Coprocessing Partially Hydrodeoxygenated Hydrothermal Liquefaction Biocrude from Forest Residue in the Vacuum Gas Oil Hydrocracking Process

Hydrodeoxygenation of biogenic feedstocks is an option to alleviate the challenges associated with their coprocessing in petroleum refinery units. This study investigates the effect of coprocessing a partially hydrodeoxygenated biocrude with vacuum gas oil (VGO) in a hydrocracking process. The biocrude, produced by hydrothermal liquefaction (HTL) of forest residues, was hydrodeoxygenated to an oxygen level of 3.6 wt % at which it became fully miscible in the VGO feed. The coprocessing feed blend was constituted of 7.5 wt % hydrodeoxygenated biocrude in 92.5 wt % VGO. Pilot plant tests were carried out in two sequential stages: hydrotreating and hydrocracking. Hydrotreating was performed first, with the purpose of meeting the sulfur and nitrogen specifications of the hydrocracking catalyst. The hydrotreated products next underwent hydrocracking to produce enough product for physical distillation. The tests were conducted using pure VGO first to set a baseline for the study and then the coprocessing feed. During both hydrotreating and hydrocracking, coprocessing required increasing the reactor temperature by 10-15 degrees C over the baseline temperature for pure VGO to offset the poisoning effect of oxygen compounds. The hydrotreating stage was also affected by reactor plugging issues attributed to unstable high-boiling material in the biocrude. In spite of this, the coprocessing scheme was shown to stand on par with the VGO baseline in terms of overall product distribution and without consuming more hydrogen. Moreover, the coprocessed naphtha, diesel, and jet fuel fractions showed only subtle differences in properties and hydrocarbon composition relative to those from VGO. Biogenic carbon measurements revealed that the coprocessed naphtha, diesel, and jet fuel fractions contained 8-9 wt % biogenic carbon.