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H 2 S/CH 4 and CO 2 /CH 4 separations show opposing trends, making simultaneous improvement challenging. This is addressed by increasing free volume to enhance competitive sorption effects and boosting diffusion selectivity through in situ crosslinking.
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Rare-earth terephthalic acid (BDC)-based metal–organic frameworks (MOFs) are promising candidate materials for acid gas separation and adsorption from flue gas streams. However, previous simulations have shown that acid gases (H 2 O, NO 2 , and SO 2 ) react with the hydroxyl on the BDC linkers to form protonated acid gases as a potential degradation mechanism. Herein, gas-phase computational approaches were used to identify the formation energies of these secondary protonated acid gases across multiple BDC linker molecules. Formation energies for secondary protonated acid gases were evaluated using both density functional theory (DFT) and correlated wave function methods for varying BDC–gas reaction mechanisms. Upon validation of DFT to reproduce wave function calculation results, rotated conformational linkers and chemically functionalized BDC linkers with -OH, -NH 2 , and -SH were investigated. Furthermore, the calculations show that the rotational conformation affects the molecule stability. Double-functionalized BDC linkers, where two functional groups are substituted onto BDC, showed varied reaction energies depending on whether the functional groups donate or withdraw electrons from the aromatic system. Based on these results, BDC linker design must balance adsorption performance with degradation via linker dehydrogenation for the design of stable MOFs for acid gas separations.
The project was to perform testing that establishes a baseline of precombustion carbon capture performance when combined with coal- and biomass-derived syngas. Goals of the project were to generate syngas from a matrix of coal types, biomass types, and varied fuel concentrations. Solvent performance and contaminant accumulation within the acid gas separation system (AGSS) were examined.
Gas-liquid chromatography of natural protein amino acids in biological substances, noting separation characteristics
A system and method for acid gas separations using porous frameworks of metal atoms coordinatively bound to polytopic linkers that are functionalized with basic nitrogen ligands that expose nitrogen atoms to the pore volumes forming adsorption sites. Adjacent basic nitrogen ligands on the metal-organic framework can form an ammonium from one ligand and a carbamate from the other. The formation of one ammonium carbamate pair influences the formation of ammonium carbamate on adjacent adsorption sites. Adsorption of acid gas at the adsorption sites form covalently linked aggregates of more than one ammonium carbamate ion pair. The acid gas adsorption isotherm can be tuned to match the step position with the partial pressure of acid gas in the gas mixture stream through manipulation of the metal-ligand bond strength by selection of the ligand, metal and polytopic linker materials.
Gas chromatography parameters of fluoro derivatives of amino acids compared for use in packed columns or sensitivity evaluation
A method for separating a Lewis acid gas from a fluid mixture, comprising contacting the fluid mixture with a reduced electroactive species; a non-aqueous electrolyte; and a stabilizing additive to form an anion adduct between the Lewis acid gas and the reduced electroactive species, wherein the electroactive species comprises an oxidized state, and at least one reduced state that bonds with the Lewis acid gas to form the anion adduct, wherein the stabilizing additive comprises a cationic Lewis acid, a hydrogen-bond donor, or a combination thereof, and the stabilizing additive is present in an effective amount to kinetically favor the forming of the anion adduct from the reduced electroactive species and thermodynamically favor the forming of the anion adduct in the thermodynamic equilibrium between the anion adduct and the reduced electroactive species.
Understanding the selectivity of metal–organic frameworks (MOFs) to complex acid gas streams will enable their use in industrial applications. In this study, ab initio molecular dynamic simulations (AIMD) were used to simulate ternary gas mixtures (H 2 O-NO 2 -SO 2 ) in rare earth 2,5-dihydroxyterephthalic acid (RE-DOBDC) MOFs. Stronger H 2 O gas-metal binding arose from thermal vibrations in the MOF sterically hindering access of SO 2 and NO 2 molecules to the metal sites. Gas-gas and gas-linker interactions within the MOF framework resulted in the formation of multiple secondary gas species including HONO, HNO 2 , NOSO, and HNO 3 ⁻. Four gas adsorption sites were identified along with a new de-protonation reaction mechanism not observable through experiment. This study not only provides valuable information on competitive gas binding energies in the MOF, but it also provides important chemical insights into transient chemical reactions and mechanisms.
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In one embodiment, a method for separating acidic gases from a gas mixture includes exposing the gas mixture to a separation membrane at an elevated temperature, where the separation membrane includes a porous support and at least one molten alkali metal hydroxide disposed within pores of the porous support.
Gas-liquid chromatographic separation applied in derivatization chemistry of protein amino acids as N-trimethylsilyl /TMS/ esters
Acid-resistant residues were prepared by HCl-HF demineralization of three H-type ordinary chondrites: Brownfield 1937 (H3), Dimmitt (H3, 4), and Estacado (H6). These residues were found to contain a large proportion of the planetary-type trapped Ar, Kr, and Xe in the meteorites. The similarity of these acid residues to those from carbonaceous chondrites and LL-type ordinary chondrites suggests that the same phase carries the trapped noble gases in all these diverse meteorite types. Because the H group represents a large fraction of all meteorites, this result indicates that the gas-rich carrier phase is as universal as the trapped noble-gas component itself. When treated with an oxidizing etchant, the acid residues lost almost all their complement of noble gases.
The problems of separation of contaminant from indigenous amino-acids in meteorites can be largely overcome by applying gas chromatographic techniques for the separation of D,L enantiomers of amino-acids as their diastereomeric derivatives and the identification of these compounds by gas chromatographic retention times and mass spectral fragmentation patterns. Two samples of Orgueil meteorite were examined. The results show that there are amino-acids indigenous to the Orgueil meteorite in addition to those present as contaminants.
Butyl esters separation from protein amino acids, using acid washed Chromosorb W of various mesh sizes