Deparaffination of light crudes through urea-n-alkane channel complexes

Nwadinigwe, Chukwuemeka A.; Eze, Sunday O.

doi:10.1016/0016-2361(90)90270-z

Cited by 8 publications

(6 citation statements)

References 4 publications

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“…McKay et al isolated waxes from neutral fractions by ion-exchange chromatography of asphalts with a 2-butanone/toluene solvent mixture at −25 °C. Nwadinigwe and Eze and Netzel and Rovani used urea adduction followed by GC to characterize materials rich in n -paraffins. The European Standard Method 12606 for isolating waxes combines an initial distillation followed by precipitation of waxes from the distillate with diethyl ether/ethanol (1:1, v/v) at −20 °C.…”

Section: Introductionmentioning

confidence: 99%

Waxphaltene Determinator Method for Automated Precipitation and Redissolution of Wax and Asphaltene Components

et al. 2012

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The new Waxphaltene Determinator method is based on the on-column precipitation and redissolution separation technique developed at Western Research Institute. Although high-performance liquid chromatography (HPLC) instrumentation and detectors are used, the separation does not involve chromatographic interaction between the material being separated and the stationary phase. It is based on freezing, melting, and solubility. The Waxphaltene Determinator uses methyl ethyl ketone at −24 °C to precipitate waxes and asphaltenes. The precipitated material is redissolved in four steps using a series of three solvents of increasing polarity, at different temperatures: heptane at −24 °C, heptane at 60 °C, toluene at 30 °C, and methylene chloride/methanol (98:2, v/v) at 30 °C. This approach allows for the detection of waxy, polar, and pericondensed aromatic components in minutes.

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Section: Introductionmentioning

confidence: 99%

Waxphaltene Determinator Method for Automated Precipitation and Redissolution of Wax and Asphaltene Components

et al. 2012

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“…McKay et al isolated waxes from neutral fractions from ion-exchange chromatography separations of asphalts using a 2-butanone/toluene solvent mixture at −25 °C. Nwadinigwe and Eze and Netzel and Rovani used urea adduction followed by gas chromatography to characterize materials rich in n -alkanes. The European standard method for isolating waxes combines an initial distillation followed by precipitation of waxes from the distillate using diethyl ether/ethanol (1:1) (v/v) at −20 °C.…”

Section: Introductionmentioning

confidence: 99%

On-Column Separation of Wax and Asphaltenes in Petroleum Fluids

et al. 2008

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The utility of a novel method based on the new on-column precipitation and redissolution technique is explored. This method, called waxphaltene determinator (WAD), is strictly solubility-based and allows for the detection of waxes and asphaltenes in minutes. The principle of the method is to first precipitate waxes and asphaltenes together on a ground polytetrafluoroethylene (PTFE)-packed column using methyl ethyl ketone at -20 °C and then redissolve the precipitate with solvents of increasing polarity at different temperatures. Waxes precipitated under these conditions are composed mainly of n-alkanes, with carbon numbers greater than C 20 , and heptane-soluble alkanes that are slightly to moderately branched. The method is first verified with model compounds, including n-alkanes and commercial waxes, and then applied to waxy crude oils and deposits. The method is compared to differential scanning calorimetry (DSC), and a linear correlation is found between the wax content by WAD and DSC. Asphaltene amounts by WAD also compare well to the gravimetric data.

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“…Cookson and Smith used urea adduction to separate the n -alkanes from the branched plus cyclic alkanes in petroleum- and coal-derived diesel fuels. Deparaffination of light crudes using the urea-adduction technique was reported by Nwadinigwe and Eze . Nwadinigwe and Nwobodo compared the molecular sieve and urea adduction as analytical techniques to determine the amounts of normal alkanes in light crudes.…”

Section: Introductionmentioning

confidence: 99%

Direct Separation and Quantitative Determination of (n-, Iso-)Alkanes in Neat Asphalt Using Urea Adduction and High-Temperature Gas Chromatography (HTGC)

Netzel

Rovani

2006

Energy Fuels

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Urea adduction and high-temperature gas chromatography were used to separate and quantify the amount of normal plus iso-alkanes (n-, iso-)alkanes in 13 neat asphalts. Treating neat asphalt directly with urea eliminated the separation steps necessary for extracting the saturate fraction containing the alkanes from the asphalt. The amounts of n-alkanes including 2-methyl and 3-methyl isomers for the 13 asphalts ranged from 0 to 1.84 wt %. Saturate fractions from three asphalts were obtained by adsorption−desorption chromatography. The amounts of (n-, iso-)alkanes and the highly branched plus cyclic alkanes were determined also for these fractions using urea adduction and were found to be in good agreement with the direct determination of (n-, iso-)alkanes in the neat asphalts. The amount of (n-, iso-)alkanes was found to correlate with the crystalline wax content measured by differential scanning calorimetry, but the method does not account for all of the crystalline wax content. In addition, the amount of (n-, iso-)alkanes does not account for the large n-alkane methylene signals observed in the hydrogen-1 and carbon-13 nuclear magnetic resonance spectra for the asphalts. No correlation was found between the amount of (n-, iso-)alkanes in asphalt and the fracture temperature. However, an apparent correlation does exist between the highly branched plus cyclic alkanes in asphalt and the fracture temperature.

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Deparaffination of light crudes through urea-n-alkane channel complexes

Cited by 8 publications

References 4 publications

Waxphaltene Determinator Method for Automated Precipitation and Redissolution of Wax and Asphaltene Components

Waxphaltene Determinator Method for Automated Precipitation and Redissolution of Wax and Asphaltene Components

On-Column Separation of Wax and Asphaltenes in Petroleum Fluids

Direct Separation and Quantitative Determination of (n-, Iso-)Alkanes in Neat Asphalt Using Urea Adduction and High-Temperature Gas Chromatography (HTGC)

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