Aromatics content naphtha

Steam Reforming. When relatively light feedstocks, eg, naphthas having ca 180°C end boiling point and limited aromatic content, are available, high nickel content catalysts can be used to simultaneously conduct a variety of near-autothermic reactions. This results in the essentiaHy complete conversions of the feedstocks to methane ... 

A fuel closely related to gasoline is naphtha, which is also a potential fuel cell fuel. Naphtha is already produced in large quantities at refineries and is a cheaper fuel than gasoline, which must have octaneboosting additives blended into it. Unlike methanol, naphtha can be distributed in the same pipelines as gasoline. From the fuel cell s perspective, it has a higher H C ratio and lower sulfur and aromatics content than gasoline. 

The main use of naphtha in the petroleum industry is in gasoline production. Light naphtha is normally blended with reformed gasoline (from catalytic reforming units) to increase its volatility and to reduce the aromatic content of the product gasoline. 

In addition, a method of petroleum classification based on other properties as well as the density of selective fractions has been developed. The method consists of a preliminary examination of the aromatic content of the fraction boiling up to 145°C (295°F), as well as that of the asphaltene content, followed by a more detailed examination of the chemical composition of the naphtha (bp < 200°C < 390°F). For this examination a graph is nsed that is a composite of cnrves expressing the relation among the percentage distillate from the naphtha. 

Sulfur compounds are most commonly removed or converted to a harmless form by chemical treatment with lye. Doctor solution, copper chloride, or similar treating agents (Speight, 1999). Hydrorefining processes (Speight, 1999) are also often used in place of chemical treatments. When used as a solvent, naphtha is selected for its low sulfur content and the usual treatment processes remove only sulfur compounds. Naphtha, with its small aromatic content, has a slight odor, but the aromatics increase the solvent power of the naphtha and there is no need to remove aromatics unless odor-free naphtha is specified. 

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. 

Figure 10. Aromatic Contents of Platformate and Thermal Reformate from Mid-continent Naphtha...

In setting the prices for the premium cases, we have incorporated a sliding price scale on some by-products hence, a range of prices appears in some rows of Table V. These price variations reflect differences in the composition of a particular by-product which result from cracking different feedstocks. By way of example, the aromatics content of a pyrolysis naphtha depends on the specific feedstock from which it is derived. The premium price of the particular pyrolysis naphtha thus depends on its BTX concentration. The nonaromatic content of the pyrolysis naphtha is valued the same as naphtha. Further details can be found in Table VI. 

KAURI-BUTANOL VALUE. A measure of the aromatic content and hence the solvent power of a hydrocarbon liquid Kauri gum is readily soluble in butanol but insoluble in hydrocarbons. The kb value is Ihe measure of the volume of solvent required to produce turbidity in a standard solution containing kauri gum dissolved in butanol. Naphtha fractions have a kb value of about 30. and toluene about 105. 

Naphthas boiling up to 185°C can be reformed at pressures up to 600 psig. Naphthas with final boiling point up to 240 C may be reformed at lower pressures. Higher olefin contents may be accepted provided that sufficient hydrogen is available in the recycle gas to saturate the feed in the desulfurization section. Higher aromatic contents may be accepted but tile catalyst life will be reduced. 

Reforming. The hydrotreated naphthas were reformed over a conventional platinum reforming catalyst in an attempt to maximize aromatics. The catalyst was Cyanamid AERO PHF-4 (0.3% Pt, 0.6% Cl). The intent was to operate the reformer at constant conditions in order to better compare naphthas. By operating at severe conditions, the expected hydrocracking activity of the catalyst would tend to purify the aromatics by selectively cracking away the paraffins. If the resultant reformate had a suitably high aromatic content, it could be fed directly to a hydrodealkylator. 

The first-day data for the seven naphthas are presented in Tables IX and X. The reformates are notable for the high aromatic content. 

With the possible exception of the SRC II straight-run naphthas, these Ce-Co reformates could be fed to a hydrodealkylator without first being extracted. However, it must be noted that hydrocracking, as evidenced by paraffin conversion, was not nearly as active as expected. In the event that a coal-derived naphtha contained a substantial portion of paraffin, particularly C6 paraffin, the aromatic content of the resultant reformate would be significantly less. 

On the w hole. these analyses show that gas oil steam cracking produces fewer light produas than the treatment of naphtha, and more heavy products which display a higher aromatics content. Hence the Cj- 200 C cut boosts the BTX (Benzene, Toluene, Xylenes) (majority benzene concentration. Similarly, fuel oil (fraction above 200 C) displays a more pronounced aromatic character. This feature makes it incompatible with straight-run distillation fuel oils. The mixture causes the deposition of asphaltenes and other... 

The hydrogen content of the different naphthas, calculated from GC analysis, is shown in Figure 7. There is a nearly linear negative correlation between hydrogen content and the concentration of aromatics. Therefore the naphtha hydrogen content diminishes with increasing IBP but increases with lower FBP. 

The following four feed parameters were found to be sufficient to characterize naphthas (25) hydrogen content (HF) molecular weight (MW) isoparaffin content (Pi) normal-paraffin content (PN). Other potential parameters were satisfactorily accounted for in the above set. For example, the inclusion of naphthenic and aromatic content as parameters did not significantly improve the yield correlation. 

Fig. 18. Correlation between octane number and aromatics content of platinum reformed gasolines, for three different sources of naphtha.

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