Reaction pathways in lubricant degradation. 3. Reaction model for n-hexadecane autoxidation

Blaine, Steven; Savage, Phillip E.

doi:10.1021/ie00001a010

Cited by 47 publications

(55 citation statements)

References 23 publications

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“…The low-temperature oxidation of hydrocarbons is of interest to researchers in a number of different fields. Examples include the oxidative degradation of lubricating oils [11,12] and combustion of fuels in novel engines. [13] The fundamental reaction pathways in condensed-phase oxidation are basically well established and have been reviewed extensively including recent comprehensive reviews by Emanuel and Gµl [14] and Denisov and Denisova.…”

Section: Introductionmentioning

confidence: 99%

Contra‐thermodynamic Behavior in Intermolecular Hydrogen Transfer of Alkylperoxy Radicals

Pfaendtner¹,

Broadbelt²

2007

ChemPhysChem

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Quantum chemical investigation of bimolecular hydrogen transfer involving alkylperoxy radicals, a key reaction family in the free-radical oxidation of hydrocarbons, was performed to establish structure-reactivity relationships. Eight different reactions were investigated featuring four different alkane substrates (methane, ethane, propane and isobutane) and two different alkylperoxy radicals (methylperoxy and iso-propylperoxy). Including forward and reverse pairs, sixteen different activation energies and enthalpies of reaction were used to formulate structure-reactivity relationships to describe this chemistry. We observed that the enthalpy of formation of loosely bound intermediate states has a strong inverse correlation with the overall heat of reaction and that this results in unique contra-thermodynamic behavior such that more exothermic reactions have higher activation barriers. A new structure-reactivity relationship was proposed that fits the calculated data extremely well: E(A)=E(o)+alphaDeltaH(rxn) where alpha=-0.10 for DeltaH(rxn)<0, and alpha=1.10 for DeltaH(rxn)>0 and E(o)=3.05 kcal mol(-1).

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Section: Introductionmentioning

confidence: 99%

Contra‐thermodynamic Behavior in Intermolecular Hydrogen Transfer of Alkylperoxy Radicals

Pfaendtner¹,

Broadbelt²

2007

ChemPhysChem

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“…In the basic research they should be replaced by simple lipid analogs such as free fatty acids and their esters. Although autoxidation of saturated hydrocarbons was the subject of many investigations (1)(2)(3)(4)(5)(6) there are only a few papers describing autoxidation of natural saturated fatty acids and their esters. Former studies on autoxidation of saturated normal hydrocarbons suggested the applicability of the results to oxidation of saturated fatty acid esters.…”

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confidence: 99%

A differential scanning calorimetry study on the oxidation of C₁₂‐C₁₈ saturated fatty acids and their esters

Litwinienko

Daniluk

Kasprzycka‐Guttman

1999

J Americ Oil Chem Soc

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The autoxidation of lauric, myristic, palmitic, and stearic acids, their ethyl esters, and palmitic and stearic triglycerides was investigated by means of the isothermal and nonisothermal differential scanning calorimetry methods under oxygen flow. The activation energies of oxidation of all investigated compounds were similar (106.0-134.3 kJ/mol) and did not depend on length of the carbon chain. Kinetic parameters of start of the oxidation were similar for each investigated fatty acid and ester. Esterification of carboxyl group did not interfere with the reaction rate. The study showed good agreement between isothermal and nonisothermal data.Paper no. J9048 in JAOCS 76, 655-657 (June 1999).There is a considerable interest in characterization of thermooxidative properties of the fatty acids, their esters, and kinetics of their oxidation. Natural fats and oils are very complicated systems of mono-, di-and triglycerides, higher lipids, phospholipids, antioxidants, and other compounds. In the basic research they should be replaced by simple lipid analogs such as free fatty acids and their esters. Although autoxidation of saturated hydrocarbons was the subject of many investigations (1-6) there are only a few papers describing autoxidation of natural saturated fatty acids and their esters. Former studies on autoxidation of saturated normal hydrocarbons suggested the applicability of the results to oxidation of saturated fatty acid esters. Moreover, it was found that autoxidation rates were increasingly proportional to the carbon chain length (1). Recent studies in which overall reactivities of n-paraffins determined by analysis of monoderivatives at the initial stage of oxidation (7) led to conclusion that the reactivity probably does not depend on length of carbon chain. Presence of two maxima on the nonisothermal differential scanning calorimetry (DSC) oxidation curves indicates that thermoxidation can be characterized by at least two-step exothermic effect. Each reaction is characterized by different kinetic parameters. Thus, the kinetic parameters of autoxidation (start of the exothermic process) and destruction of autoxidation products (occurring at higher temperatures) can be determined (8,9). In this study, oxidation of the natural saturated fatty acids: lauric, myristic, palmitic, and stearic, their ethyl esters, and glycerol tripalmitate and tristearate was investigated by DSC methods. The kinetics of the autoxidation of materials containing fatty acids was investigated by thermoanalytical procedures (10-13). However, no data concerning thermoxidative behavior of pure saturated fatty acids and esters have been reported as yet. This study was undertaken in order to establish the kinetics parameters of thermoxidation of these classes of compounds. EXPERIMENTAL PROCEDURESMaterials. The following fatty acids-lauric, palmitic, stearic-and ethyl esters-laurate, myristate, palmitate and stearate (all 99%)-were purchased from Sigma-Aldrich (St. Louis, MO). Purity of glycerol tripalmitate (BDH, Poole, United Kingdom)...

