Gasoline
EN 228
Fuels are mixtures of many different hydrocarbons obtained by refining crude oil. Fuels are liquid at room temperature and highly flammable. In addition to the natural ingredients, each type of fuel contains additives that alter or improve the properties of the fuel.
Kraft substances consist of:
- saturated, straight-chain: n-paraffins
- saturated, branched: iso-paraffins
- Saturated, ring-shaped: Napenthhene
- unsaturated, straight-chain: n-olefins
- unsaturated, branched: iso-olefins
- Unsaturated, ring-shaped: unsaturated Naptenhene
- aromatic compounds
- oxygen-containing compounds such as alcohols and ethers
Additives, e.g. improve storage stability and combustion characteristics and prevent deposits in the combustion chambers.
Fuel component:
Parafins: They provide a clean, residue-free combustion, good calorific value and a good shelf life. The octane number of n-paraffins is good only for very short chains, in long-chain paraffins it is bad to very bad. However, it increases with branched paraffins with the degree of branching and then reaches very good values.
Olefins: Olefins give a good calorific value. The combustion properties are limited.
Aromatics: From a technical point of view, they are very suitable for use. Calorific value and storability are high, the octane number very high. For environmental reasons, their share in gasoline has been limited in recent years from last 42 vol .-% to now 35 vol .-%. Due to its carcinogenic properties, benzene was even more limited to a maximum of 5% by volume to 1% by volume today.
Oxigenates: In order to keep the octane number despite the limitation of "technically favorable" components, oxygen-containing components have been added to the fuel for 20 years. While alcohols have a good octane number, they are significantly more polar compounds than the other gasoline ingredients and may be e.g. on contact with water u.U. be washed out. In the case of methanol, traces of water are already sufficient (condensation in the tank).
Density 15 °C DIN EN ISO 12185
Sulfur content DIN EN ISO 20846
Lead content DIN 51461-1
Research-Octan number, ROZ DIN EN ISO 5164
Motor-Octan number, MOZ DIN EN ISO 5163
Manganese content DIN EN 16136
Oxidation stability DIN EN ISO 7536
Corrosive effect on copper (3h at 50 ° C)
Evaporation residue DIN EN ISO 6246
Hydrocarbon groups DIN EN ISO 22854
Benzene content DIN EN ISO 22854
Oxygen content DIN EN ISO 22854
Oxygenated organic compounds DIN EN ISO 22854
Vapor pressure DIN EN 13016-1
Distillation process DIN EN ISO 3405
C / H ratio DIN EN ISO 22854
Calorific value DIN EN ISO 22854
Molecular weight DIN EN ISO 22854
Thermal conductivity ASTM D 2717
Heat capacity
Water content DIN EN ISO 12937
Octane number
The octane number is a shortening of the two values ROZ and MOZ. It indicates the knock resistance of a gasoline. Knocking is the (acoustic) expression for premature uncontrolled ignition of gasoline even in the compression process. It results in a "sudden" pressure and temperature rise in the combustion chamber. When driving, they hear it as a typical "knock". It can destroy an engine in no time. The higher the octane, the higher and tamper-proof the fuel, the more highly compressed the engine can be designed. In turn, higher compression results in a more efficient engine, i. more power and less consumption.
The value indicates the knock resistance at low and medium speed is determined according to prEN ISO 5164 with the CFR test engine (Octan engine).
limits:
NOK at least 91.0
SOK at least 95.0
SOK + at least 98.0
The volatility of the fuel
The fuel should be well vaporized, so that the engine starts well even when cold. At the same time, steam bubbles in the fuel system should not form when the engine is hot, disrupting or preventing the supply of fuel. In addition, certain dependencies between boiling temperature and fuel properties are evident in the composition. At the start of boiling, you will find short-chain paraffins and olefins with high vapor pressure and above-average octane, the boiling aromatics with low vapor pressure but also high octane. It follows, for example, that in the "middle field" of the boiling range, the octane number is rather below average.
Engine octane number, MOZ
This value indicates the knock resistance at high speed and high engine load and is also determined according to prEN ISO 5163 with the CFR test engine (Octan engine).
limits:
NOK at least 82.5
SOK at least 85.0
SOK + at least 88.0
Density
The density has an influence on the fuel consumption. Fuel is purchased by volume, but the calorific value is more constant relative to the mass. Low density therefore means lower calorific value. In addition, in engines with modern mixture treatment by densities outside the limits may lead to erroneous regulations. In addition to the value itself, the density value also requires the calculation of volume fractions from measurements using GC-OFID and GC-SST, since the results of this measurement are mass percentages.
Sulfur content
Sulfur-containing components have their origin in crude oil, which is currently in percentage range contains such compounds. Corrosive effects in general, negative effects on catalytic converters, especially when the engines are operated with lean gasoline blends, and emission limits have led to a steady lowering of the sulfur limit.
Oxidation stability
The oxidation stability describes the resistance of the fuel against the influence of atmospheric oxygen. This is especially important when storing gasoline. Olefins and di-olefins react with oxygen and alter the properties of gasoline, which ages fuel. Such a reaction is prevented by a suitable additive, which, however, can consume itself over time.
Evaporation residue
The evaporation residue, washed (gum) is a measure of a possible residue formation during the combustion of the fuel. He arises i.a. by very high boiling components (e.g., engine oil fractions) or by olefin derived polymers dissolved in the gasoline.
Corrosive effect on copper
If the fuel contains aggressive components, they can be determined using this method. In EN ISO 2160, copper strip test, exposure time 3 hours at 50 C, the copper strip must not discolour beyond a certain intensity.
Appearance
A visual process. The fuel should be clear and free of haze. This plays - in addition to contamination with sediment - especially in the possible water content of a fuel a role.
Content of hydrocarbon groups
The aromatics and olefin content are determined. The aromatics content is limited for ecological reasons, the olefin content more from technical. For the determination there are 2 methods available:
EN 14517: Determination of hydrocarbons and oxygenated compounds in petrol, multidimensional gas chromatographic method, and
ASTM D 1319: Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption, (FIA)
The gas chromatographic method provides not only the breakdown by hydrocarbon groups but also the sorting by the carbon number. However, arbitration is the FIA. However, the values from this determination must be corrected for the proportion of oxygen-containing components since the method can not detect Oxigenates.
