Methane in hydrogenation

Boron-doped diamond (BDD) thin films were synthesized at CSEM (Neuchatel, Switzerland) by the hot filament chemical vapor deposition technique (HF CVD) on p-type, low-resistivity (l-3mQcm), single-crystal, silicon wafers (Siltronix). The temperature of the filament was between 2440 and 2560 °C and that of the substrate was monitored at 830 °C. The reactive gas was a mixture of 1% methane in hydrogen, containing trimethylboron as a boron source (1-3 ppm, with respect to H2). The reaction chamber was supplied with the gas mixture at a flow rate of 51 min giving a growth rate of 0.24 pm h for the diamond layer. The obtained diamond film has a thickness of about 1 pm ( 10%) and a resistivity of 15mQcm ( 30%). This HF CVD process produces columnar, random textured, polycrystalline films [9]. 

There has been a good deal of study of the polyhalogenated methanes in hydrogen atom abstraction reactions toward hydroxyl (HO ) and chlorine radicals. These reactions are involved in both the atmospheric destruction of such compounds as well as their involvement in ozone depletion. Information is needed about these reactions to model the environmental impact of the compounds. 

Zyryanova, M., Snytnikov, R, Gulyaev, R. et al. (2013) Performance of Ni/Ce02 catalysts for selective CO methanation in hydrogen-rich gas. Chemical Engineering Journal, 238, 189-197. 

Tungsten carbide from the reaction of WClg with methane in hydrogen at 670-720 and low pressure or from the reaction of WFg with methanol (CH3OH) in hydrogen[23][24]... 

Figure 8.1 shows a series of ESEM micrographs taken immediately after an in situ chemical vapor deposition experiment. These pictures clearly indicate how the morphology of the deposited films of diamond on silicon depends upon the experimental conditions. A gas stream, at 15-20 torr, of 1% methane in hydrogen was flowed over a heated filament (2000 °C) to break down the methane into atomic carbon prior to deposition on the heated substrate (850 °C). This process was continued for 30 min to form films with a thickness of about 5 flm. The total pressure was then reduced to 4.3 torr for these pictures. 

Estimate the binary diffusion coefficient of methane in hydrogen at 200°C and 2 atm pressure using (a) Chapman-Enskog s theoretical formula, (b) Fuller s empirical correlations, and (c) Bird s correlation. 

An interesting point is that infrared absorptions that are symmetry-forbidden and hence that do not appear in the spectrum of the gaseous molecule may appear when that molecule is adsorbed. Thus Sheppard and Yates [74] found that normally forbidden bands could be detected in the case of methane and hydrogen adsorbed on glass this meant that there was a decrease in molecular symmetry. In the case of the methane, it appeared from the band shapes that some reduction in rotational degrees of freedom had occurred. Figure XVII-16 shows the IR spectrum for a physisorbed H2 system, and Refs. 69 and 75 give the IR spectra for adsorbed N2 (on Ni) and O2 (in a zeolite), respectively. 

When coal is coked at a temperature of approximately 1000°C, about 70—75% of the product is coke. Nearly 20% of the product is a light gas, mostiy methane and hydrogen, that typically is used as fuel to heat the ovens. Coal tars amount to about 4% of the product and light oil or naphtha is about 1%. Ammonia is recovered in an amount equal to about 0.3% of the feed coal. The ammonia is usually converted to ammonium sulfate and sold as a fertilizer. Littie or no ammonia [7664-41-7] is produced inlow temperature carbonization (3). 

The processes that have been developed for the production of synthetic natural gas are often configured to produce as much methane in the gasification step as possible thereby minimizing the need for a methanation step. In addition, methane formation is highly exothermic which contributes to process efficiency by the production of heat in the gasifier, where the heat can be used for the endothermic steam—carbon reaction to produce carbon monoxide and hydrogen. 

In the microwave-assisted or hot-filament-assisted CVD of diamond, methane and hydrogen gases (CH ca 1—5% and 95—99%) are used. In... 

Hydrogen sulfide and methane can be removed by aeration, although the largest reduction in hydrogen sulfide may result from oxidation by the dissolved oxygen introduced during the aeration. At low pH values, the product is sulfate, whereas at high pH values, the product is free sulfur. 

Outside the realm of typical hydrocarbon pyrolysis is the high temperature pyrolysis of methane. In one variant of this process, which has only been commercialized to produce acetylene (with some BTX), methane reacts in an electric arc at about 1500°C (17) with very short contact times. At higher temperatures or with a catalyst and added hydrogen, BTX is produced with fairly high selectivity (18). 

A disadvantage of the hydrocarbon—sulfur process is the formation of one mole of hydrogen sulfide by-product for every two atoms of hydrogen in the hydrocarbon. Technology for efficient recovery of sulfur values in hydrogen sulfide became commercially available at about the same time that the methane—sulfur process was developed. With an efficient Claus sulfur recovery unit, the hydrocarbon—sulfur process is economically attractive. 

Table A-4-1.3a, based on data in [62], shows how the MIE (mJ) of 28 vol% hydrogen and 8.5 vol% methane in air vary with circuit capacitance (pF) and electrode diameter (mm). Points refers to the use of steel gramophone needles. The table shows that MIE is decreased with decreased capacitance and electrode diameter however, as reflected in Figure 3-5.4.1 corona...

Removal of volatile matter to about 0.5 wt% can be accomplished by calcming in a rotary kiln, rotary hearth, or vertical shaft calcmer All of these processes heat green coke to temperatures in excess of 1000°C where shrinkage and subsequent densification take place. The volatile components are comprised primarily of methane, ethane, hydrogen, and hydi ogen sulfide gases which can be employed as fuel for process heat. 

Note that there is no one-carbon alkene corresponding to methane, since hydrogen can never form more than one covalent bond, and there is no other carbon atom in the structural formula. Therefore, the first compound in the alkene series is ethene, while the corresponding two-carbon compound in the alkane series, ethane, is the second compound in the series, with methane the first. 

Battelle (Seifert and Giesbrecht 1986) and BASF (Stock 1987) each conducted studies on exploding fuel jets, the former on natural gas and hydrogen jets, and the latter on propane jets. The methane and hydrogen jet program covered subcritical outflow velocities of 140, 190, and 250 m/s and orifice diameters of 10, 20, 50, and 100 mm. In the propane jet program, outflow conditions were supercritical with orifice diameters of 10, 20, 40, 60, and 80 mm. The jets were started and ignited after they had achieved steady-state conditions. 

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