Fuels, fossil alkanes

The University of Osaka is the holder of two patents regarding the least studied biorefining processes, demetallization, and bioconversion. The metals are removed from the fossil fuel, under mild conditions (room temperature and atmospheric pressure) by the microbial oxidation action and a UV-photochemical reaction [166], The bioconversion refers to conversion of high molecular weight alkanes by the action of B. thermoleovorans B23 and B. thermoleovorans H41 strains to lower molecular weight molecules [167],... 

Diesel fuel is produced by distilling raw oil, which is extracted from bedrock. Diesel is a fossil fuel, consisting of hydrocarbons with between 9 and 27 carbon atoms in a chain, as well as a smaller amount of sulfur, nitrogen, oxygen and metal compounds. It is a general properly of hydrocarbons that the autoignition temperature is higher for more volatile hydrocaibons. The hydrocarbons present in the diesel fuels include alkanes, naphthenes, olefins and aromatics. 

FIGURE 9.43 Concentrations of n-alkanes as a function of carbon number from (a) a particle sample collected in Jos, Nigeria (the dashed line represents the estimated concentrations from fossil fuel sources), (b) vegetation wax in the Jos area, and (c) particles collected over the Atlantic Ocean (adapted from Sinioneit et al., 1988). 

The principal source of alkanes is petroleum and natural gas, which contain only the more volatile alkanes. Therefore, low molecular weight alkanes, e.g. methane and small amounts of ethane, propane and other higher alkanes can be obtained directly from natural gas. Another fossil fuel, coal, is a potential second source of alkanes. Usually alkanes are obtained through refinement or hydrogenation of petroleum and coal. 

More than 130 different types of alkanes have been identified in the atmosphere [27] and they comprise a major fraction of the organic pollutants found in urban atmospheres (see Table 3). They are released in large amounts in activities connected with the extraction, refining, distribution, and combustion of fossil fuels. Alkanes are also released during the combustion of organic matter and by microbiological processes associated with the decay... 

More than 140 different alkenes have been identified in the atmosphere [27]. The sources of alkenes are similar to those for the alkanes with combustion of fossil fuel being a major source. The presence of unsaturated bonds makes these compounds much more reactive than the alkanes. The most persistent member of this class of compounds (ethene) has an atmospheric lifetime of the order of a day, while more typically the lifetimes for alkenes are measured in hours. As a result of their short lifetimes the atmospheric concentrations of alkenes are highly variable and decrease dramatically away from their source locations. The mechanisms of atmospheric oxidation of alkenes have recently been reviewed [55]. As with the alkanes the reaction of OH radicals is an important loss mechanism. This reaction proceeds mainly via addition to the unsaturated bond as illustrated for ethene in Fig. 4. In one atmosphere of air at 298 K the dominant atmospheric fate of the alkoxy radical HOCH2CH2O is decomposition via C - C bond scission, while reaction with O2 makes a 20% contribution [56]. The fate of alkoxy radicals resulting from addition of OH to alkenes is generally decomposition via C - C bond scission [8]. Thus, the OH radical initiated oxidation of propene gives acetaldehyde and HCHO, oxida-... 

Many alkanes occur in nature, primarily in natural gas and petroleum. Both of these fossil fuels serve as energy sources, formed from the degradation of organic material long ago. 

The combustion of alkanes and other hydrocarbons obtained from fossil fuels adds a tremendous amount of CO2 to the atmosphere each year. Quantitatively, data show a 20% increase in the atmospheric concentration of CO2 in the last 46 years (from 315 parts per million in 1958 to 377 parts per million in 2004 Figure 4.19). Although the composition of the atmosphere has changed over the lifetime of the earth, this may be the first time that the actions of humankind have altered that composition significantly and so quickly. 

Today, benzene and other aromatic and aliphatic hydrocarbons are obtained from fossil fuels, which formed over millions of years from the remains of living things. The main source of these compounds is petroleum, a complex mixture of alkanes, some aromatic hydrocarbons, and organic compounds containing sulfur or nitrogen atoms. 

