Benzene hydrogenation in the thiophene presence over the sulfide Ni-Mo/γ-Al2O3 catalyst under periodic operation: Kinetics and process modelling

An unsteady-state kinetic model of both benzene hydrogenation (HDA) and thiophene hydrogenolysis (HDS) on the sulfide hydrotreating catalyst Ni-Mo/Al2O3 has been developed. The model adequately describes experimental data obtained at the pressure 2 MPa, temperature 573 K and at various contact times and ratios of benzene/thiophene. The model is based on the assumption that the catalyst surface contains only one type of active sites, i.e., Ni atoms in the sulfide bimetallic species, which are responsible for both hydrogenolysis and hydrogenation reactions. On the base of the kinetic model, a theoretical analysis of the reactor performance under unsteady state conditions was carried out. The unsteady state conditions on the catalyst surface are supposed to be created by forced oscillations of thiophene concentration in the reactor inlet (periodic operation of reactor). The influence of various parameters like cycle split, length of period of forced oscillations in the reactor was investigated with respect to the conversion of the benzene. It is shown that for periodic reactor operation an average conversion was up to several times higher than a steady state value.