Hydrogen methane oxidation

Steam Reforming Processes. In the steam reforming process, light hydrocarbon feedstocks (qv), such as natural gas, Hquefied petroleum gas, and naphtha, or in some cases heavier distillate oils are purified of sulfur compounds (see Sulfurremoval and recovery). These then react with steam in the presence of a nickel-containing catalyst to produce a mixture of hydrogen, methane, and carbon oxides. Essentially total decomposition of compounds containing more than one carbon atom per molecule is obtained (see Ammonia Hydrogen Petroleum). 

The influence of Zn-deposition on Cu(lll) surfaces on methanol synthesis by hydrogenation of CO2 shows that Zn creates sites stabilizing the formate intermediate and thus promotes the hydrogenation process [2.44]. Further publications deal with methane oxidation by various layered rock-salt-type oxides [2.45], poisoning of vana-dia in VOx/Ti02 by K2O, leading to lower reduction capability of the vanadia, because of the formation of [2.46], and interaction of SO2 with Cu, CU2O, and CuO to show the temperature-dependence of SO2 absorption or sulfide formation [2.47]. 

Vanadium pentoxide and mercuric oxide were used as catalysts for the hydrogen peroxide oxidation of bis(phenylthio)methane to its monooxide 17a31 (equation 5). From the synthetic point of view, it is interesting to note that vanadium pentoxide, in addition to its catalytic action, functions also as an indicator in this reaction. In the presence of hydrogen peroxide, the reaction mixture is orange while in the absence of hydrogen peroxide a pale yellow colour is observed. Thus, it is possible to perform the oxidation process as a titration ensuring that an excess of oxidant is never present. 

Hydrogen Photosynthetic bacteria, methane oxidation A few years... 

In the presence of metal catalysts, hydrogen peroxide oxidations proceed in improved yields. The most common catalyst is an iron(II) salt which produces the well-known Fenton system or reagent. Dimethyl sulphoxide is oxidized to the sulphone using this system although a range of unwanted side-products such as methanol and methane are produced Diphenyl sulphoxide does not react using this reagent due to its insolubility and in all cases some iron(III) is formed by other side-reactions. 

The role of Os" in the oxidation of various reactants, including hydrocarbons, has been briefly investigated but no definitive data has been obtained. In most of the studies the ESR spectra have been observed following addition of a reactant to a surface which has the superoxide ion. The ESR spectrum of the superoxide ion remains essentially unperturbed upon addition of hydrogen, methane, carbon monoxide or ethylene how-... 

Sessions, A. L., Jahnke, L. L., Schimmelmann, A. and Hayes, J. M. (2002) Hydrogen isotope fractionation in lipids of the methane oxidizing bacterium Methylococcus capsulatus. Geochimica et Cosmochimica Acta 66, 3955. 

Hydrogen production by SIP can be accomplished through direct and indirect employment of hydrocarbon feedstocks (e.g., NG). In the direct employment method, iron oxide directly reacts with methane or other hydrocarbons to produce the reduced form of iron oxide and methane oxidation products, according to the following generic reaction ... 

T. Hanczar, L. Bodrossy, R. Csaki, J.C. Murrell, K. L. Kovacs (2002) Hydrogen driven methane oxidation in Methylococcus capsulatus (Bath). Arch. Microbiol., 177 167-172... 

Figure 3. Theoretical open-circuit potential as a function of conversion to total oxidation of hydrogen, methane, and n-butane at 973 K.

Titanium dioxide suspended in an aqueous solution and irradiated with UV light X = 365 nm) converted benzene to carbon dioxide at a significant rate (Matthews, 1986). Irradiation of benzene in an aqueous solution yields mucondialdehyde. Photolysis of benzene vapor at 1849-2000 A yields ethylene, hydrogen, methane, ethane, toluene, and a polymer resembling cuprene. Other photolysis products reported under different conditions include fulvene, acetylene, substituted trienes (Howard, 1990), phenol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitro-phenol, nitrobenzene, formic acid, and peroxyacetyl nitrate (Calvert and Pitts, 1966). Under atmospheric conditions, the gas-phase reaction with OH radicals and nitrogen oxides resulted in the formation of phenol and nitrobenzene (Atkinson, 1990). Schwarz and Wasik (1976) reported a fluorescence quantum yield of 5.3 x 10" for benzene in water. 

