Initiation in hydrocarbon autoxidation at elevated temperatures

Abstract

Kinetic and mechanistic investigations of liquid phase autcxidation of hexadecane at 120 to 190°C have shown that, in the early stages of oxidation, the initiation process involves homolytic decomposition of hydroperoxides. The values of a composite first order rate constant for this decomposition, k l , have been determined in stirred flow reactor experiments from the rate of formation of termination products and in batch reactor studies using inhibitor methods.Arrhenius parameters derived from these studies (log (A/s-') = 8.5 and E, = 26 kcal mol-') allow calculation of k l as a function of temperature. This permits determination of the rate of initiation as a function of hydroperoxide concentration and facilitates determination of absolute rate constants for other oxidation reactions occurring in this system.

Molecular Science of Lubricant Additives

“…Most organic materials experience this reaction as ageing processes, and lubricants are no exceptions. Therefore, they have been well studied both from engineering and scientific approaches [69][70][71][72][73]. The consensus reaction pathway is the radical chain reaction mechanism, which is initiated by the hemolytic dissociation of a C-H bond by heat or ultraviolet irradiation.…”

Detection and Identification of the Keto-Hydroperoxide (HOOCH2OCHO) and Other Intermediates during Low-Temperature Oxidation of Dimethyl Ether

“…The appearance of carbonic acid might be explained by a decomposition mechanism which was postulated by Korcek and coworkers. [89][90][91][92][93] This mechanism involves the decomposition of the keto-hydroperoxide via a cyclic intermediate forming an acid and another carbonyl species. 94 In the case of DME two decomposition pathways are conceivable (depicted in Fig.…”

Understanding low-temperature first-stage ignition delay: Propane

“…For example, due to limited understanding at the time of their study, several critical reactions were not included in the detailed model of Curran et al [14], and subsequent model studies have each retained some of these shortcomings. Three important examples include (i) the very important concerted reactions of the type RO 2 ⇌ HO 2 + alkene, where RO 2 is an alkylperoxy radical [16][17][18][19], (ii) molecular elimination of carboxylic acids and aldehydes from ketohydroperoxides [20][21][22][23][24][25], and (iii) the interception of vibrationally excited free radicals by O 2 [26,27]. The thermochemistry and elementary rate coefficients for many peroxy radicals have also been significantly revised during the last few years [28][29][30][31][32][33][34][35][36][37].…”