Two-Stage Hydrotreating of Athabasca Heavy Gas Oil with Interstage Hydrogen Sulfide Removal:  Effect of Process Conditions and Kinetic Analyses

Abstract

Two-stage hydrodenitrogenation (HDN)−hydrodesulfurization (HDS) of heavy gas oil, derived from Athabasca bitumen, has been carried out in a trickle-bed microreactor using a commercial NiMo/Al 2 O 3 catalyst. The operating conditions for the experiments were varied as follows: temperature range of 340−420 °C, reactor pressure of 950−1600 psig, liquid hourly space velocity range of 0.5−2.0 h -1, and hydrogen to heavy gas oil ratio of 600 mL/mL. Variation in the catalyst loading between stages I and II was also studied. Stage I products were stripped off any generated hydrogen sulfide and further hydrotreated in stage II to see the impact of hydrogen sulfide interstage removal on the hydrotreating activities. A comparison of the two-stage results to those of the single-stage results shows an enhancement in the hydrotreating activities. For instance, a 12.6 wt % increase in the conversion of nonbasic nitrogen was observed. The optimum conditions for higher gain in HDN and HDS due to hydrogen sulfide removal were found to be 380 °C, 7.6 MPa, and 1:3 (w/w) catalyst loading. A Langmuir−Hinshelwood model developed for the hydrogen sulfide inhibition predicts sufficiently the observed data of the two-stage process.