Asphalt was treated with sulfonating reagent, using hydrocarbon oil as solvent, instead of such halogenated hydrocarbons as 1, 1, 2-trichloroethane, perchloroethylene, etc., which might have toxicity.
Saturated aliphatic hydrocarbons were relatively stable to acids, pretreatment reagents of asphalt, therefore they could be used as solvent for asphalt.
Granulated char was obtained in hydrocarbon solvents with carbon number above 7. The grain size of the granulated char became smaller with increasing carbon number of solvent molecule.
The highest yield of granulated char was obtained in the case of noctane; its share was 90% of the total char produced.
The solubility of asphalt to aliphatic hydrocarbons was better in normal chain compounds than in branched chain compounds, and the former was more stable to acid than the latter. The average recovery of n-paraffine (carbon number 7-9) was about 98%; this value was almost the same as that of 1, 1, 2-trichloroethane.
Though the hardness of char varied according to the carbon number of solvent used, generally it was a little smaller than that of the char obtained with 1, 1, 2-trichloroethane.
Comparing at the same yield of activated carbon, the specific surface area of activated carbon obtained with hydrocarbon solvent was more or less smaller than that with 1, 1, 2-trichloroethane. But these activated carbons showed almost the same methylene blue adsorbability.