الفهرس 
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Abstract
Summary and Conclusion
Elucidation of the structure of petroleum fractions is of a great importance, and many methods have been developed for such purpose applying modern analytical techniques.
In the present study seven Egyptian crude oil samples were collected from seven oil fields located at four main different locations. They are Delta (Domiatte), Upper Egypt (Fayoum), the Eastern Desert (West bakr and Wadi Dara) and Western Desert (Al-Wahat).
Physico-chemical characteristics of the collected crude oils have been determined using ASTM, IP or UOP standard test methods. These characteristics include density, specific gravity, API gravity, kinematic viscosity, total sulfur, pour point, water content, asphaltene content, wax content, total saturates and total aromatics.
Generally, it can be concluded from the physico-chemical characteristics of the studied crude oils that 1, 2, 3 and 7 crude oils are characterized by low density and viscosity with low contents of sulphur and water. While 4, 5 and 6 crude oils have high values of these characteristics. Also, it can be noticed that crude oils 1, 2 have the highest pour point values which is directly related to the high wax content detected in these two samples.
The studied crude oils have been fractionated into their, hydrocarbon and nonhydrocarbon components, namely asphaltenes, maltenes, resins, aromatics, saturates, as well as n-paraffins and iso-paraffins. This has been carried out through solid- column chromatography, as well as gas chromatography (GC) analysis.
The gas chromatographic analysis of saturates and waxes separated from the studied crude oil samples indicates that there is a significance difference in both n-paraffins content and carbon number distribution between saturates and waxes.
The influence of the type of precipitating solvent on the asphaltene precipitation was investigated using two different solvents, n-heptane and n-pentane for extracting the asphaltene from sample No. 4. The results obtained showed that, the yields of the asphaltenes obtained by using higher carbon number solvent (n-heptane) are lower in content, but at the same time it is higher in their degree of crystallinity than those obtained by the lower carbon number solvent (n-pentane).
Four asphaltene products have been extracted from seven petroleum locations. These asphaltene samples were examined by X-ray diffraction technique and different structural parameters were calculated and compared.
The X-ray diffraction results of the asphaltenes showed that the distance between two aliphatic chains varies from 4.39 to 5.91Å, the distance between two aromatic sheets ranges from 3.50 to 3.54 Å, and the cluster diameter varies from 34.76 to 36.06 Å. The size of aromatic sheet ranges from 12.42 to 13.66 Å, whereas the average number of aromatic rings in the aromatic sheet varies from 4.67 to 6.63. Crystal sizes and strains parameters were also calculated for the studied asphaltene samples. There was no significant difference in these parameters for three of asphaltene samples (samples No. 4, 5 and 6) from Eastern Desert. On the other hand, asphaltene sample No.7 from Western Desert, showed the largest crystal size and the smallest strains.
The differences in calculated structural parameters are used for setting up fingerprinting of the studied samples. Also; structural parameters can be used for aging of the crude oil from which the asphaltene was extracted. So analysis of the structural parameters led to the conclusion that the crude oil from which asphaltene of sample No. 7 was extracted is the youngest crude oil among the studied samples.
Seven saturates and four waxes samples, extracted from the studied crude oils, were scanned by X-ray diffraction. The results indicated that waxes and saturates have nearly the same structures, with minor differences in the structural and microstructural parameters. The differences may be attributed to the presence of impurities in saturate samples.
Dispersive Raman spectroscopic technique has been applied for characterization of asphaltene, wax and saturates samples. For all asphaltene samples, the Raman spectra were visibly similar to each other, characterized with two modes (G and D1). The quantitative analysis of the Raman spectra allowed calculating the size of aromatic sheet (La) which is found to be characteristic for each asphaltene sample. Values of (La) obtained from the Raman analysis is consistent with the results derived from X-ray diffraction technique.
Saturates and wax Raman spectra were almost similar, with the same bands position, but there are some spectral differences in the relative band intensity and sharpness, indicating that wax samples are more crystalline than saturates. This result coincides with the X-ray diffraction results. The factors which may be responsible for the difference in the degree of crystallinity between wax and saturates samples are: the difference in the distribution of n-paraffin (linear crystalline molecule) in wax and saturates and the presence of impurities in saturates samples.
Asphaltene is one of the heavy fractions of petroleum responsible for serious problems during petroleum production. One of these problems is the formation of organic deposits in oil reservoirs, wells, transport pipelines and equipments. Another problem is the internal corrosion of pipelines. Three different kinds of surfactants were used to control these two problems. The studied surfactants were tested as corrosion inhibitors, as well as, asphaltene dispersants.
The inhibiting action of the used surfactants for carbon steel corrosion in the tested crude oil was investigated by weight loss and scanning electron microscopy techniques. The results obtained showed that, all the tested surfactants act as good corrosion inhibitors for carbon steel in crude oil but to different extent. The percentage inhibition efficiency decreases according to the following order: Dodecylbenzene sulfonate ˃ N2,N3-didodecyl-N2,N2,N3,N3-tetramethylbutane diammonium bromide ˃4-Nonylphenyl-polyethylene glycol.
The effect of tested surfactants as asphaltene precipitation inhibitors was studied using UV/VIS/NIR spectrophotometer. The results revealed that the three studied additives are efficient in asphaltene precipitation and the inhibition efficiency follows the same order as in corrosion inhibition. So, the three studied surfactants that are industrially applicable are efficient for inhibition of both corrosion and asphaltene precipitation.