Probing Cu-USY Zeolite Reactivity: Design of a Green Catalyst for the Synthesis of Diynes

Cu-exchanged USY zeolite was synthesized by vapor-phase exchange of parent HUSY with CuCl. Reaction parameters were varied in order to investigate the relationship between the structure of Cu+-promoted FAU zeolites and their catalytic properties in C−C bond homocoupling reaction between two acetylenic molecules (Glaser reaction). A proper choice in the CuCl chemical vaporization duration and temperature led to an increase in extra-framework aluminum species formation and thus to higher Lewis acidity. Moreover, such treatment under nitrogen flow during two days at 623 K kept the material highly crystalline. A drastic influence of the zeolite topology and properties (channels or cages, pore diameter, acidity) was noticed in the conversion of phenylacetylene. Observation of the catalyst before, during, and after the reaction, by multinuclear magic-angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and H/D isotope labeling, revealed the necessity for the zeol...