The Effects of in Situ Fluorination and Support on the Hydrodenitrogenation of Methylcyclohexylamine

The effects of in situ fluorination on the hydrodenitrogenation of methylcyclohexylamine have been studied at 310–350°C and 5.0 MPa in a continuous microflow reactor over sulfided and fluorinated sulfided NiMo catalysts supported on alumina and silica–alumina. The silica–alumina-supported catalysts exhibit higher hydrodenitrogenation activity than their alumina-supported counterparts. In situ fluorination promotes hydrodenitrogenation activity mainly by enhancing the elimination of NH3 from methylcyclohexylamine, while less of an effect is observed for the direct reaction of methylcyclohexylamine to methylcyclohexane. Kinetic parameters were obtained for the reaction network by fitting the experimental results with Langmuir–Hinshelwood equations. After fluorination, the reaction rate constants of all catalysts increase substantially for the elimination step, but only slightly for the direct reaction. The activation energies and the heat of adsorption are about the same over all catalysts. This indicates that the intrinsic activity of the active sites is not influenced by the in situ fluorination or by the support, and only the number of sites active for hydrodenitrogenation is increased by a change of the dispersion of the active phase.