Investigations on the solubilities of some disperse azo dyes in supercritical carbon dioxide

The solubilities of three disperse azo dyes, 4-(N,N-dimethylamino)-4'-nitroazobenzene (D-1), 4-(N,N-diethylamino)4'-nitroazobenzene (D-2) and Parared (D-3) in supercritical carbon dioxide have been measured at different temperatures (308, 318, 328, 338, 348 and 358 K) and in the pressure range of 122-355 bar. The measurements were performed using a simple static method. As evidenced from the experimental results, the solubilities increase with increasing density of supercritical CO2. The solubilities in supercritical CO2 decrease in the order D-2>D-1>D-3, which parallel the order of their relative melting points; the higher the melting point, the lower the solubility. The equilibrium solubility data were correlated using a semiempirical model. The calculated results show satisfactory agreement with the experimental data. (C) 2004 Elsevier Ltd. All rights reserved.