Aerobic Oxidation Of Hydrocarbons Research Articles

A superhydrophobic MOF facilitating efficient solvent-free catalytic chemical fixation of CO2 and oxidation of hydrocarbons and MOF@cotton@starch composite-based selective sensing of a herbicide

Superhydrophobic Zr-MOF unveils solvent-free chemical fixation of CO2 at 1 bar, along with efficient aerobic oxidation of hydrocarbons into fine chemicals and fast, nanomolar detection of aclonifen in wastewater, vegetables, and fruits.

Aerobic-peroxide oxidation of naphthalene in the presence of transition metal on a nanocarbon carrier

The paper describes the results of aerobic-peroxide catalytic oxidation of naphthalene in the presence of iron-containing multi-walled carbon nanotubes Fe@MWCNT. The active nanocarbon substrate containing α-iron atoms and carbides realizes by the Fenton reaction active formation of active particles and intensive oxidation of the hydrocarbon under rather mild conditions. It was found that at the temperature range 333 - 353K, in the presence of hydrogen peroxide (30% aqueous solution) and Fe@MWCNT (Fe ≈3.7 wt. %), under intense air current, the reaction proceeds without destroying the cyclic structure of the molecule with predominant formation of phthalic anhydride and naphthol. Identification of the functional groups of the main target products was performed by the infrared (IR) spectroscopy. The results obtained can be proposed for further development of such studies and bringing them into compliance with the standards of the industrial process. Keywords: aerobic oxidation of hydrocarbons; oxidation of naphthalene; hydrogen peroxide; multi-walled carbon nanotubes; nanocarbon catalysis; Fenton system, oxygencontaining aromatic compounds.

Universal Mass Production of Biomass-Derived Nanosized Porous Carbon Spheres as a Superior Nonmetal Catalyst for Aerobic Oxidation of Hydrocarbons

Universal Mass Production of Biomass-Derived Nanosized Porous Carbon Spheres as a Superior Nonmetal Catalyst for Aerobic Oxidation of Hydrocarbons

Aerobic oxidation of hydrocarbons using N-hydroxyphthalimide (NHPI) catalysts for cetane enhancement

Gasoline compression ignition (GCI) utilizes gasoline-like fuels in low temperature compression ignition (CI) engines. As a result, thermal efficiency is increased compared to that of a conventional spark ignition (SI) engine, while NOx and soot tailpipe emissions are reduced compared to those from a diesel engine. This combustion strategy requires gasoline fuel with a moderate ignition delay for cold start and high load demand conditions. This work proposes an approach to control the ignition characteristics of gasoline to widen GCI engine operation conditions. Aerobic oxidation of gasoline using N-hydroxyphthalimide (NHPI) catalyst has been suggested as an effective method to produce high cetane components, such as hydroperoxide. NHPI catalyzed oxidation reactions of toluene and market gasoline were studied at different reaction conditions using an autoclave batch reactor. The produced hydroperoxide (HP) was quantified by titration using triphenylphosphine (Ph3P) followed by Gas Chromatography (GC) analysis. In addition, an ignition quality tester (IQT) was used to estimate the derived cetane number (DCN) of the oxygenated product. The gasoline cetane number was enhanced by nine digits using gaseous oxygen at moderate conditions (10 bar, 110 °C for 3 h). Aerobic oxidation of gasoline using NHPI catalyst was found to be a promising approach to control the ignition characteristics of fuel and hence an enabler of the GCI engine concept.

Confined Cobalt on Carbon Nanotubes in Solvent‐free Aerobic Oxidation of Ethylbenzene: Enhanced Interfacial Charge Transfer

AbstractAerobic oxidation of hydrocarbons yielding corresponding oxygenated products is one of the most important chemical processes. In current work, carbon nanotubes supported encapsulated cobalt nanoparticles with carbon layers (Co@C/CNTs) were synthesized and utilized as catalysts in the oxidation of ethylbenzene (EB) in the liquid phase, exhibiting high catalytic performance. The synergistic effect between Co@C and CNTs played the vital role on facilitating the decomposition of peroxides to enhance the overall activity. The inadequate covered Co@C on CNTs surface were considered as catalytic sites. Density functional theory revealed that the exist of Co nanoparticles could improve the interaction between the catalyst and intermediate free radicals, which were significant for EB oxidation. Last but not least, the electron transfer on carbon surface was enhanced by the incorporation of Co@C nanoparticles, which greatly improved the catalytic performance on EB oxidation. This study provides a new insight into the Co‐based catalysts in the aerobic oxidation of hydrocarbons.

