Pseudo-Components Characterization

The true boiling point and specific gravity variation with the volume percent distilled are found by standard ASTM procedures. In the present case, the smooth TBP curve is replaced by a stepped curve of eleven pseudo components characterized by their 50% boiling points and specific gravities. Their molecular weights are... 

Figure 5 Illustration of pseudo-component characterization of petroleum crude into narrow boiling range compounds . A similar approach is used for estimating specific gravities of pseudo-components ...

The generation of pseudo-components for petroleum fluids has been discussed in Pseudo-Components Characterization. Once the various pseudo-components have been generated and classified, the conventional methods for multicomponent VLB apply and the methods discussed above for VLB computation can be used. 

All the above three provide extensive data sources and simulators for estimating various thermodynamic properties of pure compounds, well-defined mixtures and petroleum fluids. The respective manuals describe in detail various methods used for estimating the properties and their limitations while at the same time providing the user with choices. The Aspen Physical Property System and SUPBRTRAPP can also be used to estimate thermodynamic profrerties using the pseudo-component characterization of petroleum fluids. The reader is referred to the respective manuals/sim-ulators for details. 

Naphtha feed is often characterized using PINA analysis that simply is the weight % of K-paraffin, Ao-paraffin, naphthene and aromatic compounds. If the typical commercial indexes (specific gravity, PINA analysis and TBP curves or ASTM D86) are used properly, it is possible to empirically derive detailed naphtha composition by referring to the four different hydrocarbon classes and only to a limited number of reference components within each class. In fact, the PINA information indicates the relative abundance of the four different classes directly. The specific gravity and boiling curve allow the specification of the initial and final cuts of the hydrocarbon mixture as well as the relative presence and distribution of the reference pseudo components inside each fraction. 

This review reports the state-of-art in the development and applications of continuous thermodynamics to copolymer systems characterized by multivariate distribution functions. Continuous thermodynamics permits the thermodynamic treatment of systems containing polydisperse homopolymers, polydisperse copolymers and other continuous mixtures by direct use of the continuous distribution functions as can be obtained experimentally. Thus, the total framework of chemical thermodynamics is converted to a new basis, the continuous one, and the crude method of pseudo-component splitting is avoided. 

Monteagudo et al characterized the asphaltenes as a continuous ensemble for which the distribution function was taken from the fractal aggregation theory. The asphaltene family was discretized in pseudo-components by the Gauss-Laguerre quadrature. Only the asphaltene polydispersity was taken into account. All other components were represented by as solvent whose properties (molar volume and solubility parameter) were calculated form a cubic equations of state. Aggregation of asphaltenes was considered to be a reversible process. And it was assumed the phase equilibrium was between a liquid phase and a pseudo-liquid phase containing only asphaltenes. 

Figure 3.2 shows schematically the sequence of the five columns for the isolation of Kr/Xe. In this figure, the multi-component mixture to be separated is characterized in a simplified way as a six-component mixture (A, Kr, B, C, Xe, D). The pseudo component A combines all components that are more volatile than Kr, i.e. mainly O2 und CH4. B and C represent the components with volatilities in between those of the key components Kr and Xe and D summarizes the components less volatile than Xe. 

The steam reformer model can handle feeds from methane to naphtha, with all the t5q)ical components that are present in natural gas, as well as recycled S5mthesis purge gas, or hydrogen recovery unit tail gases. Naphtha feed is characterized as about 30 chemical species, some of which are pure components, and some are hydrocarbon fractions (pseudo components). Each hydrocarbon species participates in a reaction that includes adsorption onto the catalyst, reforming, and desorption. The model includes diffusion effects within the catalyst, as well as heat transfer resistance from the bulk gas to the catalyst surface. 

Crude heavy oils are composed by a large variety of compounds, mostly aromatics and alkylated aromatics with a carbon number from 14 to 25. These heavy aromatic hydrocarbons are very difficult to characterize, the heavier fractions like asphaltenes being impossible to characterize in any way. Because of these complexities, it is very difficult and inaccurate to select one or several pseudo-components to represent the original heavy oil for the purpose of kinetic modelling. A combination of theoretical and experimental methods must be considered to develop a suitable kinetic scheme for heavy oil pyrolysis. The approach followed by Tan et al. 

The controlled preparation and characterization of different crystal forms of the same substance has become one of the major issues of modern crystal engineering and solid-state chemistry. Even though the discovery of polymorphs of molecular crystals or of their diverse solvate forms (pseudo-polymorphs) is often serendipitous, crystal polymorphism can, to some extent, be controlled. The existence of more than one packing arrangement for the same molecular or ionic components) could be a major drawback for the purposed bottom-up construction of functional solids. Rather than attempting a thorough review of the subject, this... 

VCl2(Tp)(DMF)], and its partially oxidized analog [VOCl(Tp) (DMF)], cocrystallize in an approximately 1 1 ratio, both components existing in the solid state in a pseudo-octahedral coordination geometry.21 [VOCl(Tp)(Hpz)], also pseudo-octrahedral, has been structurally characterized.22... 

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