Study on liquid-phase hydrogenation of paranitrotoluene over Ru-based catalysts

This paper presented a study on the role of yttrium addition to Ru-based catalysts for liquid phase paranitrotoluene hydrogenation reaction. An impregnation-precipitation method was used for preparation of a series of yttrium doped Ru/NaY catalysts with yttrium content in the range of 0.0026-0.0052 g/g. Properties of the obtained samples were characterized and analyzed by X-ray diffraction (XRD), H-2-TPR, Transmission electron microscopy (TEM), ICP atomic emission spectroscopy, and Nitrogen adsorption-desorption. The results revealed that catalytic activity of NaY supported Ru catalysts increased with the yttrium content at first, then decreased with the further increase of yttrium content. When yttrium content was 0.0033 g/g, a Ru-Y/NaY2 catalyst showed the most excellent performance of paranitrotoluene hydrogenation reaction (paranitrotoluene conversion and the selectivity toward P-methyl-cyclohexylamine reached 99.9% and 82.5%, respectively). In addition, to compare with the performance of Ru-Y/NaY catalysts, the active carbon supported Ru catalysts were prepared using the same method in view of its higher surface area and adsorption capacity. Finally, the effect of solvent on the reaction over Ru-Y/NaY2 catalyst has been investigated, it was found that the best performance of paranitrotoluene hydrogenation reaction took place in protic solvents (isopropanol and ethanol). This was mainly ascribed to their polarity and hydrogen-bond accepting capability.