Demetallization of Heavy Oils: A Critical Comparative Analysis of Catalytic, Adsorptive, Thermal, and Solvent-Based Pathways

Heavy crude oils and vacuum residues contain up to ۱,۵۰۰ ppm of nickel and vanadium, sequestered within stable porphyrinic complexes embedded in asphaltene matrices. These metals poison catalysts, drive corrosion, and generate toxic emissions, fundamental barriers to heavy feedstock utilization. This review critically examines the landscape of demetallization strategies, from established industrial benchmarks to emerging laboratory-scale innovations, bridging molecular mechanismswith process engineering realities. Catalytic hydrodemetallization (HDM) achieves ۹۰–۹۸% metal removal via hydrogenolytic cleavage over sulfided NiMo/γ-Al۲O۳; yet, remains constrained by capital intensity, hydrogen demand, and progressive catalyst deactivation. Adsorptive technologies, particularly amine-functionalized sorbents, demonstrate >۹۹% vanadyl porphyrin removal under mild conditions through axial coordination. Thermal processes concentrate ۹۵–۹۸% of metals into coke, albeit with carbon rejection penalties. Emerging ionic liquids (ILs) and deep eutectic solvents (DES) exploit tunable π–π interactions and coordination chemistry, offering hydrogen-lean alternatives whose potential and limitations are critically assessed. What distinguishes this work is its comparative, mechanism-driven synthesis across otherwise fragmented technology domains. Analysis reveals that hybrid configurations, guard-bed HDM, solvent deasphalting (SDA) coupled with hydroprocessing, and ionic liquid pretreatment, offer the most promising pathways to maximize demetallization depth while reducing hydrogen and energy intensity. Persistent bottlenecks include mass transfer limitations in viscous media, solvent regeneration economics, and a fundamental gap in molecular-level understanding of metal–asphaltene interactions. Strategic directions converge refining economics, environmental regulation, and the emerging imperative to recover vanadium and nickel as critical materials for the energy transition, a perspective that reframes demetallization from a costly necessity to a strategic opportunity.

کلیدواژه ها:

Demetallization of heavy oil ، Nickel and vanadium removal ، Hydrodemetallization (HDM) ، Adsorption technology ، Thermal and thermocatalytic processes ، Solvent Deasphalting