Natural gas components

Natural-gas components include water vapor, carbon dioxide (qv), sometimes hydrogen sulfide, heavier hydrocarbons (qv), methane, nitrogen, small amounts of argon, traces of neon and hydrogen, and helium. The production of pure helium from natural gas requires three basic processing steps (73). 

The activation of methane by microwaves has long been a goal of scientists in attempts to convert this natural gas component into higher hydrocarbons valuable in petrochemistry and the chemical industry. Two pathways are being extensively investigated by research groups all over the world ... 

One of the most important challenges in the modern chemical industry is represented by the development of new processes aimed at the exploitation of alternative raw materials, in replacement of technologies that make use of building blocks derived from oil (olefins and aromatics). This has led to a scientific activity devoted to the valorization of natural gas components, through catalytic, environmentally benign processes of transformation (1). Examples include the direct exoenthalpic transformation of methane to methanol, DME or formaldehyde, the oxidation of ethane to acetic acid or its oxychlorination to vinyl chloride, the oxidation of propane to acrylic acid or its ammoxidation to acrylonitrile, the oxidation of isobutane to... 

PETROCHEMICALS. Chemicals derived from petroleum and, more specifically, substances or materials manufactured from a component of crude oil or natural gas. See Fig. 1 In this sense, ammonia and synthetic rubber made from natural gas components are petrochemicals. Many of these chemicals are described in separate articles in this encyclopedia. Check alphabetical index. 

Each quadruple point occurs at the intersection of four three-phase lines (Figure 1.2). The lower quadruple point is marked by the transition of Lw to I, so that with decreasing temperature, Qi denotes where hydrate formation ceases from vapor and liquid water, and where hydrate formation occurs from vapor and ice. Early researchers took Q2 (approximately the point of intersection of line Lw-H-V with the vapor pressure of the hydrate guest) to represent an upper temperature limit for hydrate formation from that component. Since the vapor pressure at the critical temperature can be too low to allow such an intersection, some natural gas components such as methane and nitrogen have no upper quadruple point, Q2, and... 

The advantage of the method in addition to accuracy is that, in principle, it enables the user to predict properties of mixtures from parameters of single hydrate formers. Since there are only eight natural gas components (yet an infinite number of natural gas mixtures) that form hydrates, the method represents a tremendous saving in experimental effort for the natural gas industry. The modified van der Waals and Platteeuw method is detailed in Chapter 5. 

Several researchers have studied hydrates as a means of separating gases and water, and as a means of storing mass and energy. Because many of these studies are not typically with natural gas components, they are only given cursory attention here. A few details of this section are to be found in Chapters 4 and 8. 

Parent, J.S., Investigations into the Nucleation Behaviour of the Clathrate Hydrates of Natural Gas Components, M.Sc. Thesis, University of Calgary, Alberta (1993). 

As this text is primarily concerned with natural gas hydrates, no further discussion will be given to Jeffrey s structures III-VII and the other unusual structures described above, since as stated previously these structures have yet to be found for natural gas components. 

Table 2.4 presents the diameter ratios of natural gas components (and a few other compounds) relative to the diameter of each cavity in both structures. Also presented are two unusual molecules, cyclopropane and trimethylene oxide, which can form simple hydrates of either structure si or sll hydrates of these molecules are discussed in Section 2.1.3.3, in the subsection on structural changes in simple hydrates. 

Of the natural gas components that form simple hydrates, nitrogen, propane, and iso-butane are known to form structure II. Methane, ethane, carbon dioxide, and hydrogen sulfide all form si as simple hydrates. Yet, because the larger molecules of propane and iso-butane only fit into the large cavity of structure II, natural gas mixtures containing propane and iso-butane usually form structure II hydrate (see Section 2.1.3.3 in the subsection on structural changes in binary hydrate structure). 

For si and sll, Davidson et al. (1977a, 1981) performed NMR spectroscopy and dielectric relaxation measurements where applicable, in order to estimate the barriers to molecular reorientation for simple hydrates of natural gas components, except carbon dioxide. Substantial barriers to rotation should also affect such properties as hydrate heat capacity. 

Hydrate Formation for Three-Phase Conditions of Single Natural Gas Components, Using P [kPa] = exp(a + b/T [K])... 

The equation of Table 4.1 from Kamath (1984) enables prediction of the most common regions of interest of simple natural gas components—the pressure and temperature conditions for both Lw-H-V and I-H-V. When using the equation,... 

Figure 4.2b shows that at the intersection of the Lw-V-Lhc line with the Lw-H-V line, a second quadruple point (Q2 = Lw-H-V-Lhc) is formed. Measured upper quadruple points for simple natural gas components are shown in Table 4.2. Point Q2 is the origin for two additional three-phase lines (1) a Lw-H-Lhc line that is almost vertical due to the three incompressible phases and (2) a H-V-Lhc line, of less concern, because it exists within the Lw-H-Lhc and the Lw-H-V boundaries. 

Hydration Number (M nH20) for Simple Hydrates of Natural Gas Components from Handa (1986a,b)... 

Table 6.5 lists the different thermal property measurements that have been performed on hydrates of cyclic ethers, other nonnatural gas components, and natural gas components. 

Yang, S.O., Measurements and Prediction of Phase Equilibria for Water + Natural Gas Components in Hydrate-Forming Conditions, Ph.D. Thesis, Korea University, December (2000). 

Petrochemicals are relatively pure, identifiable substances derived from petroleum or natural gas (Fig. 1). Thus, ammonia and synthetic rubber made from natural gas components can be classed as petrochemical compounds. Among the most important petrochemicals manufactured include ... 

ADSORPTION OF NATURAL GAS COMPONENTS ON ACTIVATED CARBON FOR GAS STORAGE APPLICATIONS... 

The main purpose of the present work is twofold (i) to report an extensive set of singlecomponent adsorption isotherm data of the more common natural gas components on activated carbon, and (ii) to present a means of extrapolating the measured data to higher alkanes in order to be able to span the whole composition of a typical natural gas. There is experimental evidence that for the n-alkanes series this can be done using the Adsorption Potential theory, as demonstrated recently by Holland et al. on Westvaco BAX-1100 carbon, and assumed previously by us. - ... 

Combination of the isotopic values with the methane/C2+ ratio provides a very useful tool to differentiate gases of biogenic versus thermal origin, as recognized many years ago (Bernard et al., 1976). More recent studies have also seen much greater use of the hydrogen and deuterium isotopes for natural gas components combined with the carbon values to differentiate gases derived at different levels of thermal maturities, as documented in many of the papers by Schoell et al. (1993). 

Table 3 Heating values of individual natural gas components...

Now let us consider the combustion (that is, burning) of the natural gas component ethane (C2Hg) in oxygen or air, which yields carbon dioxide (CO2) and water. The unbalanced equation is... 

The presence of hydrogen bonds also causes formation of crystalline hydrates such as NH3 H2O, SO2 H2O hydrocarbon hydrates (e.g. with natural gas components) as well as the zig-zag structure of the (HF) polymer. 

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