NOVELTY - A biphenyl synthesizing method involves preparing sample by mixing waste capacitor oil and n-hexane to produce capacitor oil stock solution. The catalyst is synthesized by adding special reagent to iron-nickel mixed salt solution to form suspension and separating nano particles of the catalyst by centrifugation, where solvent is removed. The obtained product is placed in a high-pressure reaction kettle, where the capacitor oil stock solution and auxiliary agent solution are added to the kettle. The content in the kettle is subjected to chlorination reaction.    USE - Method for synthesizing biphenyl utilized in chemical industry, medicines, pesticides, fuels and liquid crystal production field.    ADVANTAGE - The method enables synthesizing biphenyl from capacitor oil in an eco-friendly manner.    DETAILED DESCRIPTION - A biphenyl synthesizing method involves preparing sample by mixing waste capacitor oil and n-hexane at volume ratio 1:3-1:5 to produce less viscous capacitor oil stock solution. An auxiliary agent is dissolved in water to produce the auxiliary agent solution. The catalyst is synthesized by adding special reagent to iron-nickel mixed salt solution to form suspension and separating nano particles of the catalyst by centrifugation, where solvent is removed. The obtained product is subjected to vacuum rotary drying process, and the dried product is placed in a high-pressure reaction kettle, where the capacitor oil stock solution and auxiliary agent solution are added to the kettle. The content in the kettle is subjected to chlorination reaction, and the obtained liquid is cooled. The liquid is separated by special continuous liquid-liquid extraction, where the organic product is separated from aqueous phase and distilled to obtain biphenyl product. The liquid obtained after chlorination reaction is further recycled.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow-diagram illustrating a method for synthesizing biphenyl catalyst. '(Drawing contains non-English language text)'