Efficient aqueous-phase hydrogenation of m-xylylenediamine to 1,3-cyclohexandimethylamine over a highly active and stable ruthenium catalyst

Abstract

A highly active and stable ruthenium catalyst supported on alkylamine-functionalized γ-Al₂O₃ was developed for the hydrogenation of m-xylylenediamine (MXDA) to 1,3-cyclohexandimethylamine (1,3-BAC) in aqueous phase. γ-Al₂O₃ was amino-functionalized by surface silylation with 3-aminopropyltrethoxysilane, and then Ru species was anchored onto modified γ-Al₂O₃via coordination with the amino group (–NH₂). The catalyst was characterized by Fourier-transform infrared spectroscopy (FT-IR), H₂ temperature-programmed reduction (H₂-TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), CO temperature-programmed desorption (CO-TPD), inductively coupled plasma-atomic emission spectrometry (ICP-AES), etc. This modification led to the formation of highly dispersed Ru, and greatly enhanced the catalytic performance. After reaction for 5 h at a temperature of 100 °C and pressure of 4 MPa H₂, the conversion of MXDA and selectivity of 1,3-BAC reached 99.7% and 95.0%, respectively. Moreover, this modification also significantly inhibited the leaching of Ru due to the strong interaction between Ru and –NH₂ revealed by XPS and H₂-TPR characterization, and suppressed the phase transformation of γ-Al₂O₃, which greatly improved the stability of the catalyst. The MXDA conversion and 1,3-BAC selectivity had no obvious decrease after six consecutive cycles.