Accurate ranking of fluid catalytic cracking (FCC) feeds will help oil producers price their
commodities. The value of an FCC feed depends on its properties, which, in turn, contribute
toward producing high-value products with good qualities. Feed ranking based on general analyses
is the simplest way to determine the best feeds but can be misleading for some. In this study,
the authors propose a feed grading method with consideration of only concentrations of gasoline
precursors, total nitrogen, and microcarbon residue (MCR), assuming that gasoline is the most
desirable product. By assigning the merit and discount values of the three elements, the relative
gasoline yield of a feed can be calculated and its apparent feed rank established. The method
was tested on 10 feeds that were catalytically cracked in both a microactivity test (MAT) unit
and a riser pilot plant. With some exceptions, the apparent feed ranks indicated an agreeable
order with those based on individual high- and low-value MAT product yields at both constant
test severity (catalyst/oil (C/O) ratio of 7) and conversion (65 wt %). The apparent feed ranks
were also validated with the exact feed ranks determined by comparing the individual MAT yields
at an achievably high conversion, using the maximum gasoline yields as a guide. The two feed
ranks also showed good conformity, with respect to the sequence. Verification of apparent feed
ranks against riser pilot plant yields in this study was difficult, because of limited test data for
comparison. MAT yields of the 10 feeds compared better with riser pilot plant yields at the same
conversion than with yields at the same C/O ratio. Among the six cracked products, dry gas gave
the best comparison, in terms of absolute yields, whereas coke showed the worst results.
This paper demonstrates the important roles of feedstock and catalyst in determining the yield
structure during fluid catalytic cracking (FCC) of bitumen-derived vacuum gas oils (VGOs). Three
nonconventional VGOs, derived from Canadian oil-sands bitumen, were catalytically cracked in
a fluid-bed microactivity test (MAT) reactor. Two commercial equilibrium catalysts were used:
a bottoms-cracking catalyst containing rare earth exchanged Y zeolite (REY), and an octane-barrel catalyst containing rare earth ultrastable Y zeolite (REUSY) mixed with a small amount
of ZSM-5. Both catalysts were embedded in active matrixes. Results indicated that the REY
catalyst was more active, producing higher yields of valuable distillates and less coke for the
same feed, whereas the catalyst containing REUSY/ZSM-5 gave more light gases and less gasoline
(although the quality of this gasoline might be better). These results could be related to catalyst
properties including zeolite type, rare earth content, matrix pore structure, zeolite-to-matrix ratio,
and surface characteristics. The three feeds were ranked based on their yield structures, which
could be explained through feed analyses, precursor concentrations determined by GC-MS, and
product characterization data from a PIONA analyzer. MAT results were compared with riser
pilot plant data at 55 and 65 wt % conversion. In general, at the same conversion, the difference
in a given product yield from the two units could be maintained within 15%. Coke yield showed
a greater disagreement, however, due to methodological differences in the analysis.
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