Fuels boiling point distributions

Figure 7.7 Boiling point distribution of liquid fuel formed over US-Y zeolite, a commercial cracking catalyst, a pillared clay (polymer-to-catalyst ratio 2 1) and comparison with a commercial gasoline sample...

Y. Shiraga, M. A. Uddin, A. Muto, M. Narazaki, Y. Sakata, and K. Murata, Boiling point distributions and dechlorination of organic chlorine compounds in oil obtained from the degradation of PVC mixed plastic, Energy Fuels., 13, 428-432 (1999). 

The basic method of distillation (ASTM D-86) is one of the oldest methods in use because the distillation characteristics of hydrocarbons have an important effect on safety and performance, especially in the case of fuels and solvents. The boiling range gives information on the composition, the properties, and the behavior of petroleum and derived products during storage and use. Volatility is the major determinant of the tendency of a hydrocarbon mixture to produce potentially explosive vapors. Several methods are available to define the distillation characteristics of petroleum and its various petroleum products. In addition to these physical methods, other test methods based on gas chromatography are also used to derive the boiling point distribution of a sample (ASTM D-2887, ASTM D-3710, ASTM D-5307, ASTM D-6352). 

Vaporization of low-boiling-point, low-flash-point fuel components can increase the vapor pressure of a fuel. For this reason, fuel vapors are being closely monitored and regulated due to their tendency to escape into the atmosphere from fuel storage and distribution systems. Compounds with low flash points can contribute significantly to increasing fuel vapor pressure. 

Fuel oil specifications (6) were only discussed very briefly because oil end-users were not present. pH was suggested to be added in order to help in material choices. It was mentioned at the volatility index or boiling point range distribution would be valuable. However, it has been proved that the boiling point cannot be determined for pyrolysis oil because of the thermal instability of the oil (7, 4). More feedback from end-users is needed for assessing the maximum allowable variation for each property. 

Willman and Teja" have described the composition of fossil-fuel mixtures (including gas condensates, absorber oils, crude oils, coal hquids) with a bivariant log-normal distribution that depends on the boiling-point temperature and the specific gravity. This scheme was used to determine dew-points with the Patel-Teja equation of state. 

The MS analysis, whether it is done by El or FI, determines the hydrocarbon t5 e composition of the whole analyzed sample. In real practice very often it is necessary to estimate the composition of a certain distillation fraction without having to distill the sample (e.g. when the sample is available in a very small amoimt), or to prepare a blend that meets requirements in a specified boiling range. It may also be necessary to know sulfur distribution in order to choose the right cut point for a refinery stream to make a fuelblending component that will help maintain fuel spec in the particular situation at a specific refinery. All of these needs could be addressed by presenting the MS data distributed by boiling point. 

Figure 6.41 Comparison between the C5+ distribution of the plant reactor effluent and the model prediction within the boiling-point range of diesel fuel (data set 4 in MP HCR).

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