Boiling point/range measurement

Since the term total petroleum hydrocarbons (total petroleum hydrocarbons) includes any petroleum constituent that falls within the measurable amount of petroleum-based hydrocarbons in the enviromnent the information obtained for total petroleum hydrocarbons depends on the analytical method used. Therefore, the difficulty associated with measurement of the total petroleum hydrocarbons is that the scope of the methods varies greatly (Table 8.1). Some methods are nonspecific, whereas others provide results for hydrocarbons in a boiling-point range. Interpretation of analytical results requires an understanding of how the determination was made (Miller, 2000, and references cited therein Dean, 2003). 

Concentrations expressed as molality or mole fractions are temperature-independent and are most useful when a physical measurement is related to theory over a range of temperature, e.g., in freezing point depression or boiling point elevation measurements (Chapter 11). Since the density of water is close to 1 g/cm3, molal and molar concentrations are nearly equal numerically for dilute aqueous solutions (<0.1 M). 

The use of the hermetic pan with laser pinhole can be extended by using this configuration to measure boiling points of materials within a pressure DSC cell. If the boiling point is measured at a range of known pressures, the boiling point shifts can be used in the Clausius-Clapeyron equation to obtain quantitative vapor pressure data. 

Boiling point/range if measured under reduced pressure, the pressure has to be noted... 

As mentioned earlier, we must also be able to infer the paraffin, naphthene and aromatic (PNA) composition of each boiling-point range given certain measured bulk properties to completely map feed information to kinetic lumps. The API (Riazi-Daubert) [54, 55] is a popular chemical composition correlation that takes the form ... 

Beckmann thermometer A very sensitive mercury thermometer with a small temperature range which can be changed by transferring mercury between the capillary and a bulb reservoir. Used for accurate temperature measurements in the determination of molecular weights by freezing point depression or boiling point elevation. 

Pour point ranges from 213 K (—80°F) for some kerosene-type jet fuels to 319 K (115°F) for waxy No. 6 fuel oils. Cloud point (which is not measured on opaque fuels) is typically 3 to 8 K higher than pour point unless the pour has been depressed by additives. Typical petroleum fuels are practically newtonian liqmds between the cloua point and the boiling point and at pressures below 6.9 MPa (1000 psia). 

Measurements are made of the properties of boiling point (at an appropriate pressure), density, refractive index, refractive dispersion (for appropriate wave lengths), viscosity, critical solution temperature in one or more appropriate solvents, infrared absorption (normally in the range 2 to 15 microns), ultraviolet absorption (normally in the range 0.2 to 0.4 micron or 2000 to 4000 A.), elemental composition, and average molecular weight. 

Vapor-liquid equilibrium experiments were performed with an improved Othmer recirculation still as modified by Johnson and Furter (2). Temperatures were measured with Fisher thermometers calibrated against boiling points of known solutions. Equilibrium compositions were determined with a vapor fractometer using a type W column and a thermal conductivity detector. The liquid samples were distilled to remove the salt before analysis with the gas chromatograph the amount of salt present was calculated from the molality and the amount of solvent 2 present. Temperature measurements were accurate to 0.2°C while compositions were found to be accurate to 1% over most of the composition range. The system pressure was maintained at 1 atm. 1 mm... 

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