The formation of asphaltenes and its impact on the chemical and physical properties of asphalts /
Asphaltenes, both those originally present and those produced by aging, have been shown by many researchers to contribute the most to the changes in physical properties of asphalts. In this study, factors that affect the formation of asphaltenes and the contribution of asphaltenes to an asphalt'...
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1995.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742536211&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Asphaltenes, both those originally present and those produced by aging, have been shown by many researchers to contribute the most to the changes in physical properties of asphalts. In this study, factors that affect the formation of asphaltenes and the contribution of asphaltenes to an asphalt's Theological properties were experimentally determined. Asphaltenes are created as a result of oxidative aging. A unique relationship called the Asphaltene Formation Susceptibility, or AFS, exists between asphaltene formation and carbonyl formation, which is a measure of the extent of oxidation. The AFS is defined as the partial differential of asphaltene formation with respect to carbonyl formation. The AFS was found to be independent of saturate content and type of asphaltene. The AFS was also found to continuously decrease with increased asphaltene content and is a strong function of the composition of aromatics fraction. A Theological model that accounts for molecular association of asphaltenes was developed to quantitatively describe the effects of asphaltenes on the Theological properties of asphalts. The contribution that asphaltenes have to the Theological properties is strongly dependent on the asphaltene-maltene interaction. Furthermore, the magnitude of the interaction between asphaltenes and maltenes is a function of temperature and the composition of both asphaltenes and maltenes. The interaction between asphaltenes and maltenes was modeled using a salvation constant, K, that describes the degree of asphaltene association occurring in a given maltene. The model describes the temperature dependence of K and gives the Gibb's free energies of formation for asphaltene association. The Gibb's free energies for asphaltene association range from -20 to -30 KJ/mol. The model also successfully predicts that K is a increasing function of saturate content. To reduce the damages that asphaltenes do to an asphalt binder, the AFS needs to be reduced by adjusting the composition of aromatics. The saturate content also need to be low because the presence of saturates magnify the effects that asphaltenes have on the Theological properties of asphalt. |
|---|---|
| Item Description: | Vita. "Major Subject: Chemical Engineering". |
| Physical Description: | xxi, 271 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |