Measurement and Modeling of the Solubility of Anthracene and Carbazole in Compressed Isobutane

Abstract

The solubilities of anthracene and carbazole in liquid and supercritical isobutane have been experimentally determined in a static view cell, at temperatures from (367 to 418 K) and pressures from (3.2 to 8.6) MPa. The solubilities of anthracene varied from (7.3 to 51.8) mg of solute per gram of isobutane, whereas those of carbazole were from (1.4 to 9.9) mg of solute per gram of isobutane within the experimental range studied. These differences in solute solubilities have been explained attending to the higher vapor pressures of anthracene and its smaller dipole moment (and so stronger affinity to isobutane). The experimental solubilities have been compared to those of these solutes in propane and CO 2 . At similar reduced temperature and pressure conditions, it has been found that solute mole fractions are higher in isobutane than in the other two fluids (3 to 15 times and 160 to 270 times higher than in propane and CO 2 , respectively). Anthracene and carbazole solubilities in isobutane have been modeled by the Peng−Robinson equation of state. Good fit of the experimental results has been obtained (APD values of 6.7 % for anthracene and 9.7 % for carbazole).

Compressed isobutane as a solvent of heavy hydrocarbons

“…Furthermore, to compare the solubilities of these solutes to those of anthracene (PAH) and carbazole (nitrogen PAH), the solubility data of these compounds in isobutane, taken from Ref. , are also presented in Figure . It should be highlighted that results attained from this comparison agree with those obtained at other pressure and temperature conditions .…”

“…The solid solubilities were determined in an experimental apparatus (model R100CW) supplied by Thar Technology (Pittsburgh, PA). It is schematically shown in Figure and has been described in detail elsewhere . Basically, it consists of a 0.1 L cylindrical view cell with two sapphire windows mounted 90° apart.…”

“…The experimental procedure will be only briefly presented since it has been described in detail elsewhere . A solubility experiment starts by placing the solute in the view cell.…”

“…The uncertainties in the experimental solubilities are estimated by an error propagation analysis, as described in detail in Ref. . Tables show that the relative uncertainties are lower than or equal to 0.02 for DBT [i.e., u r ( Y DBT ) = u ( Y DBT )/ Y DBT ≤ 0.02], 0.04 for NPDS, and 0.03 for TTDS.…”

“…Unlike earlier extraction studies with compressed gases, which used CO 2 , in this article we propose the use of high‐pressure isobutane as solvent. Isobutane is investigated because this gas may dissolve polar and heavy hydrocarbons at a greater extent than CO 2 and propane, probably due to its higher polarity and polarizability . Furthermore, isobutane rather than n‐butane should be used in some particular environmental applications since, according to the literature, in the extraction of carbonaceous material from porous matrices, a solvent having a tertiary carbon performs better than one without that atom, assuming that both solvents have the same molecular weight.…”