Effect of Palm Fatty Acid Distillate on Hydrodesulfurization and Hydrodeoxygenation in Co-processing with Petroleum Gas Oil in Hydrotreating Unit

Abstract

Deoxygenation of palm fatty acid distillate (PFAD) to produce renewable diesel had been experimented in co-processing with petroleum light gas oil (LGO) in a pilot-scale reactor. The reaction was achieved in the fixed-bed hydrotreating reactor, over commercial CoMo/Al2O3 under 280–350 oC, 25 barg, H2/feed of 630 Nm3/m3 and 0.75 h-1 of LHSV. High conversion were achieved when varied PFAD up to 25 wt%. The presence of PFAD in LGO improved cetane index of the liquid products. Heat effect due to overall exothermic reactions was observed. Hydrogen consumption was then theoretically calculated and extrapolated for hydrotreating of pure PFAD. Further study by laboratory scale reactor with model component was to study the effects of PFAD on actvities over prolonging time at the similar conditions and catalyst by using palmitic acid, and model LGO. The presence of 4,6-DMDBT resulted in high deoxygenation conversions, while the palmitic acid decreased the desulfurization activity as a reversible effect. The modification of the reactor depicted the polymerization of unsaturated feed at heating section. Additional pretreatment by double-bond hydrogenation was benefited to both activities since the major cause of the deactivation was from the polymerized product that blocked the catalyst pore and lowered activity. The deactivated catalyst could be efficiently reactivated by 2 wt% of dimethyl-disulfide (DMDS) in n-C18 at 320 oC. These results could be valuable as foreseeing information to an improvement of an existing hydrotreating unit for co-processing PFAD with LGO.