Octane flash point

Methyl tertiary butyl ether (methyl-r-butyl ether, MTBE boiling point 55°C, flash point -30°C) has excited considerable interest because it is a good octane enhancer for gasoline (it blends as if it had a research octane number of 115 to 135). It also offers a method of selectively removing isobutylene from a mixed C4 stream, thus enabling the recovery of high-purity butene-1. Furthermore, methyl tertiary butyl ether can be isolated, then cracked to yield highly pure iso-butylene and methanol. 

The quality of the product is of primary importance in developing a recycling technology converting plastics into fuels by pyrolysis. Today the characterization of a liquid fuel from any sources is obviously based on the qualification methods and standards of fuels from mineral oil. The properties of the pyrolysis-derived fuels from plastics are expected to be similar to conventional fuels (energy content, viscosity, density, octane and cetane number, flash-point, etc.). However, in addition to the familiar ranking values it is necessary to know more about the chemical composition of the plastic pyrolysis oil, because of the peculiarities as follows ... 

Some fuel properties have long been known to be interrelated with chemical composition density and aromatic content, viscosity and distillation range, cetane number and aromatic content. Correlation studies applying various statistical computational methods revealed the contribution of chemical structural units of organic compounds to the various physical properties of hydrocarbon fluids, such as octane and cetane number, flash point, cloud point, etc. 

BENZIN (German) (8006-61-9) Forms explosive mixture with air [flash point (73 octane) —45°F/-43°C (100 octane) —36°F/—38°C]. Violent reaction with oxidizers, fluorine. Incompatible with nitric acid. Flow or agitation of substance may generate electrostatic charges due to low conductivity. 

OCTANAL (124-13-0) Forms explosive mixture with air (flash point 125°F/51°C). Reacts violently with bromine, ketones, strong oxidizers. Incompatible with strong acids, caustics, ammonia, amines, strong oxidizers. 

Octane is an eight-carbon alkane and has a boiling point of 125.6°C, a flash point of 56°F, a flammable range of 1.0 to 6.5%, and an ignition temperature of 428°F. The structure and molecular formula for pentane are shown in Figure 5.31. 

The properties of a petroleum stream are not specified in terms of compositions. Instead, properties are used, such as 5% point, final boiling point, Reid vapor pressure, flash point, and octane number. 

One of the advantages of GC-MS over an IR spectroscopic analyzer is the ability to measure distillation characteristics as well as predict other properties. There are several other materials that can be directly measured and reported. These include benzene, total aromatics, oxygenates, certain sulfur compounds and additives. The properties that can be predicted include (among others) cetane number and index, research and motor octanes, refractive index, distillation properties, aniline point, cloud point, pour point, volatility, flash point, density, conductivity, and viscosity [57]. 

From an engineering perspective, in assessing the required characteristics of the biofuels themselves, one must consider a variety of chemical, physical, and environmental properties. These include factors such as total energy content, ease of ignition (quantified by octane and cetane numbers), heat release rates, evaporative spray characteristics (vapor pressures), flammability safety (flash point), flow properties (viscosity), density, miscibility, fuel toxicity, emissions, impact on engine parts, and stability in storage. 

A system at 60° F contains one mole of propane and one mole of n-octane. Assuming ideal-solution behavior calculate (a) r at 60° F for a flash liberation from the bubble point to 14.7 psia (b) at the bubble point. 

As an example, consider Fig. 7.10a where n-hexane (H) is separated from n-octane by a series of three flashes at 1 atm (pressure drop and pump needs are ignored). The feed to the first flash stage is an equimolal bubble-point liquid at a flow rate of 100 Ibmole/hr. A bubble-point temperature calculation yields 192.3°F. Using Case 5 of Table 7.4, where the vapor rate leaving stage 1 is set... 

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