High-pressure solubility of 1,4-bis-( n-alkylamino)-9,10-anthraquinones in near- and supercritical carbon dioxide

Abstract

Solubilities of 1,4-bis-( n-alkylamino)-9,10-anthraquinones (with n-alkyl=methyl (AC01), ethyl (AC02), butyl (AC04), pentyl (AC05), octyl (AC08)) in CO 2 were measured using a flow method. The concentrations were determined in the temperature range from 299 to 345 K and at pressures from 7 to 20 MPa. The apparatus mainly consists of a supercritical fluid chromatograph using a diode array spectrophotometer for the detection of the dissolved dyestuff. The solubilities are discussed with respect to the pressure and density of the fluid phase. Intersection points of the concentration versus pressure solubility isotherms are found here for the methyl-derivative and discussed as a density effect. Additionally, the results of the different derivatives are compared and discussed with respect to the chain length of the alkyl-substituent. A maximum of the dyestuff solubility is obtained for the pentyl-derivative.