Alkane content

Ichikawa and Nakao 89) have investigated the additive effect of 2,3-dimethyl-butane on the polymerisation of 2,3-dimethylbuta-1,3-diene in thiourea canals. Although yields were reduced sharply, polymerisation was found still to occur in the presence of surprisingly high percentages of alkane. Molecular weights were reduced in this procedure for example the maximum yields of dimers were obtained with an 80 % alkane content. 

Amounts of individual n-alkanes were determined by measuring the areas under the successive peaks and above the baseline that represents an unresolved background of other components. Although the background level rises continually with column temperature, the amount relative to n-alkanes increases more from about C30-C40 than at either lower or higher carbon numbers. Estimates of the n-alkane content of all samples are included in Table II. 

The exact temperature at which the cloud point is reached depends on the total n-alkane content of the fuel, the average size of the n-alkane molecules, their size distribution and chain structure (e.g. degree of branching). Conventional diesels contain as much as 20% of long-chain n-alkanes of limited solubility in the fuel. Pyrolysis-diesels from PE feedstocks can contain more than 40% long-chain n-alkanes. Paraffins crystallize at low temperature into very thin rhombic plates which can clog filters, transfer lines, and pumps, and can lead to engine failure at low temperatures. 

The Nigerian and Venezuelan distillates are examples of naphthenic products because they are relatively low in alkane content. In particular, the Venezuelan distillate is wax-free and a de-waxing step is not required. Although naphthenic products have inferior viscosity/temperature characteristics, they have other beneficial properties which are particularly useful in industrial applications. 

Paraffinic base oils are produced from crude oils of relatively high alkane content typical crudes are from the Middle East, North Sea and US mid-continent. This is not an exclusive list, nor does it follow that all North Sea crudes, for example, are suitable for production of paraffinic base oils. The manufacturing process requires aromatics removal (usually by solvent extraction) and de-waxing. 

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. 

In general, jet fuels from shale oil have the highest and those from coal the lowest n-alkane content. The origin of these n-alkanes in the amounts observed, especially in shale derived fuels, is not readily explained on the basis of literature information. Studies of the processes, particularly the... 

Figure 2. Alkane content (%) in pctrolcuni faction 28-200 C from certain Russian oil deposits.

New types of synthetic polymeric CSP are those based on tartaramide as the selector (Andersson et al., 1996) and those based on R,R) or (S,S) trans-1,2-diaminocyclohexane (Zhong, 2005). The first one shows its best performance for strongly hydrophobic molecules, when a high alkane content in the mobile phase can be used. The second one has moderate selectivities and resolutions and a comparable loading to the cellulose-based CSP (Barnhart, 2008). It offers the possibility to reverse the elution order by choosing the other enantiomer of the chiral selector. 

Alkane Content of Hydrocarbon Minerals and Other Sediments... 

In the case of polyethylene (PE), there is an increased alkane content in the end product, whereas polystyrene leads to a higher aromatic content. Alkene formation benefits from the presence of polypropylene (PP) in the waste. The desired end products can be obtained by the adequate blending of plastics waste however, it is not always technically or economically possible to obtain the quality required. The addition of a catalyst not only improves the quality of the resultant end products, but also enables selection of the product type. 

Heptane commonly contains high-ppm levels of methylcyclohexane and various heptane isomers, low-ppm levels of other alkanes and traces of various alkenes. Odd-numbered linear alkanes are notoriously difficult to purify. In addition, as the number of carbons in the compounds increases, so does the number of possible isomers. Many of these isomers are not separated fix)m the n-alkane during large-scale manufacture. Hence, overall purity, as strictly defined by the n-alkane content, usually decreases while the number and level of impurities increase as the alkane size increases. 

The total alkane contents in vegetable oils ranges from about 10 to 200 mg/kg. Their amount in sunflower oil is 105 170 mg/kg, and in oHve oil approximately 30-100 mg/kg. The amount of alkanes in the cuticular wax of apples, for instance, is about 33% of the Hpid accompanying substances. About 97% of all hydrocarbons in the cuticular wax are represented by nonacosane ( 79), about 2% by heptacosane ( 77) and the remaining 1% consists mainly of alkanes 75, 78, Cjq and Cjj. The cuticular wax of grapefruits is composed primarily of oxygenated compounds, while the content of alkanes is only around 1%. Fats of marine organisms (e.g. fish Hver oils) contain saturated and unsaturated hydrocarbons Cjg and Cj7 or Cji as the main components. The total content of alkanes is about 10-30 mg/kg. 

Figure 3.2. Normal alkane content of scarlet prawns Plesiopenaeus edwardsianus from Aruba, Dutch West Indies. A. Stations where oil was found. B. Stations where no oil was found. (From Thompson etal., 1977.)...

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