Immiscible mixture

Catalyst recovery is a major operational problem because rhodium is a cosdy noble metal and every trace must be recovered for an economic process. Several methods have been patented (44—46). The catalyst is often reactivated by heating in the presence of an alcohol. In another technique, water is added to the homogeneous catalyst solution so that the rhodium compounds precipitate. Another way to separate rhodium involves a two-phase Hquid such as the immiscible mixture of octane or cyclohexane and aliphatic alcohols having 4—8 carbon atoms. In a typical instance, the carbonylation reactor is operated so the desired products and other low boiling materials are flash-distilled. The reacting mixture itself may be boiled, or a sidestream can be distilled, returning the heavy ends to the reactor. In either case, the heavier materials tend to accumulate. A part of these materials is separated, then concentrated to leave only the heaviest residues, and treated with the immiscible Hquid pair. The rhodium precipitates and is taken up in anhydride for recycling. 

If two immiscible liquids A and B (i.e., possessing very different 8 values) form two layers when brought together, and an elastomer of similar 6 to A is completely immersed in the (denser) B layer (schematically in Eigure 23.5), nevertheless, the elastomer will evenmaUy swell as if immersed completely in A. This arises because each liquid of an immiscible mixture stiU dissolves a minute amount of the other. At equilibrium, the chemical potential p of A will be the same, whether as pure liquid, dissolved in B, or dissolved in the elastomer. At the same temperature, the same p would apply for the elastomer immersed directly in A. However, the kinetics of absorption will be different, being much slower than... 

The basic model has already been extended to treat more complex phenomena such as phase separating and immiscible mixtures. These developments are still at an early stage, both in terms of the theoretical underpinnings of the models and the applications that can be considered. Further research along such lines will provide even more powerful mesoscopic simulation tools for the study of complex systems. 

Range of copolymer compositions in a polymer mixture, at least one component substance of which is a copolymer, that gives miscibility over a range of temperatures and pressures. Note 1 Outside the miscibility window immiscible mixtures are formed. 

One convenient way of measuring the hydrophobicity of a molecule is to measure its partition between the organic and aqueous phases when it is shaken with an immiscible mixture of an organic solvent, often n-octanol, and water. 

Abstract We formulate the balance principles for an immiscible mixture of continua with micro structure in the broadest sense for include, e.g., phenomena of diffusion, adsorption and chemical reactions. After we consider the flow of a fluid/adsorbate mixture through big pores of an elastic solid skeleton and propose suitable constitutive equations to study the coupling of adsorption and diffusion under isothermal conditions. 

Keywords Immiscible mixtures, continua with microstructure, diffusion in porous and... 

Therefore this work concerns the formulation of a proposal for the thermochemistry of an immiscible mixture of reacting materials with microstructure in presence of diffusion a new form of the integral balance of moment of momentum appears in the theory, in which the presence of the microstructure is taken into account. Moreover, the density fields can no longer be regarded as determined by the deformation fields because chemical reactions are present,... 

The hypothesis that the constituents of the mixture have a Lagrangian microstructure (in the sense of Capriz [3]) means that each material element of a single body reveals a microscopic geometric order at a closer look then it is there assigned a measure Vi(x) of the peculiar microstructure, read on a manifold Mi of finite dimension rnp e.g., the space of symmetric tensor in the theory of solids with large pores or the interval [0, v) of real number, with v tensor order parameter u%. 

We assume that the fluid component and the adsorbate in the fluid phase, present in a very low concentration, have the same kinematics given by the common velocity field Vf, so that there is no flux of molecular diffusion in the fluids. Thus we can reduce to consider an atypical two-phase immiscible mixture of a solid with big pores, of subscript s, and a particular bi-component fluid, of subscript / (see 8.4 of [11]). 

We propose the balance principles for an immiscible mixture of continua with microstructure in presence of phenomena of chemical reactions, adsorption and diffusion by generalizing previous multiphase mixture [9] and use a new formulation for the balance of rotational momentum. New terms are also included in the energy equations corresponding to work done by respective terms in the micromomentum balances. 

Giovine, P. (2003) A Continuum Theory of Soils Viewed as Peculiar Immiscible Mixtures. Mathematical and computer modelling 37, 525-532... 

Consequently, it can be concluded for the mixtures of LLL-MMM, LLL-PPP, LLL-SSS, MMM-PPP, and PPP-SSS that the TAG binary mixtures are miscible in metastable polymorphs of a and p forms when the difference in the number of carbon atoms of the fatty acid moieties. An, equals 2, whereas immiscible mixtures are found in all polymorphic forms when An is larger than 2. Results obtained for these mixture systems may indicate a relationship between polymorphism and phase behavior of the binary mixtures of the saturated-acid TAGs in such a way that rotational freedom of hydrocarbon chains and entropy of methyl-end stacking are crucial factors determining the polymorph-dependent phase behavior. 

