Relating Feedstock Composition to Product Slate and Composition in Catalytic Cracking. 1. Bench Scale Experiments with Liquid Chromatographic Fractions from Wilmington, CA, >650 .degree.F Resid

Abstract

The catalytic cracking behavior of compound types in the >650°F resid from a Wilmington, CA, 14.2°API crude was investigated. Liquid Chromatography (LC) was used to sepm'ate the resid into eight fractions. These fractions were used as feedstocks for a bench scale fluidized catalytic cracking (FCC) unit. Gasoline was produced almost exclusively from neutral (65 % of whole resid) components. Acidic and basic types were partially converted to coke plus small amounts of C! and C2 gases, with the balance primarily carrying over as heavy liquid products. Gasoline composition depended on the type and quantity of polar compounds present in the feed because both acidic and basic compounds inhibited cracking reactions (13-scission, hydrogen transfer, etc.) to varying degrees. In accordance with prior work, basic nitrogen compounds exhibited the largest inhibitory effect on cracking. Their effect is dependent on concentrations up to a limiting value which may correspond to saturation of susceptible catalyst sites. On an equal weight basis, the effect of high boiling (high molecular weight) bases was less than those occurring in the 650-1000°F distillate range. Pm'titioning of nitrogen present in acidic (e.g. carbazole) forms in the feed into liquid products was greater than for basic nitrogen. Thiophenic forms of sulfur partitioned more into liquid and less into gaseous (H2S) products than sulfide-type sulfur. Coke yield was approximately proportional to microcarbon residue test results for all feeds. Ongoing work with additional feedstocks has indicated behavior similar to that of Wilmington. Selected Wilmington liquid products are undergoing detailed analysis in order to determine relationships between feed versus product composition, particularly with respect to acidic and basic types.

Relating Feedstock Composition to Product Slate and Composition in Catalytic Cracking. 2. Feedstocks Derived from Brass River, a High-Quality Nigerian Crude

“…The scheme and methodology for crude fractionation and blending of the fractions to obtain FCC feedstocks were the same as used earlier . Briefly, the 650−1000 and >1000 °F boiling ranges of the crude were fractionated into nine fractions using LC.…”

“…The initial paper presented results obtained from bench scale experiments with liquid chromatographic (LC) fractions derived from Wilmington, CA, crude oil .…”

“…Points brought out in the study of Wilmington LC fractions included (1) the significant impact of acidic and basic feed components on FCC product slate and gasoline composition, (2) greater carryover of acidic versus basic forms of nitrogen into liquid products, (3) higher conversion of sulfide forms of sulfur to H 2 S compared to thiophenic sulfur types, and (4) correlation of FCC coke yield with feedstock microcarbon residue (MCR) data . The generality of these findings will be tested here with respect to feedstocks derived solely from Brass River as well as some containing components from both Brass River and Wilmington crudes.…”

“…As the result, the present understanding of FCC operating variable−product relationships is significantly better than feedstock−product relationships, as exemplified by a recent paper on benzene levels in FCC gasoline . A brief review of applicable papers on feedstock−product correlation was given earlier . However, recent papers on hydrogen transfer in FCC 4-6 are also pertinent because of the great impact of hydrogen transfer on the conversion process and resulting product slate.…”

“…However, recent papers on hydrogen transfer in FCC 4-6 are also pertinent because of the great impact of hydrogen transfer on the conversion process and resulting product slate. For example, the reduced aromatic content, coupled with higher olefin plus naphthene contents, of gasoline produced from feedstocks enriched in basic nitrogen compounds was attributed to reduced hydrogen transfer activity resulting from the decrease in effective catalyst acidity . The hydrogen transfer properties of a given zeolite are directly related to its acidity and free acid site density .…”