Unrevealed effect of silver species on hydrocarbon pool in ethylene conversion on ZSM-5 by 2D COS FT-IR and 2D COS UV-vis operando spectroscopies

Silver-loaded and protonic ZSM-5 zeolites were investigated for the transformation of ethylene into propylene and aromatics. <i>Operando</i> FT-IR and UV-vis spectroscopic studies provided unique insights into the influence of silver species in ZSM-5 on ethylene conversion pathways. Acetone washing altered the distribution of silver on the ion-exchanged zeolite surface. <i>Operando</i> spectroscopic studies and catalytic tests (350°C) revealed that catalytic performance strongly depended on the method of zeolite treatment. The crucial role of silver speciation is suggested in the participation of silver sites in ethylene conversion. The high stability of the acetone-washed silver-ZSM-5 sample was confirmed by analysis of coke species. Two-dimensional correlation spectroscopy (2D COS) allowed the identification of alkyl-substituted benzenium and cyclopentenyl cations as important intermediates in ethylene transformation, indicating similarities with the hydrocarbon pool (HP) mechanism. To date, the heterospectral 2D COS analysis has not been performed on <i>operando</i> spectroscopic results of heterogeneous catalytic studies; in this work, we present its application.