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/gamma-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 kg(cat) 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 kg(cat) 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 H-2 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. (C) 2014 Elsevier Ltd. All rights reserved.