Metal and sulfur removal from petroleum oil using a novel demetallization-desulfurization agent and process

Abstract

Removal of metals and sulfur is a challenging operation during the crude refining that often is the bottleneck thereby increasing costs and reducing overall energy efficiency. Specifically, soluble sulfur and metal compounds containing vanadium and nickel are the most difficult to manage leading to problems such as: elevated corrosion, rapid catalyst deactivation, and potential human exposure and health impacts. In this study, a novel demetallization-desulfurization process has been developed to selectively extract metals about 36 metals including vanadium and nickel from the core of the porphyrin ring without removing or destroying the ring. This novel process utilizes bis(2-ethylhexyl) phosphoric acid as the demetallization-desulfurization agent (DM-DSA). The primary mechanism is that the DM-DSA acts as a proton donor and selectively removes metals from the core of the porphyrin ring, thereby permitting the oil yield to be unaffected. A further benefit is the reduction in the levels of thiophene compounds via a different extraction mechanism under the same reaction conditions. This proton donor is able to form an ionic liquid under reaction conditions that extracts thiophene compounds through hydrogen bonding and electrostatic force. The maximum removal efficiency measured was 90% and 79% for vanadium and nickel, respectively, and 53% for sulfur when bis(2-ethylhexyl) phosphoric acid was mixed and reacted and subsequently separated from Basra crude oil. The novel developed process herein is environmentally friendly “green” and cost-effective since no additional operations such as emulsification are required (limited energy input), no solvents are consumed during the reaction and oil yield is not impacted.