Critical Temperatures and Pressures of Straight-Chain Saturated Dicarboxylic Acids (C₄ to C₁₄)

Abstract

The critical temperatures and pressures of nine saturated straight-chain dicarboxylic acids HOOC(CH2) n COOH with n = 2, 3, 4, 5, 6, 7, 8, 10, and 12 have been measured. All of the acids investigated are thermally unstable at their critical points. The method of pulse heating of a wire probe immersed in the liquid under study has been used. Residence times are from (0.01 to 1) ms. The experimental critical properties of dicarboxylic acids have been compared with the values calculated by the group-contribution methods of Ambrose, Joback, and Reid, Constantinou and Gani, and Marrero and Gani.

Liquid Heat Capacity Measurements of the Linear Dicarboxylic Acid Family via Modulated Differential Scanning Calorimetry

“…This is likely due to the high critical temperatures of the dicarboxylic acid family. The critical temperatures of the studied chemicals range from 841 to 849 K. 12 For reference, the critical temperatures of dodecane and decanoic acid (shown in Figure 4) are 658 and 722 K, respectively. Because of this difference in critical temperatures, the dicarboxylic experimental reduced temperatures are lower than that of the n-alkanes and carboxylic acids of similar molecular weights.…”

“…This is likely due to the high critical temperatures of the dicarboxylic acid family. The critical temperatures of the studied chemicals range from 841 to 849 K . For reference, the critical temperatures of dodecane and decanoic acid (shown in Figure ) are 658 and 722 K, respectively.…”

Critical Temperatures and Pressures of 12 Phthalates Using the Pulse-Heating Method

“…The true critical constants of an unstable substance are determined in this case by extrapolating the dependencies p c ( t *) and T c ( t *) to t * = 0. The procedure of extrapolation was given in detail previously . To use the procedure, it is necessary to know the kinetic parameters of the reaction of decomposition: the order of reaction m , the activation energy E , and the preexponential factor B , as well as the derivatives α = (d T c /d x p ) c and β = (d p c /d x p ) c that characterize the critical curve of the system (the substance under study + products of decomposition) near the critical point of the pure substance.…”

“…However, the parameters α and β are unknown. They and the critical constants of a pure substance T c ( t * = 0) and p c ( t * = 0) were calculated by processing the experimental data using the least-squares method and the formulas given in ref . The solid lines in Figure are the result of the calculation.…”

Critical Pressures and Temperatures of n-Diaminoalkanes (C2 to C12)

“…Uncertainties. The uncertainties of the critical constants measured by the pulse-heating method were discussed in detail in our previous papers. − We estimate the uncertainties for diamonoalkanes at 0.03 p c and 0.01 T c , where T c is the absolute temperature. It corresponds to from (± 0.20 to ± 0.06) MPa for the critical pressure and from (± 6 to ± 8) K for the critical temperature (see Tables and ).…”