Engineering topics
Luebke, David R.
Publications and source records attributed to Luebke, David R..
Polyphosphazene polymer development for mixed matrix membranes using SIFSIX-Cu-2 i as performance enhancement filler particles
Phosphazene-based polymers were synthesized by using different pendant groups such as trifluoroethoxy (TFE), phenoxy (PHO) and octafluoropentoxy (OFP). High performance methoxyethoxyethoxy/cyclohexoxy (MEE/CH) based polyphosphazene was developed for the first time in literature using a mixed-substitution method. The structural, chemical, and thermal properties of these polymers were analyzed using several techniques such as Gel Permeation Chromatography (GPC), Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Nuclear Magnetic Resonance (NMR). Significant differences in gas transport properties of gases have been observed between these pendant groups because of their differences in glass transition temperature and physical interaction with CO 2 . For the first time, we report on the high performance of TFE polyphophazene based mixed matrix membranes (MMMs) using a SIFSIX-Cu-2i (SIFSIX) metal organic framework (MOF) as the filler particles. These MMMs showed a significant improvement in both CO 2 permeability and CO 2 /N 2 selectivity compared to pure TFE polyphosphazene membranes. As a result, the excellent gas transport properties of these membranes make them very promising material for carbon capture applications.
Surface functionalization of metal organic frameworks for mixed matrix membranes
Mixed Matrix Membrane (MMM) are composite membranes for gas separation and comprising a quantity of inorganic filler particles, in particular metal organic framework (MOF), dispersed throughout a polymer matrix comprising one or more polymers. This disclosure is directed to MOF functionalized through addition of a pendant functional group to the MOF, in order to improve interaction with a surrounding polymer matrix in a MMM. The improved interaction aids in avoiding defects in the MMM due to incompatible interfaces between the polymer matrix and the MOF particle, in turn increasing the mechanical and gas separation properties of the MMM. The disclosure is also directed to a MMM incorporating the surface functionalized MOF.
Evaluating the energy performance of a hybrid membrane-solvent process for flue gas carbon dioxide capture
In this study, a particularly energy intensive step in the conventional amine absorption process to remove carbon dioxide is solvent regeneration using a steam stripping column. An attractive alternative to reduce the energy requirement is gas pressurized stripping, in which a high pressure noncondensable gas is used to strip CO 2 off the rich solvent stream. The gas pressurized stripping column product, having CO 2 at high concentration and high partial pressure, can then be regenerated readily using membrane separation. In this study, we performed an energetic analysis in the form of total equivalent work and found that, for capturing CO 2 from flue gas, this hybrid stripping process consumes 49% less energy compared to the base case conventional MEA absorption/steam stripping process. We also found the amount of membrane required in this process is much less than required for direct CO 2 capture from the flue gas: approximately 100-fold less than a previously published two-stage cross-flow scheme, mostly due to the more favorable pressure ratio and CO 2 concentration. There does exist a trade-off between energy consumption and required membrane area that is most strongly affected by the gas pressurized stripper operating pressure. While initial analysis looks promising from both an energy requirement and membrane unit capital cost, the viability of this hybrid process depends on the availability of advanced, next generation gas separation membranes to perform the stripping gas regeneration.
Method of fabrication of supported liquid membranes
Method for the fabrication of a supported liquid membrane having a dense layer in contact with a porous layer, and a membrane liquid layer within the interconnected pores of the porous layer. The dense layer is comprised of a solidified material having an average pore size less than or equal to about 0.1 nanometer, while the porous layer is comprised of a plurality of interconnected pores and has an average pore size greater than 10 nanometers. The supported liquid membrane is fabricated through the preparation of a casting solution of a membrane liquid and a volatile solvent. A pressure difference is established across the dense layer and porous layer, the casting solution is applied to the porous layer, and the low viscosity casting solution is drawn toward the dense layer. The volatile solvent is evaporated and the membrane liquid precipitates, generating a membrane liquid layer in close proximity to the dense layer.
Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol-ene photochemistry
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Method for the production of fabricated hollow microspheroids
The method relates to the fabrication of a polymer microspheres comprised of an asymmetric layer surrounding a hollow interior. The fabricated hollow microsphere is generated from a nascent hollow microsphere comprised of an inner core of core fluid surrounded by a dope layer of polymer dope, where the thickness of the dope layer is at least 10% and less than 50% of the diameter of the inner core. The nascent hollow microsphere is exposed to a gaseous environment, generating a vitrified hollow microsphere, which is subsequently immersed in a coagulation bath. Solvent exchange produces a fabricated hollow microsphere comprised of a densified outer skin surrounding a macroporous inner layer, which surrounds a hollow interior. In an embodiment, the polymer is a polyimide or a polyamide-imide, and the non-solvent in the core fluid and the coagulation bath is water. The fabricated hollow microspheres are particularly suited as solvent supports for gas separation processes.
