CHARACTERIZATION OF PITCHES BY LIQUID-CHROMATOGRAPHY USING CELLULOSE 3,5-DINITROBENZOATE AS THE PACKING MATERIAL

Characterization of coal tar, petroleum and PVC pitches by a liquid ch romatography using cellulose 3,5-dinitrobenzoate (DNB-cellulose) as th e packing material was investigated. Separation mechanism based on cha rge-transfer interaction between the dinitrobenzoyl group and polyarom atic compounds was expected to be useful for separation of the constit uents of the pitches. First, 26 model polyaromatic compounds were test ed to examine the characteristic feature of the packing material by th e liquid chromatography. As the results, the compounds were found to b e classified roughly into four groups with different retention volume, principally according to the number of ring condensed. The nonplanar structure and aliphatic side chain of the polyaromatic compounds also affected on the separation behavior. Both benzene soluble-hexane solub le and benzene soluble-hexane insoluble fractions of the three pitches were separated on DNB-cellulose. It was found that, coal tar pitch co ntains relatively large amounts of some highly condensed polyaromatic compounds with condensed rings of 4 to 5 and petroleum pitch does smal l amounts of such specific highly condensed polyaromatic compounds, wh ile PVC pitch does large amounts of less condensed polyaromatic compou nds and there is not significant amount of highly condensed compound i n it. Thus DNB-cellulose was useful as the convenient packing material for liquid chromatography to characterize pitches.