Evaluation of Polycyclic Aromatic Hydrocarbon Removal from Hydrocracking Recycle Streams

Large polycyclic aromatic hydrocarbon (PAH) compounds with 7 or more rings, such as coronene, can be problematic in petroleum refining processes, where they build up over time and eventually enhance coke formation. In this work, large PAH molecules were characterized in a recycling stream returning the distillation bottoms of a commercial hydrocracking reactor back into the unit. High performance liquid chromatography and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) methods were in good agreement on PAH compounds extracted with DMSO, which provided a selective way to determine PAH with up to 10 aromatic rings. However, after Soxhlet extraction with pentane PAH compounds with up to 14 aromatic rings were tentatively identified using FT-ICR MS, extending the naphthalene zig-zag pattern. With the characterization method established, solvent extraction, solvent precipitation, and adsorption processes were tested to remove the problematic, large PAH compounds from the recycle stream....