Fabrication of MMMs with improved gas separation properties using externally-functionalized MOF particles
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Toward a Materials Genome Approach for Ionic Liquids: Synthesis Guided by Ab Initio Property Maps
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Constant pressure high throughput membrane permeation testing system
The disclosure relates to a membrane testing system for individual evaluation of a plurality of planar membranes subjected to a feed gas on one side and a sweep gas on a second side. The membrane testing system provides a pressurized flow of a feed and sweep gas to each membrane testing cell in a plurality of membrane testing cells while a stream of retentate gas from each membrane testing cell is ported by a retentate multiport valve for sampling or venting, and a stream of permeate gas from each membrane testing cell is ported by a permeate multiport valve for sampling or venting. Back pressure regulators and mass flow controllers act to maintain substantially equivalent gas pressures and flow rates on each side of the planar membrane throughout a sampling cycle. A digital controller may be utilized to position the retentate and permeate multiport valves cyclically, allowing for gas sampling of different membrane cells over an extended period of time.
Carboxylate supported ionic liquid membranes for CO2/H2 gas separation
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CO 2 capture properties of lithium silicates with different ratios of Li 2 O/SiO 2 : an ab initio thermodynamic and experimental approach
The lithium silicates have attracted scientific interest due to their potential use as high-temperature sorbents for CO 2 capture. The electronic properties and thermodynamic stabilities of lithium silicates with different Li 2 O/SiO 2 ratios (Li 2 O, i 8 SiO 6 , Li 4 SiO 4 , Li 6 Si 2 O 7 , Li 2 SiO 3 , Li 2 Si 2 O 5 , Li 2 Si 3 O 7 , and a-SiO 2 ) have been investigated by combining first-principles density functional theory with lattice phonon dynamics. All these lithium silicates examined are insulators with band-gaps larger than 4.5 eV. By decreasing the Li 2 O/SiO 2 ratio, the first valence bandwidth of the corresponding lithium silicate increases. Additionally, by decreasing the Li 2 O/SiO 2 ratio, the vibrational frequencies of the corresponding lithium silicates shift to higher frequencies. Based on the calculated energetic information, their CO 2 absorption capabilities were extensively analyzed through thermodynamic investigations on these absorption reactions. We found that by increasing the Li 2 O/SiO 2 ratio when going from Li 2 Si 3 O 7 to Li 8 SiO 6 , the corresponding lithium silicates have higher CO 2 capture capacity, higher turnover temperatures and heats of reaction, and require higher energy inputs for regeneration. Based on our experimentally measured isotherms of the CO 2 chemisorption by lithium silicates, we found that the CO 2 capture reactions are two-stage processes: (1) a superficial reaction to form the external shell composed of Li 2 CO 3 and a metal oxide or lithium silicate secondary phase and (2) lithium diffusion from bulk to the surface with a simultaneous diffusion of CO 2 into the shell to continue the CO 2 chemisorption process. The second stage is the rate determining step for the capture process. By changing the mixing ratio of Li 2 O and SiO 2 , we can obtain different lithium silicate solids which exhibit different thermodynamic behaviors. Based on our results, three mixing scenarios are discussed to provide general guidelines for designing new CO2 sorbents to fit practical needs.
Development of a Conceptual Process for Selective CO 2 Capture from Fuel Gas Streams Using [hmim][Tf 2 N] Ionic Liquid as a Physical Solvent
The Ionic Liquid (IL) [hmim][Tf 2 N] was used as a physical solvent in an Aspen Plus simulation, employing the Peng-Robinson Equation of State (P-R EOS) with Boston-Mathias (BM) alpha function and standard mixing rules, to develop a conceptual process for CO 2 capture from a shifted warm fuel gas stream produced from Pittsburgh # 8 coal for a 400 MWe power plant. The physical properties of the IL, including density, viscosity, surface tension, vapor pressure and heat capacity were obtained from literature and modeled as a function of temperature. Also, available experimental solubility values for CO 2 , H 2 , H 2 S, CO, and CH 4 in this IL were compiled and their binary interaction parameters (Δ ij and l ij ) were optimized and correlated as functions of temperature. The Span-Wager Equation-of-State EOS was also employed to generate CO 2 solubilities in [hmim][Tf 2 N] at high pressures (up to 10 MPa) and temperatures (up to 510 K). The conceptual process developed consisted of 4 adiabatic absorbers (2.4 m ID, 30 m high) arranged in parallel and packed with Plastic Pall Rings of 0.025 m for CO 2 capture; 3 flash drums arranged in series for solvent (IL) regeneration with the pressure-swing option; and a pressure-intercooling system for separating and pumping CO 2 up to 153 bar to the sequestration sites. The compositions of all process streams, CO 2 capture efficiency, and net power were calculated using Aspen Plus simulator. The results showed that, based on the composition of the inlet gas stream to the absorbers, 95.67 mol% of CO 2 was captured and sent to sequestration sites; 99.5 mol% of H 2 was separated and sent to turbines; the solvent exhibited a minimum loss of 0.31 mol%; and the net power balance of the entire system was 30.81 MW. These results indicated that [hmim][Tf 2 N] IL could be used as a physical solvent for CO 2 capture from warm shifted fuel gas streams with high efficiency.
