Catalytic amination of 1,6-hexanediol for synthesis of N, N, N’, N’-tetramethyl-1,6-hexanediamine over Cu/Ni/Zn catalysts

Synthesis of N, N, N’, N’-tetramethyl-1,6-hexanediamine(TMHDA) by the amination of 1,6-hexanediol(HDO) and dimethylamine(DMA) at normal pressure over an outstanding Cu/Ni/Zn catalyst supported on aluminum oxide(γ-Al₂O₃) was studied in this article. Cu/Ni/Zn/γ-Al₂O₃(Cu: Ni: Zn = 28: 7: 12) exhibited excellent catalytic performance, which HDO was almost completely transformed and TMHDA reached 85 % selectivity at 200 °C. The amination of HDO required two hydrogenations and two dehydrogenations, and the selectivity of the amination catalyst depended on the balance of dehydrogenation and hydrogenation. Various characterization (TEM, BET, XRD, H₂-TPR, XPS) demonstrated that the addition of Zn to the Cu/Ni catalyst could reduce the agglomeration of Cu/Ni particles and change the valence distribution of Cu. The Cu/Ni/Zn/γ-Al₂O₃ catalyst was a very promising and green method for the synthesis of tertiary diamines through amination of diols.