STABILITY OF CRACKED NAPHTHAS FROM THERMAL AND CATALYTIC PROCESSES AND THEIR ADDITIVE RESPONSE .2. COMPOSITION AND EFFECT OF OLEFINIC STRUCTURES

Olefinic concentrates were separated from two naphthas, one from fluid catalytic cracking (FCC) and one thermal crackate, using column chrom atography. The composition and structure of the olefins were determine d by a combination of analytical techniques. FCC naphthas contain rela tively higher levels of conjugated dienes. The monoolefins are highly branched. The thermal crackates have higher levels of a-olefins and ab ound in mono-, di-, tri- and conjugated cyclic olefins. Stability test s on these olefinic concentrates blended in low-S,N straight-run napht ha showed that cyclic olefins are very active gum formers. Representat ive commercial antioxidants (hindered phenols and phenylenediamines) b oth gave good responses to different olefin concentrate test blends. H indered phenols had a marginally better effect.