PURPOSE: To recover a tar base in high recovery at a low cost from a crude methylnaphthalene fraction produced by the fractional distillation of coal tar using sulfuric acid as an extractant, by enlarging the specific gravity difference between the extractant and the fraction using a sulfuric acid salt.
CONSTITUTION: A tar base is separated and recovered either by (a) adding and contacting sulfuric acid and a sulfuric acid salt to a fraction containing a tar base and indole and produced by fractional distillation of coal tar and adding a base to the extracted liquid containing the tar base or by (b) adding and contacting sulfuric acid 2 to the above fraction 1 to extract (3) the tar base 9 and adding a base 7 to the extracted liquid 6. At the same time, the sulfuric acid salt solution 10 of the residual liquid is fed back and circulated to the above fraction at the stage AWD near the extraction stage 3. The process suppresses the polymerization loss of indole, facilitates the separation of the above extracted liquid and enables the separation and recovery of the tar base from the above fraction at a high recovery rate in an extremely short time.
TANAKA MAKOTO
TAKEO SETSU
