Oxidation Of Decane Research Articles

Theoretical and experimental study on the inhibition of jet fuel oxidation by diarylamine

Antioxidants addition is believed as a facile and effective way to improve jet fuel thermal oxidation stability. However, amine antioxidants, as one of the most important antioxidants, have not received sufficient attention in the field of jet fuel autoxidation yet. Herein, the inhibition efficiency and mechanism of decane and exo-tetrahydrodicyclopentadiene (THDCPD) oxidation by di-4-tert-butylphenylamine (diarylamine) was experimentally and theoretically investigated. The results show that diarylamine can significantly inhibit decane oxidation but is less efficient for THDCPD oxidation, which is attributed to the higher energy barrier of retro-carbonyl-ene reaction (rate-determining step) in THDCPD than that in decane during diarylamine regeneration. However, the addition of diarylamine will cause undesirable color change after accelerated oxidation and produce slightly more deposits during high-temperature thermal oxidative stress for both decane and THDCPD. The results provide significant implications for the future design of effective antioxidant additives for high-performance jet fuel.

Assessment of effectiveness factor in porous catalysts under non-symmetric external conditions of concentration

Abstract the present paper, the effectiveness factor of porous catalytic particles is evaluated in the absence of boundary conditions symmetry over the external surface by computational fluid dynamic (CFD) techniques. The first-order kinetics of decane oxidation, already evaluated experimentally, is taken as a representative reaction. Our study arises from the fact that, in the open literature, the effectiveness factor is usually calculated considering conditions of symmetry of concentration field around particles. However, depending on the fluid dynamics of the system, such conditions are not always established and, thus, our work aims at studying for the first time the behaviour of particle catalysts with non-uniform concentration fields over the surface. In particular, the effectiveness factor of the particles in a catalytic layer is calculated in the absence of symmetry by changing several parameters (temperature, tortuosity and mean pore diameter of particle) using two different methods, named Sphere-by-Sphere (SbS) and Equisized-Volume (EV), respectively. The results of these two methods are then compared to the theoretical one obtained in the presence of spherical symmetry. As a main result, we found that, for moderately low values of Thiele modulus (<1.3 ca.), the analytical expression of the effectiveness factor obtained under spherical symmetry can be also applied in non-symmetric conditions. On the contrary, this cannot be done for higher values of Thiele modulus, for which we propose an empirical correlation of the effectiveness factor based on a corrected Thiele modulus. The efficacy of our approach is stated by the fact that pseudo-homogeneous-mode simulations of the heterogeneous system show results that match very well those obtained in heterogeneous mode, with an important reduction of calculation time and memory. The presented methodology can be also applied to n-order kinetics.

Gas phase photocatalytic oxidation of decane at ppb levels: Removal kinetics, reaction intermediates and carbon mass balance

Abstract This study focuses on the photocatalytic oxidation of decane at ppb levels, close to indoor air conditions. Although these concentrations are typical of indoor air volatile organic compound (VOC) levels, such conditions have been poorly investigated to date. Decane conversion rates higher than 90% were reached within 15 h for the highest initial concentration tested in the operating conditions used. Despite this high decane conversion, 18 reaction intermediates were detected in the gas phase. The main compounds, in terms of concentration level in the gas phase, were formaldehyde, acetaldehyde and propanal. The amounts of these compounds in the gas phase were linearly dependent on the initial decane concentration. A reaction pathway is proposed, based on reaction intermediate temporal profiles and the literature. It consists of six main steps describing the oxidation process from decane to CO and CO2. The influence of the relative humidity level on the diversity and amounts of reaction intermediates was also studied. It was shown that moisture tends to shift the equilibrium of intermediates adsorption toward desorption, resulting in a relative increase in intermediate quantities in the gas phase. However, the monitoring of CO and CO2 formation highlighted that, at the end of the reaction, a high mineralization rate could be obtained. Finally, an overview of the photocatalytic reaction is given through the carbon mass balance determined for various reaction advancements. This approach gives an overall evaluation of the photocatalytic process performance, from primary compound removal to reaction intermediate and mineralization.

