Is it better to have a lower content of olefins in gasoline?

Isn’t it what the teacher explained to us when we were studying chemistry, during the chemical experiments – that in the experiments of burning saturated hydrocarbons, alkenes, and aromatic hydrocarbons, the smoke becomes more and more dense? I think. . . Simply put. . . In other words, the higher the olefin content, the higher the rate of combustion deposits, making complete combustion more difficult; naturally, this leads to emissions that are not conducive to environmental protection Hahaha. . . Of course, although it sounds simple, it is also backed by certain theoretical support. . . :lol

Controlling the olefin content is one of the important indicators of gasoline stability. A high olefin content makes gasoline prone to oxidation and coking. It causes gasoline to change color. Since olefins have a relatively high octane number among similar hydrocarbons, the content of olefins should be kept at a certain level; however, it is not necessary to minimize the amount of olefins as much as possible

In terms of application, the less olefins there are, the better; olefins are reactive and can easily oxidize equipment. Incomplete combustion produces chemical smoke. Gasoline with a high content of olefins is prone to oxidation and deterioration. However, olefins have a high octane rating; low olefin content results in low octane rating. Most commercial gasoline is straight-run gasoline, which is blended with catalytic gasoline and reformed gasoline (benzene and its derivatives also have high octane ratings). But benzene and olefins cause significant environmental pollution due to incomplete combustion, so there are restrictions on these two substances. The best solution is hydrogenation, which removes double bonds and facilitates alkyl isomerization. There is always a gap between reality and theory; you can’t have both fish and bear paws – it’s sufficient to meet the **standards**. Of course, it’s even better if the product quality is high; nowadays, the standards for ordering are also getting stricter

Olefins have a high sensitivity to octane number; therefore, their level cannot be too low. Moreover, too low an amount of olefins in gasoline increases production costs. However, when the olefin content is high, the increase in octane number slows down; in other words, olefins are not the only way to increase octane number. Olefins are also unstable and prone to oxidative decomposition, which affects the stability of gasoline and the performance of engines, as well as causing environmental pollution. Olefins are also valuable chemical raw materials. Therefore, the olefin content cannot be too high either. Currently, the control limit for the olefin content in gasoline is not more than 35 (v/v). This post was last edited by Shuichangshou on 2009-2-3 12:36.]

As long as it meets the standards, there’s no need for it to be as low as possible; after all, the octane rating of olefins is still quite high

It is mainly to control the stability of gasoline; olefins have poor stability and are prone to oxidation.

Using low-olefin gasoline can significantly reduce NOX emissions in exhaust gases. Unburned olefin emissions can undergo photochemical reactions with NOX to produce photochemical smog, which irritates the eyes and upper respiratory tract and damages plant leaves. Low-olefin gasoline can reduce the formation of carbon deposits and residues in the engine, as well as the buildup of carbon deposits in components such as engine nozzles and intake valves. This leads to more complete combustion, which not only extends the vehicle’s service life but also reduces fuel consumption. Olefins in gasoline are beneficial for octane rating. In China’s refining processes, catalytic cracking is the primary method used to produce gasoline, and its characteristic is a high content of olefins. To compensate for the loss in octane rating caused by reduced olefin levels, process modifications require substantial investment, and their economic viability is questionable.

What those upstairs have said is already very comprehensive. The high content of olefins in gasoline leads to poor combustion, which significantly increases the concentrations of NOx and other toxic substances in exhaust gases. The olefin content in gasoline is too low; since olefins, especially isomerized olefins, have a higher octane number than alkanes and particularly straight-chain alkanes, they reduce the octane number of gasoline. The upper and lower limits for each are determined by the **and regional gasoline standards. For example, the olefin content in gasoline must not exceed 35% on a volume basis, and the octane rating of 90-octane gasoline must be at least 90 (and so on). Furthermore, the olefin content in gasoline is primarily determined by upstream processing and treatment, although it can also vary to a limited extent through blending. Since FCC gasoline typically accounts for a large proportion in the blend, around 90%, the olefin content of FCC gasoline essentially determines the economic viability of controlling the olefin content in gasoline to meet standards. For FCC catalysts intended for gasoline production, apart from process considerations, their selection is essentially based on the balancing of conflicting factors such as a low gas-oil ratio, a low olefin content, and a high octane rating. When gasoline is a non-target product of FCC, such as when it has a high olefin content, reducing this olefin content often comes at a cost: for example, hydrogenation processes (primarily for desulfurization and olefin reduction) increase hydrogen consumption, and moreover, the octane rating of gasoline decreases due to the presence of olefins. These are the economic and technical reasons why Wesmo controls the olefin content in gasoline.

The gasoline hydrotreatment process involves desulfurization only, without removing unsaturated olefins, with the aim of reducing losses in octane number.

Olefins have reactive chemical properties and exhibit strong photochemical reactivity; their evaporation emissions can cause photochemical pollution.

In particular, the dienes contained within it can lead to the formation of carbon deposits and coking in the nozzles and intake systems of automotive fuel systems during use, thereby deteriorating engine performance and worsening exhaust emissions.

The points made on the 4th and 5th floors are good; I agree.

In short, too high an olefin content in gasoline leads to poorer stability； A low olefin content results in a lower octane rating, and both conditions can affect the proper operation of the engine. The olefin content index should be controlled.

A lower olefin content is not necessarily better! On the one hand, olefins contribute to increasing the octane rating of gasoline; on the other hand, too low an olefin content can lead to a decrease in gasoline yield and increased processing costs. The adverse effects of olefins, in addition to affecting the stability of gasoline, are also manifested in carbon deposition and gum formation in the fuel supply system; these problems can be resolved by using fuel with a reduced olefin content.

In terms of emissions, NOx emissions are complex and are not solely related to the olefin content； An emission that is closely related to olefins is the emission of “1,3-butadiene”.

A low content of olefins results in a lower octane rating; high olefin content in gasoline leads to poor stability； Neither situation is favorable and can affect the proper operation of the engine. Therefore, it is necessary to control the olefin content level; it’s not the case that the lower it is, the better – of course, a high level is also not desirable

A low content of olefins results in a lower octane rating; high olefin content in gasoline leads to poor stability； Neither situation is favorable and can affect the proper operation of the engine. Therefore, it is necessary to control the olefin content level; it’s not the case that the lower it is, the better, but of course a high level is also not desirable. The new National V standard introduced in 2016 features a lower sulfur content, as well as a lower olefin content; the octane rating has also been reduced. Therefore, olefins do have a certain impact on octane rating.

Yes, gasoline olefins are beneficial for octane rating, but they affect emission standards, and environmental regulations are becoming increasingly strict.

Everyone’s opinions are great; I’ve learned from them

Olefins in gasoline are key factors affecting its octane rating; the components responsible for a high octane rating in gasoline are aromatics and olefins. However, a high content of olefins can affect the stability of gasoline; therefore, it’s not true that the lower the olefin content, the better, nor is it true that the higher the content, the better.