Abstract: For the high sulfur content of expanded graphite prepared and an unstable expansion volume by the traditional method, natural graphite flake graphite was used as raw material, KMnO4 as oxidant, HClO4 and H3PO4 as intercalating agent, the expansion of expandable graphite by microwave oven and muffle furnace.The orthogonal experiment was used to determine the optimum process conditions.The results show that the optimum reaction conditions are as follows: graphite (g)∶mixed acid (mL)∶potassium permanganate (g) =1∶4.5 mL (3.6 mL perchloric acid∶0.9 mL phosphoric acid)∶0.3, reaction temperature 30 ℃, reaction time 60 min, filtering and washing to pH 5-7, drying at 80 ℃, and expanding in the microwave oven, the expanded graphite has the largest volume of 350 mL/g.

Key words: sulphur-free;expanded graphite;preparation;characterization