Three-dimensional modeling and simulation of a micrometer-sized particle hierarchical structure with macro- and meso-pores

This study is focused on modeling and simulation of hierarchically structured catalytic media with macro- and meso-pores. The hierarchical structures are expected to enhance the contact between reactants and active catalytic sites. However, heterogeneous simulations of such structures are not computationally feasible for a practical scale, so that a multi-scale approach involving a pseudo-homogeneous approximation is required. This work aims at determining a suitable form for effectiveness factor in the reaction rate and effective diffusivity to be used in a pseudo-homogeneous approximation. To do that, computational fluid dynamics (CFD) simulations of hierarchical structure of particles are carried out in both heterogeneous and homogeneous mode within 240–300°C and Thiele modulus around 2.4 or less. The analysis is applied to decane oxidation as representative of the oxidation of exhausted gas from Diesel engines. After providing a validation of the analysis on a single catalyst spherical particle, simulations in heterogeneous mode are carried out under isothermal conditions. The results suggest that the effective diffusivity for the pseudo-homogeneous approximation should include porosity and tortuosity of ensemble, which is evaluated considering the particles as dense. Additionally, detailed profile analysis suggests that the analytical expression of the effectiveness factor valid for spherical particles under isothermal conditions could be used in the pseudo-homogeneous approximation. Then, simulations in homogeneous mode are carried out under both isothermal and non-isothermal conditions to confirm the above-cited suggestions. The obtained results demonstrate the suitability of the chosen effectiveness factor and effective diffusivity.

An Attempt at Enhancing the Regioselective Oxidation of Decane Using Catalysis with Reverse Micelles

The regioselective oxidation of linear alkanes to give terminal oxidation products represents a major challenge for catalysis. A number of previous approaches have shown that confinement and encapsulation can offer an experimentally viable way forward. Against this background we have investigated the use of a system comprising gaseous oxygen, a homogenous catalyst (ammonium metavanadate) confined in an aqueous solution within reverse micelles formed in decane using bis(2-ethylhexyl)sulfosuccinate. At low conversion and at short reaction times we show that the approach does lead to a small enhancement in the selectivity to terminal products, but unsurprisingly the surfactant is more readily oxidised than decane and so the small positive effects of the micellar catalyst system are short-lived.

Non-lattice surface oxygen species implicated in the catalytic partial oxidation of decane to oxygenated aromatics

The one-step transformation of C(7)-C(12) linear alkanes into more valuable oxygenates provides heterogeneous catalysis with a major challenge. In evaluating the potential of a classic mixed-metal-oxide catalyst, we demonstrate new insights into the reactivity of adsorbed oxygen species. During the aerobic gas-phase conversion of n-decane over iron molybdate, the product distribution correlates with the condition of the catalyst. Selectivity to oxygenated aromatics peaks at 350°C while the catalyst is in a fully oxidized state, whereas decene and aromatic hydrocarbons dominate at higher temperatures. The high-temperature performance is consistent with an underlying redox mechanism in which lattice oxide ions abstract hydrogen from decane. At lower temperatures, the formation of oxygenated aromatics competes with the formation of CO(2), implying that electrophilic adsorbed oxygen is involved in both reactions. We suggest, therefore, that so-called non-selective oxygen is capable of insertion into carbon-rich surface intermediates to generate aromatic partial oxidation products.

Computational Fluid Dynamics Simulation of a Three-Dimensional Catalytic Layer for Decane Oxidation: Case Study of Reaction on Particle Surface

Computational fluid dynamics (CFD) simulations of a reactive catalytic layer of micrometer-sized particles with a submicrometer interparticle distance for decane oxidation are described. The investigation used two main approaches. The heterogeneous approach simulates particles at the reactive particle surface, by use of a monodispersed face-centered cubic structure of eight unit cells in series. In contrast, the pseudohomogeneous approach investigates the particle system as a homogeneous system (approximation) having dimensions and geometrical properties (tortuosity and porosity) identical to those of the heterogeneous one. Heterogeneous system results show that mass transfer resistance can be regarded as negligible in the whole range of parameters investigated (temperature and interparticle distance). Particularly, the difference in results obtained by the two approaches is negligible up to the highest temperature considered (400 °C), with a maximum discrepancy of about 2.4%. An analogous result is found...

