Saybolt distillation

Nonfractionating. ASTM designation D-86 applied to gasoline, naphtha, kerosene, etc., is the best known nonfractionating distillation and it is frequently called simply an ASTM and sometimes an Engler because a similar Engler distillation was once widely used. Likewise, the older Saybolt distillation for crude oil has now been standardized ... 

Fig. 4-21. A correlation of tme-boiling-point and Saybolt distillation curves (based mainly on crude oils). OH Gas J.)...

Experimental Vaporization Curves. When such complex materials as gasoline and petroleum fractions are dealt with, the application of the aforementioned equilibrium laws is cumbersome. Furthermore, the component analyses of these heavy oils cannot be easily obtained and even if such analyses are-availalUe, accurate vapor-pressure or equilibrium data for the compounds or fractions contained in them are not always available. At present most equilibrium relations are obtained by determining experimental flash-vaporization curves or by computing such curves from the empirical relationships discussed in Chap. 4. Empirical flash curves can be estimated from true-boiling-point or ASTM curves, and with less accuracy from Hempel or Saybolt distillation curves. 

Kinematic, cs Saybolt Universal Seconds ASTM distillation, 0 F ... 

Table IV gives the properties of the SRC-II fuel oil compared to a low-sulfur residual oil utilized in a recent combustion test. The SRC-II fuel oil is a distillate product with a nominal boiling range of 350-900°F, a viscosity of 40 Saybolt seconds at 100°F and a pour point below -20°F. Thus, it is readily pumpable at all temperatures normally encountered in transportation of the fuel oil. The fuel oil has a very low content of ash and sediment as well as a low Conradson carbon residue. These characteristics are favorable from the standpoint of particulate emissions during combustion. Tests of compatibility with typical petroleum fuel oils and on stability of the coal distillates over time have not revealed any unusual characteristics that would preclude utilization of these coal-derived fuels in conventional boiler applications.

Properties Volatile, colorless liquid. Fp -90.595C, bp 98.428C, refr index 1.38764 (20C), d 0.68368 (20C), flash p 25F (-3.89C) (CC). Soluble in alcohol, ether, chloroform insoluble in water distillation range 93.3-98.9C vap press 2.0 psi (a)(37.7C) (max). Color Saybolt +30 (min), maximum sulfur content 0.01 wt %, corrosive passes ASTM D 130-30 test, autoign temp 433F (222C). 

Viscosity measured at 40°C and 100°C Base stocks are primarily manufactured and sold according to their viscosities at either 40°C or 100°C, using kinematic viscosities (see later). Viscosity grades are now defined by kinematic viscosity in centistokes (cSt) at 40°C formerly they were established on the Saybolt universal seconds (SUS) scale at 100°F. Higher viscosity base stocks are produced from heavier feedstocks (e.g., a 100 cSt at 40°C oil is produced from a HVGO and cannot be made from a LVGO since the molecular precursors are not present). As viscosity increases, so does the distillation midpoint. 

The typical characteristics of the variation of viscosity with temperature can be seen in a plot of hydrocarbon viscosities at two temperatures. Figure 3.1 shows the relationship for n-paraffins,1-3 and when both axes are converted to logarithms a linear relationship results. Figure 3.2 (the temperatures employed for this type of diagram are now usually 40°C and 100°C, whereas in the past 100°F and 210°F were used correspondingly, units for viscosity were originally in Saybolt universal seconds (SUS) they are now in centistokes. Distillation fractions through base stocks show similar behavior. 

For the development of this tool, it was expected that paraffinic cuts will have lower densities (and specific gravities) than naphthenic ones of about the same distillation range. The VGC concept arose from semilog plots of Saybolt viscosities at 100°F versus specific gravities (Figure 4.1) for a series of distillate cuts from different crude sources. Similar patterns were evidently present for fractions from different crudes. 

For laboratory distillation ordinary standardized, round-bottomed flasks provided with ground joints are used. They may have short or long necks and nominal capacities up to 500 ml. The Engler (Fig. 235) and Saybolt flasks (TGL 0-12363) are examples of special devices designed for standardized distUlation techniques. In addition, a distilling flask with capacities from 25 to 1000 ml (TGL 0-12364) has been standardized (Fig. 313). 

F. psia Refractive index, 20/0 Color, Saybolt Acidity, distillation residue Nonvolatile matter, grams/100 ml Sulfur content, weight percent Copper corrosion Doctor test Flash point, approximate. F 0.48 0.5 0.5 1.433 ... 

Grade of fuel oil Rash point, F(=c) Pour point, °F (°C) Water and sediment, % by vol Carbon residue on 10% bottoms, % Ash, % by wt Distillation temperatures, °F (°C) Saybolt viscosity, s Kinematic viscosity, centistokes Gravity, deg API Copper strip corrosion... 

The most common name is neutral (N) which was derived in the days when the lube distillates were acid treated (sulfuric acid) followed by clay filtration. After clay treating the oil was acid free or neutral. The viscosity number in this example, 150 N, is the approximate viscosity of the base stock (Note the ASTM viscosity classification refers to an industrial oil grade system, not the base stock viscosity system) expressed in Saybolt Seconds Universal (SSU) at 100 F. 

The petroleum industry uses the Saybolt colorimeter Test Method D 156 for measuring and defining the color of hydrocarbon solvents however, this system of color measurement is not commonly employed outside of the petroleum industry. It has been reported by various sources that a Saybolt color of +25 is equivalent to 25 in the platinum-cobalt system or to colors produced by masses of potassium dichromate ranging between 4.8 and 5.6 mg dissolved in 1 L of distilled water. Because of the differences in the spectral... 

These may be used to estimate the central portion of the various distillation curves or those central ranges of percentage which are substantially straight lines. Figures 4-20 (Hempel) and. 4-21 (Saybolt) indicate another method of correlating distillation curves. 

Includes ASTM, Saybolt, and so-called 10 per cent distillations. 

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