Physicochemical concepts

The solvent extraction of coal is, in essence, a mild form of chemical conversion because in addition to the pnrely solvent action, there may also be molecular alterations that are definite and irreversible. Coal-solvent interactions are complex (Szeliga, 1987) but, in more general terms, extraction is usually enhanced by temperature in addition, the presence of hydrogen will significantly alter the molecular changes. 

When coal is heated in a slurrying vehicle, it is liquefied at 400°C-500°C (750°F-930°F). Though the reaction mechanism involving conversion of coal to oil is very complex, it appears that the interaction of coal with solvent at the initial stage of the reactions plays the vital role to determine the sequential conversion of coal substances—first to a pyridine-soluble solid and thereafter to benzene-soluble liquid hydrocarbons and low-boiling products. Thus the isolation and identification of the products of coal-solvent interactions to yield pyridine-soluble matter may provide information regarding the suitability of the coal for liquefaction. 

The rates of the fragmentation reactions in the coal feedstock are rapid and, for the most part, nonreversible (unless combination with other moieties to form coke occurs) and depend on the nature of coals. The microcomponents, as identified by the microscopic examination of coal particles as vitrinite and exinite, are the most reactive materials that undergo rapid fragmentation. The other components—semifusinite and fusinite— produce insignificant amounts of liquid products but may act as nuclei for coke formation, which might be deleterious to ultimate conversion. 

Since the different microcomponents react differently, it would be necessary to separate them as several gravity-cut by a flotation technique and establish their reactivity separately. The reactivity of the as-mined coal (composite sample), along with the reactivity of the microcomponents, would be a valuable parameter. A suitable test method would also provide data for yield and composition of gaseous products and minimum hydrogen requirement that has to be fed in the reactor using solvent as a carrier. The spectroscopic characterization of the extractable matter would provide information helpful in downstream processing of the primary liquefaction products. 

The extractive capabilities of various solvents have been correlated, amongst other phenomena (Given, 1984), with the internal pressure (Pj) of the solvent  

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The technical terms homogeneity and inhomogeneity defined in analytical chemistry must be distinguished from the physicochemical concept of homogeneity and heterogeneity (Danzer and Ehrlich [1984]). Whereas the thermodynamical definition refers to morphology and takes one-phase-or multi-phase states of matter as the criterion, the analytical-chemical definition is based on the concentration function... 

The objective of this chapter is to highlight fundamental chemical and physicochemical aspects of general importance for sewer systems and in-sewer processes. The contents are selected with this in mind, and the focus is on chemical and physicochemical concepts adapted to this purpose. The chapter is written to serve as a solid background for understanding process-related aspects considering the sewer as a reactor. 

GastroPlus [137] and IDEA [138] are absorption-simulation models based on in vitro input data like solubility, Caco-2 permeability and others. They are based on advanced compartmental absorption and transit (ACAT) models in which physicochemical concepts are incorporated. Both approaches were recently compared and are shown to be suitable to predict the rate and extent of human absorption [139]. 

It is important to understand admixture-cement and also admixture- admixture interactions so that optimum use of these materials can be made, admixture-cement incompatibility can be prevented, better troubleshooting of field problems is enabled, and the prediction of concrete properties is made possible. In the following pages some examples of problems that arise from admixture-cement and admixture-admixture interactions are cited, and an outline of the physicochemical concepts involved in the interference with cement hydration and interparticle interactions that limit admixture performance, and cause incompatibility and field problems is presented. 

In the following sections, physicochemical concepts which apply to admixture-cement interactions and the manner in which chemical admixtures can interfere in the cement hydration process and in particle- particle interactions are described. 

Atherton, J.H. (1999) Process Development Physicochemical Concepts. Ox lord Science Publications, Oxford University Press, Oxford, Chapter 8. 

Molecular descriptors may suggest some underlying physicochemical concepts involved. The correlation of Y with a particular X descriptor does not necessarily imply causality it implies only that when X increases, Y may also increase or decrease with it, for whatever reason. 

Based on these studies, the utilization for surfactants as a soil-washing agent appears to be a promising strategy for many future site remediations. Figure 3 illustrates three conceptual systems that will aid the description of the physicochemical concepts of CAD partitioning in the systems of soil and micellar surfactant solution. 

Atherton JH, Carpenter KJ. Process Development—Physicochemical Concepts. Oxford, UK Oxford University Press, 1999. 

Atherton, J. H. and Carpenter, K. J., Process Development Physicochemical Concepts, Oxford... 

In the past, emulsion properties were seen from a physical point of view to involve forces and hydrody-namic motion in the interdrop thin film. Thanks to the physicochemical concepts developed for the enhanced oil-recovery processes, a newer physicochemical approach, based on a molecular description of the interaction between the interfacially adsorbed surfactant and the oil and water phases, is now available and will be emphasized here. 

Structural, Synthetic and Physicochemical Concepts in Aluminophosphate-based Molecular Sieves. Flanigen, E.M. Patton, R.L. Wilson, S.T. Stud. Surf. Sci. Catal., 37(Innovation Zeolite Mater. Sci.), 13-27, 1990. 

The phenomena known as substituent effects are one of the most important issues in chemistry, biochemistry, and related fields. Their influences on chemical/physicochemical properties and pharmaceutical activity of heterocyclic systems are mainly described through the use of the Hammett substituent constants. Only in a few cases have other physicochemical descriptors been used for this purpose. However, even in those cases, their applicability is verified by the comparison of the new correlations with the one obtained by using the classical approach. Among new physicochemical concepts of the substituent effect, the most promising seems to be the cSAR approach (2014JOC(79)7321). 

Focusing on physicochemical concepts that form the basis of understanding colloidal and interfacial phenomena—rather than on experimental methods and techniques-this book is an excellent primer for students and scientists interested in colloidal and interfacial phenomena, their mutual relations and connections, and the fascinating role they play in natural and man-made systems. 

In this chapter, both a set of physicochemical conceptual assumptions used in model simplification and a set of mathematical tools for this purpose are presented. First, we are going to explain physicochemical concepts of simplifications using models of chemical transformations. In this case, the transport processes are considered to be fast, and the models consist of ordinary differential equations (non-steady-state processes) or algebraic equations (steady-state processes). 

In section 2 we have already mentioned that there exists a problem of a physicochemical concept of "phase" for a thin film with thickness less than a certain thickness. Phase is a certain amoimt of substance which has an interface, and at any point of which thermodynamic functions are constants. However, as the thin film thickness reduces, both of its surfaces ap>p)roach each other gradually, and at the certain moment this principle is violated and a thin film no longer corresponds to the "phase" concept. 

The atmospheres of the planets and their satellites in the Solar System have been investigated by Earthbound and space-borne telescope spectroscopy and more directly by a succession of space missions to these planets. Much information has been gathered by the full resources of spectroscopy ranging from the X-ray regirai to that of radiofrequencies and, in space missions, by mass spectroscopy and a host of other analytical instruments. The harvest has been extensive and has provided matter for applications of physicochemical concepts, laws and properties in rationalising the observations. Detailed pictures have been obtained not only of the composition and dynamic characteristics of these atmospheres but also some insight into the compositirMi of planetary interiors. 

The main objective of this first volume of the Detergents series is to provide the reader with the basic physicochemical concepts and relevant understanding of the properties and mechanisms of actions of the entire spectrum of detergent formulation components. This is necessary for the production, formulation, marketing, consumption, and disposal of innovative, safer, and more effective detergent products. 

The new physicochemical concept of resonance will certainly find application to such biological problems as those presented here. 

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