Where does the immense variety of organic compounds come from Amazingly enough, the ultimate source of nearly all synthetic organic compounds is petroleum. Petroleum is a fossil fuel that consists almost entirely of hydrocarbons, especially alkanes. How can alkanes be converted into compounds as different as alkyl halides, alcohols, and amines ... 

The Naval Research Laboratory has related the freezing point of JP-5 type fuels to the n-alkane content, specifically n-hexadecane (1). This relationship applies to jet fuels derived from alternate fossil fuel resources, such as shale oil, coal, and tar sands, as well as those derived from petroleum. 

Hydrocarbons in New York Bight Surface Sediment. As an example of the problems involved let us consider the case of hydrocarbons in surface sediments of the New York Bight. Our previous work on alkanes and cycloalkanes in that area has been published (18). By applying the previously discussed criteria we were able to conclude that the bulk of the alkanes and cycloalkanes were of fossil fuel origin. The measurements of polynuclear aromatic hydrocarbons (PNAs) in one of our samples from this area indicated that the bulk of those hydrocarbons were of pyrolytic origin (19). 

An earlier study (11) of alkanes, cycloalkanes, and phenanthrenes in another sediment core from this location showed an interesting trend of decreasing concentrations between the upper 2 cm and 54-58 cm, which pointed towards fossil fuel combustion as the principal source of hydrocarbons in these surface sediments. The core was collected in August 1975 with a 21-cm-diame-ter, 1-m-long sphincter corer (14). Three sections of the core were used for this study Sample 4, the top 4 cm Sample 5, 20-24 cm and Sample 6, 38-42 cm. There was no sulfide present in the top 8 cm. An oxic, bioturbation zone of about 4 cm is indicated by the 210Pb depth profile and benthic ecology studies (12,15). 

The second limitation of Py-GC-MS is that the complex pyrolysate was not just pyrolysis products it consisted of evaporation and combustion products of HS. ° It was reported that free compounds, e.g., alkanes, and fatty acids in HS macromolecules evaporated quickly under pyrolysis, and stmctural units split off through burning in the presence of oxygen and can be further incorporated into HS. For example, lipids, e.g., alkanes, fatty acids, dicarboxylic acids, and ketones were often found as free or solvent-extractable compounds in soils and soil HS. These compounds can be synthesized by microorganisms and plants, and can occur upon combustion of fossil fuels and biomasses. Alkylfurans and methoxylated phenols were considered pyrolysis products of... 

Alkanes are widespread both on Earth and on other planets. The atmospheres of Jupiter, Saturn, Uranus, and Neptune contain large quantities of methane (CH4), the smallest alkane, which is an odorless and flammable gas. In fact, the blue colors of Uranus and Neptune are due to methane in their atmospheres. Alkanes on Earth are found in natural gas and petroleum, which are formed by the decomposition of plant and animal material that has been buried for long periods in the Earl s crust, an environment with little oxygen. Natural gas and petroleum, therefore, are known as fossil fuels. 

The application of and N.M.R. spectroscopy, gas chromatography (G.C.) and mass spectrometry (M.S.) in the separation and identification of alkanes extracted from fossil fuels is illustrated with three Turkish lignites (including one extracted by supercritical gas), coal tar and petroleum crude. Elution of hydrocarbons from a silica-gel column may be monitored by N.M.R. and molecular-sieve sub-fractionation into normals and branched/cyclics by G.C., together with... 

Alkanes in Fossil Fuels. Sedimentary rocks, which range in age from Recent years) to the pre-Cambrian period ( 3 x 10 ... 

Over the last two decades, developments in G.C., mass spectrometry (M.S.), N.M.R. spectroscopy and other physical techniques have appreciably extended the ability of chemists to undertake detailed analyses of fractions extracted from coal and other fossil fuels. In this paper, we survey some of the characterization techniques for alkanes, emphasising particularly... 

Examples of Hydrogen Distribution in Fossil-Fuel Alkane Extracts Measured from 100 MHz H N,M,R Spectra ... 

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