Epoxidation of DL-limonene using an indenyl molybdenum(II) tricarbonyl complex as catalyst precursor

Abstract The complex IndMo(CO) 3 Me (Ind = η 5 -C 9 H 7 ) is an effective catalyst precursor for the epoxidation of DL-limonene using the following oxidant solutions: (i) commercial tert -butylhydroperoxide in decane (TBHPdec), (ii) commercial aqueous TBHP (TBHPaq) pre-mixed with limonene (TBHP_lim), or (iii) TBHPaq pre-mixed with 1,2-dichloroethane (TBHPdce); simple pre-drying treatments of the reaction solutions were applied prior to feeding the catalyst precursor to the batch reactor. The best results were found for the efficiently pre-dried reaction system (iii), which gave higher 1,2-epoxy-p-meth-8-ene yield at 35 min/55 °C than (i) (82% and 73% yield, respectively). This approach avoids the undesirable partial oxidation of decane, which would imply costly work-up procedures to remove high boiling point impurities from the epoxides. These results together with studies on the reactivity of different olefins indicate fairly high regioselectivity toward the epoxidation of the internal double bonds.

Transformation of CH 4 and liquid fuels into syngas on monolithic catalysts

Active components comprised of fluorite-like Ln x (Ce 0.5Zr 0.5) 1− x O 2− y (Ln = La, Pr, Sm) and perovskite-like La 0.8Pr 0.2Mn 0.2Cr 0.8O 3 mixed oxides and their composites with yttria-doped zirconia (YSZ) promoted by precious metals (Pt, Ru) and/or Ni were supported on several types of heat-conducting substrates (compressed Ni–Al foam, Fecralloy foil or gauze protected by corundum layer, Cr–Al–O microchannel cermets, titanium platelets protected by oxidic layer) as well as on honeycomb corundum monolithic substrate. These structured catalysts were tested in pilot-scale reactors in the reactions of steam reforming of methane, selective oxidation of decane and gasoline and steam/autothermal reforming of biofuels (ethanol, acetone, anisole, sunflower oil). Applied procedures of supporting nanocomposite active components on monolithic/structured substrates did not deteriorate their coking stability in real feeds with a small excess of oxidants, which was reflected in good middle-term (up to 200 h) performance stability promising for further up-scaling and long-term tests. Equilibrium yield of syngas at short contact times was achieved by partial oxidation of decane and gasoline without addition of steam usually required to prevent coking. For the first time possibility of successive transformation of biofuels (ethanol, acetone, anisole, sunflower oil) into syngas at short contact times on monolithic catalysts was demonstrated. This was provided by a proper combination of active component, thermal conducting monolithic substrates and unique evaporation/mixing unit used in this research.

Study of the Catalytic Mechanism of the Enzyme Catalase on Organic Hydroperoxides in Non-Polar Organic Solvent

Catalases are enzymes composed of a protein and a prosthetic group made up of iron porphyrin. The aim of the present research, was to study the catalytic mechanism of catalase on organic hydroperoxides rather than on hydrogen peroxide, when operating in organic solvents such as decane or hexane. The investigation was performed using gas chromatography and amperometry to analyse the reagents and reaction products of the catalytic reaction of catalase on tertbutylhydroperoxide or on cumene hydroperoxide, carried out in decane. The analytical results pointed to the hypothesis that, in this case, the organic solvent is involved in the reaction. In the absence of other reducing agents, therefore, a small percentage of it is oxidized and this redox reaction presumably involves the molecular oxygen present in solution, the consumption of which is determined experimentally through amperometry. This interpretation was confirmed in the gas chromatograms performed by the appearance of new peaks formed as a result of the enzymatic reaction in decane which are presumably to be attributed to species derived from the oxidation of decane, such as decanol.

Mechanistic Modeling of Lubricant Degradation. 2. The Autoxidation of Decane and Octane

Automated mechanism generation was used to study the condensed-phase oxidation of decane and octane as a means to gain insights into the degradation of lubricating oils. Part 1 of this series established a library of structure−reactivity relationships that enables the estimation of all kinetic data required for solving large reaction mechanisms that model lubricant degradation. Specific reaction rules are proposed that enable automated mechanism generation to be used, for the first time, to study condensed-phase free-radical oxidation of large substrates. Models of decane oxidation were generated, and good agreement with available experimental data was achieved. The optimized parameters were then used to generate predictive models of octane autoxidation.

Gas-Phase Photodegradation of Decane and Methanol onTiO2: Dynamic Surface Chemistry Characterized by Diffuse Reflectance FTIR

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to study illuminatedTiO2surfaces under both vacuum conditions, and in the presence of organic molecules (decane and methanol). In the presence of hole scavengers, electrons are trapped at Ti(III)–OH sites, and free electrons are generated. These free electrons are seen to decay by exposure either to oxygen or to heat; in the case of heating, reinjection of holes into the lattice by loss of sorbed hole scavenger leads to a decrease in Ti(III)–OH centers. Decane adsorption experiments lend support to the theory that removal of surficial hydrocarbon contaminants is responsible for superhydrophilicTiO2surfaces. Oxidation of decane led to a mixture of surface-bound organics, while oxidation of methanol leads to the formation of surface-bound formic acid.

