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.

Vanadium(IV) Complexes with Methyl-Substituted 8-Hydroxyquinolines: Catalytic Potential in the Oxidation of Hydrocarbons and Alcohols with Peroxides and Biological Activity

Methyl-substituted 8-hydroxyquinolines (Hquin) were successfully used to synthetize five-coordinated oxovanadium(IV) complexes: [VO(2,6-(Me)2-quin)2] (1), [VO(2,5-(Me)2-quin)2] (2) and [VO(2-Me-quin)2] (3). Complexes 1–3 demonstrated high catalytic activity in the oxidation of hydrocarbons with H2O2 in acetonitrile at 50 °C, in the presence of 2-pyrazinecarboxylic acid (PCA) as a cocatalyst. The maximum yield of cyclohexane oxidation products attained was 48%, which is high in the case of the oxidation of saturated hydrocarbons. The reaction leads to the formation of a mixture of cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone. When triphenylphosphine is added, cyclohexyl hydroperoxide is completely converted to cyclohexanol. Consideration of the regio- and bond-selectivity in the oxidation of n-heptane and methylcyclohexane, respectively, indicates that the oxidation proceeds with the participation of free hydroxyl radicals. The complexes show moderate activity in the oxidation of alcohols. Complexes 1 and 2 reduce the viability of colorectal (HCT116) and ovarian (A2780) carcinoma cell lines and of normal dermal fibroblasts without showing a specific selectivity for cancer cell lines. Complex 3 on the other hand, shows a higher cytotoxicity in a colorectal carcinoma cell line (HCT116), a lower cytotoxicity towards normal dermal fibroblasts and no effect in an ovarian carcinoma cell line (order of magnitude HCT116 > fibroblasts > A2780).

Photooxidation of Heavy Crude Oil Spilled in Tropical Soil

Photooxidation was an important weathering process for spilled oil at the on tropical soil following a heavy crude oil spill, leading to the rapid formation of polar or oxygenated hydrocarbons, little is known photo-oxidation of hydrocarbons in soils. This study described the effect of solar radiation on heavy crude oil contaminated tropical soil. Physicochemical parameter of heavy crude oil showed the following values; API was 21.9, which was within the range of heavy crude oil, the density of the heavy crude was 0.8952 g/cm3. We examined the effect of ultraviolet light on crude oil using gas chromatography method for day 0, 14, 28 and 42. The results show a remarkable reduction in the total petroleum hydrocarbon [4664.56 mg/l to 1548.85 mg/kg] and poly aromatic hydrocarbon content of heavy crude oil [37.44 mg/kg to 2.12 mg/kg] from day zero to day 42. The saturated compounds was resistant, but the aromatic compounds were particularly sensitive to photo oxidation. This study provides quantitative measures of oil degradation under relevant field conditions, and improves our understanding of the role of sunlight on the fate of spilled oil on natural soil biota.

Role of PhOH and Tyrosine in Selective Oxidation of Hydrocarbons

Earlier, we established that nickel or iron heteroligand complexes, which include PhOH (nickel complexes) or tyrosine residue (nickel or iron complexes), are not only hydrocarbon oxidation catalysts (in the case of PhOH), but also simulate the active centers of enzymes (PhOH, tyrosine). The AFM method established the self-organization of nickel or iron heteroligand complexes, which included tyrosine residue or PhOH, into supramolecular structures on a modified silicon surface. Supramolecular structures were formed as a result of H-bonds and other non-covalent intermolecular interactions and, to a certain extent, reflected the structures involved in the mechanisms of reactions of homogeneous and enzymatic catalysis. Using the AFM method, we obtained evidence at the model level in favor of the involvement of the tyrosine fragment as one of the possible regulatory factors in the functioning of Ni(Fe)ARD dioxygenases or monooxygenases of the family of cytochrome P450. The principles of actions of these oxygenases were used to create highly efficient catalytic systems for the oxidation of hydrocarbons.

Simultaneously Enhanced Activity and Selectivity for C(sp3)–H Bond Oxidation Under Visible Light by Nitrogen Doping

Selective oxidation of saturated C(sp3)–H bonds in hydrocarbon to target chemicals under mild conditions remains a significant but challenging task because of the chemical inertness and high dissociation energy of C(sp3)–H bonds. Semiconductor photocatalysis can induce the generation of holes and oxidative radicals, offering an alternative way toward selective oxidation of hydrocarbons under ambient conditions. Herein, we constructed N-doped TiO2 nanotubes (N-TNTs) that exhibited remarkable activity and selectivity for toluene oxidation under visible light, delivering the conversion of toluene and selectivity of benzaldehyde of 32% and > 99%, respectively. Further mechanistic studies demonstrated that the incorporation of nitrogen induced the generation of N-doping level above the O 2p valance band, directly contributing to the visible-light response of TiO2. Furthermore, hydroxyl radicals generated by photogenerated holes at the orbit of O 2p were found to be unselective for the oxidation of toluene, affording both benzaldehyde and benzoic acid. The incorporation of nitrogen was able to inhibit the generation of hydroxyl radicals, terminating the formation of benzoic acid.