Azeotropes finding

Given the mixture AB, forming minimum or maximum azeotrope, find a suitable entrainer E and feasible separation sequences that can deliver A and B of high purity, at least one operation being distillation. The entrainer may be present already in the mixture, or being added and recycled. 

In some cases we may find it expeditious and convenient to remove an undesired impurity (or even the desired product) azeotropically and then deal with the streams. For example, in the separations of vanillin from close-boiling substances such as p-hydroxybenzaldehyde, azeotropic distillation with dibenzylether is claimed to be useful (Dimian and Kersten, 1997). 

Once in a while, you throw together two liquids and find that you cannot separate part of them. And I don t mean because of poor equipment, or poor technique, or other poor excuses. You may have an azeotrope, a mixture with a constant boiling point. 

A mixture of acetone and chloroform is to be separated into pure products [Hostrup et al. (1999)]. Since they also form an azeotrope, one alternative to satisfy the separation objective is to find a suitable solvent for separation by extractive distillation. This type of problem in product design is usually encountered during the purification or recovery of products, by-products, reactants or removal of undesirable products from the process. Also, it can be noted that failure to find a suitable solvent may result in the discard of the product. Alternatively, a functional chemical product manufacturer may be interested to find, design and develop a new solvent. In this case, the solvent is the chemical product. 

We would like to find a solvent that breaks the azeotrope between acetone-chloroform (or moves the azeotrope point sufficiently to one side to allow separation by distillation) so that high purity acetone and chloroform can be recovered by extractive distillation. The solvent should be more selective to chloroform than acetone. The solvent, acetone and chloroform must form a totally miscible liquid. The solvent must not form azeotrope with either acetone or chloroform. The solvent should be easy to recover and recycle. The solvent should have favorable EH S properties. 

Cost and commercial availabiUty More and more lab suppliers and a few large-scale suppliers offer ionic Uquids. For a more frequent use of these solvents the commercially available variety has to be increased and cost should be reduced. There is good reason that cost reductions will be possible in the near future because at least some of the ionic liquids will potentially find use in very large apphcations besides catalysis. They are discussed for fuel desulfurization, separations, hquefication, gasification and chemical modification of sohd fuels, as electrolytes or in connection with synthesis and apphcation of new materials. Also apphcations such as azeotrope-breaking liquids, thermal fluids or lubricants are under consideration. Because of economy of scale in combination with such apphcations, the price of the solvent will decrease significantly. 

This equation contains the counterion concentration Cj + which depends on the total surfactant concentration. It follows that x would depend on c j+ and hence would vary above the cmc. This contradiction implies that azeotrope micellization cannot occur if = J3(x). Of course, if c c, the C + would be constant and azeotropy can again occur. If d fdx = 0, azeotropy can be also possible. For ySj = / 2 = 0.7, Cj = 0, c /cj = 3.0, and w(x) = A + B ( 2x-l), which is the Redlich-Kbter expansion (12), with A = -3 and B = 0, one finds from Equation 21 that 0.8113. No value of Qj can be calculated if = 0.7, / 2 = 0.3, and / (x) = iX + /32(1 x). Figures 1 and 2 illustrate this point showing monomer and micelle concentrations (or inventories) for a = 0.8113. In the ionic/ionic case, the micelle composition x and the ratio Cj/c2 are constant above the cmc. In the ionic/nonionic case (Figure 2) the micelle composition varies with total surfactant concentration. Osborne-Lee and Schechter (22) have found evidence of azeotrope micellization for... 

Another field in which azeotropic distillation is finding application is in the separation of the complex mixtures of organic acids, aldehydes, ketones, and alcohols produced by the Hydrocol process. As petroleum stocks are utilized more and more for the production of chemicals, processing of azeotropic mixtures and the use of azeotropic separations should assume increasingly greater importance. 

Salts soluble in ethanol as well as water have been found to break the azeotrope, while salts which are very soluble in water and only slightly soluble in the alcohol move the azeotrope to richer ethanol regions without breaking it. Furthermore, the salts or compounds which dissolve more in one component are found to raise the volatility of the other component. This finding is in conformity with that of previous workers in the field (8,11,12,13,18,19,23,24,27). In this work the equilibrium diagrams were obtained at atmospheric pressure (690-700 mmHg), and under saturation conditions. 

One can also recognize that application of sufficient pressure (above the equilibrium osmotic pressure n) to the right-hand chamber in (7.67) must cause the solvent flow to reverse, resulting in extrusion of pure solvent from solution. This is the phenomenon of reverse osmosis, an important industrial process for water desalination. Reverse osmosis is also used for other purification processes, such as removal of H20 from ethanol beyond the azeotropic limit of distillation (Section 7.3.4). Reverse osmosis also finds numerous applications in wastewater treatment, solvent recovery, and pollution control processes. 

