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Chemical, physical and electrical properties of aged dodecylbenzene 2: thermal ageing of single isomers in air

Chemical, physical and electrical properties of aged dodecylbenzene 2: thermal ageing of single isomers in air
Chemical, physical and electrical properties of aged dodecylbenzene 2: thermal ageing of single isomers in air
The linear isomer of dodecylbenzene (DDB), 1-phenyldodecane, was aged at temperatures of 105 and 135 oC in air and the resultant products were analyzed using a range of analytical techniques. On ageing, the 1-phenyldodecane darkened, the acid number, dielectric loss and water content increased and significant oxidation peaks were detected in the infrared spectrum. When aged in the presence of copper, a characteristic peak at 680 nm was also detected by UV/visible spectroscopy but, compared with previous studies of a cable-grade DDB, the strength of this peak was much increased and no appreciable precipitate formation occurred. At the same time, very high values of dielectric loss were recorded. On ageing in the absence of copper, an unusually strong infrared carbonyl band was seen, which correlates well with the detection of dodecanophenone by gas chromatography / mass spectrometry and nuclear magnetic resonance spectroscopy. It was therefore concluded that the ageing process proceeds via the initial production of aromatic ketones, which may then be further oxidized to carboxylic acids. In the presence of copper, these oxidation products are present in lower quantities, most of these oxidation products being combined with the copper present in the oil to give copper carboxylates. The behavior is described in terms of a complex autoxidation mechanism, in which copper acts as both an oxidizing and a reducing agent, depending on its oxidation state and, in particular, promotes elimination via the oxidation of intermediate alkyl radical species to carbocations.
1393-1405
Hosier, Ian L.
6a44329e-b742-44de-afa7-073f80a78e26
Vaughan, Alun S.
6d813b66-17f9-4864-9763-25a6d659d8a3
Sutton, Simon
571c7136-1eb6-44e1-8979-ca0829469a6b
Davis, Fred J.
ea0f7935-9a20-4e2f-b9f4-7e85d1925a66
Hosier, Ian L.
6a44329e-b742-44de-afa7-073f80a78e26
Vaughan, Alun S.
6d813b66-17f9-4864-9763-25a6d659d8a3
Sutton, Simon
571c7136-1eb6-44e1-8979-ca0829469a6b
Davis, Fred J.
ea0f7935-9a20-4e2f-b9f4-7e85d1925a66

Hosier, Ian L., Vaughan, Alun S., Sutton, Simon and Davis, Fred J. (2008) Chemical, physical and electrical properties of aged dodecylbenzene 2: thermal ageing of single isomers in air. IEEE Transactions on Dielectrics and Electrical Insulation, 15 (5), 1393-1405. (doi:10.1109/TDEI.2008.4656249).

Record type: Article

Abstract

The linear isomer of dodecylbenzene (DDB), 1-phenyldodecane, was aged at temperatures of 105 and 135 oC in air and the resultant products were analyzed using a range of analytical techniques. On ageing, the 1-phenyldodecane darkened, the acid number, dielectric loss and water content increased and significant oxidation peaks were detected in the infrared spectrum. When aged in the presence of copper, a characteristic peak at 680 nm was also detected by UV/visible spectroscopy but, compared with previous studies of a cable-grade DDB, the strength of this peak was much increased and no appreciable precipitate formation occurred. At the same time, very high values of dielectric loss were recorded. On ageing in the absence of copper, an unusually strong infrared carbonyl band was seen, which correlates well with the detection of dodecanophenone by gas chromatography / mass spectrometry and nuclear magnetic resonance spectroscopy. It was therefore concluded that the ageing process proceeds via the initial production of aromatic ketones, which may then be further oxidized to carboxylic acids. In the presence of copper, these oxidation products are present in lower quantities, most of these oxidation products being combined with the copper present in the oil to give copper carboxylates. The behavior is described in terms of a complex autoxidation mechanism, in which copper acts as both an oxidizing and a reducing agent, depending on its oxidation state and, in particular, promotes elimination via the oxidation of intermediate alkyl radical species to carbocations.

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Published date: October 2008
Organisations: EEE

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Local EPrints ID: 266833
URI: http://eprints.soton.ac.uk/id/eprint/266833
PURE UUID: a967196e-1655-4d72-aa45-6651e8f63583
ORCID for Ian L. Hosier: ORCID iD orcid.org/0000-0003-4365-9385
ORCID for Alun S. Vaughan: ORCID iD orcid.org/0000-0002-0535-513X

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Date deposited: 27 Oct 2008 09:39
Last modified: 15 Mar 2024 03:18

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Contributors

Author: Ian L. Hosier ORCID iD
Author: Alun S. Vaughan ORCID iD
Author: Simon Sutton
Author: Fred J. Davis

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