Aromatic fuels

Low temperature viscosities have an important influence on fuel atomisation and they affect engine starting. Cycloparaffinic and aromatic fuels reach unacceptably high viscosities at low temperatures. A kinematic viscosity of 35 mm /s (=cSt) represents the practical upper limit for pumps on aircraft, whereas much higher limits are acceptable for ground iastaHations. 

Furnace Black One of the three principal processes used for making carbon black the others being the Thermal Black and the Channel Black processes. In the Furnace Black process, aromatic fuel oils and residues are injected into a high velocity stream of combustion gases from the complete burning of an auxiliary fuel with an excess of air. Some of the feedstock is burned, but most of it is cracked to yield carbon black and hydrogen. The products are quenched with water. 

Only full decarboxylation (Reaction 4) produces a paraffin-like product (H/C = 2), all the other methods produce more aromatic fuel precursors and need full hydrogenation (Reaction 7) if paraffins are aimed for. 

Since the early 1980s, zeolites have been considered for the upgrading of biomass-derived fluids into aromatic fuels [74, 75], Researchers of the Univerite Laval (Quebec, Canada) performed pioneering work on model compounds (phenols and furans) [76, 77]. A recent study investigating the transformation of alco-... 

Data on aerosol formation from irradiated automobile exhaust 5.193.23. 239 confirm the marked sensitivity to hydrocarbon type observed in individual hydrocarbon studies. Aerosol formation increases with the olefinic and aromatic fuel content. However, changes in mode of engine operation (acceleration, idle) and inorganic variables (sulfur dioxide, relative humidity) have a more pronounced effect on aerosol formation than change in fuel composition. ... 

Source Detected in groundwater beneath a former coal gasification plant in Seattle, WA at a concentration of 180 g/L (ASTR, 1995). Acenaphthene is present in tobacco smoke, asphalt, combustion of aromatic fuels containing pyridine (quoted, Verschueren, 1983). Acenaphthene was detected in asphalt fumes at an average concentration of 18.65 ng/m (Wang et al., 2001). Present in diesel fuel and corresponding aqueous phase (distilled water) at concentrations of 100 to 600 mg/L and 4 to 14 g/L, respectively (Lee et al, 1992). 

Aromatic fuel The prior results were obtained using propane (not very sooty) and ethylene (considerably more sooty) as fuels. The results were extended to a very sooty aromatic fuel by choosing benzene, as it had a sufficient vapor pressure to be entrained into the fuel flow. 

Conversion of heterocyclic aromatic compounds or other aromatic fuel components to paraffins by hydroprocessing can help increase the cetane number of diesel fuel. Fuel paraffins have significantly higher cetane number values than fuel aromatics. For this reason, the cetane number of ultra-low sulfur diesel fuel will typically be one to five numbers greater than higher-sulfur grade fuels. 

Since highly aromatic fuels have little wax, they possess better natural low-temperature handling properties than paraffinic fuels. Also, the cloud point, pour point and low-temperature filtration of aromatic diesel fuel will typically be much lower than a paraffinic diesel fuel. 

Certain elastomeric materials used as gaskets, seals, and hoses can be degraded by aromatic fuel components. Elastomers such as natural rubber, neoprene, Buna-N, and ethylene-propylene will all swell in the presence of aromatic fuel components. 

Degradation of elastomers used in transfer lines and hoses by aromatic fuel components is undesirable. For this reason, elastomers used in fuel storage and distribution systems are often made of hydrocarbon-resistant elastomers such as Viton , polyvinyl chloride (PVC) and Teflon . 

Compared to highly aromatic fuels, paraffinic fuels combust and bum with less smoke and soot. This is primarily due to the fact that paraffins are hydrogen-rich compared to aromatics. The hydrogen-rich nature of paraffins enables the combustion process to progress more completely to C02 and H20. This is demonstrated by the following reaction equations ... 

When highly paraffinic, low-aromatic fuels are used in these same systems, aromatic components can leach from the seals and cause seals to shrink. As a result, fuel begins to leak from the fuel intake and distribution system. 

Deposits on intake valves are also caused primarily by olefins, especially diolefins, and higher-molecular-weight aromatic fuel components. The higher temperatures within the intake valve region promote the formation of deposits which are more carbonaceous than those which form on fuel injector tips. Also, components of the lubricating oil additive package are often found within the matrix of intake valve deposits. 

Combustion of highly aromatic fuel can enhance the formation of carbonaceous deposits... 

Kaiser, E. W., W. O. Siegl, D. F. Cotton, and R. W. Anderson, Effect of Fuel Structure on Emissions from a Spark-Ignited Engine. 2. Napthalene and Aromatic Fuels, Environ. Sci. Technol., 26, 1581-1586 (1992). 

The installed capacities for hydrotreating distillates are predominantly moderate-pressure reactors (up to 3 MPa). Typical conditions used in today s commercial processes are summarized in Table IV (7). In the U.S., the Clean Air Act mandated that low-emission fuels will have to be developed for future use. Industry responded quickly, and by 1994 typical diesel fuels in the U.S. contained 0.05% S, with average cetane numbers of 42 and 31-37% aromatics. California imposed stricter standards, requiring 0.05% S and a minimum of 48 cetane with an emission that did not exceed that of a 10% aromatic fuel. This is the present standard for California Air Resources Board (CARB) certification. Through the development of improved processing and additives that lower emissions, Chevron was the... 

Wear and Jonash (83) reported that for unstable combustion, the highest efficiency was obtained for paraffinic and aromatic fuels with low boiling points. Better efficiency... 

Sealing Compound, One Part Silicone, Aircraft Firewall Adhesive/Sealant, Fluorosilicone Aromatic Fuel Resistant, One Part Room Temperature Vulcanizing... 

Paraffin Olefin Aromatics Fuel oil Cracked gas Residue ... 

Both types of anti-knock are more effective in paraffinic fuels then in olefinic or aromatic fuels, and can even promote knock when added to some alcohols. In Fig. 7.9 the response of some pure hydrocarbons to the addition of 3ml/US gal of tetra-ethyl lead is shown, in terms of Performance Number. Almost all the alkanes lie on a steeper line than the alkenes. The exceptions are low octane number alkenes, which are largely straight alkane chains, and a few highly-branched alkanes (which also have high sensitivity, see Section 7.2.3). Notwithstanding the subtleties of lead additives, a broad explanation in chemical kinetic terms is that the antiknock acts to increase radical termination rates and, consequently, has proportionately less effect in those fuels where the termination rates are already high. 

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