Premium
The characterisation of synthetic sulphonate and phenate detergents by nuclear magnetic resonance and infrared spectroscopy
Author(s) -
van de Ven A. M. C.,
Johal P. S.,
Jansen L.
Publication year - 1993
Publication title -
lubrication science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.632
H-Index - 36
eISSN - 1557-6833
pISSN - 0954-0075
DOI - 10.1002/ls.3010060102
Subject(s) - chemistry , alkyl , hydrolysis , nuclear magnetic resonance spectroscopy , carbon 13 nmr , nmr spectra database , micelle , proton nmr , solvent , carbonate , organic chemistry , spectral line , aqueous solution , physics , astronomy
Sulphonate and phenate detergents are used in many modern oil formulations. Overbased sulphonates form micelles, whereas in overbased phenates the excess metal carbonate is incorporated in the molecule as a carbonate chain. This is the cause of broad unresolved peaks in the NMR spectra of these detergents. Hydrolysis removes the excess metal carbonate and converts the sulphonates and phenates to sulphonic acids and phenols respectively. Especially in the 1 H‐ and 13 C‐NMR spectra, a substantial resolution enhancement is achieved after hydrolysis. These spectra reveal much more structural information. One of the features that can be calculated from the 13 C‐NMR spectra is the mean alkyl chain length. In this study a number of commercially available sulphonate and phenate detergents have been investigated. For the sulphonates the alkyl chain length was found to range from 17–22 carbon atoms, and for the phenates the alkyl chain length proved to be approximately 9–12 carbon atoms. The phenate alkyl chains showed significantly more branching than those in the sulphonates. In the 1 H‐NMR spectra, the position of the acidic proton signals is influenced by the measurement temperature, water concentration and solvent. The effect of these parameters was studied in detail. A combination of sample preparation techniques, such as dialysis, and hydrolysis and spectroscopic techniques, such as IR and NMR, can be used successfully to characterise detergents in terms of their molecular structure.