Study on deactivation of Cu–Zn–Al catalysts in the synthesis of N-ethylethylenediamine

The performance of a Cu–Zn–Al catalyst employed in the synthesis of N-ethylethylenediamine from ethylenediamine and ethanol was studied. The results showed that the activity of the Cu–Zn–Al catalyst decreased with time-on-stream. Fresh and deactivated catalysts were characterized by XRD, XPS, N2 adsorption–desorption and TEM. It was found that the crystallite size of Cu and ZnO in the deactivated catalyst were much bigger than those for the fresh catalyst. In addition, channels in the deactivated catalyst were blocked by carbonaceous deposits, so the surface area and pore volumes of the deactivated catalyst were much smaller than in the fresh catalyst. Therefore, it was concluded that the deactivation of the Cu–Zn–Al catalyst was mainly caused by the growth in the Cu and ZnO crystallite sizes and carbonaceous deposits.