Turning waste into wealth: high-acid-value waste oil upgraded to high-performance natural ester insulating oil in one efficient process

Traditional natural ester insulating oils are mostly produced from edible vegetable oils, leading to high costs and competition with food supplies. China produces a huge amount of kitchen waste cooking oil annually. However, due to its high acid value and serious degradation, it is difficult to directly prepare high-performance insulating oil, and related research has long been lacking.

In this study, a multi-stage coupled refining process consisting of phosphoric acid degumming, alkali refining deacidification, activated carbon adsorption decolorization/deodorization and winterization was constructed. The high-acid-value waste cooking oil with an initial acid value of 21.04 mg KOH/g was deeply purified to 0.024 mg KOH/g; the dielectric dissipation factor at 90℃ decreased from 1.335 to 0.0197, and the power frequency breakdown voltage increased from 27.9 kV to 72 kV. All physical, chemical and electrical properties meet the requirements of DL/T 1811—2018 for natural ester insulating oil. By adding BHT antioxidant, the initial oxidation temperature of the oil was increased from 143.12℃ to 180.34℃, significantly enhancing the long-term stability.

This achievement realizes the resource conversion of waste cooking oil into high-performance insulating oil, balancing environmental protection, safety and the “dual carbon” goals, and provides a new eco-friendly insulation material solution for the construction of green power grids. The work entitled “Study on the Preparation of Natural Ester Insulating Oil from High-Acid-Value Waste Cooking Oil Based on Multi-Stage Coupled Refining Process” was published on Journal of Engineering Studies (published on Mar. 16, 2026).