SEPARATION OF PETROLEUM-HYDROCARBONS USING DEALUMINATED MORDENITE MOLECULAR-SIEVE .2. ALKYLNAPHTHALENES AND ALKYLPHENANTHRENES

A pentane solution of a crude oil fraction containing diaromatic and t riaromatic hydrocarbons was subjected to a liquid chromatographic tech nique using dealuminated mordenite molecular sieves as the stationary phase and pentane as the mobile phase. Two fractions were obtained: on e containing hydrocarbons not retained by the sieves that were eluted from the column and the other from acid digestion of the sieves and re covery of the liberated hydrocarbons. The hydrocarbons in each fractio n were analysed using GC-MS techniques. Mass chromatograms showing dim ethylnaphthalenes, trimethylnaphthalenes, tetramethylnaphthalenes, met hylphenanthrenes and dimethylphenanthrenes revealed significant differ ences between the two fractions. Alkylnaphthalenes with substituents i n both positions 1 and 4 were invariably excluded from the molecular s ieve. Some alkylnaphthalenes with substituents in positions 1, 3 and 7 were weakly sorbed by the sieves whereas other isomers were strongly sorbed. Analysis of methylphenanthrenes and dimethylphenanthrenes show ed that compounds with substituents in position 9 or 10 were excluded from the sieve channels. Some inhibition to sorption was displayed by compounds with substituents in position 4 whilst phenanthrenes substit uted in position 2 appeared to be readily sorbed. The technique is use ful for separating some alkylnaphthalene and alkylphenanthrene isomers that are difficult to separate using other, more conventional chromat ographic techniques.