Syncrude fractions

Table II. Microcoulometric and Titration Data for Syncrude Fractions...

Alvarez, R, Berrueco, C., Venditti, S., Morgan, T.J., Tay, F.H., Kazarian, S.G., George, A., Millan, M., Herod, A.A., Kandiyoti, R. (2009) Structural molecular mass characterization of Syncrude fractions from Athabasca oil sands. Paper in preparation. 

Composition of the C3 and Heavier Gas and Oil Fractions from the Syncrude Produced by the German Normal-Pressure and Medium-Pressure Co-LTFT Processes... 

The complete oil fraction from FT synthesis was treated over bauxite, a natural silica-alumina, at a temperature around 400°C. This bauxite treatment step was a commercial process, called the Perco process, which was used as a sulfur removal step in oil refineries. The acid-catalyzed conversion of the syncrude over bauxite... 

The Arge Fe-LTFT syncrude (Table 18.8)29 was much heavier than the syncrude of the two German Co-LTFT processes (Table 18.2). The Arge Fe-LTFT syncrude exemplified a high a-value Fischer-Tropsch product with a significant linear paraffinic wax fraction. The syncrude (Table 18.8) from the Kellogg Fe-HTFT synthesis was very similar in carbon number distribution to that of Hydrocol Fe-HTFT synthesis (Table 18.5). 

The Fe-HTFT syncrude is fractionated in an atmospheric distillation unit to produce mainly naphtha and distillate, with a small amount of residue that is used as fuel oil (not shown in Figure 18.7). No vacuum distillation unit has been included in the design, since it would be superfluous with the limited residue production. The natural gas liquids are fractionated separately. 

Short-chain olefins are not refined and the gaseous LTFT products are employed as fuel gas. Production of this fraction is limited by Co-LTFT synthesis, and with the product being less olefinic than iron-based Fischer-Tropsch syncrude, less benefit would be derived from the inclusion of an olefin oligomerization unit. Furthermore, adding complexity would go against the design objectives of the SMDS process. 

Tar Sands Canadian tar sands either are strip-mined and extracted with hot water or employ steam-assisted gravity drainage (SAGD) for in situ recovery of heavy oil (bitumen). The bitumen is processed into naphtha, kerosine, and gasoline fractions (which are hydrotreated), in addition to gas (which is recovered). Current production of syncrude from Canadian tar sands is about 113,000 T/d (790,000 B/d) with expected increases to about 190,000 T/d (1.7 MB/d) by 2010. 

Utilization of coal and oil shale to produce liquid and gaseous synfuels results in the generation of many hazardous sub-tances. Workers in these synfuel plants are likely to be exposed to potentially carcinogenic materials present in coal tars and oils. Among the various pathways of exposure, skin contamination by direct contact transfer or by adsorption of vapors and particulates into the skin presents a serious occupational health hazard. The skin irritant and potential carcinogenic properties of raw syncrudes and their distillate fractions have been reported (1. 2, 3). 

The heavy oil, which contained nearly 90% of the nitrogen in the syncrude, was fractionated by liquid displacement chromatography on Florisil. The nonpolar, nonnitrogen-containing hydrocarbons were washed from the Florisil column with n-heptane, a very weak base concentrate was displaced with benzene, and a weak base concentrate was displaced with benzene-methanol azeotrope. 

Hydrocarbon-type Characterization. Table I lists the four fractions, their wt % of the syncrude, and their hydrocarbon-type compositions. The values for polar material for the two naphthas and the light oil are estimates based on their nitrogen contents. The polar material value for the heavy oil is based on the recovered weights from the Florisil separa-... 

Characterization of Intermediate Fractions. Nonaqueous poten-tiometric titration was used to characterize the nitrogen compounds in three intermediate fractions from the production of the syncrude. Table VII lists these three fractions, their source, and the titration results. Also... 

The first fraction listed is the 550°F-f- heavy oil produced by hydrogenation of the 550°-850°F heavy oil from distillation and coking of the in situ crude oil. This is the same fraction listed in Tables I and II as the syncrude heavy oil fraction. The second fraction listed in Table VII is the 350°-550°F light oil produced in the foregoing hydrogenation, and the third fraction is the 175°-350°F heavy naphtha produced in the same hydrogenation. 

The fourth fraction in Table VII is the 350°-550°F light oil produced from the hydrogenation of the 350°-550°F light oil resulting from the distillation and coking of the in situ crude to which had been added an aliquot amount of the light oil shown as the second fraction in Table VII. The fifth fraction is the 175°-350°F heavy naptha from this hydrogenation. Only the second, third, and fifth listed fractions are intermediate fractions the first and fourth are final, syncrude ones. 

The synthetic crude was produced by hydrogenating the IBP-350°F naphtha, the 350°-550°F light oil, and the 550°-850°F heavy oil fractions obtained from in situ crude shale oil by distillation followed by coking of the 850°F-f- residuum. Characterization of the syncrude was accomplished by examining the following fractions CB-175°F light naphtha, 175°-350°F heavy naphtha, 350°-550°F light oil, and 550°-850°F heavy oil. 

V (Ni-Mo) and the lowest yields with catalysts III (Ni-W) and IV (Ni-W). The highest conversion, i.e., material converted to products boiling below 550°F, was attained with catalyst VI (Ni-Co-Mo). The lowest conversion was attained with catalyst IV (Ni-W), a hydrocracking catalyst. The highest yields of naphtha and light oil were attained with catalysts I (Co-Mo) and VI (Ni-Co-Mo). Because of its high sustained denitrification activity, catalyst V (Ni-Mo) was selected for use in the preparation of syncrude by hydrogenation of the in situ distillate fractions. 

Table X. Comparison of NPC and in Situ Syncrudes and Distillate Fractions...

Hydrogenation tests made on the 600°-1000°F heavy gas oil from in situ crude shale oil showed that a nickel-molybdenum-on-ahimina catalyst was superior to either cobalt-molybdenum-on-alumina or nickel-tungsten-on-alumina catalysts for removing nitrpgen from shale oil fractions. This nickel-molybdenum-on-alumina catalyst was used in the preparation of the synthetic crude oil. A high yield of premium refinery feedstock whose properties compared favorably with those of a syncrude described by the NPC was attained by hydrogenating the naphtha, light... 

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