Impact of As-Prepared and Purifıed Multi-Walled Carbon Nanotubeson the Liquid-Phase Aerobic Oxidatıon of Hydrocarbons

The article presents simple kinetic approaches to study the effect of multi-walled carbon nanotubes (MWCNTs) additives on the aerobic oxidation of hydrocarbons and to propose real acceptable mechanisms of the process. The aerobic liquid phase low-temperature oxidation of ethylbenzene conducted in the presence of multi-walled carbon nanotubes has been used as a model pattern. Kinetic analysis established the catalytic action associated with the presence of the iron compounds in inner channels of MWCNTs. These compounds are identified as ferric carbides provoking decomposition of the ethylbenzene hydroperoxide and thereby suppressing the competitive route of alky-peroxide radicals addition to the nanocarbon cage. Thus the reaction finally proceeds in the autocatalytic mode.Contradictory conclusions on the effect of CNTs on the oxidation chain processes existing in the literature are associated with the lack of control over nature and content of metal impurities in channels of nanotubes.

Room Temperature Aerobic Peroxidation of Organic Substrates Catalyzed by Cobalt(III) Alkylperoxo Complexes

Room temperature aerobic oxidation of hydrocarbons is highly desirable and remains a great challenge. Here we report a series of highly electrophilic cobalt(III) alkylperoxo complexes, CoIII(qpy)OOR supported by a planar tetradentate quaterpyridine ligand that can directly abstract H atoms from hydrocarbons (R'H) at ambient conditions (CoIII(qpy)OOR + R'H → CoII(qpy) + R'• + ROOH). The resulting alkyl radical (R'•) reacts rapidly with O2 to form alkylperoxy radical (R'OO•), which is efficiently scavenged by CoII(qpy) to give CoIII(qpy)OOR' (CoII(qpy) + R'OO• → CoIII(qpy)OOR'). This unique reactivity enables CoIII(qpy)OOR to function as efficient catalysts for aerobic peroxidation of hydrocarbons (R'H + O2 → R'OOH) under 1 atm air and at room temperature.

The Variation of Microbial (Methanotroph) Communities in Marine Sediments Due to Aerobic Oxidation of Hydrocarbons

Methanotrophs in marine sediments and overlying water attenuate the emissions of methane into the atmosphere and thus play an important role for the global cycle of this greenhouse gas. However, gas released from natural hydrocarbon seeps are not pure methane but commonly mixed hydrocarbons. Currently, how methanotrophic bacteria behave in the co-presence of methane and heavier hydrocarbons remains unknown. In this paper, the bacteria were cultured aerobically in fresh sediment samples (collected from Bohai Bay in eastern China) at 28°C under the atmospheres of pure methane and methane+ethane+propane mixed gas, respectively. The prevailing terrigenous n-alkanes and fatty acids in the original sediment samples varied consistently after incubations, confirming the proceeding of aerobic bacterial activities. The real-time quantitative PCR assay and sequencing of the 16S rRNA and particulate methane monooxygenase (pmoA) genes revealed the changes of microbe communities to a methanotroph-dominating structure after incubations. Particularly, after incubations the family Methylococcaceae (type I methanotrophs) became dominant with proportions higher than 40%, whereas Methylocystaceae (type II methanotrophs) nearly disappeared in all incubated samples. Moreover, the species of methanotrophs from the samples treated with pure methane were dominated by Methylobacter luteus, whereas Methylobacter whittenburyi took the predominant proportion in the samples treated with mixed gas. The phenomenon suggests that some methanotrophs may also utilize ethane and propane. Collectively, this study may help to gain a better understanding of the effects and contributions of microbial activities in marine hydrocarbon seep ecosystems.

New Understanding of Selective Aerobic Oxidation of Ethylbenzene Catalyzed by Nitrogen‐doped Carbon Nanotubes

AbstractSelective aerobic oxidation of hydrocarbons undergoes a free‐radical chain reaction to yield corresponding value‐added products is the significant process in the chemical industry. Nanocarbons with heteroatoms doping as free‐metal catalysts have been proved to be excellent alternatives in various fields of reactions. In this work, nitrogen doped carbon nanotubes (NCNTs) were applied for the aerobic oxidation of ethylbenzene (EB) in the liquid‐phase. The catalytic performance was unexpectedly suppressed, even lower than the control experiment, which is totally different from earlier publications. Mechanistic studies demonstrated that N doping would inhibit the abstraction of α‐H from EB molecule and end the radical propagation, thus suppressing the overall activity. Addition of TBHP would be helpful for the α‐H abstraction and forming alkyl radicals, which start the Franck‐Rabinowitch cage reaction and promote radical propagation in the presence of carbon catalysts. Herein, a higher catalytic efficiency with 46 % EB conversion and 72 % AcPO selectivity were obtained over NCNTs with O2 and TBHP as dual‐oxidants.

