Cyclohexane

Methods of intensification of the process of liquid-phase cyclohexane oxidation in the presence of complex catalytic systems, catalytic solutions and individual catalysts have been considered in the article. Quantitative and qualitative influences of binary catalytic systems which contain cobalt naphthenate and organic modifiers of different nature have been determined. The research confirmed the assumption of complexation involving components of the catalytic solutions in the reaction mixture. The structural formula of possible intermediate catalytic complex has been built.

A nano-crystalline three-dimensional mesoporous KIT-6 and V-KIT-6 materials are synthesized through a new sol-gel method. The above-synthesized materials are characterized by various advanced techniques. The mesoporosity is confirmed by Low angle Powder X-ray diffraction, BET-surface area analysis, and Transmission electron microscopic analysis. The vanadium incorporation is established by Field emission scanning electron microscopy, Fourier transform Infrared spectroscopy, Raman spectroscopy, Electron spin resonance spectroscopy, and Ultraviolet-visible diffuse reflectance spectroscopy. V-KIT-6 catalyzes cyclohexane oxidation using H2O2 and gives cyclohexanol and cyclohexanone as the products. The conversion (83 % in 1 h) is remarkably higher in its class of compounds due to the presence of three-dimensional mesoporosity. The catalysts are found to be stable even after five successive cycles. A plausible vanadium species and catalytic reaction mechanism are also proposed.
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Hydrocarbons play important role in the petrochemicals industry, such as a primary energy source for current civilization. The predominant use of hydrocarbons is as a combustible fuel source. The majority of hydrocarbons found on earth naturally occur in crude oil. Due to their similar chemical structure and physical properties, the separation and purification of individual component of hydrocarbons are quite challenging. Various methods have been proposed for this particular application, it is, however, most of these methods employ volatile and hazardous chemicals compounds. In recent years, ionic liquids have been proposed as “green” solvent due to their excellent chemical and physical properties. Large numbers of ionic liquids have been proposed as potential solvent for this particular application. However, it should be highlighted that with huge number of potential ionic liquids available, the experiment try-and-error is not practical. A tool to a priori predict the best of best...

Influence of individual catalysts – oligomeric chelate complexes of cobalt and copper in the cyclohexane oxidation process was investigated. The method of of metal-complex catalysts synthesis was shown. The influence of complex oligomers and their ligands on the parameters of the cyclohexane oxidation process was analyzed.

International Journal of Recent advances in Physics (IJRAP) is a peer-reviewed, open access journal, addresses the impacts and challenges of Physics. The journal documents practical and theoretical results which make a fundamental contribution for the development of Physics.

Research of the influence of oxygen and nitrogen containing organic additives to the catalyst on the main parameters of the process of cyclohexane oxidation have been conducted. A wide range of nitrogen and oxygen containing compounds and compounds based on polyglycols with varying molecular weight have been used as additives. The obtained results have been analyzed in view of the structural features of the studied additives and the probability of their interaction with the catalyst and intermediate products of oxidation with subsequent formation of intermediate complexes or associates.

The use of gold as a promotor of alkane hydrocarboxylation is reported for the first time. Cyclohexane hydrocarboxylation to cyclohexanecarboxylic acid (up to 55% yield) with CO, water, and peroxodisulfate in a water/acetonitrile medium at circa 50 °C has been achieved in the presence of gold nanoparticles deposited by a colloidal method on a carbon xerogel in its original form (CX), after oxidation with HNO₃ (-ox), or after oxidation with HNO₃ and subsequent treatment with NaOH (-ox-Na). Au/CX-ox-Na behaves as re-usable catalyst maintaining its initial activity and selectivity for at least seven consecutive cycles. Green metric values of atom economy or carbon efficiency also attest to the improvement brought by this novel catalytic system to the hydrocarboxylation of cyclohexane.

The use of gold as a promotor of alkane hydrocarboxylation is reported for the first time. Cyclohexane hydrocarboxylation to cyclohexanecarboxylic acid (up to 55% yield) with CO, water, and peroxodisulfate in a water/acetonitrile medium at circa 50 °C has been achieved in the presence of gold nanoparticles deposited by a colloidal method on a carbon xerogel in its original form (CX), after oxidation with HNO₃ (-ox), or after oxidation with HNO₃ and subsequent treatment with NaOH (-ox-Na). Au/CX-ox-Na behaves as re-usable catalyst maintaining its initial activity and selectivity for at least seven consecutive cycles. Green metric values of atom economy or carbon efficiency also attest to the improvement brought by this novel catalytic system to the hydrocarboxylation of cyclohexane.

ABSTRACT Gold (1 wt.%) was loaded on several types of carbon materials (activated carbon, polymer based carbon xerogels, multi-walled carbon nanotubes, nanodiamonds, microdiamonds, graphite and silicon carbide) using two different methods (sol immobilisation and double impregnation). Samples were characterised by N2 adsorption at −196 ◦C, temperature programmed desorption, high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectrometry, high-angle annular dark-field imaging (Z-contrast), X-ray photoelectron spectroscopy and atomic absorption spectroscopy. The obtained Au/carbon materials were used as catalysts for the oxidation of cyclohexane to cyclohexanol and cyclohexanone, with aqueous H2O2, under mild conditions. The most active catalyst was prepared by supporting gold nanoparticles on carbon nanotubes by the sol method, achieving an overall turnover number of ca. 171 and an overall yield of 3.6% after 6 h reaction time. These values are comparable to the industrial process (that uses Co catalysts and high temperature), but were obtained at ambient temperature with considerable low loads of catalyst (Au catalyst to substrate molar ratio always lower than 1 × 10−3), which is of relevance for establishing a greener catalytic process for cyclohexane oxidation. Moreover, a very high selectivity towards the formation of cyclohexanol and cyclohexanone was achieved, since no traces of by-products were detected. The promoting effect of pyrazine carboxylic acid was observed and an optimum peroxide-to-catalyst molar ratio was found to be 2 × 104. Further increase of the oxidant amount results in decreased yield due to overoxidation reactions at higher H2O2 amounts. Catalyst recycling was tested up to six consecutive cycles for the most active catalytic system (gold deposited on carbon nanotubes by sol immobilisation), and it was found that the catalyst maintains almost the original level of activity after several reaction cycles (there was only a 6% drop in activity after the sixth cycle) with a rather high selectivity to cyclohexanol and cyclohexanone and with no catalyst leaching. The differences in activity for the other samples can be explained in terms of gold nanoparticle size and the textural properties of the carbon support.