The difference in H2 selectivity between Pt and Rh can be explained by the relative instability of the OH species on Rh surfaces. For the H2-O2-H2O reaction system on both and Rh, the elementary reaction steps have been identified and reaction rate parameters have been determined using laser induced fluorescence (LIF) to monitor the formation of OH radicals during hydrogen oxidation and water decomposition at high surface temperatures. These results have been fit to a model based on the mechanism (22). From these LIF experiments, it has been demonstrated that the formation of OH by reaction 10b is much less favorable on Rh than on Pt. This explains why Rh catalysts give significantly higher H2 selectivities than Pt catalysts in our methane oxidation experiments. 

The above analysis indicates clearly that contrary to views expressed by many workers on methane oxidation, the termolecular reaction of CH3 + 02 must be of major importance at these temperatures. Benson (10) has expressed the view that the bimolecular reaction is unimportant even at high temperature and has suggested that the CH302 radical forms CH3O2H by hydrogen abstraction from H02, H202, or possibly H2. Preliminary analysis suggests that even if this were the case, a second-order... 

Compare modeling predictions with the experimental data shown in Fig. 14.11, assuming plug flow. Evaluate how well the the model describes methane oxidation under these conditions. Using the model, assess whether addition of hydrogen may enhance methanol selectivity. 

Equations (2.28) and (2.29) indicate that the molar number of the products caused by the oxidation of hydrogen H2 and carbon monoxide CO are smaller than the total molar number of the reactants. Concerning the oxidation of CH4, the molar number of the products and reactants are equal. Thus, there is theoretically no change in the entropy for the last case. This is the reason for the low dependency of the Gibbs free enthalpy of the methane oxidation from the temperature. 

It also follows from these experiments that the formation of formaldehyde in low amounts is explained by the presence of methanol in the initial mixture, because under current conditions H202 is mostly consumed for its deep oxidation. Similar results were obtained at methanol oxidation with hydrogen peroxide in the absence of methane (Table 4.3, tests 9-11). Comparison of these data with the results of methane oxidation with hydrogen peroxide under identical conditions (tests 1 and 2) indicates qualitative and quantitative differences in reaction products. 

Let us note once again that comparison of the results on methanol oxidation with hydrogen peroxide with methane oxidation data under atmospheric pressure (refer to Table 4.3, Figures 4.10 and 4.11) indicates significant differences in these processes. Methane is oxidized to formaldehyde at a higher rate and higher selectivity than at methanol oxidation. Low methanol yields at methane oxidation compared with formaldehyde confirm parallel proceeding of formaldehyde and methanol synthesis from methane. 

The reaction of methane oxidation with hydrogen peroxide under pressure was studied on an automated micropilot flow unit with integral reactor based on the standard double reactor OL 105/02 system. The OL 105/02 system is usually used in studies of pressurized homogeneous and heterogeneous processes in gas and liquid [123]. The micropilot unit has two equal reactors of 250 cm3 volume and is equipped with standard metering, recording and control instruments. 

The study of the aqueous H202 concentration effect on the course of the reaction shows almost full methane conversion with high hydrogen yield (74%) and a carbon dioxide concentration decrease to 0.4% in the presence of 15% hydrogen peroxide at 880 °C [130], Experimental results from temperature influence on methane oxidation to hydrogen-containing gas are presented in Figure 4.18. It is obvious that besides total methane conversion,... 

The study of the kinetics and mechanism of high-temperature methane oxidation with hydrogen peroxide to a hydrogen-containing gas considers that a new elementary reaction is responsible for the final product formation, H2 and C02 ... 

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