You cannot use CompositionScopeDefinition in conjunction with an AssemblyCatalog.
http://stackoverflow.com/questions/16943121/defining-scope-in-mef-with-compositionscopedefinition?answertab=votes#tab-top
http://stackoverflow.com/questions/16943121/defining-scope-in-mef-with-compositionscopedefinition?answertab=votes#tab-top