The identification and quantification of nitrogen-containing compounds in thermally cracked naphtha was investigated. A pretreatment method using nickel (II) carbonate was developed to completely remove fatty acids from this naphtha as nickel salts. On acidification of the nickel salts, it was possible to identify the acid species removed from the naphtha. It was further observed that with increasing temperature the pretreatment increasingly removed phenolic compounds as their nickel salts. Simple column chromatography with silica stationary phase was applied to separate the nitrogen-containing compounds from the acid-free naphtha using consecutive elution with <i>n</i>-pentane, dichloromethane and acetone. The nitrogen-containing compounds were mainly eluted in the acetone fraction and to a lesser extent in the dichloromethane fraction. The procedure simplified the matrix sufficiently so that analysis by gas chromatography coupled with mass spectrometry was possible to identify the major nitrogen-containing compounds. Pyridine derivatives were the dominant class of nitrogen-containing compounds. When practical, identification by mass spectrometry was confirmed by analysis of the equivalent commercially obtained nitrogen-containing compounds. Quantification was performed by gas chromatography coupled with flame ionization and nitrogen phosphorous detectors. Relative response factors for a selection of nitrogen-containing compounds were experimentally determined to improve overall quantification.

Nitrogen-containing compounds in thermally cracked naphtha

251st National Meeting (2016)

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