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“…6 When the oil temperature T is 130°C, the primary product ROOH starts to be generated within an hour after the commencement of heating. Reducing T from 130 to 120°C delays the inception of ROOH generation, reduces the peak concentration, increases the time required for achievement of peak concentration from 2 to 8 h, and reduces the (time) gradient of concentration decay by about 3 times.…”

Section: Resultsmentioning

confidence: 99%

Lubricant Degradation and Related Wear of a Steel Pin in Lubricated Sliding Against a Steel Disc

Singh

Gandra

Schneider

et al. 2011

ACS Appl. Mater. Interfaces

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In lubricated sliding contacts, components wear out and the lubricating oil ages with time. The present work explores the interactive influence between lubricant aging and component wear. The flat face of a steel pin is slid against a rotating steel disk under near isothermal conditions while the contact is immersed in a reservoir of lubricant (hexadecane). The chemical changes in the oil with time are measured by vibrational spectroscopy and gas chromatography. The corresponding chemistry of the pin surface is recorded using X-ray photoelectron spectroscopy while the morphology of the worn pins; surface and subsurface, are observed using a combination of focused ion beam milling and scanning electron microscopy. When compared to thermal auto-oxidation of the lubricant alone, steel on steel friction and wear are found to accentuate the decomposition of oil and to reduce the beneficial impact of antioxidants. The catalytic action of nascent iron, an outcome of pin wear and disk wear, is shown to contribute to this detrimental effect. Over long periods of sliding, the decomposition products of lubricant aging on their own, as well as in conjunction with their products of reaction with iron, generate a thick tribofilm that is highly protective in terms of friction and wear.

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Reaction pathways in lubricant degradation. 3. Reaction model for n-hexadecane autoxidation

Cited by 47 publications

References 23 publications

Contra‐thermodynamic Behavior in Intermolecular Hydrogen Transfer of Alkylperoxy Radicals

Contra‐thermodynamic Behavior in Intermolecular Hydrogen Transfer of Alkylperoxy Radicals

A differential scanning calorimetry study on the oxidation of C₁₂‐C₁₈ saturated fatty acids and their esters

Lubricant Degradation and Related Wear of a Steel Pin in Lubricated Sliding Against a Steel Disc

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Reaction pathways in lubricant degradation. 3. Reaction model for n-hexadecane autoxidation

Cited by 47 publications

References 23 publications

Contra‐thermodynamic Behavior in Intermolecular Hydrogen Transfer of Alkylperoxy Radicals

Contra‐thermodynamic Behavior in Intermolecular Hydrogen Transfer of Alkylperoxy Radicals

A differential scanning calorimetry study on the oxidation of C12‐C18 saturated fatty acids and their esters

Lubricant Degradation and Related Wear of a Steel Pin in Lubricated Sliding Against a Steel Disc

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About

A differential scanning calorimetry study on the oxidation of C₁₂‐C₁₈ saturated fatty acids and their esters