Gasoline component streams

Process Stream Separations. Differences in adsorptivity between gases provides a means for separating components in industrial process gas streams. Activated carbon in fixed beds has been used to separate aromatic compounds from lighter vapors in petroleum refining process streams (105) and to recover gasoline components from natural and manufactured gas (106,107). 

The benzene leaves the olefins plant fractionator mixed with the other gasoline components so it is handled the same way as a refinery stream. An aromatics concentrate is made and run through one of the two separation processes you just read about, solvent extraction or extractive distillation. 

Why the emphasis on freedom An example will help. I was asked to measure the sulfuric acid content in a gasoline component. My first idea was to separate the acid from the stream and measure the amount of acid and relate that back to the original concentration. My separator worked well at high levels but when I got down to the level of interest, below 100 ppm, the separator did not work at all. However, when we got to that level, the solution became turbid. The solution was to install an on-line turbidity detector instead of building a complex separator and analysis device, to measure acid in the 10-100-ppm level. This worked, but certainly was not the first approach. 

The liquids output represents a combination of transportation and utility fuels as summarized in Table III. All of the naphtha is to be reformed on site to produce a very high aromatic stock. With an exceptional octane blending value, this stream will find ready application as a gasoline component, but perhaps more important, it is also a source of substantial quantities of petrochemical raw materials as noted in Table IV. The potential yield of BTX and phenolics along with the low boiling paraffins should make such a plant an important factor in the future supply picture for these materials. 

Environmental studies suggest that light gasoline components are detectable in the atmospheres of large metropolitan areas. New environmental laws limit the volatility of gasoline, so refiners must use other processing streams to meet volatility requirements. However, the fuel must provide performance to consumers, for example, by minimizing... 

Benzene, toluene, and xylene (BTX) are valuable as chemical feedstocks and have been solvent extracted for this purpose from refinery streams for decades. Governmental regulations limiting the amount of benzene in gasoline have provided incentives for the extraction of aromatics from gasoline components in recent years and are found in most refineries today. 

Table 5.3. Component Streams and Processes for Gasoline Production...

As a complementary process to reforming, isomerization converts normal paraffins to iso-paraffins, either to prepare streams for other conversions nCi —> /C4 destined for alkylation or to increase the motor and research octane numbers of iight components in the gasoiine pooi, i.e., the C5 or Cs-Ce fractions from primary distillation of the crude, or light gasoline from conversion processes, having low octane numbers. 

Other natural gas Hquids include natural gasoline [8006-61 -9] which is composed of the pentanes and heavier components of the natural gas stream, and ethane [74-84-0]. Most recendy ethane has become the principal product of natural gas processing plants. 

It is the ultimate objective of a refinery to transform the fractions from the distillation towers into streams (intermediate components) that eventually become finished products. This also is where a refinery makes money, because only through conversion can most low-value fractions become gasoline. The most widely used conversion method is called cracking because it uses heat and pressure to "crack"... 

Pygas is fractionated to make a Cs heart cut, a stream with the styrene concentrated in it. This is usually done before the pygas is hydrotreated in preparation for using it as a gasoline blending component. Otherwise the styrene would hydrogenate as well. 

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