Toluene-benzene mixtures

Example 8-5 Boiling Point Curve and Equilibriiun Diagram for Benzene-Toluene Mixture... 

Figure 8-19. X-y diagram for benzene in benzene-toluene mixture at 760 mm Hg total pressure, Example 8-5.

Figure 8-20. Boiling point diagram for benzene-toluene mixture using K values, total pressure 760 mm Hg for Example 8-6.

A benzene-toluene mixture is to be separated in a tower packed with 1-in. fieri saddles. The feed is 55.2 mol% (liquid feed, saturated), and an overhead of 90 mol% benzene, and bottoms of not more than 24 mol% benzene is desired. Using the data of Ref. 51 plotted in Figure 9-98, determine the number of transfer units in the rectifying and stripping sections using a reflux ratio (reflux to product, L/B) = 1.35. 

Prepare a benzene-toluene mixture by placing 0.05 mL of each liquid in a 25 mL graduated flask and making up to the mark with methanol. Take 1.5 mL of this solution, place in a lOmL graduated flask and dilute to the mark with methanol this solution contains benzene at the same concentration as solution 5, and toluene at the same concentration as solution 5. Measure the absorbances of this solution at the two wavelengths selected for the Beer s Law plots of both benzene and toluene. Then use the procedure detailed in Section 17.48 to evaluate the composition of the solution and compare the result with that calculated from the amounts of benzene and toluene taken. 

Mixtures of isomers, such as o-, m- and / -xylene mixtures, and adjacent members of homologous series, such as n-hexane-n-heptane and benzene-toluene mixtures, give close to ideal liquid-phase behavior. For this case, yt = 1, and Equation 4.28 simplifies to ... 

The following values represent the equilibrium conditions in terms of mole fraction of benzene in benzene-toluene mixtures at their boiling-point ... 

The reduction in the required number of plates as R is increased beyond Rm will tend to reduce the cost of the column. For a column separating a benzene-toluene mixture, for example, where Xf = 0.79, xd = 0.99 and xw = 0.01, the numbers of theoretical plates as given by the McCabe-Thiele method for various values of R are given as follows. The minimum reflux ratio for this case is 0.81. 

To understand how the diagram works, let s imagine starting with the 50 50 benzene/toluene mixture and heating it to its boiling point (92.2°C on the diagram). The lower curve represents the liquid composition (50 50), but the upper curve represents the vapor composition (approximately 71 29 at 92.2°C). The two points are connected by a short horizontal line called a tie line to indicate that the... 

Sarca and Laali199 have used triflic acid in butylmethylimidazolium hexafluor-ophosphate BMIM][PF6 ionic liquid for the benzylation of various arenes with benzyl alcohol [Eq. (5.76)]. When compared with Yb(OTf)3, triflic acid proved to be a better catalyst showing higher selectivity (less dibenzyl ether byproduct) by exhibiting similar activity (typically complete conversion). Of the isomeric products, para isomers dominate. Experimental observations indicate that dibenzyl ether originates from less complete protonation of benzyl alcohol and, consequently, serves as a competing nucleophile. Both substrate selectivity (kT/kB) and positional selectivity (ortho/para ratio) found in competitive benzylation with a benzene-toluene mixture (1 1 molar ratio) are similar to those determined in earlier studies, indicating that the nature of the electrophile is not affected in the ionic liquid. 

Table 5.16. Adamantylation of Benzene-Toluene Mixture with 1-Haloadamantanes in the Presence of B(OTf)3 ... 

Laali et al.234 have developed a method to the highly selective pura-adamantylation of arenes (toluene, ethylbenzene, anisole) with haloadamantanes (1-chloro- and 1-bromoadamantane, l-bromo-3,5,7-trimethyladamantane) and 1-adamantanol promoted by triflic acid in butylmethylimidazolium triflate [BMIM][OTf] ionic liquid. In contrast to reactions mn in 1,2-dichloroethane, little or no adamantane byproduct was detected in [BMIM][OTf. Furthermore, no isomerization of para-tolyladamantane was observed supporting the intramolecular nature of the formation of meta isomers. In competitive experiments with benzene-toluene mixture (1 1 molar ratio), high substrate selectivities were found (kT/kB = 16-17) irrespective of the alkylating agent. This is in sharp contrast to values about unity measured in 1,2-dichloroethane. 

Assuming the relative volatility of a benzene-toluene mixture is 2.90, the vapor-liquid equilibrium compositions can be calculated as shown in Table 5.1. The resultant curve is plotted in Fig. 5.1a. 

Example 5.1 A benzene-toluene mixture consists of 50 moles of benzene and 50 moles of toluene. It is desired to reduca the residual benzene concentration to 0.1 mole fraction. Calculate the overall material balance for this distillation. 

