Aromatics from sulfurated methanes

The potential of MIL-47 and MIL-53(A1) for adsorption of other types of aromatic adsorbates has also been explored, for instance, of dichlorobenzene, cresol, or alkylnaphthalene isomers [17, 98]. The removal of sulfur-containing aromatics from fuels via physisorption on MOFs has been investigated on several instances in literature, for instance, via the selective removal of thiophene from a stream of methane gas by MIL-47 [99], the removal of tetrahydrothiophene from methane by... 

Allyl (27, 60, 119-125) and benzyl (26, 27, 60, 121, 125-133) radicals have been studied intensively. Other theoretical studies have concerned pentadienyl (60,124), triphenylmethyl-type radicals (27), odd polyenes and odd a,w-diphenylpolyenes (60), radicals of the benzyl and phenalenyl types (60), cyclohexadienyl and a-hydronaphthyl (134), radical ions of nonalternant hydrocarbons (11, 135), radical anions derived from nitroso- and nitrobenzene, benzonitrile, and four polycyanobenzenes (10), anilino and phenoxyl radicals (130), tetramethyl-p-phenylenediamine radical cation (56), tetracyanoquinodi-methane radical anion (62), perfluoro-2,l,3-benzoselenadiazole radical anion (136), 0-protonated neutral aromatic ketyl radicals (137), benzene cation (138), benzene anion (139-141), paracyclophane radical anion (141), sulfur-containing conjugated radicals (142), nitrogen-containing violenes (143), and p-semi-quinones (17, 144, 145). Some representative results are presented in Figure 12. 

The aromatic poly(benzothiazole) from 15 and 29 is almost amorphous and easily soluble in strong acids such as concentrated sulfuric acid and methane-sulfonic acid.26 It also dissolves in organic solvents such as HMPA and o-chlorophenol. The increased solubility and amorphous nature of this polymer is also ascribed to reduced intermolecular forces and to looser packing owing to the presence of highly distorted diphenylhexafluoroisopropylidene units in the polymer backbone. 

To circumvent such problems, up to two-thirds of the acid gas has been removed from the flame and sent directly to the catalytic reactor, the so-called "long bypass" scheme. This strategy has worked with mixed success in natural gas plants, where hydrocarbons in the acid gas are C1-C3 paraffins, chiefly methane, and no olefins. Such a configuration has been put forward for use in coal gasification plants. In the writer s opinion it is unworkable if the bypassed acid gas contains even traces of olefins or aromatics these compounds react with SO2 to form tarry products which foul the catalyst and discolor the product sulfur. 

Periana et al. have reported a mercury system that catalyzes the partial oxidation of methane to methanol.81 Hg(II) is typically considered to be a soft electrophile and is known to initiate electrophilic substitution of protons from aromatic substrates. The catalytic reaction employs mercuric triflate in sulfuric acid, and a key step in the catalytic cycle is Hg(II)-mediated methane C—H activation. For methane C—H activation by Hg(II), an oxidative addition reaction pathway via the formation of Hg(IV) is unlikely. Thus, an electrophilic substitution pathway has been proposed, although differentiation between proton transfer to an uncoordinated anion versus intramolecular proton transfer to a coordinated anion (i.e., o-bond metathesis) has not been established. Hg(II)-based methane C H activation was confirmed by the observation of H/D exchange between CH4 and D2S04 (Equation 11.9). 

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. 

Tn synthesizing low sulfur fuels from coal the Stone Webster process A uses the step-by-step addition of hydrogen to coal under conditions which minimize coke production. The first step involves the conversion of solid coal to a liquid by mild hydrocracking in the presence of a recycle solvent. In the next step these liquids react further with hydrogen under more severe conditions to produce methane, ethane, and aromatics. 

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