Enhanced Gas Absorption in the Ionic Liquid 1- n -Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide ([hmim][Tf 2 N]) Confined in Silica Slit Pores: A Molecular Simulation Study
Two-dimensional NP{sub xy}T and isostress-osmotic (N{sub 2}P{sub xy}Tf{sub 1}) Monte Carlo simulations were used to compute the density and gas absorption properties of the ionic liquid (IL) 1-n-hexyl-3- methylimidazolium bis(Trifluoromethylsulfonyl)amide ([hmim][Tf{sub 2}N]) confined in silica slit pores (25-45 Å). Self-diffusivity values for both gas and IL were calculated from NVE molecular dynamics simulations using both smooth and atomistic potential models for the silica. Simulations show that the molar volume for [hmim][Tf{sub 2}N] confined in 25-45 Å silica slit pores are 12-31% larger than for the bulk IL at 313-573 K and 1 bar. The amounts of CO{sub 2}, H{sub 2}, and N{sub 2} absorbed in the confined IL are typically 1.1-3 times larger than in the bulk IL due to larger molar volumes for the confined IL compared to the bulk IL. The CO{sub 2}, N{sub 2}, and H{sub 2} molecules are generally absorbed close to the silica wall where the IL density is very low. This arrangement causes the self-diffusivities for these gases in the confined IL to be 2 to 8 times larger than in the bulk IL at 298-573 K. The solubility for water in the confined and bulk ILs are similar, which is likely due to strong water interactions with [hmim][Tf{sub 2}N] through hydrogen-bonding resulting in the confined IL molar volume playing a less important role in determining H{sub 2}O solubility. Water molecules were largely absorbed in the IL-rich region rather than close to the silica wall. The self-diffusivities for water correlate with the confined IL. The confined IL exhibits self-diffusivities larger than the bulk IL at lower temperatures, but smaller than the bulk IL at higher temperatures. The findings from simulations are consistent with available experimental data for similar confined IL systems.
Interactions in 1-ethyl-3-methyl imidazolium tetracyanoborate ion pair: Spectroscopic and density functional study
Density Functional Theory is used to investigate a weakly coordinating room-temperature ionic liquid, 1-ethyl-3-methyl imidazolium tetracyanoborate ([Emim]{sup +}[TCB]{sup -}). Four locally stable conformers of the ion pair were located. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of several hydrogen bonds. Further investigation through the Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations provided insight into the origin of interactions in the [Emim]{sup +}[TCB]{sup -} ion pair. Strength of molecular interactions in the ionic liquid was correlated with frequency shifts of the characteristic vibrations of the ion pair. Harmonic vibrations of the ion pair were also compared with the experimental Raman and Infrared spectra. Vibrational frequencies were assigned by visualizing displacements of atoms around their equilibrium positions and through Potential Energy Distribution (PED) analysis.
Understanding the effect of side groups in ionic liquids on carbon-capture properties: a combined experimental and theoretical effort
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Spectroscopic and computational analysis of the molecular interactions in the ionic liquid ion pair [BMP]+[TFSI]-
1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]{sup +}[TFSI]{sup -}) ion pairs were studied using DFT at the B3LYP/6-31 + G(d) level. Nine locally stable conformations of the ion pair were located. In the most stable conformation, [TFSI]{sup -} takes a cis conformation and lies below the pyrrolidinium ring. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of nine hydrogen bonds. Interaction energies were recalculated at the Second-order Møller–Plesset (MP2) level to show the importance of dispersion interaction. Further investigation through natural bond orbital (NBO) analysis provided insight into the importance of charge transfer interactions in the ion pair. Harmonic vibrations of the ion pair were calculated and compared with vibrations of the free ions as well as the experimental infrared spectrum. Assignments and frequency shifts are discussed in light of the inter-ionic interactions.