The by-product benzene plus toluene and the fuel gas rates are calculated, from Eqs. (2) and (3), to be 5.2 and 3.6 lb/h, respectively. The raw materials and product values can be compared again. The benzene-toluene mixture is valued at 0.10/lb and the fuel gas at 0.18/lb (both based on heating value) condensed water has no value. The value of the feeds, ethylbenzene and steam, is 33.54/104 lb of styrene. The value of the product plus the by-products and fuel gas is 44.84/104 lb of styrene. The value of the outputs still exceeds that of the inputs, but the margin has narrowed. 

Vapor-liquid equihbrium data for benzene-toluene mixtures at atmospheric pressure are presented in Fig. H-g,... 

Equilibrium diagram for benzene-toluene mixtures at total pressure of 760 mm Hg (McCabe-Thiele method for determining number of theoretical plates). 

Fig. 1-16. Vapor-liquid composition curve lor benzene-toluene mixtures.

Fig. 1-25. Effect of repeated distillations of a benzene-toluene mixture.

Figure 8-21. x-y diagram for benzene In benzene-toluene mixture, 760 mmHg total pressure, based on K-values, Example 8-6. 

Several choices are available in defining the standard state of the solute. If the solute is a liquid which is miscible with the solvent (as, for example, in a benzene-toluene mixture), then the standard state is again the pure liquid. Several different standard states have been used for solutions of solutes of limited solubility. In developing a relationship between drug activity and thermodynamic activity, the pure substance has been used as the standard state. The activity of the dmg in solution was then taken to be the ratio of its concentration to its saturation solubility. The use of a pure substance as the standard state is of course of limited value since a different state is used for each compound. A more feasible approach is to use the infinitely dilute solution of the compound as the reference state. Since the activity equals the concentration in such solutions, however, it is not equal to unity as it should be for a standard state. This difficulty is overcome by defining the standard state as a hypothetical solution of unit concentration possessing, at the same time, the properties of an infinitely dilute solution. Some workers have chosen to... 

Water and snow Extraction of organic mercury immediately after sampling addition of organic mercury standards addition of KB and a benzene/ toluene mixture isolation and volume reduction of organic layer GC/AAS 4 ng (dimethyl mercury) 5 ng (ethyl mercury) No data Paudyn and Van Loon 1986... 

The benzene-toluene mixture of Example 6.1 is to be separated into approximately 50 kmol/h distillate and 50 kmol/h bottoms products. The column is to be operated at a reflux ratio of one. Determine the effect of the number of stages and feed location on the purity of the products. 

It is required to separate the benzene-toluene mixture of Example 6.1 into a benzene-rich distillate with 0.80 mole fraction benzene and a toluene-rich bottoms with 0.05 mole fraction benzene. The separation is to be made using a distillation column with 15 theoretical stages that include a partial condenser and a partial reboiler. Calculate the reflux ratio required to achieve the specified separation and determine the optimum feed location. What effect would lowering the number of stages to ten have on the reflux ratio and the optimum feed location ... 

Eollowing are two examples (16.1 and 16.2) of a distillation column that demonstrate the effect of applying different pairing strategies. In both examples the control loops for the column pressure and the liquid levels in the condenser accumulator and the column bottom are determined independently based on practical considerations. Thus, the column pressure is controlled by various techniques that may involve the condenser coolant rate, and the liquid levels are controlled by the product flow rates. What remains to be decided is how to pair the distillate and bottoms compositions with the reflux rate and the reboiler heat duty. The same distillation column is used in both examples, having a total condenser and a reboiler, one feed and two products. The column is designed to separate a benzene-toluene mixture into benzene and toluene products with specified purities. 

We see, from the results (independent of which group assignment is used for toluene) that the benzene-toluene mixture, which contains chemically similar species, is virtually an ideal solution. The water-toluene and water-benzene mixtures consist of very dissimilar species and, therefore, the mixtures are very nonideal. Ethanol contains a hydrocarbon end and a polar -OH end. Consequently, it is almost equally compatible (or incompatible) with both water and hydrocarbon solvents and forms only moderately nonideal mixtures with both this behavior is predicted above. 

The case of benzene-toluene mixture discussed above is an example of a solution which follows Raoult s law sufficiently closely. Solutions which obey Raoult s law are called ideal or perfect solutions. According to this law, the total vapour pressure, P, of an ideal solution gets expressed by the relation ... 

Example 13-4 This example is based on an example presented by Bolles and Fair.3 Determine the flood velocity, the column diameter, the pressure drop per foot of packing, HL, HG, and HOG for the separation of a benzene-toluene mixture in a packed column. The column conditions to be used for design purposes are as follows ... 

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