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A critical approach to viscosity index
- Source :
-
Fuel . Nov2009, Vol. 88 Issue 11, p2199-2206. 8p. - Publication Year :
- 2009
-
Abstract
- Abstract: The viscosity index (VI) is a useful tool for lubricant users and refiners, since it is a measure of the effect of temperature changes on the viscosity of the oil. However, it was found that the viscosity index does not correlate with the flow activation energy Ea , which is the theoretically defined dependence of the viscosity on temperature. In this way, two oils may have the same flow activation energy but a viscosity index varying by up to 120. We therefore believe that the VI does not always give a proper representation of the effect of temperature on the kinematic viscosity. 13C NMR spectroscopy was used to identify the molecules with a high VI. Twenty different oil samples produced from eight different vacuum gas oils with viscosity indices ranging from −104 to 146 were analyzed and key parameters identified for high VI molecules: long alkyl chains, methyl branching in the centre of the molecule, low content of aromatic compounds, no ethyl branching and no tertiary carbons. A correlation based on four selected peaks was developed, giving a very good prediction of the viscosity index. [Copyright &y& Elsevier]
Details
- Language :
- English
- ISSN :
- 00162361
- Volume :
- 88
- Issue :
- 11
- Database :
- Academic Search Index
- Journal :
- Fuel
- Publication Type :
- Academic Journal
- Accession number :
- 43310588
- Full Text :
- https://doi.org/10.1016/j.fuel.2009.05.016