Methane sulfurated, transformation

Fig. 13-2 The chemical and physical transformations of sulfur in the atmospheric cycle. Circles are chemical species, the box represents cloud-liquid phase. DMS = CH3SCH3, DMDS = CH3SSCH3, Siv = (S02)aq + HSOi" + SO3 + CH20HS03, and MSA (methane sulfonic acid) = CH3SO3H. The chemical transformations are as... 

Eastern Manus Basin Desmos cauldron (3 42 S, 151°52 E) 2000 Caldera of basalt/basaltic andesite at an intersection of a spreading center and a transform fault Sulfide ores were not recovered. Megaplume-like methane anomalies in water column over the caldera. Ferruginous oxide deposits. Pyrite and native sulfur disseminated in basaltic andesite. 

The ready availability of carbon disulfide from methane and sulfur in oxide-catalyzed reactions484 [Eq. (3.59)] and its further transformation over zeolites485 [Eq. (3.60)] or other catalysts offer an alternative way to the production of hydrocarbons from methane ... 

Oxidation of Methane. A variety of new catalyst systems have been disclosed, and new reagents were developed with the aim to perform selective transformation of methane to methanol, methyl esters, and formaldehyde. Much work was carried out in strongly acidic solutions, which enhances the electrofilicity of the metal ion catalyst, and the ester formed is prevented from further oxidation. An important advance in the selective oxidation of methane to methanol is Periana s 70% one-pass yield with high selectivity in sulfuric acid solution under moderate conditions.1073 The most effective catalyst is a Pt-bipyrimidine complex. Pt(II) was shown to be the most active oxidation state generating a Pt-methyl intermediate that is oxidized to yield the product methyl ester. A density functional study... 

Formic acid transformed by concentrated sulfuric acid into water and carbon monoxide carbon monoxide converted to methane in chromatographic system. 

There are numerous theoretical and experimental results demonstrating that simple molecular solids transform into nonmolecular phases at high pressures and temperatures, ranging from monatomic molecular solids such as sulfur [61], phosphorous [62] and carbon [63] to diatomic molecular solids such as nitrogen [8, 9,40], carbon monoxide [12] and iodine [20, 21], to triatomic molecules such as ice [24, 25], carbon dioxide [10, 31, 37] and carbon disulfide [64, 65] to polyatomics such as methane [27, 28] and cyanogen [11], and aromatic compounds [29]. In this section, we will limit our discussion within a few molecular triatomics first to review the transformations in two isoelectronic linear triatomics, carbon dioxide and nitrous dioxide, and then to discuss their periodic analogies to carbon disulfide and silicone dioxide. 

As shown in equation (27), methanesulfonic acid can be transformed to methyl bisulfate, which is easily hydrolyzed to methanol. Hence, the synthesis of methanesulfonic acid is regarded as a methane conversion to methanol. Metal peroxides such as Ca02 catalyze the reaction of methane and fuming sulfuric acid to give methane sulfonic acid at a rather low temperature (eq. (29)) (49). 

In their pioneering work, Periana et al. [88] reported that Pd(II)/H2S04 catalytic system catalyzed direct conversion of methane to methanol and acetic acid with a combined selectivity of >90% at 455 K in liquid sulfuric acid. It was concluded that carbon atoms in acetic acid originate from methane and methanol, with the latter being primarily formed from methane. The reaction is initiated by the electrophilic CH activation with Pd(II) to yield Pd-CHs species. The activation is accelerated by sulfuric acid. The primarily formed Pd-CHs species is further transformed to methanol with simultaneous reduction of Pd(II) to Pd(0). The reduced Pd species are also formed upon methanol oxidation to some CO species. The latter participate in the carbonylation of the Pd-CHs species. To close the catalytic cycle Pd(0) is oxidized to Pd(II) by sulfuric acid. Since gas-phase O2 did not influence the reaction rate and the selectivity, free radicals were excluded as reaction intermediates. 

Hydroj l radical is a key species in chemical transformations of a number of trace species in the atmosphere. Some aspects of the involvement of hydroxyl radical in such transformations are discussed in the next two chapters. Among the important atmospheric trace species that react with hydroxyl radical are carbon monoxide, sulfur dioxide, hydrogen sulfide, methane, and nitric oxide. 

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