Hydrocarbon type prediction

It is important to characterize FCC feeds as to their molecular structure. Once the molecular configuration is known, kinetic models can be developed to predict product yields. The simplified correlations above do a reasonable job of defining hydrocarbon type and distribution in FCC feeds. Each correlation provides satisfactory results within the range for which it was developed. Whichever correlation is used, the results should be trended and compared with unit operation. 

Some products are highly predictable (e.g., jet fuels) with specific fractions of defined components others, for example, automotive gasolines, contain broader ranges of hydrocarbon types and amounts. Table D-l in Appendix D provides a comprehensive list of petroleum hydrocarbons. 

Since most TPH contamination involves a complex mixture of hydrocarbons, it is unlikely that aqueous readings beyond the NAPL zone will be near the limits of solubility (based on assumptions of a pure hydrocarbon type in equilibrium with water). If concentrations are near or above solubility limits, NAPL was probably present in the sample. TPH materials are relatively insoluble in water, with only the BTEX chemicals or some short-chain aliphatic hydrocarbons showing any appreciable potential for water solubility. When they are part of complex mixtures, the individual components never reach the concentrations predicted from their solubility constants as individual chemicals. For example, chemicals like benzene or toluene, which may constitute a small percentage within an initial bulk product like gasoline, jet fuel, or diesel fuel, have a much greater tendency to stay dissolved in the NAPL system than to become integrated into the water-based system beyond the NAPL boundary. Therefore, the effective solubility of these chemicals as part of a complex mixture is less than it would be in a release of the pure chemical. 

Perhaps the most commonly used spectrometric method for analysis of viscous oils is infrared spectroscopy. General instructions for qualitative hydrocarbon type and functional group analysis are widely available. Papers have also been published for quantitative analysis of hydrocarbon types [/O]. FT-IR techniques have been reported for use in predictive maintenance programs to monitor the concentration of additives and degradation products in used oils [11 ]. 

A micellar solution containing a fluorinated surfactant and a selected hydrocarbon surfactant can exceed the surface activity predicted for an ideal solution in which the components do not interact. This synergism increases the effectiveness of the surfactant and, because of the lower cost of hydrocarbon-type surfactants, results in considerable savings. Because perfluorinated surfactants are not biodegradable (Chapter 10), the use of fluorinated surfactants at lower concentrations is also advantageous from the environmental point of view. 

An adequate prediction of multicomponent vapor-liquid equilibria requires an accurate description of the phase equilibria for the binary systems. We have reduced a large body of binary data including a variety of systems containing, for example, alcohols, ethers, ketones, organic acids, water, and hydrocarbons with the UNIQUAC equation. Experience has shown it to do as well as any of the other common models. V7hen all types of mixtures are considered, including partially miscible systems, the... 

The example of a binary mixture is used to demonstrate the increased complexity of the phase diagram through the introduction of a second component in the system. Typical reservoir fluids contain hundreds of components, which makes the laboratory measurement or mathematical prediction of the phase behaviour more complex still. However, the principles established above will be useful in understanding the differences in phase behaviour for the main types of hydrocarbon identified. 

Vapor densities for pure compounds can also be predicted by cubic equations of state. For hydrocarbons, relatively accurate Redlich-Kwong-type equations such as the Soave and Peng-Robinson equations are often used. Both require only T, and (0 as inputs. For organic compounds, the Lee-Erbar-EdmisteF" equation (which requires the same input parameters) has been used with errors essentially equivalent to those determined for the Lydersen method. While analytical equations of state are not often used when only densities are required, values from equations of state are used as inputs to equation of state formulations for thermal and equilibrium properties. 

In alternant hydrocarbons (p. 55), the reactivity at a given position is similar for electrophilic, nucleophilic, and free-radical substitution, because the same kind of resonance can be shown in all three types of intermediate (cf. 20,22, and 23). Attack at the position that will best delocalize a positive charge will also best delocalize a negative charge or an unpaired electron. Most results are in accord with these predictions. For example, naphthalene is attacked primarily at the 1 position by NOj, NHJ, and Ph, and always more readily than benzene. 

On the basis of the results in acetonitrile, it might be reasonable to assume that the values for A//het(R-R ) and AG°het(R-R ) are apparently close to each other also in sulfolane, since the dielectric constant (43.3) and the donor number (14.8) of this solvent are close to those of acetonitrile (37.5 and 14.1, respectively). On the basis of this assumption, Arnett s equation (28) was examined for reactions of type (23). For these reactions, except for [3-2], only the AGhet(R-R ) values are avtiilable. As shown in Fig. 3, the values for this system are about 10 kcal moP less than predicted from (28). The negative deviation can also be ascribed to steric congestion in these hydrocarbon molecules. The large negative deviations, similar to those observed in sulfolane, are also seen in Fig. 3 for the values of AGSet(R-R ) in DMSO. 

Since the nitrogen in pyridine is electron attracting it seemed reasonable to predict that the trihalopyridynes would also show the increased electrophilic character necessary to form adducts with aromatic hydrocarbons under similar conditions to those employed with the tetra-halogeno-benzynes. The availability of pentachloropyridine suggested to us and others that the reaction with w-butyl-lithium should lead to the formation of tetrachloro-4-pyridyl-lithium 82 84>. This has been achieved and adducts obtained, although this system is complicated by the ease with which pentachloropyridine undergoes nucleophilic substitution by tetrachloro-4-pyridyl lithium. Adducts of the type (45) have been isolated in modest yield both in the trichloro- and tribromo- 58) series. 

A human error or reliability analysis (HRA) can be performed to identify points that may contribute to an accidental loss. Human errors may occur in all facets of a the hydrocarbon industry. They are generally related to the complexity of the equipment, human-equipment interfaces, hardware for emergency actions, and procedures for operations, testing and training. The probabilities of certain types of errors occurring are normally predicted as indicated in Table 29. Individual tasks can be analyzed to determine the probability of an error occurring. From these probabilities, consequences can be identified which detemline the risk of a particular error. 

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