Abstract
Desulfurization and hydrogenation of aromatics in diesel oil were investigated in an isothermally operated trickleβbed reactor 500 mm long and with a 19βmm ID, using commercial bifunctional NiMo/Al~2~O~3~ catalysts. The operating temperature, pressure, liquid hourly space velocity, gas/oil ratio, and the initial concentration of H~2~S were 300β380Β°C, 2β8 MPa, 1β4 h^β1^, 100β500 m^3^~(NTP)~/m^3^ and 0β8 vol %, respectively. The increase in pressure and decrease in liquid hourly space velocity lead to deeper desulfurization and hydrogenation of both aromatics. Although a higher gasβtoβoil ratio and lower initial concentration of H~2~S enhance the desulfurization reaction, these parameters play almost no role for hydrogenation. Desulfurization increases sharply with increased temperature, but with the same change in temperature the conversion of aromatics increases only up to 360Β°C, above which it falls sharply. This behavior is explained by the approaching of chemical equilibria by the reversible hydrogenation reactions of the aromatics at higher temperatures. A mechanistic mathematical model was developed for a twoβphase flow reactor, considering both mass transfer and chemical reaction in the reactor. The kinetic equations for desulfurization and for the hydrogenation of monoβ, diβ and polyaromatics were established. Simulated results are compared satisfactorily with the experimental observations.