Due to the depleting production of conventional petroleum, heavy oil is turned to as an alternative. However, the presence of trace nickel and vanadium in heavy oil poses problems for the refining process in producing lighter-end products. Such problems are its tendency to poison the catalyst, accumulate during distillation, and corrode the equipment. The objective of this work is to remove the metal porphyrins from model oil using the thermally stable ionic liquid 1-butyl-3-methylimidazolium octylsulfate, [BMIM][OS] assisted by subcritical toluene (above boiling point, 110.6°C and below a critical point, 318.6°C at 41.264 bar) in a novel attempt. The experiments were conducted at 150ºC to 210ºC under a mixing time of 30 to 90 minutes while the pressure was monitored. Four metal porphyrins are used: nickel etioporphyrin, nickel tetraphenylporphyrin, vanadium oxide etioporphyrin, and vanadium oxide tetraphenylporphyrin. The results show that more than 40% of removal is achieved for all metal porphyrins, which shows great potential for further technological improvement. The Nuclear Magnetic Resonance (NMR) shows that the ionic liquid did not decompose at the process temperature, which proves great stability. The extraction of metal porphyrins follows the second-order extraction model with an R2 of more than 0.98.

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