Thermal Decomposition Of Hydroperoxides Research Articles

Catalytic activity of iron-containing carbon nanotubes in the oxidation reaction of the diesel fuel fraction

Liquid-phase aerobic oxidation of petroleum hydrocarbons catalyzed by carbon nanoparticles is focused on the real practical implementation over the rational processing of multicomponent petroleum feedstock. The use of metal-containing carbon nanostructures as catalysts allows known oxidation processes to be considered in the most modern strapping and simultaneously raises related questions about kinetics and mechanism of the process. This paper describes the formal kinetic regularities of the liquid-phase aerobic oxidation of the diesel fuel paraffin-naphthenic fraction in the presence of iron-containing multiwalled carbon nanotubes Fe@MWCNT. The purpose of the work is to determine the activity of the catalyst and the mechanism of its action. The reaction was carried out at 80°C, at which thermal decomposition of hydroperoxides is known to be almost non-existent and the reaction does not initiate. The induction period, the profile of the kinetic curves, and the oxygen uptake rate were taken as criteria for catalyst activity. As a result, it was shown that Fe@MWCNT additives have a significant ability to increase the rate of aerobic oxidation of diesel fractions. A general scheme of catalytic oxidation of hydrocarbons of the petroleum fraction in which the catalyst on a nanocarbon carrier reduces the dissociation energy of the C-H bond and activates the decomposition of hydroperoxides into active reactive particles has been proposed. Keywords: metal-containing carbon nanotubes; petroleum hydrocarbons; diesel fuel; paraffin-naphthenic fraction; oxidation induction period; catalytic hydroperoxide decomposition; oxygen uptake rate.

Graft copolymerization kinetics of acrylic acid onto the poly(ethylene terephthalate) surface by atmospheric pressure plasma inducement

AbstractAfter one atmospheric pressure plasma treatment of poly(ethylene terephthalate) (PET) film, acrylic acid (AAc) in aqueous solution was successfully graft‐copolymerized onto PET films. The effects of reaction time, AAc monomer concentration and reaction temperature on grafting behavior of AAc were systematically studied. Possible reaction kinetics of plasma‐induced graft copolymerization, starting from initial hydroperoxide decomposition, were proposed. Through the Arrhenius analysis about graft copolymerization kinetics of AAc monomers on PET surface, it was revealed that the activation energies of decomposition, propagation and termination were 98.4, 63.5, and 17.5 kJ/mol, respectively. The temperature around 80 °C was favorable not only for the formation of oxide radicals through the thermal decomposition of hydroperoxide on PET surface but also for the extension of graft copolymer chain through direct polymer grafting. Poly(acrylic acid) (PAAc) grains grafted onto PET surfaces possessed relatively uniform size and both PAAc grain size and surface roughness increased with increasing the grafting degree of AAc. The increase of grain size with increasing grafting degree results from the possibility of forming long chain graft copolymers and their shielding of reactive sites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1594–1601, 2008

A kinetic investigation of thermally initiated emulsion copolymerization of styrene and methylmethacrylate without conventional initiators

AbstractThe thermally initiated emulsion copolymerization of styrene (ST) and methyl methacrylate (MMA) was carried out in the absence of conventional initiators. The hydroperoxide (HPO) concentration in the monomers, sodium dodecyl sulfate (SDS), deionized water, and the formulation of those for emulsion copolymerization were measured. The HPO concentration in ST and MMA increased with the storage time, and were considered to be the major sources of HPO. The thermal decomposition of hydroperoxide in monomers, the thermal initiation of ST by Mayo mechanism, and the complex formation between SDS and the monomers were proposed to be three main sources of the radical generation. It was confirmed that new polymer particles were generated throughout the polymerization process, and consequently resulted in a broader distribution of polymer particle size, compared with that for conventional emulsion polymerization. Approximately 80 wt % of monomer conversion was obtained in the presence of SDS at 373 K in 24 h. The initiation rate of the 30 wt % monomer charge was faster than those of 10 wt % and 20 wt % monomer charge. The latex instability at higher solid content was improved by adding electrolyte to promote the electrostatic repulsion force between the polymer particles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 455–467, 2002; DOI 10.1002/app.2343

Effect of oleic and linoleic acids on the production of deep-fried odor in heated triolein and trilinolein.

To determine sources of desirable deep-fried flavor in frying oils, degradation products from heated triolein and trilinolein with 5-31% polar compounds representing low to high deterioration were evaluated by purge-trap gas chromatography-mass spectrometry-olfactometry. (E,E)-2,4-Decadienal, 2-heptenal, 2-octenal, 2,4-nonadienal, and 2,4-octadienal produced deep-fried odor at moderate-strong intensities in heated trilinolein. However, unexpected aldehydes-2,4-decadienal, 2,4-undecadienal, 2,4-nonadienal, and 2-octenal (all <15 ppm)-were produced in triolein heated for 6 h. These dienals possibly were produced by hydroperoxidation and/or hydroxylation followed by dehydration of 2-alkenals. The 2-alkenals were produced from thermal decomposition of hydroperoxides, epoxides, and keto and dimeric compounds produced during the heating of triolein. These aldehydes produced low intensities of deep-fried odor in triolein. This information helps to explain sources of the deep-fried flavor that is characteristic of high linoleic frying oils but which is only at low intensity levels in high oleic frying oils.

Rapid estimation of peroxide content of soybean oil by measuring thermoluminescence

AbstractThermoluminescence measurements can serve as a simple and rapid procedure for the estimation of peroxide content of soybean oil. The thermoluminescence intensity, measured at 100°C, increases in proportion (r=0.978) to the peroxide value (from 0.5 to 18.0 meq/kg) of soybean oil, without any interference by the tocopherol contents. The emission spectrum had a maximum wavelength at around 440–480 nm, suggesting that excited triplet carbonyls formed during thermal decomposition of hydroperoxides are involved. The thermoluminescence measurement is readily available for the simple and rapid estimation of the peroxide content of soybean oil, with no need for chemical reagents and delicate skills.