Clement R. Yonker

Organic liquid CO2 capture agents with high gravimetric CO2 capacity

We report a new class of CO2 binding organic liquids that chemically capture and release CO2 much more efficiently than aqueous alkanolamine systems. Mixtures of organic alcohols and amidine/guanidine bases reversibly bind CO2 chemically as liquid amidinium/guanidinium alkylcarbonates. The free energy of CO2 binding in these organic systems is very small and dependent on the choice of base, approximately −9 kJ mol−1 for DBU and Bartons base and +2 kJ mol−1 for 1,1,3,3-tetramethylguanidine. These CO2 capturing agents do not require an added solvent because they are liquid, and therefore have high CO2 capacities of up to 19% by weight for neat systems, and slightly less when dissolved in acetonitrile. The rate of CO2 uptake and release by these organic systems is limited by the rate of dissolution of CO2 into and out of the liquid phase. Gas absorption is selective for CO2 in both concentrated and dilute gas streams. These organic systems have been shown to bind and release CO2 for five cycles without losing activity or selectivity.

In Situ Multinuclear NMR Spectroscopic Studies of the Thermal Decomposition of Ammonia Borane in Solution

The development of condensed phase hydrogen storage materials for fuel cell powered vehicles capable of meeting the 2015 system target goals of >82 g H2 L-1 volumetric density and >90 g H2 kg-1 gravimetric density has attracted recent interest. The details of the mechanisms for hydrogen release from AB are not completely understood; however, significant progress has been made in furthering our understanding of these mechanisms. This work was funded by the Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE) as part of the Chemical Hydrogen Storage Center and carried out at the Pacific Northwest National Laboratory (operated by Battelle for DOE).

Solubility of fluorinated metal diethyldithiocarbamates in Supercritical carbon dioxide

Abstract Supercritical fluid separations of metal complexes in CO 2 have received little attention in the literature. This is believed to be caused by low solubilities of these compounds in supercritical CO 2 . The solubilities of several metals complexed with bis(trifluoroethyl)dithiocarbamate have been determined spectroscopi cally and their behavior in supercritical CO 2 studied using UV-VIS and FT-IR spectroscopy. Fluorination of the ligands in these metal chelates was found to increase solubilities of the complexes by several orders of magnitude.

Reversible Uptake of COS, CS2, and SO2: Ionic Liquids with O-Alkylxanthate, O-Alkylthiocarbonyl, and O-Alkylsulfite Anions

CO(2)-binding organic liquids (CO(2)BOLs) are mixtures of a base (typically an amidine or guanidine) and an alcohol, and have been shown to reversibly capture and release CO(2) with low reaction energies and high gravimetric CO(2) capacity. We now report the ability of such liquid blends to chemically bind and release other acid gases such as CS(2), COS, and SO(2) analogously to CO(2). These systems bind with sulfur-containing acid gases to form colored ionic liquids with new O-alkylxanthate, O-alkylthiocarbonyl, and O-alkylsulfite anions. The capture and thermal stripping of each acid gas from these systems and their applicability towards flue gas desulfurization is discussed.

A reversible zwitterionic SO2-binding organic liquid

N,N-Dibutylundecanolamine is a liquid that chemically binds SO2 to form a viscous zwitterionic liquid that contains 35% by wt. SO2 at standard temperature and pressure. SO2 is chemically bound to the alcohol component as an alkylsulfite, which is then stabilized by the amine. The zwitterionic liquid can be reverted to its non-ionic form and recycled by thermally stripping the SO2 under vacuum at temperatures near 70 °C. N,N-Dibutylundecanolamine is a potential flue gas desulfurizing solvent because it is chemically selective to bind SO2 but not basic enough to chemically bind CO2.

