Physical properties, estimation methods

This section briefly describes the physical property estimation methods (hal have been used in this honk... 

Lyman WS, Reehl WF, Rosenblatt RH (1982) Handbook of Chemical-Physical Property Estimation Methods. McGraw-Hill, New York... 

Physical property estimation methods may be classified into six general areas (1) theory and empirical extension of theory, (2) corresponding states, (3) group contributions, (4) computational chemistry, (5) empirical and quantitative structure property relations (QSPR) correlations, and (6) molecular simulation. A quick overview of each class is given below to provide context for the methods and to define the general assumptions, accuracies, and limitations inherent in each. 

Collected bio-oil and determined solubility parameters and physical property estimation methods for the components of the bio-oil product of peanut shell pyrolysis. 

Horvath, A.L. (1985) Handbook of Aqueous Electrolyte Solutions Physical Properties, Estimation Methods and Correlation Methods. EUis Horwood, West Sussex, England. 

Using conventional physical property estimating methods (3,4), convert the weight units into volumetric and molar units. 

Various applications deal with the selection of appropriate physical property estimation methods because each estimation method has its own benefits and shortcomings. Based on the chemical and physical properties of a component or a mixture and other constraints like pressure, temperature or composition the best estimation method has to be selected. Typical rules ate Method xy gives good results for mixtures with nonpolar components, the results are acceptable for mixtures containing polar components, but the method should not be applied for mixtures with associating components . It should be noticed that estimation methods often need additional physical properties as input data which have to be estimated as well. As a result, a selection and valuation technique has to be applied which searches all over a tree of possible estimation methods. ... 

General Properties of Computerized Physical Property System. Flow-sheeting calculations tend to have voracious appetites for physical property estimations. To model a distillation column one may request estimates for chemical potential (or fugacity) and for enthalpies 10,000 or more times. Depending on the complexity of the property methods used, these calculations could represent 80% or more of the computer time requited to do a simulation. The design of the physical property estimation system must therefore be done with extreme care. 

Critica.1 Properties. Several methods have been developed to estimate critical pressure, temperature, and volume, U). Many other properties can be estimated from these properties. Error propagation can be large for physical property estimations based on critical properties from group contribution methods. Thus sensitivity analyses are recommended. The Ambrose method (185) was found to be more accurate (186) than the Lyderson (187) method, although it is computationally more complex. The Joback and Reid method (188) is only slightly less accurate overall than the Ambrose method, and is more accurate for some specific substances. Other methods of lesser overall accuracy are also available (189,190) (T, (191,192) (T, P ),... 

Group contribution techniques are based on the concept that a particular physical property of a compound can be considered to be made up of contributions from the constituent atoms, groups, and bonds the contributions being determined from experimental data. They provide the designer with simple, convenient, methods for physical property estimation requiring only a knowledge of the structural formula of the compound. 

Horvath, A. L., Handbook of Aqueous Electrolyte Solutions, Physical Properties, Estimation and Correlation Methods, Ellis Horwood, Chichester, 1985. 

Methods have been presented, with examples, for obtaining quantitative structure-property relationships for alternating conjugated and cross-conjugated dienes and polyenes, and for adjacent dienes and polyenes. The examples include chemical reactivities, chemical properties and physical properties. A method of estimating electrical effect substituent constants for dienyl and polyenyl substituents has been described. The nature of these substituents has been discussed, but unfortunately the discussion is very largely based on estimated values. A full understanding of structural effects on dienyl and polyenyl systems awaits much further experimental study. It would be particularly useful to have more chemical reactivity studies on their substituent effects, and it would be especially helpful if chemical reactivity studies on the transmission of electrical effects in adjacent multiply doubly bonded systems were available. Only further experimental work will show how valid our estimates and predictions are. 

Thermodynamic data (enthalpy of reaction, specific heat, thermal conductivity) for simple systems can frequently be found in date bases. Such data can also be determined by physical property estimation procedures and experimental methods. The latter is the only choice for complex multicomponent systems. 

We again consider the distillation unit introduced in Example 1, updated with temperature information for each of the streams, including some that were previously considered to be internal to the system box. The temperatures have been estimated using a physical property estimation system. There are a number of such computer-based tools and most simulation software systems will include property estimation methods. Figure 3 shows these temperatures as well as the results obtained in the mass balance step above. As more streams are included in this diagram, we have new unknowns related to flow rates. Specifically, we now have the vapour stream, V, from the top of the column to the condenser and the liquid reflux stream, L, from the condenser back into the column. The relationship between the liquid reflux stream back into the column and the actual distillate product stream (D) is given by the reflux ratio ... 

Lidle D (Ed.) (1983), Handbook of Chemistry and Physics 63. Edition, CRC Press, Boca Raton Lyman WJ, Reehl WF, Rosenblatt DH (Eds.) (1990), Handbook of Chemical Properties Estimation Methods - Environmental Behaviour of Organic CompoundsAmerican Chemical Society, Washington, D.C. 

These QSPR methods can be used to predict any chemical property that is dependent upon molecular structure. Publications are available that provide examples of uses in a wide variety of applications for chemical or physical property estimation or biological activity estimation. Our group has published papers on property estimation dealing with normal boiling points, critical temperatures, surface tension, Henry s law constants, aqueous solubility, supercritical CO2 solubility, autoignition temperature, gas chromatographic retention times, and ion mobility constants. Several specific examples are given as illustrations of the capabilities of the method. 

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