The Role of Co-ZSM-5 Catalysts in Aerobic Oxidation of Ethylbenzene

Various forms of cobalt catalysts have been studied extensively for selective aerobic oxidation of hydrocarbons. However, it remains unclear whether cobalt can directly activate molecular oxygen under mild reaction conditions. Here we investigated the catalytic roles of cobalt in ethylbenzene oxidation with and without a hydroperoxide initiator. The contribution of different cobalt species was studied by varying the metal loading on Co-impregnated ZSM-5 samples. Quantitative EPR was used to determine the impact of cobalt catalysts on the free radical concentrations. This work provided strong evidence that cobalt, in several different forms, catalyzes hydrocarbon oxidation by facilitating peroxy bond cleavage, instead of direct oxygen activation.

Synergistic Catalytic Effect of N-Hydroxyphthalimide/Cobalt Tetraamide Phthalocyanine and Its Application for Aerobic Oxidation of Hydrocarbons and Alcohols

The activation of oxygen for selective oxidation of organic molecules, such as hydrocarbons and alcohols, remains a major catalytic challenge. We have developed a catalytic system combining N-hydroxyphthalimide (NHPI) with cobalt tetraamide phthalocyanine [CoPc(CONH2)4] for the oxidation of hydrocarbons and alcohols at 75 °C under an oxygen atmosphere. CoPc(CONH2)4 was synthesized by trimellitic anhydride-urea method, and its structure was confirmed by FT-IR, UV–Vis and XRD. This catalyst, in synergy with NHPI/O2 system, exhibited excellent catalytic ability and high selectivity in the oxidation of hydrocarbons and alcohols. Based on the experimental results, a reasonable reaction mechanism was proposed for the oxidation of alkanes and alcohols, respectively. Cobalt tetraamide phthalocyanine (CoPc(CONH2)4) was synthesized by a simple solid-thermal method, and the synergistic catalysis oxidation of NHPI and CoPc(CONH2)4 was studied. A synergistic catalysis system for the aerobic oxidation of hydrocarbons and alcohols by N-hydroxyphthalimide combined with cobalt tetraamide phthalocyanine has been developed.

An Improved Catalytic Performance of Fe(III)-promoted NHPI in the Oxidation of Hydrocarbons to Hydroperoxides

N-hydroxyphthalimide (NHPI) is a promising catalyst in aerobic oxidation of hydrocarbons to corresponding hydroperoxides. We have found that a trace amount of Fe(benz)3 or Fe(acac)3 (in concentration of less than 10−1 mmol/l and with the ratio of Fe(III): NHPI = 1:500) considerably accelerates the oxidation of cyclohexene and ethylbenzene, while retaining the selectivity to hydroperoxides at a level of 90%. As a consequence, the reaction temperature could be lowered down to 50–60 °C. The promoting effect of the additives was attributed to the ability of Fe(III) complexes to generate phthalimido-N-oxyl radicals (PINO) without participation in any transformations of hydrocarbon intermediates and hydroperoxides, thus ensuring selective formation and stability of the hydroperoxides.

Carbon nanotubes catalysis in liquid-phase aerobic oxidation of hydrocarbons: Influence of nanotube impurities

