Selective synthesis of cis-2,6-dimethylpiperazine catalyzed by a Cu-Cr-Fe/γ-Al2O3 catalyst Original Research Article

A continuous process for the synthesis of cis-2,6-dimethylpiperazine was described in this paper. The cyclization of N-β-hydroxypropyl-1,2-propanediamine proceeded effectively over a Cu-Cr-Fe/γ-Al2O3 catalyst in a fixed-bed reactor. Cu0 and Cu+ were believed to be the active sites of the catalyst. Fe was found to play an important role on the catalyst activity and stability. Effects of solvents, temperature and hydrogen pressure were examined; solvents were found to be very important for this reaction. Remarkable differences were found between the catalysts used in water and those used in dioxane by the XPS and SEM characterizations. The loss of Fe and some carbon deposit on the catalyst surface were detected and supposed to be the main reasons of the catalyst deactivation in water, whereas the catalyst showed an excellent service life in dioxane. Finally, cis-2,6-dimethylpiperazine was obtained with a total yield of over 70% under the optimum reaction conditions. Thus, a highly selective process for the synthesis of cis-2,6-dimethylpiperazine was established here.