TABLE OF CONTENTS To introduce the general ideas, we present first two particularly simple methods for reduction of vapor-liquid equilibria. These are followed by a brief introduction to more accurate, but also mathematically more complex, procedures.
Given five experimental vapor-liquid equilibrium data for the binary system methanol (1) 1, 2-dichloroethane (2) at 50 C, calculate the P ? y ? x diagram at 50 C and predict the P ? y ? x diagram at 60 C.
| Experimental Data at 50 C | ||
|---|---|---|
| 100 x 1 | 100 y 1 | P, bar |
| 30 | 59.1 | 0.6450 |
| 40 | 60.2 | 0.6575 |
| 50 | 61.2 | 0.6665 |
| 70 | 65.7 | 0.6685 |
| 90 | 81.4 | 0.6262 |
solution To interpolate in a thermodynamically consistent manner, we must choose an algebraic expression for the molar excess Gibbs energy. For simplicity, we choose the van Laar equation (See Table 8-3). To evaluate the van Laar constants A ? and B ?, we rearrange the van Laar equation in a linear form [ ]
Constants D and C are found from a plot of x 1 x 2( g E/ RT) ?1 vs. x 1. The intercept at x 1 = 0 gives D ? C, and the intercept at x 1 = 1gives D + C. The molar excess Gibbs energy is calculated from the definition
For the five available experimental points, activity coefficients ? 1 and ? 2 are calculated from...
