Octane number in gasoline

Reactions between paraffins and olefins to form highly branched paraffins are carried out in a slurry reactor to increase the octane number in gasoline. [Chem.Eng. Sci. 51, 10,2053 (1996)]. 

Another example where molecular sieving and preferential adsorption control the separation is the separation of CO2/CH4 in CHA and DDR zeolite membranes [43,81]. The separation of CO2 from natural gas is important during its transport and combustion because of the acidic and corrosive character of CO2 in the presence of humidity and moreover, it reduces the methane number (similar to the octane number in gasoline) which is important for getting high efficiency during combustion. 

The transformation of light alkanes (C2-C4) over H-ZSM-5 and Ga or Zn modified H-ZSM-5 catalysts to aromatic hydrocarbons has been studied intensively in recent years, since it would expand the raw material base for the manufacture of aromatics [1, 2]. The aromatics produced can be used as feed-stock for plastics, as chemical source for many chemical processes, as additives for increasing the octane number in gasoline, etc. 

To the refiner, the question of octane numbers in future gasolines is of primary importance because it determines the course of operations, the development or on the contrary the stagnation of such and such a process. Table 5.12 thus gives an example of the typical composition by origin and concentration of different base constituents of three grades of the most common motor fuels distributed today in Europe conventional premium gasoline at 0.15 g Pb/1, Eurosuper and Superplus. 

Table 1 shows the major gasoline additives that were introduced from the 1920s through the 1980s. The increase in octane number of gasoline with use of these additives is shown. 

Figure 9.15. MTBE, methyl t-butyl ether, a common octane booster in gasoline, has an octane number of 116. Other boosters are ETBE (ethyl t-butyl ether RON = 118) and TAME (t-amyl methyl ether RON = 111).

Another important use of RMs is the maintenance of conventional scales. The octane number of gasoline is an example of such a scale. The scale is defined through chemicals. This definition can be realized through RMs. Another example is the pH scale, which is defined by buffers with pH = 4, pH = 7, and pH = 10. These buffers are defined as mixtures of salts, dissolved in water. These define the pH scale can be used by laboratories for the purpose of calibrating their pH meters. 

The application of alcohol and gasoline-alcohol mixtures in the gasoline (Otto) engines began in the first half of the twentieth century. It is possible to find information about various studies on the change in octane numbers of gasoline-alcohol... 

One cannot talk about the chemistry of gasoline without understanding octane number. When gasoline is burned in an internal combustion engine to CO2 and H2O, there is a tendency for many gasoline mixtures to bum unevenly. This is caused basically by ignition before the piston of the engine is in the proper position. Such nonconstant and unsmooth... 

The efficacy of an additive, such as tetraethyl lead on the octane number of gasoline, shows a concave curve so that the first cubic centimeter of additive would achieve much more than the second cubic centimeter, and the third cubic centimere would do even less. This can also be described by the term diminished return, which is described by d f/dx < 0, which is the characteristic of a function with a diminishing value of df/dx with increase in x. 

Two studies in 1985 and 1992 focused on the use of superacids in isomerization.20,21 An important advantage of these catalysts is that they may be used at lower temperature because of their greatly increased ability to bring about carbo-cationic process. For example, aluminum chloride, still one of the important isomerization catalysts in industry, can be used at about 80-100°C. In comparison, superacids are active in alkane isomerization at room temperature or below. In addition to avoid side reactions under such conditions, lower reaction temperatures favor thermodynamic equilibria with higher proportion of branched isomers, which is fundamental in increasing the octane number of gasoline. 

MTBE is easily made by the selective reaction of isobutylene and methanol over an acidic ion-exchange resin calalysi. in ihe liquid phase and at temperatures below HK> 5( To be economically competitive. MTBE s use as an octane enhancer in gasoline lias been dependent on low cost isobutylene. There are a number of possible isobutylene sources lor making MTBF. 

Lead Susceptibility—The increase in octane number of gasoline imparted by the addition of a specified amount of tetraethyl lead. 

Today, NIR analyzers are being used in the refineries to determine many different properties in addition to the octane numbers of gasoline. One refinery is measuring 25 properties of their gasoline every 45 seconds. Once the spectrum has been acquired, it just takes some calculations on the attached computer to determine additional analytical properties, such as boiling points, olefin content of the gasoline, aromatic content, methyl... 

---