Homogeneous Partial Oxidation Of Methane Research Articles

Investigation of the partial oxidation of methane/n-heptane-mixtures and the interaction of methane and n-heptane under ultra-rich conditions

The homogeneous partial oxidation of methane is an interesting approach to obtain useful chemicals like synthesis gas, higher hydrocarbons, aldehydes or alcohols. Because of the low reactivity of methane, the homogeneous conversion needs high temperatures to proceed at reasonable reaction rates. Additives like n-heptane form reactive intermediates at comparatively low temperatures and initiate the conversion. To study the kinetics of doped conversion reactions, fuel-rich diluted methane/n-heptane/oxygen/argon-mixtures (2 ≤ Φ ≤ 20) were investigated in a plug-flow reactor at a pressure of 6 bar, at intermediate temperatures between 423 and 973 K and at relatively long residence times (7 ≤ τ ≤ 14 s). The product composition at the reactor outlet is analyzed by gas chromatography and mass spectrometry. Species profiles as a function of equivalence ratio and temperature are compared with simulations, and serve as validation data for different reaction mechanisms. Rates of production and reaction paths are analyzed to investigate the interaction of methane and n-heptane during the oxidation process. They show that the chemical interaction of the oxidation products of both fuels has a promoting effect on the formation of different useful products like carbon monoxide, methanol or ethane. To prove this observation, mole fraction profiles as a function of temperature were compared between experiments with an equivalence ratio of Φ = 8 using neat methane, neat n-heptane and methane/n-heptane mixtures as fuels. The results show that the yields of these species are much higher in case of the methane/n-heptane mixture compared to the yields obtained in the neat methane and neat n-heptane conversions or the sum of both.

Formation of concentric shell carbon by homogeneous partial oxidation of methane

It has been shown that the carbon soot produced as a byproduct of partial oxidation of methane consists of carbon nanoparticles of almost ideal spherical morphology and perfect concentric onion-like structure. The particles are unusually big for carbon onions and have outer diameter of 10–50 nm while the inner cage is rather typical for onions and has diameter below 1 nm. The concentric graphitic structure and spherical symmetry along with the absence of amorphous carbon are confirmed by transmission electron microscopy, electron diffraction, EDX spectroscopy and Raman investigation. The spherical particles get deposited on a wall of a partial oxidation reactor as loose particles embedded in a low density organic ovary, which can be detected by its luminescence or by cautious electron microscopy imaging. It is important that unlike literature reports on giant onions, the carbon deposit was dominated by these giant spheres. This process may be considered as a prototype for a production method for giant concentric shell carbon particle black.

Rhodium bis(quinolinyl)benzene complexes for methane activation and functionalization.

A series of rhodium(III) bis(quinolinyl)benzene (bisq(x)) complexes was studied as candidates for the homogeneous partial oxidation of methane. Density functional theory (DFT) (M06 with Poisson continuum solvation) was used to investigate a variety of (bisq(x)) ligand candidates involving different functional groups to determine the impact on Rh(III)(bisq(x))-catalyzed methane functionalization. The free energy activation barriers for methane C-H activation and Rh-methyl functionalization at 298 K and 498 K were determined. DFT studies predict that the best candidate for catalytic methane functionalization is Rh(III) coordinated to unsubstituted bis(quinolinyl)benzene (bisq). Support is also found for the prediction that the η(2)-benzene coordination mode of (bisq(x)) ligands on Rh encourages methyl group functionalization by serving as an effective leaving group for SN2 and SR2 attack.

Direct Partial Oxidation of Natural Gas to Liquid Chemicals: Chemical Kinetic Modeling and Global Optimization

The direct homogeneous partial oxidation of methane to methanol is investigated through modeling and a limited set of experiments. The experiments are conducted in a laminar flow quartz reactor at 100 bar and 598−763 K under undiluted conditions. The modeling is performed with a detailed chemical kinetic model, previously validated against a range of high-pressure data on oxidation of CO/H2 and small hydrocarbons. Modeling predictions compare well also with the experimental data obtained in the present study. On the basis of the chemical kinetic modeling, the effect of the main process parameters is discussed and the process is optimized, using a numerical global optimization methodology based on interval analysis. The experimental data, as well as the optimization results, indicate yields of methanol in the upper range of those reported in literature. However, the values are well below the commercial target.

