Paraffin content

Straight run diesei fuels have a high paraffin content, which is desirable, incidentally, for obtaining high cetane numbers. The higher the distillation end point, the higher is the heavy paraffin content (with a carbon number greater than C24). 

Paraffin content (bitumen) NFT 66-015 Insolubility at -20°C in an alcohol-ether mixture... 

Fig. 2. Density vs paraffin content of gas turbine fuels (150—288°C fractions).

Figure 2-77 shows how the weight distributions of the different molecular types vary during the fractional distillation of a naphthenic crude oil. Saturated aliphatic hydrocarbons (i.e., paraffins and naphthenes) are the predominant constituents in the light gasoline fraction. As the boiling point is raised, the paraffin content decreases, and the NSO content increases continuously. About 75 wt% of tbe residuum is composed of aromatics and NSO compounds. 

Like aniline point, the K factor differentiates between the highly paraffinic and aromatic stocks. However, within the narrow range (K = 11.5-12.0), the K factor does not correlate between aromatics and naphthenes. Instead, it relates fairly well to the paraffin content (Figure 2-11). The K factor does not provide information as to the ratio of naphthene and paraffin contents. The ratio of naphthenes to paraffins can vary considerably with the same K values (Table 2-8). 

Trend the feed API gravity, K factor, and aniline point. Verify any changes in paraffin content of the feed. 

At 220°C a water-paraffin mixture is distilled off in a circulating evaporator (8). The product mixture passes to a second circulating evaporator (9) where the paraffin is stripped at 270°C with overheated water vapor, and finally the paraffin content in the resulting alkanesulfonate melt is further reduced by vapor stripping in a packed column (10). A heat transfer oil dissipates excess heat. 

In situ degradation of long chain molecules to reduce viscosity and paraffin content... 

The amount of benzene produced in a reformer will depend on the composition of the feed. Every crude oil has naphtha with different PNA (paraffin, naphthene, aromatics) content. In commercial naphtha trading, the PNA content is often an important specification. High naphthene and aromatic content would indicate a good reformer feed. High paraffin content would indicate a good olefin plant feed. 

The PONA results at constant conversion (72 vol%) in the series from EKZ4 to BETA 500 show gasoline olefin content increased from 8.6 percent to 16.4 percent, paraffin content decreased from 54.7 percent to 46.8 percent, and naphthene and aromatics contents remained constant. Research octane increased 4.2 numbers while motor octane increased 1.2 numbers. The aromatics content of the LCO as measured by the aniline point decreased with the aniline point increasing from 42 to 62. LCO yield increased from 16.0 volume percent to 18.0 volume percent, while the coke yield decreased dramatically from 4.2 percent to 2.4 percent. 

While such data are not included in this report, our work has also shown that in FCC operations the acidic matrix is able to better crack and isomerize more n-paraffins, thus reducing the n-paraffin content in middle distillate and thereby the characteristic high cloud point associated with it, while also raising octane number by removing or isomerizing n-paraffins in the gasoline fraction. 

Some of the important fuel characteristics associated with high paraffin content in fuel are described as follows ... 

Paraffins function poorly as a solvent for some organic compounds. This fact can have various consequences. For example, gums, deposits, and fuel degradation products will not be dissolved or held in solution by high-paraffin-content fuels. As a result, gums and degradation products will fall from solution and settle onto fuel system parts such as storage tank bottoms and fuel system lines. The KB value for selected petroleum products is provided in TABLE 5-4. 

For most distillate fuels, cloud point temperatures can range from 50°F to -10°F (10.0°C to -23.3°C) or lower. However, typical cloud point temperatures fall between 6°F and 16°F (-14.4°C and -8.9°C). Distillate blends having a high paraffin content will often have cloud point and pour point values close together, sometimes within 5°F (2.8°C). Highly aromatic blends will usually have cloud and pour point values further apart in temperature. 

A high cetane number can be related to a high diesel paraffin content... 

Assonov and Rossi report that with a proportion of 2 g of paper per 100 g of explosive, the content of paraffin should be less than 2.5 g. With this paraffin content the amount of toxic gases formed is 26.4 l./kg of carbon monoxide and 37.7 l./kg of nitric oxides. 

The first four of these properties have been discussed. Pour point is the lowest temperature, expressed as a multiple of 5°F, at which the liquid is observed to flow when cooled under prescribed conditions. Cloud point is the temperature at which paraffin wax begins to solidify and is identified by the onset of turbidity as the temperature is lowered. Both tests qualitatively measure the paraffin content of the liquid. 

Yield,a Run wt % of feed Cloud point, K Pour point, K n-paraffin content, wt % ... 

The selectivity of the sieves for n-paraffins decreases as the ratio of supercritical fluid to wax distillate feed is decreased. n-Paraffin content is shown as a function of this ratio in Figure 11, at both high and low-to-moderate molecular sieve loadings. 

A test was made with 2,3-dimethylbutane as the supercritical solvent it has a lower critical temperature than 2,2,4-trimethyl-pentane. Operating at a temperature of 508-512 K, a pressure of 4.10-4.37 MPa, a molecular sieve/oil ratio of 6.39, and a solvent/ oil ratio of 21.3, the molecular sieve capacity attained is 5.73 g/100 g of molecular sieves (as compared to 3.2 g/100 g of molecular sieves with 2,2,4-trimethylpentane at 550 K). The n-paraffin content of the wax distillate was reduced by 88% to a level of 2 wt %, giving a pour point of 266 K. The yield of denormal oil was lower (63%) and the n-paraffin content of the desorbate was lower (44%) at this lower temperature level. This is probably due to increased capillary condensation. Conversely, operation at temperatures greater than 550 K should produce less capillary condensation and purer n-paraffin product. It would be interesting to try supercritical solvents with critical temperatures in the 600-670 K range. 

A test was made with 2-methylpentane as the supercritical solvent at 514 K and 4.37 MPa, at a molecular sieve to oil ratio of 5.85 and a solvent to oil ratio of 20.1. The n-paraffin content of the wax distillate was reduced by 77% to a level of 3.8 wt %. In this test, an extraordinary gain in molecular sieve weight occurred. A significant amount of the 2-methylpentane was recovered upon desorption of the molecular sieves with ammonia. 

---