Methane in natural gas

In gas separation with membranes, a gas mixture at an elevated pressure is passed across the surface of a membrane that is selectively permeable to one component of the mixture. The basic process is illustrated in Figure 16.4. Major current applications of gas separation membranes include the separation of hydrogen from nitrogen, argon and methane in ammonia plants the production of nitrogen from ah and the separation of carbon dioxide from methane in natural gas operations. Membrane gas separation is an area of considerable research interest and the number of applications is expanding rapidly. 

Kvenvolden KA (1995) A review of the geochemistry of methane in natural gas hydrate. Org... 

Kvenvolden, K.A. A Review of the Geochemistry of Methane in Natural Gas Hydrate... 

Most gas separation processes require that the selective membrane layer be extremely thin to achieve economical fluxes. Typical membrane thicknesses are less than 0.5 xm and often less than 0.1 xm. Early gas separation membranes [22] were adapted from the cellulose acetate membranes produced for reverse osmosis by the Loeb-Sourirajan phase separation process. These membranes are produced by precipitation in water the water must be removed before the membranes can be used to separate gases. However, the capillary forces generated as the liquid evaporates cause collapse of the finely microporous substrate of the cellulose acetate membrane, destroying its usefulness. This problem has been overcome by a solvent exchange process in which the water is first exchanged for an alcohol, then for hexane. The surface tension forces generated as liquid hexane is evaporated are much reduced, and a dry membrane is produced. Membranes produced by this method have been widely used by Grace (now GMS, a division of Kvaemer) and Separex (now a division of UOP) to separate carbon dioxide from methane in natural gas. 

The simplest alcohol, methanol, is commonly known as wood alcohol, because it was once obtained by heating wood in the absence of air, a process that also produced charcoal. Now methanol is synthesized from methane in natural gas. Methanol itself has a relatively low toxicity. However, methanol is oxidized (metabolized) in the liver to formaldehyde and then to formic acid, both of which are much more toxic. 

Fuel cells are finding use as permanent power sources. A power plant built in New York City contains stacks of hydrogen-oxygen fuel cells, which can be rapidly put on-line in response to fluctuating power demands. The hydrogen gas is obtained by decomposing the methane in natural gas. A plant of this type has also been constructed in Tokyo. 

Most of the natural fuels we use are what are called fossil fuels - they are the remains of organisms which were alive millions of years ago. All living things contain carbon. When anything bums, the elements in it combine with oxygen from the air. When these fuels bum, the carbon in them is oxidised to carbon dioxide. They all contain hydrogen as well, and when they bum the hydrogen is oxidised to water. For example, when methane (in natural gas) is burned, the equation for the reaction is ... 

Many reactions are conveniently carried out entirely in the gas phase. Molecules in the gas phase are highly mobile, and the collisions necessary for chemical reactions occur frequently. Two examples are the key steps in the production of hydrogen from the methane in natural gas. The first is the reforming reaction ... 

Catalytic total oxidation of volatile organic compounds (VOC) is widely used to reduce emissions of air pollutants. Besides supported noble metals supported transition metal oxides (V, W, Cr, Mn, Cu, Fe) and oxidic compounds (perovskites) have been reported as suitable catalysts [1,2]. However, chlorinated hydrocarbons (CHC) in industrial exhaust gases lead to poisoning and deactivation of the catalysts [3]. Otherwise, catalysts for the catalytic combustion of VOCs and methane in natural gas burning turbines to avoid NO emissions should be stable at higher reaction temperatures and resists to thermal shocks [3]. Therefore, the development of chemically and thermally stable, low cost materials is of potential interest for the application as total oxidation catalysts. 

When methane in natural gas undergoes complete combustion, carbon dioxide and water are produced in an exothermic reaction. 

Objective 32 from methane in natural gas) by a process called the Monsanto process. The... 

Prinzhofer A, Pematon E (1997) Isotopically light methane in natural gas bacterial imprint or diffusive fractionation Chem Geol 142 193-200... 

Many chemical reactions that involve oxygen produce energy (heat) so rapidly that a flame results. Such reactions are called combustion reactions. We have considered some of these reactions previously. For example, the methane in natural gas reacts with oxygen according to the following balanced equation ... 

Although the methane in natural gas represents a tremendous source of energy for our civilization, an even more abundant source of methane lies in the depths of the ocean. The U.S. Geological Survey estimates that 320,000 trillion cubic feet of methane is trapped in the deep ocean near the United States. This amount is 200 times the amount of methane contained in the natural gas deposits in the United States. In the ocean, the... 

A primary standard is prepared by an absolute method with the gravimetric method being the preferred technique. The basic technique involves weighing minor and major components into a cylinder. This basic method can be modified to prepare samples at very low concentrations (parts per trillion) and containing very specific and complex mixtures such as hydrocarbons. The imcertainly in the preparation procednre may be determined by preparing a family of primary standards and intercomparing those standards by analysis. As will be illustrated, it is very important to have standards which are very close and bracket the concentration of the unknown in question. This is especially important when analyzing natural gas. In this case, two methods may be used to determine the concentration of methane in natural gas. However, one method will lead to a much lower imcertainty and thus, a lower imcerlainty in the BTU value of the natural... 

A substance that has combined with oxygen is described as having been oxidized, and the reaction is classified as oxidation. All combustion reactions are oxidations. In the combustion of the methane in natural gas, for example, the carbon is oxidized to carbon dioxide and the hydrogen is oxidized to water. 

Gas mixture separation processes are based on the specific pore size distribution of CMS, which permits diffusion of different gasses at different rates. These processes aim to either recover and recycle valuable constituents from industrial waste gases, or to separate small gas molecules by preferential adsorption. The latter is at present the most important large scale application of CMS. Separations that have been accomplished include oxygen from nitrogen in air, carbon dioxide from methane in natural gas, ethylene from ethane, linear from branched hydrocarbons (such as n-butane from isobutane), and hydrogen from flue gases [6]. 

Thus, solar energy is actually a form of fusion energy. A fusion reaction releases a tremendous amount of energy. Compare the energy of the deuteron/triton fusion reaction with that released by the burning of the methane in natural gas (see Section 15-1). 

The second method of production of acetylene is based on the cracking either of methane in natural gas or of higher hydrocarbons in, for example, a naphtha feedstock. Various processes have been devised for these cracking operations, which in the case of methane, may be represented as ... 

Adsorption of H2S is an important process, for example, for natural gas purification. In this process, not pure H2S but a mixture of methane and H2S (and also other components like CO2 and hydrocarbons such as ethane and propane) come into contact with the adsorbent, and competitive adsorption has to be considered. As shovm in Figure 3.3.41b, the loading of the molecular sieve by H2S (for a given partial pressure of H2S) is reduced by about 20% if we increase the total pressure to 60 bar by the addition of CH4. Even if methane is only weakly adsorbed compared to H2S (Figure 3.3.41a), the high partial pressure of methane in natural gas considerably reduces the loading with H2S, since H2S is partly replaced by methane by competitive adsorption. This phenomenon has to be considered in many adsorption processes, as examined below in more detail. 

By studying many types of experiments, chemists have found that chemical reactions occur at wideiy differing rates. For example, in the presence of air, iron rusts very siowiy, whereas the methane in natural gas bums rapidly. The speed of a chemical reaction depends on the energy pathway that a reaction follows and the changes that take place on the molecular level when substances interact. In this chapter, you will study the factors that affect how fast chemical reactions take place. 

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