Acetone-methanol system

We will postpone a detailed discussion of the THF-water system until Chapter 6 where quantitative comparison of the steady-state designs and dynamic controllability of heat-integrated and nonheat-integrated systems are presented. 

Knapp and Doherty studied heat-integration of binary homogeneous azeotropic systems using extractive distillation methods. One of their examples considered the acetone-methanol system with water as the solvent. They did not consider pressure-swing distillation, nor did they consider dynamics and control. 

The minimum reflux ratios are found with 103 stages to be 2.3 and 2.6 in the low- and high-pressure columns, respectively. The number of stages required for reflux ratios about 1.2 times these minima are 52 in the low-pressure column and 62 in the high-pressure 

The first eolumn in Table 5.1 gives design parameters and economic data for this pressure-swing distillation system. Column diameters are found using Aspen Tray Sizing. 

Energy cost is assumed to be 4.7 per million kJ, and a payback period of three years is used to calculate annual capital cost. The total annual cost (TAC) of this system is 4,520,000 per year. 

---

When there is significant random error in all the variables, as in this example, the maximum-likelihood method can lead to better parameter estimates than those obtained by other methods. When Barker s method was used to estimate the van Laar parameters for the acetone-methanol system from these data, it was estimated that = 0.960 and A j = 0.633, compared with A 2 0.857 and A2- = 0.681 using the method of maximum likelihood. Barker s method uses only the P-T-x data and assumes that the T and x measurements are error free. 

FIG. 13-72 Effect of solvent concentration on activity coefficients for acetone-methanol system, (a) water solvent, (h) MIPK solvent. 

FIG. 13-73 Residue curve maps for acetone-methanol systems, (a) With water, (h) With MIPK. 

FIG. 13-75 Number of theoretical stages versus solvent-to-feed ratio for extractive distillation, a) Close-boiling vinyl acetate-etbyl acetate system with phenol solvent, (h) A2eotropic acetone-methanol system with water solvent. 

The classical solvent precipitation fractionation technique provides reproducible fractionations for determining molecular weight distributions of CTPB and almost 100% recovery of the sample from the column. A solvent-nonsolvent combination which has been used effectively is the toluene—acetone-methanol system, where acetone and methanol are used as the nonsolvents. The precipitating fractions are required to stand approximately 24 hours to ensure complete separation. Each fraction is vacuum stripped of solvent at approximately 30 °C., and the molecular weight of each fraction is then determined by either VPO or intrinsic viscosity. 

In any event, it can be concluded that in acetone there are strong associations between bromosuccinic acid and lithium bromide ions. The largest concentration of bromosuccinic acid studied (Series IV) is approximately equal to the lowest concentration studied for the acetone-water and acetone-methanol systems. As expected, the data show the association with the acid to be much greater than with either the methanol or the water. From the K and a values it is evident that the association between the salt and dimethyl bromosuccinate is much less than the association of the salt with bromosuccinic acid but greater than the salt-acetone association. In view of this, it is concluded that the association between the bromide ion and the second solvent accounts for the change in K. Knowledge of the precise nature of the association will have to await further investigations. 

The Porter equation is the simplest realistic expression for gE- It is appropriste for "symmetrical binary mixtures shewing small deviations from ideality, for example, the acetone-methanol system depicted in Fig. 1.4-1,... 

Knapp and Doherty present the economic optimum design of an acetone-methanol separation using water as the extractive solvent. The design used in this chapter is based on their work. Kossack et al. presented a systematic synthesis framework for extractive distillation systems and the acetone-methanol system was considered. 

An informative paper by Kossack et al. discusses in detail the steady-state economic design issues and presents several examples that use a variety of solvents for the separation of acetone and methanol. Some solvents drive the acetone overhead in the extractive column, while others drive the methanol overhead in the extractive column. The authors discuss the effect of solvent selection on issues such as selectivity, capacity, and boiling point. In this section we extend this work to compare the dynamic performance of the acetone-methanol system with different solvents. 

Chlorobenzene has a different effect on the acetone-methanol system than water or DMSO. In both of the previous two solvent systems, acetone is driven overhead in the extractive column. Methanol is captured by the solvent and later separated in the solvent-recovery methanol column. In the chlorobenzene system, methanol is driven overhead in the extractive column. Acetone is captured by the solvent and later separated in the solvent-recovery acetone column. Since acetone is lighter than methanol, the solvent must fight against the... 

---