Evaporation Analogies Between Light Hydrocarbons Effect of Molecular Mass of Purge gas

Abstract

The evaporation of benzene, cyclohexane, n-heptane, toluene, 2-xylene, 3-xylene and 4-xylene was studied in H₂, He, N₂ or CO₂ as purge gases for control of the introduced methods of evaluation and the sensitivity limits of TG measurements. I_i as a function of (1−α) and the following equation proved very suitable for a quantitative comparison of 28 independent and different TG measurements and for a very sensitive characterization of the thermal processes, even within an energy level difference of 3 kJ mol⁻¹, in spite of the known great inconsistency in the formal kinetic parameters:

$$\ln A \cong \overline {\left( {1/RT_{i} } \right)} {\kern 1pt} {\kern 1pt} \bar E_{i} {\kern 1pt} - \overline {n\ln \left( {1 - {\alpha }} \right)_{_{i} } } + {\kern 1pt} {\kern 1pt} \overline {\ln \left( {\ln {d\alpha /d}t} \right)_{_{i}}} $$

The purge gases definitely influence the evaporation. The influence on the average vapour pressure is an exponential function of the product of the molecular mass and the boiling temperature.

With regard to the number of factors in the TG measurement, and the great sensitivity of I_i and the above function, it can be supposed that these equations exhibit some multivariate regression character, besides their natural parameter content.

The evaluation methods introduced help to extend the application of TG.