Displaces methane

Coal beds typically contain large amounts of methane-rich gas that is adsorbed onto the surface of the coal. The current practice for recovering coal bed methane is to depressurize the bed, usually by pumping water out of the reservoir. An alternative approach is to inject C02 gas into the bed. Tests have shown that the adsorption rate for COz to be approximately twice that of methane, giving it the potential to efficiently displace methane and remain sequestered in the bed. C02 recovery of coal bed methane has been demonstrated in limited field tests, but much more work is necessary to understand and optimize the process, particularly the capacity of coal beds with respect to COz and methane. 

Another means to reduce man-made carbon dioxide emissions is sequestration in the land or the ocean. When carbon dioxide is produced locally it may be possible to efficiently separate it from other gases, concentrate it, and dispose of it. A number of complex scenarios may be envisioned to accomplish this disposal, from pumping it into the ocean, to displacing methane in coal mines, to storage in depleted hydrocarbon reservoirs. 

Injecting carbon dioxide into deep, unmineable coal seams where it is adsorbed to displace methane (effectively natural gas) is another potential use or disposal strategy. Currently, the economics of enhanced coal bed methane extraction are not as favorable as enhanced oil recovery, but the potential is large. 

Despite these high HCN yields, methanol ammoxidation technology for HCN manufacture has not displaced methane ammoxidation by the Andrussow process (see below) because of the former s inherent economic disadvantage in feedstock costs. Methanol, since it is currently manufactured on a large scale from methane-derived synthesis gas (CO and H2), is intrinsically a more expensive source of carbon than methane. 

In general, each nomial mode in a molecule has its own frequency, which is detemiined in the nonnal mode analysis [24]- Flowever, this is subject to the constraints imposed by molecular synmietry [18, 25, 26]. For example, in the methane molecule CFI, four of the nonnal modes can essentially be designated as nonnal stretch modes, i.e. consisting primarily of collective motions built from the four C-FI bond displacements. The molecule has tetrahedral synmietry, and this constrains the stretch nonnal mode frequencies. One mode is the totally symmetric stretch, with its own characteristic frequency. The other tliree stretch nonnal modes are all constrained by synmietry to have the same frequency, and are refened to as being triply-degenerate. 

Because of the large price differential between propane and propylene, which has ranged from 155/t to 355 /1 between 1987 and 1989, a propane-based process may have the economic potential to displace propylene ammoxidation technology eventually. Methane, ethane, and butane, which are also less expensive than propylene, and acetonitrile have been disclosed as starting materials for acrylonitrile synthesis in several catalytic process schemes (66,67). 

Iodine reacts with hydrocarbons to form iodine compounds, but compared to the other halogens, the equiUbria are unfavorable because the displacement step with the iodine atom is endothermic, requiring 4066.3 J (971.9 cal) for methane and 799.9 J (191.2 cal) for toluene. Hydrogen iodide can be used to reduce an alkah iodide to hydrocarbon plus molecular iodine. 

Methane sulfonic acid, trifluoroacetic acid, hydrogen iodide, and other Brmnsted acids can faciUtate 3 -acetoxy displacement (87,173). Displacement yields can also be enhanced by the addition of inorganic salts such as potassium thiocyanate and potassium iodide (174). Because initial displacement of the acetoxy by the added salt does not appear to occur, the role of these added salts is not clear. Under nonaqueous conditions, boron trifluoride complexes of ethers, alcohols, and acids also faciUtate displacement (87,175). 

R. McClelland I might add a couple of comments to that. Certainly, Consolidated Natural Gas as well as a number of other mid-Westem utilities are looking at medium Btu gas for some applications. But these are typically in locations where you have a high density of large commercial or industrial consumers that can burn low Btu gas. Certainly, from the comments that I have heard in the utility industry, I think Bill Bair is right. For residential and commercial applications, to the extent the gas industry has to increase supplies beyond that which might be displaced by medium Btu industrial gas substitution, we will certainly need methanation. 

A change in the amount of any substance that appears in the reaction quotient displaces the system from its equilibrium position. As an example, consider an industrial reactor containing a mixture of methane, hydrogen, steam, and carbon monoxide at equilibrium ... 

Use of benzotriazole in the preparation of diphenylmethanes and triphenylmethanes has been reviewed." Benzotriazole is condensed with an aldehyde and then allowed to react with naphthols to form a diphenyl-methane benzotriazole derivative such as 69 (Scheme 9). The benzotriazole moiety in 69 is displaced by a Grignard reagent to give triphenylmethanes.79 100 This method allows for the preparation of triarylmethanes which contain three different aromatic rings. Compounds 70-72 are prepared by this method. 

In the synthesis of 162, catalytic hydrogenation of lysergic acid proceeds from the less hindered side of the molecule to afford the derivative with the trans ring junction (158). As above, reduction of the methyl ester (159) gives the corresponding carbinol. This is then converted to the methane sulfonate (160), and that function is displaced with cyanide ion to afford the acetonitrile derivative 161. 

Quaternary ammonium azides will displace halogens in a synthesis of alkyl azides. Dichloromethane has been used as a solvent, although this can slowly form diazido-methane which may be concentrated by distillation dining work-up, thereafter easily exploding [1]. An accident attributed to this cause is described, and acetonitrile recommended as a preferable solvent, supported polymeric azides, excess of which can be removed by filtration are also preferred in place of the tetrabutylam-monium salt [2]. A similar explosion was previously recorded when the quaternary azide was generated in situ from sodium azide and a phase transfer catalyst in a part aqueous system [3,4],... 

Displacing the methane tied up in deep unmineable coal adds another small carbon sink to the portfolio of options and this process is called enhanced coal bed methane recovery. When injected into a coal bed, C02 can replace adsorbed methane. By doing so, coal beds can serve as a C02 reservoir and a source for methane production (Parson and Keith, 1998). This method is attractive in the sense that most of the injected C02 will be immobilized by either physical or chemical adsorption on the coal surface. 

Other reservoir properties being similar, high-rank coals are more favorable for C02 storage because of their methane displacement efficiency (related to lower sorption selectivity for C02 compared to methane and higher absolute sorption of methane with increasing rank see Figs 1 and 3). Higher ranks of coal are also more... 

We note that hydrogen as well as methane, ethane and toluene have been reported [25], but do not currently have good explanations in the schemes shown above. For the methane and ethane, one would have to resort to either radical displacement reactions of the methyl ester shown in Scheme 18.3 in the middle... 

In contrast with the azoles, diazoles and their benzo derivatives tend to react with dichlorocarbene to yield the tris(diazolyl)methanes, presumably via the initial formation of the N-dichloromethyl derivative [6, 13]. Only in more activated polymethyl derivatives does reaction occur at a ring carbon atom. In a similar manner (7.7.1.B), 2-chloropyridine and 2-chloroquinoline react with dichlorocarbene at the ring nitrogen atom to yield, after nucleophilic displacement of the chloro group, the 1 -dichloromethyl-2-oxo derivatives (13-25%) [14] (Scheme 7.38). 2-Chlorobenzothiazole reacts in an analogous manner, but other pyridine and quinoline derivatives fail to react. It is also noteworthy that the dichloromethyl group is unusually stable and is not converted into the formyl group. 

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