 2-butene isomerisation reactions over well-definedsupported WOx, MoOx, and ReOx species. A combination of steady-state and transient kineticanalysis with spatial- and time-resolved in-situ catalyst characterization will be appliedto establish relationships between kinetic parameters of individual reaction steps with solidstateproperties and to improve the understanding of the deactivation behavior. The resultswill ultimately enable to design better catalysts on scientific basis and to derive improvedoperating strategies for metathesis reactors.