Pure carbon nanotubes (CNTs) have a high electron affinity and as such are able to actively absorb free radicals. This functional feature of CNTs leads to a linear chain breakage with the formation of inert spin adducts and effective inhibition of the oxidation process. However, there is a clear contradiction in this issue in the literature with the analysis of research results indicating that CNTs exhibit antioxidant activity mainly in polymeric materials, under conditions of diffusional restrictions for oxygen access. While, in the liquid-phase oxidation of hydrocarbons by CNTs (CNTs synthesised by the thermal catalytic pyrolysis of carbon-containing raw materials (CVD-process)), the CNTs enhance catalytic processes. In this study the aerobic liquid phase oxidation of cumene and initiated (by azobisisobutyronitrile) at low-temperature (333 K) in the presence of multi-walled carbon nanotubes (MWCNTs) obtained by thermal catalytic pyrolysis of cyclohexane (catalyst-ferrocene) has been undertaken. Kinetic analysis establishes that the catalysis of the oxidation process is associated with the presence of metal compounds in the structure of the MWCNTs. These metals are residues of metal catalysts remaining in the synthesis and in the process of pyrolysis. The metals are converted, as a rule, into metal carbides and are not easily removable by treatment with mineral acids. Thus, in the presence of metals in the composition of MWCNTs, interfering parallel reactions are observed with two processes running in parallel — MWCNTs + R• (RO2 •) → •MWCNTs-R (RO2) and ROOH + M @ MWCNTs → RO• radicals (RO2•). The branching of the chain processes involving hydroperoxides suppresses the route of attachment of alkyl and peroxide radicals to the carbon cage structure of the nanotubes and the reaction proceeds in an autocatalytic mode. Contradictory conclusions regarding the effect of CNTs on the chain processes in the oxidation of organic substances (hydrocarbons, polymers) that exist in the literature are attributed to the lack of control over the presence and nature of the metal containing impurities in the CNTs.

Liquid phase aerobic oxidation of cyclic and linear hydrocarbons using iron metal organic frameworks as solid heterogeneous catalyst

Aerobic oxidation of hydrocarbons is one of the research fronts in organic chemistry as well as in chemical engineering. In this aspect, many efforts are devoted to develop heterogeneous catalysts that can convert hydrocarbon to its corresponding alcohol/ketone (ol/one) with selectivity more than 90%. However, achieving this target becomes difficult due to possible secondary reactions of initially formed ol/one mixture. Hence, this study aims to report the catalytic activity of Fe(BTC) (BTC: 1,3,5-benzenetricarboxylate) and tetrabutylammonium bromide (TBAB) in aerobic oxidation of cyclooctane at 73% conversion to its respective ol/one with 84% selectivity after 24 h at 120 °C in the absence of any radical initiators. Interestingly, the selectivity of ol/one is higher than 90% at cyclooctane conversion around 20% under present reaction conditions. Reusability and leaching experiments demonstrate the stability of Fe(BTC) during the oxidation reaction. Furthermore, the present catalytic system can also be extended to oxidize other linear hydrocarbons to their respective ol/one products with the selectivity ranging between 88–97 %.

Surface modification of multi-walled carbon nanotubes to produce a new bimetallic Fe/Mn catalyst for the aerobic oxidation of hydrocarbons

Fe/Mn bimetallic heterogenized catalyst [Fe/Mn(THPP)@MWCNT] was prepared by the simultaneous attachment of Mn and Fe porphyrins onto the surface of functionalized multi-walled carbon nanotubes. This new bimetallic nanohybrid displays a superior catalytic performance (81%) in comparison with their analogous monometallic counterparts (36% and 44% for Fe- and Mn-porphyrin respectively) in the oxidation of hydrocarbons with molecular oxygen as the sole oxidant. Experiments comparing bimetallic catalyst with equivalent physical mixtures of monometallic catalysts revealed the catalytic synergistic effect amongst metallic active centers onto the surface of the same nanotube, introducing a new class of bimetallic porphyrin-based catalysts for oxidation reactions.

Mesoporous Metal Oxide Encapsulated Gold Nanocatalysts: Enhanced Activity for Catalyst Application to Solvent-Free Aerobic Oxidation of Hydrocarbons.

Here, we present a series of experimental studies to encapsulate ultrasmall gold nanoparticles into mesoporous metal oxide via an in situ self-assembly method. Notably, the 2.0Au@mZnO catalyst (∼2.0 nm gold nanoparticles loading on mesoporous ZnO nanospheres) shows excellent catalytic activity for indane oxidation (120 °C, conversion 88.5%) and affords much high turnover frequencies (9521 h-1). The catalytic activity of these gold-based catalysts was found to be correlated with the size of gold nanoparticles and the types of metal oxide supports. With a decrease in gold nanoparticle size, the catalytic conversion efficiency of indane oxidation increased. In addition, such catalysts possessed high thermal and chemical stability and could be reused more than 10 times without a remarkable loss of catalytic activity.

