Hydrodesulfurization of dibenzothiophene in a micro trickle bed catalytic reactor under operating conditions from reactive distillation

The hydrodesulfurization (HDS) of dibenzothiophene (DBT) is investigated over a commercial NiMoP/γ-Al₂O₃ catalyst in a micro trickled bed reactor (Micro-TBR) at operating conditions of a reactive distillation (RD) column. An analysis with and without reaction is carried out to have a first understanding on the complex interaction between kinetics and transport phenomena. A set of well-accepted criteria is evaluated to elucidate the presence of heat and mass transport limitations. Residence time distribution (RTD) experiments are performed to evaluate axial dispersion through the estimation of axial dispersion coefficient (D_axial,L) from a convection-dispersion model. Experiments with reaction are carried out using hydrogen and DBT as feedstock at reaction temperatures from 533 to 599 K, pressures from 1.5 to 2.5 MPa and inlet molar flow of DBT from 4 to 12×10^-8 mol.s^-1. A pseudo heterogeneous model accounting for mass transport limitations is used to describe experiments under reaction conditions. The main findings can be summarized as follows: most of RD operating conditions lead to the presence of interfacial mass transport limitations at both interfaces L-S and G-L; convection-dispersion model is able to describe satisfactorily RTD observations, suggesting that axial dispersion phenomena are negligible; conversion of DBT ranges from ca. 22 to 90% having a selectivity to by-product molecules from 30 to 80%, respectively; and the pseudo heterogeneous reaction model describes observations adequately obtaining activation energies ranging from 49 to 62 kJ mol^-1 at pressures from 1.5 to 2.5 MPa, respectively. Estimated activation energies are comparatively lower than the activation energies reported in literature for the conventional HDS process, i.e. 40-160 kJ.mol^-1, thereby suggesting an apparent catalytic energy savings by using RD technology.