Mass transfer under distillation of positive, neutral, and negative system in the I.D. 0.3 m column packed with structured packing

Abstract

The distillation of three binary test systems differing in the surface tension gradient along the column, namely: cyclohexane/n-heptane (negative), cyclohexane/toluene (neutral), n-hexane/cyclohexane (positive), has been performed under total reflux in the i.d. 0.3 m distillation column packed with MellapakPlus 452. Y structured packing. Although all constituents are C6 – C7 hydrocarbons with close physical properties in the gas phase, the resulting HETP differ by up to 20 %. Further analysis suggests that system negativity causes the approx. 30 % decrease of the effective interfacial area with respect to positive and neutral systems, which behave comparably. Indeed, observation of the distillation on the inclined plate in the IR spectra shows breakage of the negative system liquid films into rivulets, supporting the result.