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4861140 
Journal Article 
Waxes and asphaltenes in crude oils 
Thanh, NX; Hsieh, M; Philp, RP 
1999 
1 
Organic Geochemistry
ISSN: 0146-6380 
30 
2-3 
119-132 
English 
WOS:000079191500002 
High molecular weight (HMW) hydrocarbons (> C-40) and asphaltenes are important constituents of petroleum and can cause problems related to crystallization and deposition of paraffin waxes during production and transportation as well as in the formation of tar mats. However, traditional methods to isolate asphaltene fractions, by adding 40 volumes in excess of low boiling point solvents such as pentane, hexane or heptane, can produce asphaltene fractions which are contaminated with a significant amount of microcrystalline waxes (>C-40) The presence of these microcrystalline waxes in the asphaltene fractions has the potential to provide misleading and ambiguous results in modeling and treatment programs. The sub-surface phase behaviour of an asphaltene fraction will be quite different from that of a wax-contaminated asphaltene fraction. Similarly accurate modelling of wax drop-out requires information on pure wax fractions and not asphaltene-dominated fractions. Hence the goal of this paper is to describe a novel method for the preparation of wax-free asphaltene fractions. In addition, this method provides a quantitative subdivision of the wax fraction into pentane soluble and insoluble waxes which, when correlated with physical properties of crude oil such as viscosity, pour point, cloud point, etc., may help explain causes of wax deposition during production, transportation and storage of petroleum. (C) 1999 Elsevier Science Ltd. All rights reserved. 
waxes; asphaltenes; crude oils; high temperature gas chromatography; depositional environments; high molecular weight hydrocarbons