Density of hydrocarbons

The first relation assumes that the density of hydrocarbon is constant in the interior of the micelle. If we ignore curvature corrections the free energy per amphiphile in a micelle is from eqn (3.1) and (4.2)... 

Owing to the particular structure of the substrate with a surface bearing a relatively high density of hydrocarbon chains protruding toward the continuous medium, the diffusion of sorbate inside these chains cannot be ignored, which may constitute the rate controlling step. This diffusion process could be described by Weber and Morris [44], which is based on Pick s Second Law [45]. 

Figure 5. CORRELATION BETWEEN GAS DENSITY OF HYDROCARBONS AND REFRACTIVE INDEX From this quantitative change, it is possible to detennine the difference in refractive index.

We have not been able to find open literature publieations on predieting the density of hydrocarbon liquids based on chemical composition. In contrast, there have been many attempts to develop empirieal eorrelations to predict the eetane munber. Unfortunately, most of those attempts have had rather limited success, which, in the end, led to the introduction of the term cetane index to describe cetane munber estimates generated with the various correlations. 

TABLE A1.1 Average Relative 15/1S C Density of Hydrocarbon Type Qroupe ... 

Efforts to obtain synthetic hydrocarbon fuels from CO2 have been motivated by the unparalleled energy density of hydrocarbons, which constitute the backbone of mankind s energy infrastructure [36], and by the need to cope with increasing atmospheric CO2 released by the burning of fossil fuels. Synthetic fuels originating from CO2 may become a potential component of a carbon energy cycle, as shown schematically in Equation 1.3, where the fuels can be methane, a longer-chain hydrocarbon, methanol, or C2-C3 alcohols [7]. 

The standard specific gravity is the ratio of the density of a hydrocarbon at 15.55°C (60°F) to that of water at the same temperature. It differs from the specific gravity d] which is the ratio of the density of a hydrocarbon at 15°C to that of water at 4°C. 

The density of heavy fuels is greater than 0.920 kg/1 at 15°C. The marine diesel consumers focus close attention on the fuel density because of having to centrifuge water out of the fuel. Beyond 0.991 kg/1, the density difference between the two phases —aqueous and hydrocarbon— becomes too small for correct operation of conventional centrifuges technical improvements are possible but costly. In extreme cases of fuels being too heavy, it is possible to rely on water-fuel emulsions, which can have some advantages of better atomization in the injection nozzle and a reduction of pollutant emissions such as smoke and nitrogen oxides. 

Hydrocarbons are of a lower density than formation water. Thus, if no mechanism is in place to stop their upward migration they will eventually seep to the surface. On seabed surveys in some offshore areas we can detect crater like features ( pock marks ) which also bear witness to the escape of oil and gas to the surface. It is assumed that throughout the geologic past vast quantities of hydrocarbons have been lost in this manner from sedimentary basins. 

The z-factor must be determined empirically (i.e. by experiment), but this has been done for many hydrocarbon gases, and correlation charts exist for the approximate determination of the z factor at various conditions of pressure and temperature. (Ref. Standing, M.B. and Katz, D.L., Density of natural gases, Trans. AIME, 1942). 

The oil density at surface is readily measured by placing a sample in a cylindrical flask and using a graduated hydrometer. The API gravity of a crude sample will be affected by temperature because the thermal expansion of hydrocarbon liquids is significant, especially for more volatile oils. It is therefore important to record the temperature at... 

In Section 5.2.8 we shall look at pressure-depth relationships, and will see that the relationship is a linear function of the density of the fluid. Since water is the one fluid which is always associated with a petroleum reservoir, an understanding of what controls formation water density is required. Additionally, reservoir engineers need to know the fluid properties of the formation water to predict its expansion and movement, which can contribute significantly to the drive mechanism in a reservoir, especially if the volume of water surrounding the hydrocarbon accumulation is large. 

When a customer agrees to purchase gas, product quality is specified in terms of the calorific value of the gas, measured by the Wobbe index (calorific value divided by density), the hydrocarbon dew point and the water dew point, and the fraction of other gases such as Nj, COj, HjS. The Wobbe index specification ensures that the gas the customer receives has a predictable calorific value and hence predictable burning characteristics. If the gas becomes lean, less energy is released, and if the gas becomes too rich there is a risk that the gas burners flame out . Water and hydrocarbon dew points (the pressure and temperature at which liquids start to drop out of the gas) are specified to ensure that over the range of temperature and pressure at which the gas is handled by the customer, no liquids will drop out (these could cause possible corrosion and/or hydrate formation). 

This observation that the length of the hydrocarbon chain could be varied from 16 to 26 carbon atoms without affecting the limiting area could only mean that at this point the molecules were oriented vertically. From the molecular weight and density of palmitic acid, one computes a molecular volume of 495 A a molecule occupying only 21 A on the surface could then be about 4.5 A on the side but must be about 23 A long. In this way one begins to obtain information about the shape and orientation as well as the size of molecules. 

The refractive index of a liquid is recorded as where t is the temperature at which the measurement is made, and D refers to the wave length of the D line of sodium. As already pointed out, it is usual to determine both the refractive index and the density of the liquid at 20° in any case they should be determined at the same temperatme. These two constants are useful in assisting the characterisation of a pure hquid they are particularly valuable for ahphatic hydrocarbons and similar compounds where the methods of characterisation by the formation of solid derivatives are not entirely satisfactory. 

The absolute viscosities of the perfluorinated inert Hquids are higher than the analogous hydrocarbons but the kinematic viscosities are lower due to the higher density of the perfluorinated compounds. The viscosity index, ie, the change in viscosity with temperature, is generally higher for the perfluorinated Hquids than for hydrocarbons. 

The quantity of catalyst used for a given plant capacity is related to the Hquid hourly space velocity (LHSV), ie, the volume of Hquid hydrocarbon feed per hour per volume of catalyst. To determine the optimal LHSV for a given design, several factors are considered ethylene conversion, styrene selectivity, temperature, pressure, pressure drop, SHR, and catalyst life and cost. In most cases, the LHSV is ia the range of 0.4—0.5 h/L. It corresponds to a large quantity of catalyst, approximately 120 m or 120—160 t depending on the density of the catalyst, for a plant of 300,000 t/yr capacity. 

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