Sulfur and nitrogen-doped porous cobalt carbon catalyst for high efficient aerobic oxidation of hydrocarbons

The selective oxidation of hydrocarbons to corresponding ketones under green reaction conditions is of more and more important in chemical processes due to environmental and economic pressure. In this respect, we successfully prepared high efficient sulfur and nitrogen-doped porous cobalt carbon catalyst through a simple but efficient one-pot method. Potassium thiocyanate (KSCN) is using as sulfur source and complexing agent, what’s more, KSCN also acts as pore-forming agent to create larger specific surface area. In addition, the as-obtained catalyst shows high catalytic performance for oxidation of hydrocarbons under solvent-free and oxygen as oxidant conditions, especially for ethylbenzene, the conversion is up to 82% with 88% of selectivity for acetophenone, which is an exciting result due to the relative low activity of oxygen in comparison with tert-butyl hydroperoxide as oxidant. This is due to structure defect and Co4S3 by the doping of KSCN in CoNC catalysts, which may result in the improvement of the catalytic performance of the catalysts.

Mn(III)-porphyrin/graphene oxide nanocomposite as an efficient catalyst for the aerobic oxidation of hydrocarbons

In this study, manganese porphyrin was grafted on the surface of graphene oxide nanosheets via covalent bonding to produce a heterogeneous catalyst. The prepared nanocomposite was characterized using X-ray diffraction, UV–vis spectroscopy, scanning electron microscopy, Fourier transform infrared, and thermogravimetric analysis. Atomic absorption spectroscopy was also used to determine the amount of the loaded catalyst. The catalytic efficiency of the immobilized Mn-porphyrin was investigated for the aerobic oxidation of alkenes and saturated alkanes in acetone under mild reaction conditions. The prepared heterogenized catalyst displays superior catalytic performance as compared to the homogeneous catalyst. Moreover, the excellent turnover number (more than 31,767) achieved for the oxidation of styrene indicates the high longevity of the supported catalyst. The catalyst structure is preserved well after the oxidation reaction and is simply reused at least five times, without any significant loss of the catalytic efficiency. In this research, Mn(THPP)OAc has been grafted on the GO surface to provide an effective catalytic system for the oxidation of various alkenes and alkanes to the corresponding oxidation products, such as epoxy and alcohols.

Cobalt/N-Hydroxyphthalimide(NHPI)-Catalyzed Aerobic Oxidation of Hydrocarbons with Ionic Liquid Additive

A highly efficient and solvent-free system of cobalt/NHPI-catalyzed aerobic oxidation of hydrocarbons was developed using imidazolium-based ionic liquid (IL) as an additive. These amphipathic ILs were found self-assemble at the interface between the organic hydrocarbons and the aqueous phase of catalyst combination (Co/NHPI), with forming a solution of reversed multilamellar vesicles for catalysis. The initial reaction rate was influenced by both the composition of microdomains and the structure of IL launched. Consequently, a proper water content (χH2O) of wet IL was requisite to reach the optimum reactivity. Besides, the interfacial boundary between aqueous and organic phase composed by C2-alkylated imidazolium ILs, such as [bdmim]SbF6 and [C12dmim]SbF6, not only has ternary aggregates (hydrocarbons/IL/H2O) of higher stability but renders O2 a faster diffusion rate and higher concentration, thereby offering a high reactivity of the protocol towards hydrocarbon oxidation.

Metalloporphyrin-mediated aerobic oxidation of hydrocarbons in cumene: Co-substrate specificity and mechanistic consideration

Selective aerobic oxidation of hydrocarbons by molecular oxygen to afford valuable oxygen-containing functional compounds is a key challenge in modern chemical industry. Herein, an efficient catalytic system including metalloporphyrins as ideal catalysts and cumene as a co-substrate was developed for the aerobic oxidation of hydrocarbons to afford products with high yields and excellent chemoselectivities. Notably, this biomimetic process was found to be similar to cytochrome P450 monooxygenase-catalyzed reactions according to Michaelis–Menten kinetics. Experimental results and in situ monitoring techniques including the kinetic study, in situ ultraviolet–visible spectroscopy, and in situ electron spin resonance spectroscopy indicated that in situ generated cumyl hydroperoxide acted as an actual oxidant. Its formation was possibly mediated by metalloporphyrins to generate numerous free-radical species, and the high-valent MnIV–oxo π-cation radicals were regarded as active species in the aerobic oxidation. Consequently, both the co-substrate specificity and the possible reaction mechanism were systematically investigated based on the control experiments and results obtained from our previous studies.