Enhanced Methanol Yields from the Direct Partial Oxidation of Methane in a Simulated Countercurrent Moving Bed Chromatographic Reactor

A laboratory-scale simulated countercurrent moving bed chromatographic reactor (SCMCR) for the direct, homogeneous partial oxidation of methane to methanol has been constructed and tested. Reaction conditions were evaluated from independent experiments with a single-pass tubular reactor. Separation was effected by gas−liquid partition chromatography with 10% Carbowax on Supelcoport. At the optimal reaction conditions of 477 °C, 100 atm, and feed methane-to-oxygen ratio of 16, the methane conversion in the SCMCR was 50%, the methanol selectivity was 50%, and the methanol yield was 25%. Factors affecting methane conversion were investigated. Possible ways to improve the methane conversion, and hence the methanol yield, are discussed.

Homogeneous Partial Oxidation of Methane Catalyzed by NO<sub>x</sub> under Oxidizing Conditions

Homogeneous Partial Oxidation of Methane Catalyzed by NO<sub>x</sub> under Oxidizing Conditions

Homogeneous Oxidation of Methane to Methanol: Effect of CO2, N2, and H2 at High Oxygen Conversions

The effect of increasing levels of CO2, N2, and H2 in the feed on the homogeneous partial oxidation of methane was studied at reaction conditions giving high oxygen conversions. The reaction was carried out in a quartz lined tubular reactor at 643−703 K, 30−50 bar and residence times of 30−100 s. Air was used as the oxidizing agent and the CH4/O2 ratio in the feed was varied from 8 to 16. Kinetic modeling studies were also carried out by using a free radical scheme consisting of a set of 46 elementary reactions. The results predicted by the model are in fair agreement with the experimental data. Increasing CO2 levels in the feed (3−15%) did not have an adverse effect on methane conversion and methanol selectivity but increased HCHO selectivity to a small extent. Increasing O2 concentrations in the feed was found to increase the HCHO/CH3OH ratio as well as temperature required for high conversions. The need for higher temperatures is probably due to the increase in N2 levels in the feed. The methane conver...

95/00401 The relevance of thermokinetic interactions and numerical modelling to the homogeneous partial oxidation of methane

95/00401 The relevance of thermokinetic interactions and numerical modelling to the homogeneous partial oxidation of methane

The relevance of thermokinetic interactions and numerical modeling to the homogeneous partial oxidation of methane

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe relevance of thermokinetic interactions and numerical modeling to the homogeneous partial oxidation of methaneBrian F. Gray, John F. Griffiths, Gary A. Foulds, Brian G. Charlton, and G. Stewart WalkerCite this: Ind. Eng. Chem. Res. 1994, 33, 5, 1126–1135Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://doi.org/10.1021/ie00029a009RIGHTS & PERMISSIONSArticle Views107Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Partial oxidation of methane, methanol, and mixtures of methane and methanol, methane and ethane, and methane, carbon dioxide, and carbon monoxide

The homogeneous partial oxidation of methane involves the primary reactions of methane oxidation as well as the secondary reactions with the reaction products formaldehyde, methanol, and carbon monoxide. The complex free-radical set of reactions are modeled using a pseudo-first-order reaction parallel-series network of the three reactions: methane to methanol, methane to carbon monoxide, and methanol to carbon monoxide. The secondary reaction of methanol to carbon monoxide increases as the oxygen concentration in the feed increases. For experiments with 100% oxygen conversions, increases in residence time and temperature result in further loss of methane and methanol to CO. For temperatures greater than 710K some oxidative coupling occurs to produce ethane. The selectivity of methanol was 34-55% for feeds of 2.3-4.4% oxygen and 95-98% methane and 50 atm. The selectivity was highest at low conversions and low oxygen feed concentrations.

Direct conversion of methane to methanol in a flow reactor

The gas-phase homogeneous partial oxidation of methane with oxygen was studied over a range of operating conditions in a high-pressure tubular reactor. The experimental data indicated that methanol selectivities of 70 - 80% could be achieved at methane conversions of 8 - 10% by operating at suitable reaction conditions. The higher methanol selectivities obtained in this study were probably due to the use of a Pyrex glass liner in the reactor, which may have minimized surface reactions.