Relating Feedstock Composition to Product Slate and Composition in Catalytic Cracking. 3. Feedstocks Derived from Maya, a Mexican Crude

Abstract

The fluid catalytic cracking (FCC) behavior of compound types present in the >650°F resid from Maya crude was investigated. Distillation and liquid chromatography 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, nitrogen, nickel, and vanadium partitioning; and, in selected cases, gasoline composition. Results obtained from Maya fractions were compared to those obtained from earlier FCC studies of compound types from Wilmington, CA, and Brass River, Nigeria, >650°F resids. A conceptual model was proposed that adequately predicted FCC product slates obtained from >650°F neutral fractions from Maya and the other crudes. An important premise of the model was primary production of gasoline and C 3 /C 4 gases from alkyl side chains and acyclic paraffins in feeds with concurrent conversion of aromatic and naphthenic cores to cycle oils. The product slates calculated from the model agreed well with those determined experimentally. Highly aromatic feedstock constituents presumably formed only coke and light gases. A calculation of hydrogen transfer resulting from cracking indicated no significant hydrogen exchange between aliphatic gasoline or C 3 /C 4 gas precursors and naphthenic/aromatic cores. Implications of the model toward improving FCC feed pretreatment and performance evaluation are discussed.

Relating Feedstock Composition to Product Slate and Composition in Catalytic Cracking. 5. Feedstocks Derived from Lagomedio, a Venezuelan Crude†

“…The feeds exhibiting the lowest conversion and gasoline yield were those containing the distillate base fractions. Sulfur partitioning to H 2 S was relatively high for most feeds, as observed previously. − Similarly, nitrogen partitioning to liquid products was appreciably higher for feeds enriched in distillate acids or bases. As with the other crudes, relative carryover of nitrogen into liquids was highest for feeds enriched in distillate acids.…”

“… a 650−950 °F Neutrals were analyzed according to methodology described in ref . b Product distribution calculated according to parameters described in ref . c From Table . …”

“…The above separation procedure was based on the work of Copelin as well as Snyder and Buell . The assumed value for molar absorptivity was based on the absorbance of amides isolated from Maya 650−930 °F acids . This method could also be applied to base fractions as well as whole distillates/resids with minor adjustments in quantites charged to the Al 2 O 3 column and, particularly for base fractions, wavenumber for determination of absorbance.…”

“…Basic nitrogen (N B ) was determined via nonaqueous titration as described previously; concentrations of basic and amide forms of nitrogen as well as of Ni and V were used to predict gasoline yields, as discussed below. The procedure for determining Ni and V in feeds and products was described in the third paper of this series …”

“…This information is being sought in an effort to improve FCC processing of conventional feedstocks and to extend FCC to lower quality feedstocks, such as atmospheric resids from heavy oils. The first three papers presented results from feedstocks derived from Wilmington (CA), Brass River (Nigeria), and Maya (Mexico) crudes; the fourth dealt with a model for calculating nine product subclasses from mass spectral analysis of hydrocarbon and sulfur types in the feed. − …”