Hydrocarbons, liquid dependence

The diminution of E with an increase of T occurs practically linearly and is approximated by the number —0.1 N/ K. The surface tension of natural hydrocarbon liquids depends both on temperature and pressure. On Fig. 17.2, a typical dependence of E upon pressure is shown for natural gas condensate. 

Theories of electron mobility are intimately related to the state of the electron in the fluid. The latter not only depends on molecular and liquid structure, it is also circumstantially influenced by temperature, density, pressure, and so forth. Moreover, the electron can simultaneously exist in multiple states of quite different quantum character, between which equilibrium transitions are possible. Therefore, there is no unique theory that will explain electron mobilities in different substances under different conditions. Conversely, given a set of experimental parameters, it is usually possible to construct a theoretical model that will be consistent with known experiments. Rather different physical pictures have thus emerged for high-, intermediate- and low-mobility liquids. In this section, we will first describe some general theoretical concepts. Following that, a detailed discussion will be presented in the subsequent subsections of specific theoretical models that have been found to be useful in low- and intermediate-mobility hydrocarbon liquids. 

Table 10.4 lists the values of trap density and binding energy obtained in the quasi-ballistic model for different hydrocarbon liquids by matching the calculated mobility with experimental determination at one temperature. The experimental data have been taken from Allen (1976) and Tabata et ah, (1991). In all cases, the computed activation energy slightly exceeds the experimental value, and typically for n-hexane, 0/Eac = 0.89. Some other details of calculation will be found in Mozumder (1995a). It is noteworthy that in low-mobility liquids ballistic motion predominates. Its effect on the mobility in n-hexane is 1.74 times greater than that of diffusive trap-controlled motion. As yet, there has been no calculation of the field dependence of electron mobility in the quasi-ballistic model. 

The residual saturation capacity of soil is generally about one third of its waterholding capacity. Immobilization of a certain mass of hydrocarbon is dependent upon soil porosity and physical characteristics of the product. The volume of soil required to immobilize a volume of liquid hydrocarbon can be estimated as follows ... 

Clearly, if one takes a smaller value of D, one gets a higher value of IVj j, for a given distance Rufj. Kirkwood and Westheimer (1938), Westheimer and Kirkwood (1938), and Westiieimer and Shookhoff (1939) indeed argued that one should take a much smaller dielectric constant, since the intervening medium between the two protons more closely resembles a hydrocarbon liquid rather than water. In fact, for any dicarboxylic acid one can define an effective dielectric constant to fit the experimental value of W, by an equation of the form (4.8.13), with Dg being dependent on the proton-proton distance, the type and size of the acid and the solvent. 

POLAR. Descriptive of a molecule in which the positive and negative electrical charges are permanently separated, as opposed to non-polar molecules in which the charges coincide, Polar molecules ionize in solution and impart electrical conductivity. Water, alcohol, and sulfuric acid are polar in nature most hydrocarbon liquids are not. Carboxyl and hydroxyl groups often exhibit an electric charge, The formation of emulsions and the action of detergents are dependent on tills behavior,... 

Electrical Conductivity. Hayashi et al. (14) have made electrical conductivity measurements in irradiated styrene, a-methylstyrene, and isobutyl vinyl ether. The observed specific conductivities in these monomers were of the same order of magnitude, at a given dose rate, as that measured in cyclohexane. Since the G values for ion production in most hydrocarbon liquids are approximately the same, they concluded that the conducting species in the monomer systems must have had approximately the same molecular size as cyclohexane. Also, since the observed specific conductances of the three monomers and that of cyclohexane showed a square-root dependence on the dose rate, they concluded that the behavior of kinetically independent oppositely charged carriers was being observed, with very little effect of the applied field on the recombination process. 

As a byproduct of the measurements in the fully scavenged systems the sum of the mobilities of the molecular ions was determined for 10 hydrocarbon liquids varying in viscosity from 0.3 to 3 cP. As expected the values were close to linearly dependent on the viscosity of the solvent with an average value for rj[ii S ) + ld S )] of 0.75 0.25 X 10 cm /Vs with rj the viscosity in centipoise. ... 

The structure of the hydrocarbon layer depends on the temperature and presence of adsorbate molecules. Thus, the thickness of the surface layer, 8, at the temperature of liquid nitrogen in comparison to room temperature is different. In respect to the latter case estimation of 8 can be done by small angle scattering of X-rays. 

Properties Water-white to amber liquid depending on purity hygroscopic. D 1.20, refr index 1.420, bp (pure compound) 135-138C (1 mm Hg). Miscible with water and all organic solvents except aliphatic hydrocarbons hydrolyzed in water with formation of mono-, di-, and triethyl orthophosphates water solutions attack metals commercial material contains 40% TEPP. 

The Fischer-Tropsch process is the most notable of the various synthetic fuel processes and has products that range from lighter hydrocarbon liquids like naphtha to diesel fuel and heavier hydrocarbons like lubes and waxes. The final product mix is dependent upon operating conditions and process units, such as inclusion of hydrocracking functionality. By varying the design and operating conditions in the reaction section, the plant can optimize production of the desired product slate (5). 

IR measures the frequencies of molecular vibrations which depend on the masses of atoms and the force constants (i.e. the stiffness ) of chemical bonds (see Topic C8). Spectra can be measured for pure gaseous and liquid samples, but solids are usually measured by grinding them to make a mull with a heavy hydrocarbon liquid ( nujol ) which has relatively few, and well known, IR bands. Many types of chemical bond, such as C-H and C=0, give bands with characteristic IR frequencies and can thus be identified. In the case of compound X discussed above, bands appear which are characteristic of aromatic C-H bonds (suggesting a C6H6 benzene ring) and of C=0 groups bound to... 

Foam fluids are essentially two-phase fluids that consist of an inner phase and an outer phase. The inner phase is generally gaseous, usually N2 however, it can be liquid or dense vapor as is the case when C02 is used. The external phase is primarily composed of a saline—water mixture with either a surfactant or gellant depending upon the viscosity and stability requirements. Other external fluids commonly used are either hydrochloric add or alcohol—water mixtures. Diesel fuel, reformates, or other hydrocarbon-based solvents can also be used as external-phase fluids but require N2 as the energizer. Carbon dioxide and hydrocarbons produce a single-phased fluid, because C02 is very soluble in hydrocarbon liquids. 

Nonhydrocarbon Solvents, Although an asphaltene fraction can be removed from petroleum by using a wide variety of hydrocarbon liquids (14), the use of nonhydrocarbon solvents as deasphalting media and their influence on asphaltene dispersibility and compatibility has also been investigated. Dispersibility of asphaltenes in petroleum is suggested to be conveniently related to the surface tension of the system components (8, 20, 21, 22, 23). Obviously, asphaltene dispersion and compatibility is complex and is dependent on several factors and varies markedly with the character of the added liquid. 

Ammonia production by partial oxidation of hydrocarbon feeds depends to some degree on the gasification step. The clean raw synthesis gas from a Shell partial oxidation system is first treated for sulfur removal, then passed through shift conversion. A liquid nitrogen scmbbing step follows. 

Under practice conditions, the foam stability depends on the nature of the surface in contact with the foam. Foam-hydrocarbon liquid interactions are best studied [27], and it has been shown that hydrocarbons should be dispersed in an aqueous phase to prevent a foam collapse, i.e. it is necessary, in parallel with the foam formation, to produce stable oil-in-water emulsions (or microemulsions) in order to avoid any contact of the foam films with the hydrocarbon droplets. 

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