Enhancement of decane-SCR-NO x over Ag/alumina by hydrogen. Reaction kinetics and in situ FTIR and UV–vis study

Decane-SCR-NO x , oxidation of NO and decane by molecular oxygen, and these reactions enhanced by hydrogen over Ag/alumina were investigated by monitoring of gaseous product composition, surface intermediates (in situ FTIR), and the state of silver (in situ UV–vis) under realistic reaction conditions in the steady-state and transient modes. It has been shown that oxidation of NO or decane by oxygen is greatly affected by the presence of decane or NO. Monodentate nitrates are formed preferentially and are more reactive compared with the bidentate species. Oxidation of decane mostly yields surface acetates, and the presence of NO x favors the formation of formates (acrylates). The reaction steps most enhanced by the addition of hydrogen to the SCR-NO x reaction are the transformations of the intermediate CN species into NCO and oxidation of the hydrocarbon to formates (acrylates). Although NO–NO 2 oxidation is also enhanced by hydrogen, this effect does not contribute to the increased rate of the SCR-NO x reaction. A small part of very reactive Ag + (estimated to be <5%) is reduced to metallic charged Ag n δ + clusters ( n ⩽ 8 ) during both the decane- and H 2/decane-SCR-NO x reactions. The number of Ag n δ + clusters formed depends mainly on the level of NO conversion to nitrogen, regardless of whether the conversion level is attained by the addition of hydrogen or by an increased concentration of decane or oxygen in the feed. The time-resolved responses of NO x –N 2 conversion and of the number of Ag n δ + clusters to the addition/removal of hydrogen from the reactants indicate that the Ag n δ + clusters are mainly formed because of the reducing effect of adsorbed CH x O-containing reaction intermediates. The active sites are suggested to be single Ag + ions or small Ag 2O species. Hydrogen itself takes part in the SCR-NO x reaction. It is supposed that it dissociates, forms Ag-hydride, and enhances SCR-NO x by initiation radical reactions.

Modeling concepts for larger carbon number alkanes: A partially reduced skeletal mechanism for n-decane oxidation and pyrolysis

A new, partially reduced skeletal chemical kinetic mechanism for the oxidation and pyrolysis of n -decane was developed. This mechanism was validated against newly obtained n -decane flow reactor data. The proposed model was also compared against n -decane oxidation jet-stirred reactor data and n -decane/air shock tube ignition delay data obtained from the literature. The mechanism is an extension of a similar mechanism developed for n -heptane recently published by this laboratory. The current conceptual approach differs from that in our previous modeling of n -heptane oxidation in that it includes detailed chemistry of n -decane and the five n -decyl radicals, and it incorporates both internal hydrogen isomerization reactions and β -scission pathways for the various system radicals. To include this additional detailed reaction information and simultaneously minimize the number of species present in the model, an important assumption was made regarding the distribution of radical isomers. It was assumed that the different isomers of a given alkyl radical are in equilibrium at each carbon number above the C 4 level, thereby allowing the inclusion of the reaction channels associated with each isomer, without imposing the computational penalty associated with including each isomer as a separate species in the mechanism. As a result, only a single radical is needed to represent all the isomers associated with it. Thus, the new mechanism contains detailed reaction chemistry information, while maintaining the compactness necessary for use in combined fluid mechanical/chemical kinetic computational simulations. In addition to verifying this approach for n -decane, the approach was shown to be compatible with the modeling of n -heptane. The hierarchical nature of this modeling technique should prove amenable for use in developing compact mechanisms for other large n -alkanes, and this partially reduced skeletal model can serve as a validated starting model for developing more compact representations.

Influence of homogeneous decane oxidation on the catalytic performance of lean NOx catalysts

Extensive homogeneous gas‐phase reactions were observed when decane was used as the hydrocarbon reductant for the selective reduction of NOx. The catalytic performance of a SnO2/CoOx/Al2O3 catalyst was found to be strongly dependent on the extent of the homogeneous reaction in the pre‐catalytic volume. The effect of the homogeneous reaction on the catalytic performance also depended on whether SO2 was present in the feed. By filling the pre‐catalytic volume with 25–35 mesh irregularly shaped quartz chips, gas‐phase reaction was suppressed significantly. This methodology was used to evaluate the inherent catalytic performance of SnO2/CoOx/Al2O3 and SnO2/Al2O3 catalysts with decane as a reductant. It was found that in the absence of SO2, SnO2/Al2O3 was a better catalyst than SnO2/CoOx/Al2O3, but in the presence of 30 ppm of SO2 the latter was a far better catalyst.

