Hydrocarbon type distribution

From a study of gasoline cver-cracking with either ZSM-5 or REHY, the resulting total hydrocarbon distributions by carbon number are grossly similar. In both cases, predominantly C2 - C5 products are formed from C6+ components. However, there are significant differences in detail, notably in hydrocarbon-type distributions. 

Figure 2. Hydrocarbon type distribution in naphthas from entrained-solids retort crudes (19)...

Table 7. Hydrocarbon Type Distribution by Boiling Point - Manual Slicing... 

Srica, V. Mlihl, J. Jednacak, M. Duric, A., Determination of Hydrocarbon Type Distribution of Coking Gasolines by N.M.R. Spectrometry, Fuel, 1992, 72,775-778. Teeter, R.M. 1992. Software for calculation of hydrocarbon types. Walnut Creek, CA ... 

Results for samples that have been depentanized must be identified as being for the Q and heavier portion of the sample. Alternatively, the Cs and lighter portion of the sample can be analyzed for olefins and saturates in accordance with Test Method D 2427. Using these values and the percentage of overhead and bottoms, the hydrocarbon type distribution in the total sample can be calculated. 

Fuel modification in terms of volatility, hydrocarbon types, or additive content. Some of the fuels currently being used are liquefied petroleum gas (LPG), liquefied natural gas (LNG), compressed natural gas (CNG), fuels with alcohol additives, and unleaded gasoline. The supply of some of these fuels is very limited. Other fuel problems involving storage, distribution, and power requirements have to be considered. 

It is important to characterize FCC feeds as to their molecular structure. Once the molecular configuration is known, kinetic models can be developed to predict product yields. The simplified correlations above do a reasonable job of defining hydrocarbon type and distribution in FCC feeds. Each correlation provides satisfactory results within the range for which it was developed. Whichever correlation is used, the results should be trended and compared with unit operation. 

Roussis, S. Exhaustive Determination of Hydrocarbon Compound Type Distributions by High Resolution Mass Spec-... 

Results from both analyses were combined to give carbon distribution in the range 0-10 by several hydrocarbon types namely iso, normal and cyclo paraffins, iso, normal, and cyclo olefins, and mono-ring aromatics. For convenience these groups are abbreviated to IP, NP, CP, IO, NO, CO, and AR respectively, and suffixed by the relevant carbon number i.e. IP-5 equates to total C5 iso-paraffins. 

More detailed results of gasoline over-cracking with ZSM-5 or Y are given in Tables 4 and 5 where, for each hydrocarbon type and carbon number, the difference in moles i.e. moles product - moles (parent) are presented. From these, delta mole distributions for total hydrocarbon and for paraffins and olefins can be compared (Figures 1-5). 

The ring-number tabulations in Tables II, III, IV, and V are satisfactory for a simplified summary of composition and comparison. The typical Co-Mo or Ni-Mo catalyst commonly used for upgrading will saturate many of the multiple aromatic rings, depending upon severity and activity, but frequently not the last ring of a condensed-ring polyaromatic. Thus, the total number of rings is a measure of the complexity of the hydrocarbon structure. As noted earlier, more detailed data on the distribution of hydrocarbon types in these liquids are available when needed. 

Figure 7. Distribution of hydrocarbon types for monoaromatic subfractions...

Molecular Weight Distributions. Information on the molecular weight distribution of coal-derived oils is important in evaluating the characteristics of chemical structure, since degradation of the macromo-lecular coal structure results in complicated molecular species. The GPC technique for elucidation of the molecular weight distribution of polymer compounds is applied widely. The application of GPC to the heavy oil derived from coal and petroleum is performed for sample preparation and chemical characterization. Actual distributions cannot be derived from the GPC elution data because each hydrocarbon type has a different elution behavior. 

GEOSECS surface samples show a n-paraflBn distribution with a maximum at C28 which is significantly different from the C23 maximum observed for the envelope. The hydrocarbons under the envelope are a complex mixture as shown by the hydrocarbon type analysis. 

Thus the first level of compositional information is group type totals as deduced by adsorption chromatography form the distribution of saturates, olefins, and aromatics in materials that boil below 315°C (600°F) (ASTM D-1319). Adsorption methods (ASTM D-2007) can also be used to determine hydrocarbon types in kerosene, but, with all adsorption methods, allowances must be made for the loss of volatile constituents during the workup procedure. Thus column chromatography would be best done with a stabilized (volatile constituents removed to a predetermined temperature) feedstock. 

Generally, for any series of similar waxes, an increase in molecular weight increases viscosity and melting point. However, many of the other physical and functional properties are more related to the hydrocarbon types and distribution than to the average molecular weight. 

---