Effect of Iodine Treatment on Carbonization of Coal Tar Pitch

Abstract

The effect of iodine treatment on carbonization of coal tar pitch was investigated. Coal tar pitch with softening point of 101°C was used as a starting material. The pitch specimen, molded into 6 mm in diameter and 20mm in length, and iodine powder of about twice of the specimen weight were put into a test tube. After sealing the tube, they were heated at 90°C for iodine treatment. The specimens were preoxidized at 170°C for 3 hours in air flow to stabilize the pitch. Then preoxidized specimens were heated for carbonization at a rate of 2.5°C/min up to 800°C in Ar flow. The duration at the highest temperature was 1 hour. From the result of solvent fractionation using benzene and pyridine, iodine treatment and preoxidation treatment was known to increase molecular weight of components in the pitch. Carbon yield of the specimen was increased from 56% to 76% by iodine treatment for 20 hours. Microstructure of the carbonized specimens changed from flow type texture to mosaic one with increasing period of the iodine treatment.