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

Abstract

The fluid catalytic cracking (FCC) behavior of compound types present in the >650°F resid from Lagomedio 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 Lagomedio fractions were compared to those obtained from earlier FCC studies of compound types from Wilmington, CA, Maya (Mexican), and Brass River (Nigerian) >650°F resids. An equation is presented for prediction of gasoline yield for feedstocks derived from Lagomedio as well as other crudes. Gasoline yield (wt % of feed) is calculated from these feedstock parameters: the atomic ratio of hydrogen divided by carbon plus sulfur (H/(C + S)), the fraction of the feed volatilized at the cracking temperature f c T, effective metal content (M eff ) Ni + V/4) expressed in µequiv/g, basic nitrogen (N B , wt %) and amide-type nitrogen (N Am , wt %). The relation is G ) 10.25[H/(C + S) + log(f c T)] -1.5M eff -29(N B + N Am ) + 30.2. Calculated and experimental gasoline yields typically agreed within 1.5 wt %, which is the pooled standard deviation for the experimental data. An infrared spectrophotometric method is provided for determination of N Am ; the other parameters are measured using standard methods or previously published procedures.

Relating Feedstock Composition to Product Slate and Composition in Catalytic Cracking. 6. Feedstocks Derived from Merey, a Venezuelan Crude

“…The distribution of compound types in the Merey crude was similar to that of the Lagomedio crude . The largest difference in the compound-type distributions between the two >650 °F resids was the greater proportion of strong acids in the Merey crude (4.9 wt %), compared to that in the Lagomedio crude (3.5 wt %).…”

“…In a study that compared coke (carbon residue) formation to the composition of vacuum residues, data for Merey fit correlations that had been derived for it and the other resids in the study, thereby implying that Merey exhibits typical behavior for its compositional characteristics . It is a significantly lower-quality crude, compared to Lagomedio, which is the Venezuelan crude that was used to derive feedstocks for the most recent paper in this series …”

“…The amide nitrogen content was determined by IR spectrometry . The basic nitrogen content was determined via nonaqueous titration, as described previously; the concentrations of basic and amide forms of nitrogen, as well as that of nickel and vanadium, were used to predict gasoline yields, as discussed below.…”

“…The first three papers presented results from feedstocks that were derived from Wilmington (California), Brass River (Nigeria), and Maya (Mexico) crudes. − The fourth paper involved a model for calculating nine product subclasses from mass spectral analysis of hydrocarbon and sulfur types in the feed . The fifth paper presented a revised gasoline correlation that included the atomic ratio of hydrogen to the sum of carbon plus sulfur, the feed fraction volatized at the cracking temperature, and the effective metals and nitrogen contents (both basic and amide type) . This nitrogen type determination is particularly relevant to the current research on mechanisms for NO x formation in the regenerator …”

“…The basic nitrogen content is denoted as [N B ], and the amide nitrogen content denoted as [N Am ]; both terms are given in terms of weight percent. The measurement of amide nitrogen was discussed in the last paper . Qian and co-workers presented evidence for strong interaction of both basic and amide nitrogen compounds with active catalyst sites in their FCC coke studies …”