In the past decades,a number of in situ MAS NMR techniques under continuous-flow (CF) conditions have been developed for the study of heterogeneously catalyzed reactions under industrial conditions [1].These techniques make it possible to directly investigate the formation and transformation of surface species under steady-state conditions and,in some cases,simultaneously analyze the reaction products by gas chromatograph [1].The most frequently applied technique for in situ MAS NMR investigations of heterogeneously catalyzed reactions under flow conditions is based on the injection of a carrier gas loaded with vapors of the reactants into the spinning MAS NMR rotor via an injection tube [2].A recent development is the direct coupling of UV/Vis and CF MAS NMR spectroscopy under flow conditions [3].