Study of retention processes in capillary supercritical fluid chromatography with binary fluid mobile phases

Abstract The ability to alter retention and selectivity through organic modifiers in capillary supercritical fluid chromatography (SFC) has been studied. The role of methanol, acetonitrile, and 2-propanol solvent modifiers on retention with supercritical carbon dioxide was investigated for selected solutes. The retention of these probe molecules was seen to decrease with increasing mole fraction of the solvent modifier in the fluid phase. Selectivity of the column for polar analytes was shown to change while selectivity remained constant for non-polar probe molecules. Binary fluids in capillary SFC appear promising for extending the range of amenable separations, as with packed column SFC, but also retain advantages related to the ease of density programming.

Thin fluoropolymer films and nanoparticle coatings from the rapid expansion of supercritical carbon dioxide solutions with electrostatic collection

Abstract Application of nanometer thick fluoropolymer films onto metal and semiconducting substrates is described. In the first step, nanometer-sized polymer particles are generated by a process of homogeneous nucleation during the rapid expansion of supercritical fluid solutions. These gas-phase particles are then charged as they are being formed by application of a high voltage to the expansion nozzle. In this way the charged nanoparticles can be collected on a solid surface forming uniform coatings with thicknesses from tens of nanometers to several micrometers thick. Supercritical carbon dioxide solutions of three different fluoropolymers were used to generate different types of coatings. This represents a ‘green’ process for film deposition. A further unique aspect of this process is that the small charged nanoparticles can be deposited to electrically conducting microscopic regions with a spatial resolution better than 50 nm.

Anhydrous tertiary alkanolamines as hybrid chemical and physical CO2 capture reagents with pressure-swing regeneration

Anhydrous DMEA, DEEA and DIPEA are found to absorb carbon dioxide under pressure via chemical binding and physical absorption. The chemical CO2-bound derivatives of these materials are zwitterionic alkylcarbonate salts which are characterized by high-pressure 13C NMR. DMEA, DEEA and DIPEA absorb 20 wt.%, 17 wt.% and 16 wt.% carbon dioxide, respectively, at 300 psig (20.6 ATM). An increasing chemical carbon dioxide uptake capacity trend of DMEA > DEEA > DIPEA is observed while the physical CO2 absorption trend is DIPEA > DEEA > DMEA. DMEA captures up to 45 mole % (20 wt.%) of CO2 at 500 psig via both chemical binding and physical absorption. The amount of chemically bound and physically absorbed CO2 is directly linked to the CO2 pressure over the liquid. The zwitterion DMEA-CO2 regenerates CO2 and DMEA upon depressurization, allowing for an economical pressure swing regeneration rather than thermal regeneration. DMEA absorbs/releases CO2 repeatedly with no decline in capacity.

Effect of denisty on enthalpy and entropy of transfer for supercritical fluid chroamtography

Abstract The effect of density on the enthalpy of transfer and the entropy of transfer of the solute between the mobile and stationary phase was investigated for capillary supercritical fluid chromatography (SFC) using carbon dioxide as the mobile phase. The solutes were n -alkanes and n -alkanols and the stationary phases were coated in-situ cross-linked SE-54 and OV-17. Enthalpies were seen to decrease as fluid density increased over a range of 0.20 to 0.50 g/cm 3 . The range of enthalpies were from −5.9 to −8.4 kcal/mol for OV-17 and −3.9 to −8.6 kcal/mol with Se-54. The entropy range from −7.1 to −16.2 cal/mol · K for SE-54 and −12.5 to −17.0 cal/mol · K for Ov-17. The results demonstrate the interdependence of enthalpy and entropy of transfer with supercritical fluid desnity during chromatographic separations.

Effect of temperature and modifier concentration on retention in supercritical fluid chromatography

Abstract Use of binary modifiers in supercritical fluid chromatography (SFC) enhances the solvating capabilities of the supercritical mobile phase, allowing the mobile phase to be chemically tailored to a specific separation. The effects of temperature, density and modifier mole fraction on the retention process in capillary SFC was studied. Selectivity, as well as the enthalpy of solute transfer, were seen to be dependent on modifier concentration. Specific molecular interactions between the binary fluid and the solutes as well as enhanced solvation of the bonded stationary phase are suggested by the experimental data.