Influence of Matrix Composition on the Solubility of Hydroxybenzoic Acid Isomers in Supercritical Carbon Dioxide

Partitioning behavior of organic contaminants in carbon storage environments: a critical review

Carbon capture and storage is a promising strategy for mitigating the CO(2) contribution to global climate change. The large scale implementation of the technology mandates better understanding of the risks associated with CO(2) injection into geologic formations and the subsequent interactions with groundwater resources. The injected supercritical CO(2) (sc-CO(2)) is a nonpolar solvent that can potentially mobilize organic compounds that exist at residual saturation in the formation. Here, we review the partitioning behavior of selected organic compounds typically found in depleted oil reservoirs in the residual oil-brine-sc-CO(2) system under carbon storage conditions. The solubility of pure phase organic compounds in sc-CO(2) and partitioning of organic compounds between water and sc-CO(2) follow trends predicted based on thermodynamics. Compounds with high volatility and low aqueous solubility have the highest potential to partition to sc-CO(2). The partitioning of low volatility compounds to sc-CO(2) can be enhanced by cosolvency due to the presence of higher volatility compounds in the sc-CO(2). The effect of temperature, pressure, salinity, pH, and dissolution of water molecules into sc-CO(2) on the partitioning behavior of organic compounds in the residual oil-brine-sc-CO(2) system is discussed. Data gaps and research needs for models to predict the partitioning of organic compounds in brines and from complex mixtures of oils are presented. Models need to be able to better incorporate the effect of salinity and cosolvency, which will require more experimental data from key classes of organic compounds.

Separation processes for organic molecules using SCF Technologies

Supercritical fluids have been applied for many years for the separation of solutes from solids or solute mixtures in both exploratory and industrial applications. In the pharmaceutical industry the generation of pure solid states without impurities is important as the presence of impurities can result in a change in chemical properties or lead to physical instability. The literature on the separation and purification of solutes from solid matrices and solute mixtures using supercritical fluids, with the main emphasis on pharmaceutically important molecules, is reviewed in this article. Also discussed is the application of supercritical fluids in the control of process impurities such as chemical intermediates and residual solvent and in polymorphic control and chiral resolution. As the generation of organic molecules of pharmaceutical interest with high purity is important in pharmaceuticals this review additionally provides a brief overview of highly selective chemical reactions in supercritical fluids.

Supercritical CO2 extraction and purification of compounds with antioxidant activity

Supercritical fluid extraction (SCFE), based on the utilization of a fluid under supercritical conditions, is a technology suitable for extraction and purification of a variety of compounds, particularly those that have low volatility and/or are susceptible to thermal degradation. The interest in SCFE is promoted by legal limitations of conventional solvents for food and pharmaceutical uses. The physicochemical properties of supercritical CO2 (higher diffusivity, lower viscosity, and lower surface tension than conventional solvents) facilitate mass transfer and allow an environmentally friendly operation. This article presents a comprehensive compilation of data on the supercritical CO2 extraction of antioxidant compounds from vegetal materials, with particular attention to those of a phenolic nature. Aspects concerning the supercritical operation for extraction and fractionation of antioxidants compounds are considered, including equilibrium solubility of pure compounds and effects of the operational conditions on the antioxidant activity of isolated fractions. The data are compared to those reported for synthetic antioxidants and natural extracts obtained by conventional solvent extraction from vegetal matrices.

Water-in-CO2 emulsions: reaction vessels for the production of tetra-ethyl pyrone

Water-in-CO2 (W/C) emulsions formed using a nickel Triton X-100 surfactant complex (Ni-surfactant) were used as microreactors for the carbon-carbon coupling reaction between hex-3-yne and CO2 to produce tetra-ethyl pyrone (TEP). The structure of the product, which was isolated in the CO2 phase, was determined using gas chromatography mass spectrometry (GC-MS) and infrared spectroscopy. The Ni-surfactant acted as both an emulsion forming agent and a water soluble catalyst for this carbon-carbon coupling reaction. The optimum yield of TEP was determined to be 69% after 72 h, at a temperature of 70 degrees C and a pressure of 206 bar. The ease with which the emulsion could be collapsed allowed the facile separation of products from the catalyst and any unreacted starting material. Product selectivity in the W/C emulsions was found to be greater than that obtained using conventional organic methodologies.