Heat release kinetics in the reaction of decane with nitric acid

The kinetics of the reaction of decane with nitric acid (25.07–75.53 %) at 57.8 to 119 °C in an acid-decane-gas triphasic system was studied. The main contribution to the rate of heat release is made by the oxidation of decane with nitrogen dioxide in the organic phase proceedingvia the mechanism of a degenerate branched-chain reaction. Nitration plays the role of a chain termination reaction. The acid phase is the source of NO2, whose content increases with oxidation. The equilibrium of the nitrogen dioxide distribution in the triphasic system was analyzed. The kinetic law of the reaction, the dependences of the reaction constants of the initial and catalytic stages on temperature and the acid phase composition were determined. The results allow one to calculate the rate of heat release in the decane-HNO3 system under any conditions of the process.

The oxidation of decane in the liquid and gaseous phases

Studies have been made of the uncatalysed oxidation of decane in both the liquid and gaseous phases in the same temperature region; this hydrocarbon is probably the lowest molecular mass alkane for which such a direct comparison can be made. Although the mechanisms of oxidation in both phases are in many ways similar, some notable differences exist. The absence of C 10 O-heterocycles and the relatively high selectivity of initial attack of decane in the liquid phase can be ascribed to a ‘cage effect’, so that abstractive reactions are predominantly intermolecular. Rather unexpectedly, in the gas phase, the initial attacking radical, even at the low temperatures used, is almost exclusively the hydroxyl radical. In the gas phase there is a marked dependence on oxygen concentration of the rates of formation of the various classes of products, particularly decane dihydroperoxides. The low solubility of oxygen in liquid decane and hence its small concentration may thus also be partly responsible for the absence of dihydroperoxides among the liquid-phase oxidation products. Lower molecular mass oxygenated compounds, which are the most abundant products of the gaseous oxidation of decane, appear to be derived mainly from further reactions of decane dihydroperoxides; and the small amounts of such products found in the liquid phase are con­sistent with the virtual absence of their normal precursors under these conditions. The analytical technique used has permitted the first unambi­guous quantitative determination of very small amounts of hydroper­oxides produced during the gaseous oxidation of hydrocarbons.

Alkane oxidation by a particulate preparation from Candida.

The oxidation of decane by a cell-free particulate preparation from Candida intermedia was studied. Decane is oxidized to decanoate via decanol and decanaldehyde. Oxidation of decane to decanol requires molecular oxygen. Decanol is oxidized to decanaldehyde by a nicotinamide adenine dinucleotide-linked dehydrogenase differing greatly in specificity from ordinary yeast alcohol dehydrogenase. Decanaldehyde is oxidized to decanoate by a nicotinamide adenine dinucleotide-linked dehydrogenase that oxidizes long-chain aldehydes but not short-chain aldehydes. The enzymes that oxidize decane, decanol, and decanaldehyde are all induced when decane is present in the medium. These enzymes are apparently located in the cell membrane.

Microsomal hydroxylation of decane

1. 1. Aliphatic hydrocarbons (hexane, octane and decane) were oxidized in the microsomes from the livers of mouse, rat, rabbit, beef, pigeon and chick embryo. 2. 2. The oxidation of decane by mouse liver microsomes required NADPH and O 2. Decanol, decanoic acid, and decamethyleneglycol were identified as the major decane oxidation products, suggesting that the decane oxidation is initiated by the hydroxylation of decane to decanol. 3. 3. The Michaelis constant for the decane hydroxylation was 0.5 mM. The pH optimum was approx. 8.1. The reaction was strongly inhibited by CO, SKF 525-A, or tert.-butyl isocyanide. The decane hydroxylation system was considerably unstable, in comparison with the decanoate ω-oxidation system. These results suggest that the two hydroxylation systems are not identical. 4. 4. As with drug hydroxylation, the activity of decane hydroxylation was increased markedly by treatment of rats with phenobarbital. However, unlike aniline hydroxylation, the decane hydroxylation was highly active in the microsomes from kidney and lung as well as in those from liver.