Use of Hydrocarbons

Selective double-bond migration of linear and cyclic alkenes without skeletal rearrangement is achieved by treatment with basic reagents ([Eq. (1.29)] see also Chapter 4)  

Reactions of hydrocarbons, particularly those with relatively low ionization potentials (aromatics and n systems but not necessarily alkanes) frequently proceed via single-electron transfer (SET) processes involving radical ions.96 These reactions are particularly significant in oxidation reactions (Chapter 9). 

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Highly pure / -hexane is used to extract oils from oilseeds such as soybeans, peanuts, sunflower seed, cottonseed, and rapeseed. There has been some use of hydrocarbons and hydrocarbon-derived solvents such as methylene chloride to extract caffein from coffee beans, though this use is rapidly being supplanted by supercritical water and/or carbon dioxide, which are natural and therefore more acceptable to the pubHc. 

The presence of polysulfonates in petroleum sulfonates used in lube formulations has a destabilizing effect on the formulation stabiUty and function of the sulfonate in motor oils, etc. Special techniques are utilized to help reduce the carryover of residual sludge components, including the use of hydrocarbon solvents such as hexane or heptane to faciUtate separation of sludge, often with centrihigation. Other desludging procedures include water wash, H2SO4 wash, clay percolation, and filtration. 

Sulfonates for Enhanced Oil Recovery. The use of hydrocarbon sulfonates for reducing the capillary forces in porous media containing cmde oil and water phases was known as far back as 1927—1931 (164,165). Interfacial tensions between 10 and 10 N/m or less were estabUshed as necessary for the mobilization and recovery of cmde oil (166—169). 

The earliest method for manufacturiag carbon disulfide involved synthesis from the elements by reaction of sulfur and carbon as hardwood charcoal in externally heated retorts. Safety concerns, short Hves of the retorts, and low production capacities led to the development of an electric furnace process, also based on reaction of sulfur and charcoal. The commercial use of hydrocarbons as the source of carbon was developed in the 1950s, and it was still the predominate process worldwide in 1991. That route, using methane and sulfur as the feedstock, provides high capacity in an economical, continuous unit. Retort and electric furnace processes are stiU used in locations where methane is unavailable or where small plants are economically viable, for example in certain parts of Africa, China, India, Russia, Eastern Europe, South America, and the Middle East. Other technologies for synthesis of carbon disulfide have been advocated, but none has reached commercial significance. 

The effect of ozone is complicated in so far as its effect is largely at or near the surface and is of greatest consequence in lightly stressed rubbers. Cracks are formed with an axis perpendicular to the applied stress and the number of cracks increases with the extent of stress. The greatest effect occurs when there are only a few cracks which grow in size without the interference of neighbouring cracks and this may lead to catastrophic failure. Under static conditions of service the use of hydrocarbon waxes which bloom to the surface because of their crystalline nature give some protection but where dynamic conditions are encountered the saturated hydrocarbon waxes are usually used in conjunction with an antiozonant. To date the most effective of these are secondary alkyl-aryl-p-phenylenediamines such as /V-isopropyl-jV-phenyl-p-phenylenediamine (IPPD). 

Example 11-5. Use of Hydrocarbon Mixtures as Refrigerants (Used by Permission of the Carrier Corporation.)... 

The realisation that yeasts would produce dtric acid from n-paraffins was veiy attractive in the late 1960 s. Petroleum byproducts were plentiful and very cheap and there was detailed knowledge available on these processes because the use of hydrocarbon-utilising yeasts for single cell protein was well developed. The strategy was to use n-alkane to produce high yields erf dtric add-producing Candida spp. and to harvest two useful end products rather than just one. The process has not been commerdally successful however. Candida spp. produce mixtures of dtric add and isodtric add and the latter is not a useful product. In addition, since 1973 when petroleum prices rose sharply and have in fact continued to rise, the n-paraffins are no longer a cheap substrate. 

The difficulties encountered in the early studies of anionic polymerization of methyl methacrylate arose from the unfortunate choice of experimental conditions the use of hydrocarbon solvents and of lithium alkyl initiators. The latter are strong bases. Even at —60 °C they not only initiate the conventional vinyl poly-addition, but attack also the ester group of the monomer yielding a vinyl ketone1, a very reactive monomer, and alkoxide 23). Such a process is described by the scheme. 

The increased use of hydrocarbon fuels in the last five decades is slowly increasing the concentration of carbon dioxide in the atmosphere, which produces more carbonic acid, leading to an imbalance in the natural carbon dioxide content of the atmosphere, which, in turn, leads to more acidity in the rain. In addition, there is a greenhouse effect, and the average temperature of the Earth may be increasing. 

Petroleum refining also produces substantial amounts of carbon dioxide, which with hydrogen sulfide, corrode refining equipment, harm catalysts, pollute the atmosphere, and prevent the use of hydrocarbon components in petrochemical manufacture. When the amount of hydrogen sulfide is high, it may be removed from a gas stream and converted to sulfur or sulfuric acid. Some natural gases contain sufficient carbon dioxide to warrant recovery as dry ice. 

