The fluid catalytic cracking (FCC) behavior of compound types
present in the >650 °F resid
from Brass River (Nigerian) crude was investigated. Liquid
chromatography and distillation
were employed for separation of selected compound type fractions from
the resid; the resulting
fractions were then cracked using a bench scale FCC unit. The FCC
behavior for each compound
type was defined in terms of the resulting product distribution (yields
of gas, gasoline, etc.) sulfur
and nitrogen partitioning, and in selected cases, gasoline composition.
Results obtained from
Brass River fractions were compared to those obtained from an earlier
FCC study of compound
types from
Wilmington, CA, >650 °F
resid. Correlations were derived for gasoline and coke
yields
from feedstocks derived from either crude. Brass River is a sweet,
paraffinic crude which gives
rise to a >650 °F resid with very favorable FCC characteristics.
Although the bulk of the FCC
gasoline was produced from cracking hydrocarbon types present,
significant gasoline production
also occurred from heteroatomic compounds (acids/bases) in Brass River.
Conversely, negligible
gasoline production was observed previously from cracking Wilmington
acid/base types. However,
feedstocks from both crudes exhibited greater conversion of sulfide
sulfur to H2S compared to
thiophenic forms of sulfur, and greater carryover of acidic forms of
nitrogen (e.g., carbazole)
compared to basic forms (e.g., quinoline). Overall gasoline
composition depended on hydrocarbon
type composition of feedstocks but was also influenced by presence of
acids and/or bases in the
feed. On the other hand, the detailed distribution of isomers
within a given gasoline homolog,
e.g., C3-benzenes or C9 isoparaffins, was
nearly independent of feed composition. Results
obtained
for Brass River will serve as benchmarks for future FCC data obtained
from low-quality feedstocks.