Paraffin stock

In general, FCC feeds are predominately paraffinic. The paraffinic carbon content is typically between 50 wt% and 65 wt% of the total feed. Paraffinic stocks are easy to crack and normally yield the greatest amount of total liquid products. They make the most gasoline and the lea.st fuel gas, but also the lowest octane number. 

Ranges from 12.5 for paraffinic stocks to 10.0 for the highly aromatic stocks also called the Watson characterization factor. 

Also, the optimization and planning of crude allocations in Mobil s worldwide refinery system is the principal objective of Mobil s supply and distribution planning group. Overall corporate profits can be maximized by proper crude allocations to the various refineries. Similar to the refinery LPs, the reformer representation in the crude supply and distribution LP was improved. Table XX gives an example of how sensitive reformer operation can depend on the type of naphtha reformed. A significant improvement in performance and octane potential results from processing a naphthenic stock compared to a paraffinic stock. This improved performance must be balanced against differences in crude cost. 

Dilute an aliquot of the paraffin stock solution 1 100 to produce a 10 ng/pl solution. For example, add 5 ml solvent followed by 50 pi paraffin stock solution (see recipe) to a 10-ml brown bottle and seal with a Teflon-lined screw cap. Store at room temperature near the GC for months if necessary. 

The liquid products tend to be unsaturated and, because sulfur compounds are relatively more concentrated in heavy portions of crude oil, also tend to be rather high in sulfur content. The octane number of the gasoline depends upon the character of the feed, and typically ranges from 60-65 for paraffinic stocks to as high as 80 for highly naphthenic stocks. The coke can be used as fuel but in many cases is of a high quality suitable for use in the manufacture of carbon electrodes for the aluminum or other electrometallurgical industries. 

Paraffinic and naphthenic (cycloparaffinic) stocks may be used for the formulation of lubricating oils, each with favorable characteristics for particular uses. Paraffinic stocks are generally preferred for their superior lubricating power and oxidation resistance. Naphthenic stocks, on the other hand, have naturally lower pour points, i.e, they maintain flow characteristics at lower pour-points than paraffinics (Table 18.8) and are better solvents, features which are more important for applications such as heat transfer, metal working, and fire-resistant hydraulic fluids [33]. Any residual aromatics in the lubricating base stock will have been removed before formulation by solvent extraction, using N-methylpyrrolidone, furfural, or less frequently today, phenol (Eq. 18.39). 

The viscosity-temperature relationship of the base stock (improve the viscosity index [VI]) has to be enhanced—by aromatics removal—to meet industry requirements for paraffinic stocks. 

Figure 2.6 shows that specific gravity of chloropaiafBn is only sUghtly affected by parafBn type but increases rapidly with increase in chlorine concentration. This is unlike viscosity which is strongly affected by both the properties of paraffin stock and the chlori-... 

From 125 to 400 per cent Selecto (based on charge stock) is employed, depending upon the stock, and 150 to 400 per cent propane. In general, the naphthenic stocks require more propane, and the paraffinic stocks require more Selecto. Contacting is accomplished at about 85°F. 

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