Methane method

A chemisorption teclmique developed by Koinai et al., based on CO methanation, was successfrilly used to analyze noble metal dispersions of both fresh and vehicle-aged Pt/Rli and Pd/Rli commercial automotive three-way catalysts. The teclmique is relatively rapid (< 2 hours), extremely sensitive, and largely free from complications due to adsorption of CO on non-noble metal components of the washcoat (support, promoters, stabilizers, etc.). Particle sizes of the vehicle-aged catalysts, calculated by applying the spherical particle assumption to the dispersions measured by the CO methanation method, agreed well with particle sizes calculated from x-ray diffraction line-broadening data. These results indicate that the CO methanation teclmique can be applied routinely to obtain fast and accurate measurements of noble metal surface areas in automotive catalysts retrieved from tlie field, even tliose with metal dispersions ca. 2% or less. 

Energies at the PCT80 level are calculated relative to ground-state RhXL systems and methane Method indicates the geometry optimization method. 

Methan methane Methode method methylieren methylate Methylierung/Methylieren... 

The critical temperature of methane is 191°K. At 25°C, therefore, the reduced temperature is 1.56. If the dividing line is taken at T/T = 1.8, methane should be considered condensable at temperatures below (about) 70°C and noncondensable at higher temperatures. However, in process design calculations, it is often inconvenient to switch from one method of normalization to the other. In this monograph, since we consider only equilibria at low or moderate pressures in the region 200-600°K, we elect to consider methane as a noncondensable component. 

The original method for the manufacture of ethyne, the action of water on calcium carbide, is still of very great importance, but newer methods include the pyrolysis of the lower paraffins in the presence of steam, the partial oxidation of natural gas (methane) and the cracking of hydrocarbons in an electric arc. 

Basically, two different methods arc commonly used for representing a chemical struchiive in 3D space. Both methods utilize different coordinate systems to describe the spatial arrangement of the atoms of a molecule under con.sidcration. The most common way is to choose a Cartesian coordinate system, i.e., to code the X-, y-, and z-coordinates of each atom, usually as floating point numbers, For each atom the Cartesian coordinates can be listed in a single row. giving consecutively the X-, )> , and z-valnc.s. Figure 2-90 illustrates this method for methane. 

VViberg and Rablen found that the charges obtained with the atoms in molecules method were relatively invariant to the basis set. The charges from this method were also consistent v it i the experimentally determined C-H bond dipoles in methane (in which the carbon is p isitive) and ethyne (in which the carbon is negative), unlike most of the other methods they examined. 

Silyl ethers serve as preeursors of nucleophiles and liberate a nucleophilic alkoxide by desilylation with a chloride anion generated from CCI4 under the reaction conditions described before[124]. Rapid intramolecular stereoselective reaction of an alcohol with a vinyloxirane has been observed in dichloro-methane when an alkoxide is generated by desilylation of the silyl ether 340 with TBAF. The cis- and tru/u-pyranopyran systems 341 and 342 can be prepared selectively from the trans- and c/.y-epoxides 340, respectively. The reaction is applicable to the preparation of 1,2-diol systems[209]. The method is useful for the enantioselective synthesis of the AB ring fragment of gambier-toxin[210]. Similarly, tributyltin alkoxides as nucleophiles are used for the preparation of allyl alkyl ethers[211]. 

Chlorination of methane provides approximately one third of the annual U S pro duction of chloromethane The reaction of methanol with hydrogen chloride is the major synthetic method for the preparation of chloromethane... 

The process can be operated in two modes co-fed and redox. The co-fed mode employs addition of O2 to the methane/natural gas feed and subsequent conversion over a metal oxide catalyst. The redox mode requires the oxidant to be from the lattice oxygen of a reducible metal oxide in the reactor bed. After methane oxidation has consumed nearly all the lattice oxygen, the reduced metal oxide is reoxidized using an air stream. Both methods have processing advantages and disadvantages. In all cases, however, the process is mn to maximize production of the more desired ethylene product. 

The manufacture of the highly pure ketene required for ketenization and acetylation reactions is based on the pyrolysis of diketene, a method which has been employed in industrial manufacture. Conversion of diketene to monomeric ketene is accompHshed on an industrial scale by passing diketene vapor through a tube heated to 350—600°C. Thus, a convenient and technically feasible process for producing ketene uncontaminated by methane, other hydrocarbons, and carbon oxides, is available. Based on the feasibiHty of this process, diketene can be considered a more stable form of the unstable ketene. 

Direct conversion of methane [74-82-8] to methanol has been the subject of academic research for over a century. The various catalytic and noncatalytic systems investigated have been summarized (24,25). These methods have yet to demonstrate sufficient advantage over the conventional synthesis gas route to methanol to merit a potential for broad use. 

On dehydration, nitro alcohols yield nitro-olefins. The ester of the nitro alcohol is treated with caustic or is refluxed with a reagent, eg, phthaUc anhydride or phosphoms pentoxide. A mil der method involves the use of methane sulfonyl chloride to transform the hydroxyl into a better leaving group. Yields up to 80% after a reaction time of 15 min at 0°C have been reported (5). In aqueous solution, nitro alcohols decompose at pH 7.0 with the formation of formaldehyde. One mole of formaldehyde is released per mole of monohydric nitro alcohol, and two moles of formaldehyde are released by the nitrodiols. However, 2-hydroxymethyl-2-nitro-l,3-propanediol gives only two moles of formaldehyde instead of the expected three moles. The rate of release of formaldehyde increases with the pH or the temperature or both. 

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