Stearic acid-modified NiFe2O4 nanocatalysts for efficient heavy oil upgrading

This study successfully synthesized a highly dispersible magnetic nanocatalyst (NiFe₂O₄@SA) based on stearic acid modification for efficient catalytic upgrading of heavy oil. Through comprehensive characterization methods including SEM, EDS, XRD, XPS, FTIR, TGA, contact angle measurements, dispersion tests, and VSM, the structure, surface properties, thermal stability, dispersion, and strong magnetic properties of the catalyst were investigated. When applied to heavy oil upgrading, this catalyst significantly reduced the viscosity of heavy oil and upgraded heavy oil. The effects of four different upgrading strategies on heavy oil viscosity reduction were evaluated: (1) direct aquathermolysis, (2) aquathermolysis with tetralin as a hydrogen donor, (3) aquathermolysis with only the NiFe₂O₄@SA catalyst (without adding hydrogen donor), and (4) aquathermolysis with NiFe₂O₄@SA as catalyst and tetralin as hydrogen donor. Comprehensive analyses of the heavy oil before and after upgrading were conducted using viscosity measurement, SARA fractionation, elemental analysis, GC-MS, ¹H NMR, and FT-IR. The results showed that program 4# significantly reduced the viscosity of heavy oil (by 76.6 %) and greatly improved its quality. More importantly, the NiFe₂O₄@SA catalyst demonstrated excellent reusability: after multiple cycles of use, heavy oil upgrading efficiency (viscosity reduction) remained stable; elemental analysis results of the upgraded oil after five cycles further confirmed the sustainability of its performance. Crucially, TGA analysis, contact angle measurements after prolonged high-temperature treatment, and VSM testing of the catalyst after recycling indicated that its thermal stability, surface properties, and magnetic property were well preserved, highlighting its outstanding durability. This study provides a new strategy for developing efficient, stable, and recyclable heavy oil upgrading catalysts.