Properties of gas sparged coal tar pitch compositions Original Research Article

Two pitches have been modified to varying degrees by gas sparging at 400°C for various times. The process gas used was either 1% oxygen in nitrogen or 5% hydrogen in nitrogen. Results indicate that for pitch A, the product is independent of sparge gas and that sparging does not benefit the carbon yield with respect to the raw pitch. Some improvement in toluene insoluble content is observed, however, it would appear that this does not translate to the formation of additional carbon. Overall, the results indicate that the predominant reaction giving rise to the hardening of the pitch is stripping of volatile matter. Pitch B shows different behaviour, whilst with the hydrogen sparge gas the results are similar to pitch A, the oxygen sparge gas shows marked improvement in the yield of carbon from the raw pitch. The improvement in pitch B with oxygen is presumably due either to an oxidative molecular growth mechanism or to the incorporation of oxygen functionality into the pitch and a consequential reduction in volatility.