First, we will refer to the direct use of hydrocarbon fuels in an SOFC as direct utilization rather than direct oxidation. Second, we recognize that the broadest definition of direct utilization, exclusive from mechanistic considerations, should include rather conventional use of fuel by internal reforming, with steam being cofed to the fuel cell with the hydrocarbon. Indeed, this nomenclature has been used for many years with molten-carbonate fuel cells. However, because internal reforming is essentially limited to methane and because the addition of steam with the fuel adds significant system complexity, we will focus primarily on systems and materials in which the hydrocarbons are fed to the fuel cell directly without significant amounts of water or oxygen. 

Examination of the effect of solvents on this reaction revealed that use of ethereal solvents such as THE and dimethoxyethane (DME) generally favors the formation of the cyclopentenone 13 a, while use of hydrocarbon solvents favors another reaction pathway, that is, rearrangement of 12 a to an ethyl 1-octynyl ketone-Co2(CO)6 complex 14a. For example, by carrying out the reaction in refluxing hexane, the complex 14 a is obtained in approximately 70% yield, along with the cyclopentenone 13a in 13% yield 112,13]. 

Phenan thro line (182) can be used instead of thiocyanate to form a complex with Fe(III) ions resulting from the oxidation of Fe(II), and the measurement is made at 500 to 510 nm. The use of 182 has the advantage of stability in the presence of air and also of allowing the use of hydrocarbon solvents for increased solubility of certain analytes. The method was applied for determination of hydroperoxides in natural rubber and synthetic elastomers, in the range of 10 to 20 ppm active oxygen. The sensitivity can be improved to less than 1 ppm, depending on the color of the sample solution. ... 

Petroleum oils are widely used in the treatment of citrus crops in California. They have proved to be the most efficient insecticide per unit of cost for most of the dominant pests of citrus in this area. In an effort to improve oil sprays from the standpoint of both tree safety and insecticidal effectiveness, the research on oil sprays at the University of California Citrus Experiment Station has been intensified. Part of this new effort has involved close cooperation with other laboratories, particularly with the New York State Agricultural Experiment Station at Geneva. The same petroleum fractions and other hydrocarbon compositions were tested simultaneously against citrus and deciduous fruit pests. This coordinated approach has been mutually advantageous, and it is expected that it will lead to an understanding of the fundamental principles involved in the use of hydrocarbon oils as insecticides in general. 

Consequently, the direct use of hydrocarbon gases as fuel is usually considered to be impractical, although Whitesides and co-workers18 describe an aqueous fuel cell in which methane reacts with aqueous iron (III) ions over a platinum black catalyst to form CO2 and iron(II) the Fe2+ solution... 

Use of Hydrocarbonization of Coal in Synthetic Liquid Fuel Processes... 

Initially, we will be concerned with the physical properties of alkanes and how these properties can be correlated by the important concept of homology. This will be followed by a brief survey of the occurrence and uses of hydrocarbons, with special reference to the petroleum industry. Chemical reactions of alkanes then will be discussed, with special emphasis on combustion and substitution reactions. These reactions are employed to illustrate how we can predict and use energy changes — particularly AH, the heat evolved or absorbed by a reacting system, which often can be estimated from bond energies. Then we consider some of the problems involved in predicting reaction rates in the context of a specific reaction, the chlorination of methane. The example is complex, but it has the virtue that we are able to break the overall reaction into quite simple steps. 

The hydrocarbon standard provides a universal scale (retention index, RI) for the characterization of volatile odorants. Since a single determination may require the use of more than one instrument (GC, GC-O, GC-MS), it is crucial that every time a run is made using new operating conditions, a new calibration is recorded using the hydrocarbon standard. This is the only way that RI data from one instrument can be compared with that from another provided that the stationary phase is the same. RIs do not vary with the operating conditions, while retention times do. (See more on the use of hydrocarbon standards in unitgu.)... 

It is difficult to select rationally a penetration enhancer for a given permeant. Accelerant potencies appear to be drug specific, or at best may be predictive for a series of permeants with similar physicochemical properties (such as similar partition coefficients, molecular weights, and solubilities). Some broad trends are apparent, such as the use of hydrocarbon monoterpenes for lipophilic permeants, but the level of enhancement expected for these agents is unpredictable. 

Global Warming An increase in the near-surface temperature of the Earth. Global warming has occurred in the distant past as the result of natural influences, but the term is most often used to refer to a theory that warming occurs as a result of increased use of hydrocarbon fuels by man. See Climate Change (Greenhouse Effect). ... 

A single-chamber solid oxide fuel cell (SC-SOFC), which operates using a mixture of fuel and oxidant gases, provides several advantages over the conventional double-chamber SOFC, such as simplified cell structure with no sealing required and direct use of hydrocarbon fuel [1, 2], The oxygen activity at the electrodes of the SC-SOFC is not fixed and one electrode (anode) has a higher electrocatalytic activity for the oxidation of the fuel than the other (cathode). Oxidation reactions of a hydrocarbon fuel can... 

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