Intermediate phase asphalt raw material for producing carbon fibers and preparation method thereof

The present invention relates to an intermediate phase asphalt raw material for producing carbon fibers and a preparation method thereof, wherein the intermediate phase asphalt raw material intermediate phase content determined through the polarizing microscope method is 100%, S1/S2 in the infrared absorption spectrogram of the intermediate phase asphalt is more than 1.7, S1 is the area of the absorption peak at the wavelength of 2800-2990 cm , S2 is the area of the absorption peak at the wavelength of 2990-3150 cm , S3/S4 in the C nuclear magnetic resonance spectrogram of the intermediate phase asphalt is less than 19, S3 is the area of the absorption peak with the chemical shift of 23.8-58.0 ppm, and S4 is the area of the absorption peak with the chemical shift of 8.0-23.8 ppm. According to the present invention, methylnaphthalene and other naphthalene compounds are adopted as raw materials, hydrogen fluoride-boron trifluoride is adopted as a catalyst, and the polymerization conditions are controlled to prepare the intermediate phase asphalt. Compared with the intermediate phase asphalt in the prior art, the intermediate phase asphalt of the present invention has characteristics of excellent spinnability, excellent pre-oxidation property and simple preparation process control, and can be adopted as the industrial production raw material of the high strength and high modulus asphalt-base carbon fibers.