It can be seen from that figure that the -transitions of the two component materials are separated by about 20 degrees. If the blend is an immiscible mixture, it is expected that there would be two transitions observed which are 20 degrees apart, or, at least, it is expected that a single significantly broadened transition would be observed. 

Another type of dependence of effective interfacial width wD on film thickness D was observed [130] for immiscible mixture of deuterated polystyrene (dPS) and poly(methyl methacrylate) (PMMA) (at T TC) an increase, from wd=1.8(4) nm for a dPS layer thickness D=6 nm to wd(D=100 nm)=2.5(4) nm, follows the logarithmic dependence wD°clnD (intrinsic interfacial width w= 1.5 nm). This may reflect [6,224] long range forces acting from the external interfaces on the internal interface Ie(x,y). On the contrary, the relation wd D1/2 found for random olefines [121] corresponds [6,224] to short range forces. We note also that capillary waves in dPS/PMMA system were observed [130] already for the thickness-to-intrinsic width ratio D/w<85 ... 

There are two further possibilities for preventing segregation in complex immiscible mixtures. The first one Implies crosslinking reaction of the dispersed phase, associated with interfacial bonding and leads to the well-known dynamic vulcanisation (17). The second one results from mechanical interlocking of the phases which are created in interpenetrated polymer networks (IPN). 

Determination of Activity Coefficients from Measured LLE Data for an Essentially Immiscible Mixture... 

The types of diverters vary extensively, from mechanical systems to chemical diverting techniques. The latest generation of diversion techniques involves pumping an immiscible mixture of two fluids such as emulsions or foams. Emulsions have not been used as extensively as foams as a diversion technique, because they are more difficult to clean up in low-pressured reservoirs. Foams, however, with similar properties to emulsions, tend to clean up very easily. 

When fluids can seep through pores, interacting mechanically with the solid skeleton, the material is composed of more than one constituent thus we need to use a mixture theory in which we could clearly make out each part filled by different constituents on a scale which is rather large in comparison with molecular dimensions so we put forward a new continuum theory of an immiscible mixture consisting both of a continuum with ellipsoidal microstructure (the porous elastic solid) and of two classical media (see, also, the conservative case examined by Giovine (2000)). In accordance with Biot (1956), we consider virtual mass effects due to diffusion we also introduce the microinertia associated with the rates of change of the constituents local densities, as well as the one due to the deformation of the pores close to their boundaries. 

On the right-hand side of the same equations we recognize usual quantities introduced in (microstructured) immiscible mixtures (see Passman Batra (1984) and Giovine (1990, 2000)) pYj and p,C are the densities per unit volume of microstructural body forces for the fluid, or adsorbate, and solid phase, respectively Sj is the microstress vector and 2 the third-order microstress tensor, which is symmetric in the first two indices and normally related to the boundary microtractions, even if, in some cases, it could express weakly non-local internal effects dy and represent the growth of micromomenta which permits the interchange between phases. 

In this work we propose an immiscible mixtures consisting of a continuum with ellipsoidal microstructure (the porous elastic solid) and of two classical fluids (a fluid carrier and an adsorbate) to... 

Our model about the porous matrix includes, as a particular case, previous void theories which does not anticipate any size effects in torsion on the other hand the virtual inertia considered in our immiscible mixture allows the presence of an inviscid drag term depending on changes of the radius of the material elements, other than on the relative velocities, a term which is usually absent in previous theories (see Giovine (1990)). 

PET and PEN form immiscible mixtures. Improved miscibility can be obtained by performing a transesterification reaction between both ingredients to produce copolyesters, which act as compatibilizers in the interface of the blend. This reaction, when carried out in a melt extruder, depends strongly on temperature and residence time, in particular, within 50-80 wt% PEN content [63]. Physical and mechanical properties of the resulting blend depend on the degree of transesterification and also on the resulting copolymer... 

To make an analogy with metals polymer blends are sometimes referred to as polymer alloys. Thus the term alloy has been used to describe miscible or immiscible mixtures of polymers that are usually blended as melts. Another definition often used for a polymer alloy is that it is an immiscible PB having a modified interface and/or morphology. The general relationship between blends and alloys is shown in Figure 4.39. The term compatibilization in the figure refers to a process of modification of interfadal properties (discussed later) of an immiscible PB, leading to the creation of a polymer alloy. 

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