Co-processing of Raw and Hydrotreated HTL Biocrudes with Heavy Gas Oil: Impact on Catalyst Properties and Product Quality

Hydrothermal liquefaction (HTL) of biomass produces biocrude with a high oxygen content, leading to blending and miscibility challenges with petroleum fuels. Co-processing biocrudes with refinery streams improves sustainability but can accelerate catalyst deactivation and cause solid or coke formation during secondary processing. To address these issues, biocrude derived from the HTL of canola and mustard meal (1:3 wt./wt %) was upgraded via hydrotreatment. NiMo catalysts supported on sawdust-derived hydrochar reduced the oxygen content from 9.2 to 3.2 wt %. Blends of raw and hydrotreated biocrude with hydrotreated heavy gas oil (HHGO) were prepared at 2, 5, and 10 wt %. These blends were characterized before and after co-processing with NiMo catalysts. Nonhomogeneous phase was observed in the blends before co-processing. After co-processing, the blends showed improved homogeneity and miscibility. TGA analysis was used to identify the coke content and the possible regeneration temperature. Coke formation for 10% raw biocrude blends was 8.3 wt %, whereas 10% hydrotreated biocrude blends had a lower coke content of 4.3 wt %. Increasing the blending ratio led to higher coke formation. Raman spectroscopic analysis confirmed the presence of amorphous soft coke and graphitic coke, while NMR analysis identified aliphatic and aromatic structures in the coke deposits. Pretreating HTL biocrude can help minimize problematic oxygen compounds and reduce catalyst deactivation during co-processing. The combination of improved blend stability, inhibition of polymerization, lower viscosity, and good compatibility at low blend ratios indicates that hydrotreated biocrudes could be viable for refinery use.