Performance of Ru/La2O3–ZnO Catalyst for the Selective Hydrogenation of Benzene to Cyclohexene

Abstract

Cyclohexene is an important intermediate product for a highly efficient and greener formation of major end products like adipic acid, nylon 6, and nylon 6.6. By using a complex tetra-phase system (g/l/l/s) including hydrogen (g), water (l), an organic phase, i.e., benzene (l), and a supported ruthenium catalyst (s) it is possible to get the desired intermediate cyclohexene based on benzene. We prepared an oxide-supported ruthenium catalyst that was applied together with minimal amounts of the additive NaDCA (sodium dicyanamide) in a batch and continuous apparatus for the selective benzene hydrogenation. We compared these two processes and reached by an optimization of the reaction parameters in continuous process selectivities up to 50% at conversions of 36%. This corresponds to cyclohexene yields of 18% over a period of 100 h. Finally, the catalyst was characterized using X-ray diffraction (XRD), transmission electron spectroscopy (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES), and laser scattering to understand the performance of the catalyst and the effect of the small deactivation.

Keywords

• benzene
• cyclohexene
• ruthenium
• hydrogenation
• continuous
• tetra-phase system