Oil samples

An important application of this type of analysis is in the determination of the calculated cetane index. The procedure is as follows the cetane number is measured using the standard CFR engine method for a large number of gas oil samples covering a wide range of chemical compositions. It was shown that this measured number is a linear combination of chemical family concentrations as determined by the D 2425 method. An example of the correlation obtained is given in Figure 3.3. 

A container full of hydrocarbons can be described in a number of ways, from a simple measurement of the dimensions of the container to a detailed compositional analysis. The most appropriate method is usually determined by what you want to do with the hydrocarbons. If for example hydrocarbon products are stored in a warehouse prior to sale the dimensions of the container are very important, and the hydrocarbon quality may be completely irrelevant for the store keeper. However, a process engineer calculating yields of oil and gas from a reservoir oil sample will require a detailed breakdown of hydrocarbon composition, i.e. what components are present and in what quantities. 

Figure 9-20. Left Kohonen map showing the projection ofthe olive oil samples. Middle Map of Italy showing the regions of origin for the olive oils, Right Key giving the regions and their codes,...

The information given for the commercial oils represents data critically selected from pubUshed rehable sources or, in some cases, analyses performed in the authors laboratories on authentic oil samples. These data are provided as a general guide to composition only and are not meant to be exclusive of analytical results obtained by other researchers on similar oils. Where the Hterature provides ranges of composition, these have, in several cases, been included. Many variables affect the composition of essential oils. 

Figure 1 Plot of weathering ratio (C3-dibenzo thiophenes C3-ehrysenes) versus souree ratio (C3-dibenzothio-phenes C3-phenanthrenes) for fresh and degraded oil samples from three different erude oil spills (Reprinted with permission from Environ. Sci. Technol, 30, 2332. 1996 Ameriean Chemieal Soeiety)...

An oil sample should be withdrawn from the system and analyzed in the laboratory. The usual tests of the used oil include (1) viscosity, (2) pH and neutralization number, and (3) precipitation. The test results will... 

Multidimensional chromatography has also been applied for the analysis of industrial chemicals and related samples. Industrial samples which have been analyzed by multidimensional chromatography include coal tar, antiknock additives in gasoline (3), light hydrocarbons (4, 5), trihaloalkanes and trihaloalkenes in industrial solvents (6-8), soot and particulate extracts, and various industrial chemicals that might be present in gasoline and oil samples. 

When John Phillips, in 1991, presented the practical possibility of acquiring a real comprehensive two-dimensional gas chromatographic separation (33), the analytical chemists in the oil industry were quick to pounce upon this technique. Venkatramani and Phillips (34) subsequently indicated that GC X GC is a very powerful technique, which offers a very high peak capacity, and is therefore eminently suitable for analysing complex oil samples. These authors were able to count over 10 000 peaks in a GC X GC chromatogram of a kerosine. Blomberg, Beens and co-workers... 

Figure 14.20 GC cliromatogram of the total sulfur compounds in a heavy gas oil sample.

Figure 14.21 GC cliromatogram of the dibenzothiophenes fraction of a heavy gas-oil sample. Peak identification is as follows 1, dibenzotliiophene 2, 4-methyldibenzothiophene 3, 2-methyldibenzothiophene 4, 3-methyldibenzothiophene 5, 4,6-dibenzotliiophene 6, other C2-dibenzothiophenes, 7, C3-dibenzothiophenes 8, C4- and liigher dibenzothiophenes.

Figure 14.22 Contour plot of the GC X GC separation of a heavy gas oil sample the thin lines indicate the borders between the groups.

The pour point represents the lowest temperature at which the liquid fuel will pour. This is a useful consideration in the transport of fuels through pipelines. To determine the pour point, an oil sample contained in a test tube is heated up to 115°F (46°C) until the paraffin waxes have melted. The tube is then cooled in a bath kept at about 20°F (11°C) below the estimated pour point. The temperature at which the oil does not flow when the tube is horizontally positioned is termed the pour point. 