Alcoholates of nonreducing saccharides (soluble or insoluble) and of saccharide derivatives may also be prepared by the method of Wolfram and coworkers.92-9 A mixture of the carbohydrate and sodium hydroxide in 1-butanol is refluxed, preferably under a nitrogen atmosphere, find all of the water of formation is removed by concurrent azeotropic distillation. This method is preferred when no trace of hydroxide adduct or water is desired in the Anal product. Butoxide ion is a possible contaminant, how-... 

It is known that upon distillation of the reaction mixture of the reductive amination of acetone diisopropylamine and isopropanol forms a binary azeotrope making the separation extremely difficult. Therefore, the goal of this work was to find the modes and ways for the suppression of the formation of isopropanol via selec tive poisoning the skeletal nickel catalyst by a second metal such as tin. 

Although, the reaction is normally carried out in boiling toluene, other solvents able to form an azeotrope with water, such as benzene or xylenes, can also be used. d Cyclohexanone is the most common oxidant because it is cheap, easy to remove and possesses a strong oxidizing power. JV-methyl-4-piperidone is finding an increased... 

The separation problem is defined as finding at least one feasible separation sequence for breaking a binary azeotrope AB by means of an entrainer C using only homogeneous distillation. The solution of this problem depends greatly on the existence of distillation boundaries. There are two possibilities ... 

When D < 0, only one azeotrope exists in the system as in the case of the terminal model. When D > 0, the number n = 0,1,2, 3 of the azeotropic compositions coincides with the number of the sign changes in the sequence A, B, C, D of Eq. (5.5) coefficients. This procedure of finding the number n is equivalent to that proposed in Ref. [14] but is much more convenient for practical applications. 

Any trajectory can end when p - I at a stationary point (SP), in which all the right-hand parts of equations (5.2) equal zero. In the case of the terminal model (2.8) all such SPs are those solutions of the non-linear set of the algebraic equations (4.13) which have a physical meaning. Inside m-simplex one can find no more than one SP, the location of which is determined by the solution of the linear equations (4.14). In addition to such an inner azeotrope of the m-simplex, azeotropes can also exist on its boundaries which are n-simplexes (2 S n m - 1). For each of these boundary azeotropes (m — n) components of vector X are equal to zero, so it is found to be an inner azeotrope in the system of the rest n monomers. Moreover, the equations (4.13) always have m solutions x( = 8is (where 8js is the Cronecker Delta-symbol which is equal to 1 when i = s and to 0 when i =(= s) corresponding to each of the homopolymers of the monomers Ms (s = 1,. ..,m). Such solutions together with all azeotropes both inside m-simplex and on its boundaries form a complete set of SPs of the dynamic system (5.2). 

In this case according to Fig. 3 a phase space is found to be a tetrahedron, inside which an azeotrope of one of the eight types, presented in Fig. 8, may be located. In order to know which of them is to be realized one should find the signs of coefficients at, a2, a3 of characteristic equation (5.11) and also their combinations ... 

The general formulae (5.1), (5.3), and (5.7) are still valid under the transition to the more complicated models described in Sect. 2. In the case of the penultimate model it concerns also the dynamic Eqs. (5.2) into which now one should substitute the dependence j (i) obtained after the solution of the problem of the calculation of the stationary vector tE(x) of the Markov chain corresponding to this model. Substituting the function X1(x1) obtained via the above procedure (see Sect. 3.1) into Eq. (5.2) for the binary copolymerization we can find its explicit solution expressed through the elementary functions. However, this solution is rather cumbersome and has no practical importance. It is not needed even for the classification of the dynamic behavior of the systems, which can be carried out only via analysis of Eq. (5.5) by determining the number n = 0,1,2, 3 of the inner azeotropes in the 2-simplex [14], The complete set of phase portraits of the binary... 

In the category of physical continuation methods are the thermodynamic homotopies of Vickery and Taylor [AIChE J., 32, 547 (1986)] and a related method due to Frantz and Van Brunt (AIChE National Meeting, Miami Beach, 1986). Thermodynamic continuation has also been used to find azeotropes in multicomponent systems by Fid-kowski et al. [Comput. Chem. Engng., 17, 1141 (1993)]. Parametric continuation methods may be considered to be physical continuation methods. The reflux ratio or bottoms flow rate has been used in parametric solutions of the MESH equations [Jelinek et al., Chem. Eng. Sd.,28, 1555(1973)]. 

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