Enhanced Solubility of Oxygen and Carbon Monoxide in CO₂-Expanded Liquids

Abstract

CO 2 -expanded liquids are attractive solvent mixtures for many reactions since they have the potential to be designed to dissolve liquid and gaseous reactants, as well as catalysts, can have improved mass transfer compared to traditional liquid-phase reactions, can reduce the amount of volatile organics solvent necessary, and can ameliorate safety concerns. Of primary importance in evaluating CO 2 -expanded liquids for reactions involving permanent gases is the solubility of those gases in the liquids in the presence of CO 2 . Here, we report the solubility of O 2 and CO in CO 2 -expanded acetonitrile, acetone, and methanol at temperatures between 25 and 40 °C and pressures to 90 bar. The solubility of O 2 and CO in the CO 2 -expanded liquids is enhanced over the solubility in the absence of CO 2 at the same O 2 or CO fugacity. However, in no case in the mixed gas system did the O 2 or CO solubility substantially exceed what one could achieve with the pure O 2 or pure CO at the same total pressure. Thus, the enhancement of the solubility of O 2 and CO by CO 2 is relatively modest under the conditions investigated. Most importantly, we found that the Peng-Robinson equation of state, using only binary interaction parameters fit to binary data, was quite successful in predicting the phase behavior of the ternary systems.

Performances of Pd Nanoparticles on Different Supports in the Direct Synthesis of H2O2 in CO2-Expanded Methanol

“…We also observed a promotion effect by using CO 2 -expanded methanol with respect to methanol alone in the direct synthesis of H 2 O 2 Top Catal (2011) 54:718-728 719 [13][14][15]. The use of CO 2 -expanded methanol allows enhancing the solubility of O 2 and H 2 [48,49]. It is possible to define an enhancement factor (EF) as the ratio of the solubility of O 2 or H 2 in the liquid phase of the ternary mixture to the solubility of pure O 2 or H 2 in the solvent at the same O 2 or H 2 fugacity and temperature.…”

“…It is possible to define an enhancement factor (EF) as the ratio of the solubility of O 2 or H 2 in the liquid phase of the ternary mixture to the solubility of pure O 2 or H 2 in the solvent at the same O 2 or H 2 fugacity and temperature. At 40°C, the EF for O 2 for a CO 2 -O 2 -Methanol increases from 0.98 (at about 15 bar) to 1.27 (at about 53 bar) [48]. At the same temperature and analogous gas phase composition, the EF for H 2 remains instead nearly constant, being 1.43 at about 25 bar and 1.48 at about 90 bar [49].…”

Heterogeneous Catalysis in Supercritical Media: 1. Carbon Dioxide

“…In the former case, the properties of the supercritical solvent are made to approach those of an organic solvent by adding an organic substance. In the latter case, dissolution of, for instance, CO 2 in the organic liquid increases the liquid's capacity of dissolving gases and the diffusion rates rise (e.g., [8,9]). This way, the properties of the liquid phase approach those of supercritical fluids.…”

The Catalytic Efficacy of Co(salen)(AL) in O2 Oxidation Reactions in CO2-Expanded Solvent Media: Axial Ligand Dependence and Substrate Selectivity

“…The use of CO 2 -expanded solvents (CXLs) builds on previous studies in these labs that have established CXLs as optimal media for certain O 2 oxidations, including those of phenols with cobalt oxygen carriers [6a]. Improved oxygen solubility [7], tunable properties, such as solubilities of solids, diffusivity, and polarity of the reaction medium, and the wide range of suitable organic solvents that can be partnered with CO 2 [8], make CXLs an ideal choice for reactions of this kind. The enhanced O 2 availability in CXLs permits the evaluation of intrinsic catalyst activities under conditions wherein O 2 starvation is either eliminated or significantly mitigated.…”