This test indicates the amount of metallic constituents in a crude oil. The ash left after completely burning an oil sample usually consists of stable metallic salts, metal oxides, and silicon oxide. The ash could be further analyzed for individual elements using spectroscopic techniques. 

Lubricating oil analysis, as the name implies, is an analysis technique that determines the condition of lubricating oils used in mechanical and electrical equipment. It is not a tool for determining the operating condition of machinery. Some forms of lubricating oil analysis will provide an accurate quantitative breakdown of individual chemical elements, both oil additive and contaminates, contained in the oil. A comparison of the amount of trace metals in successive oil samples can indicate wear patterns of oil wetted parts in plant equipment and will provide an indication of impending machine failure. 

Oil analysis has become an important aid to preventive maintenance. Laboratories recommend that samples of machine lubricant be taken at scheduled intervals to determine the condition of the lubricating film that is critical to machine-train operation. Typically eleven tests are conducted on lube oil samples ... 

Viscosity is one of the most important properties of lubricating oil. The actual viscosity of oil samples is compared to an unused sample to determine the thinning of thickening of the sample during use. Excessively low viscosity will reduce the oil film strength, weakening its ability to prevent metal-to-metal contact. 

Oxidation of lubricating oil can result in lacquer deposits, metal corrosion, or thickening of the oil. Most lubricants contain oxidation inhibitors. However when additives are used up, oxidation of the oil itself begins. The quantity of oxidation in an oil sample is measured by differential infrared analysis. 

Total acid number (TAN) is a measure of the amount of acid or acid-like material in the oil sample. Because new oils contain additives that affect the TAN number, it is important to compare used oil samples with new, unused, oil of the same type. Regular analysis at specific intervals is important to this evaluation. 

There are three major limitations with using tribology analysis in a predictive maintenance program equipment costs, acquiring accurate oil samples and interpretation of data. 

The capital cost of spectrographic analysis instrumentation is normally too high to justify in-plant testing. Typical cost for a microprocessor-based spectrographic system is between 30,000 and 60,000. Because of this, most predictive maintenance programs rely on third party analysis of oil samples. 

Lubricating oil samples from all equipment included in the program should be taken on a monthly basis. As a minimum, a full spectrographic analysis should be conducted on these samples. Wear particle or other analysis techniques should be made on an as-needed basis. 

Viscosity indicates the chemical composition of an oil sample. As the viscosity of a sample increases, paraffins increase, hydrogen content increases, and the aromatic fraction decreases. 

Procedure. Weigh out accurately about 5 g of the oil sample, dissolve in a small volume of white spirit and transfer to a 50 mL graduated flask use the same solvent to wash out the weighing bottle and finally to make up the solution to the mark. 

Figure 16. Gas chromatogram of a crude oil sample showing the possible existence of adamantane and diamantane in the sample.

Of added interest in this study was the finding that the enantiomeric ratios of a-terpineol also differ widely among populations. In southern populations and the population from the northwestern tip of the island, the amount of (+)-a-terpineol was shown to range from 92.3 to 97.0%, while this enantiomer made up 85.6% in the upper-middle population, but only 66.0% in the population from the southeastern tip of the island. It would be of interest to see if the enzymes responsible for the biosynthesis of a-terpineol have different stereochemical requirements in these populations, or whether some isomerization has occurred in the formation, preparation, or analyses of these oil samples. 

Improved high-pressure liquid chromatography (HPLC) methods have been developed for the analysis of quaternary salt type corrosion inhibitors in brine waters [400]. However, these methods are not suitable for imidazolines and amido-amines. A method based on fluorescence detection has been described for the quantitative analysis of the imidazoline- and amido-amine-type corrosion inhibitors in both oil field water and crude oil samples by HPLC [1174]. 

Figure 8.21 Separation of an olive oil sample after esterification with pivalic anhydride on a 10 cm x 2 mm I. D. silica gel cclumn with hexane-dichloromethane (4+1) containing 0.05% acetonitrile...

Morriss et al. [14] correlated the log mean (LM) T2 relaxation times with viscosity for a number of crude oil samples and viscosity standards using Eq. (3.6.2), as is illustrated in Figure 3.6.1,... 

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