Process for separating and purifying high-purity alpha-methylnaphthalene by supercritical extraction method

The invention relates to the field of purification processes of alpha-methylnaphthalene, in particular to a process for separating and purifying high-purity alpha-methylnaphthalene by a supercritical extraction method, which comprises the following steps: S1, adding metal halide into a raw material containing alpha-methylnaphthalene according to a certain weight ratio, reacting for 3-8 hours, removing solid substances, adding a washing solvent into filtrate according to a certain weight ratio, and reacting for 3-8 hours; after fully oscillating, standing for 20 to 40 minutes; s2, adding an extracting agent into the solution in the step S1, transferring into a supercritical reactor, heating, separating and collecting gas-liquid products, and condensing collected gas to obtain the high-purity alpha + beta methylnaphthalene composition, s3, adding the composition in the step S2 and an alcohol solvent into a crystallizer according to a certain proportion, stirring and cooling to the final crystallization temperat