Pyridine hydrodenitrogenation over industrial NiMo/γ-Al2O3 catalyst: Application of gas phase kinetic models to liquid phase reactions

A systematic methodology for simulating gas–liquid–solid kinetics starting from a gas–solid kinetics model has been developed and applied to pyridine hydrodenitrogenation over an industrial NiMo/γ-Al2O3 catalyst. Data have been acquired in two independent, dedicated experimental programmes: i.e. an extended set of gas phase experiments that were previously carried out in a Berty type reactor setup at 573–633 K, 1.5–4.0 MPa and space times between 0.36 and 1.8 kgcat s/mmol and a more limited set of liquid phase experiments that were performed as part of the present work in a Robinson–Mahoney reactor setup at 543–613 K, 6.0–8.0 MPa and space times between 0.65 and 3.0 kgcat s/mmol. At liquid phase conditions the pyridine conversion ranged from 47% to 70%, while at gas phase conditions the pyridine conversion ranged from 17% to 72%. The reaction temperature and H2S inlet partial pressure were found to be most significantly affecting the selectivity to intermediates and products in both experimental programmes. 1-pentylpiperidine formation, a bimolecular reaction product exclusively observed at liquid phase conditions, could be ascribed to the differences in phases present during the kinetic measurements as well as to the differences in molar H2 and H2S to pyridine inlet ratios used and the resulting surface concentrations. A kinetic model constructed using the gas phase data was extended to liquid phase conditions by accounting for (i) liquid phase non-ideality, (ii) solvent adsorption effects and (iii) the additionally observed response, i.e. 1-pentylpiperidine. The latter was found to be produced via condensation between piperidine and pentylamine.