Effect of Cu+/Cu2+ Ratio on the Catalytic Behavior of Anhydrous Nieuwland Catalyst during Dimerization of Acetylene

The relative contents of Cu+ and Cu2+ in solutions of anhydrous Nieuwland catalyst and CuCl2-added anhydrous Nieuwland catalyst were detected by X-ray photoelectron spectroscopy (XPS). Results indicated that Cu+ could be transformed into Cu2+ during the process of acetylene dimerization into monovinylacetylene, leading to deactivation of the catalyst. Moreover, the addition of Cu2+ inhibited the oxidation of Cu+ into Cu2+ and enhanced the performance and lifetime of the catalyst. The optimum molar ratio of Cu+ to Cu2+ was approximately 2:1; at this ratio, up to 40% acetylene conversion may be achieved.