Overall isobutene conversions in excess of 95% are achievable, but the n-butene
conversion is much lower, in the order of 10%, so that an n-butene recycle should be
maintained if maximum conversion is desired. Selectivity to the desired diisobutenes
or isobutene/n-butene codimers is in the 85–90% range, while production of trimers
(C12 =) is about 10–15%, and the production of heavier compounds (tetramers, etc.)
is negligible.Atypical trimethylpentane (TMP) product from an FCC C4 feed at about
10% n-butene per-pass conversion can be characterized as follows