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1. Carbon Molecular Sieve-derived POC/Mixed-Matrix Membranes for Gas Separation

   kowey, Isha; Rownaghi, Ali (May 2023, North American Membrane Society 2023)

   Membrane-based separations offer the potential for the lowest energy demand requirements of all separation options. Among all nanoporous membranes, the carbon molecular sieves (CMS), metal-organic frameworks (MOFs), and mixed-matrix membranes (MMMs) with angstrom level molecular discrimination properties makes them appealing for separating a wide spectrum of gas-pairs. Here we present results of gas selectivity and diffusion of different gases (C2H6, C2H4, C3H8, C3H6, H2, N2, CO2, and CH4) in porous organic cages (POCs) incorporated into fluorinated copolyimides polymers (FCPs). The FCPs were synthesized by the iridization reaction of fluorinated dianhydrides, nonfluorinated dianhydride, and nonfluorinated diamine. Asymmetric hollow fiber membranes formed by the dry-jet/wet-quench spinning process. Once fresh FCP fibers were synthesized, they were crosslinked with POCs, vacuum dried at 90 °C. We investigated the uptake, gas selectivity and diffusion of different gases (C2H6, C2H4, C3H8, C3H6, H2, N2, CO2, and CH4) over synthesized POC-mixed matrixed membranes (POC-MMM) at 25 °C and pressures up to 1 bar. At 1 bar and 25 °C, C2H6, C2H4, C3H8, C3H6 adsorption capacities reached to 42.61, 2.56, 2.77 and 2.65 mmol/g over POC-MMM, respectively, while CO2, CH4, CO, N2 and H2 adsorption capacities of 1.48, 0.84, 0.33, 0.11, and 0.068 mmol/g, respectively. Furthermore, stable CMS membrane were formed by pyrolysis of POC-MMMs under an inert argon atmosphere at 1 atm. To test the gas transport properties of CMS-derived POC/MMM, a lab-scale hollow fiber module with two-five fibers was constructed. The results of longer-term operation of synthesized CMS membrane that was continuously operated for 264 h (10 days) with an equimolar binary H2/CO2, CH4/CO2 and C3H6/C3H8 feed at 25°C and 1 bar feed pressure. The modification yielded promising results in the reduction of physical aging of CMS membranes. 

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2. Porous Organic Cages-Stabilized Carbon Molecular Sieve for Efficient Gas Separation

   Sharif, Usman; Kowey, Isha; Rownaghi, Ali (November 2023, 2023 AIChE Annual Meeting)

   Here we present results of gas selectivity and diffusion of different gases (C2H6, C2H4, C3H8, C3H6, H2, N2, CO2, and CH4) in porous organic cages (POCs) incorporated into fluorinated copolyimides polymers (FCPs). The FCPs were synthesized by the thermal and chemical imidization reaction of fluorinated dianhydrides, nonfluorinated dianhydride, and nonfluorinated diamine. Asymmetric hollow fiber membranes formed by the dry-jet/wet-quench spinning process. Once fresh FCP fibers were synthesized, they were crosslinked with POCs, vacuum dried at 90 °C. We investigated the uptake, gas selectivity and diffusion of different gases (C3H8, C3H6, CO2, and H2) over synthesized POC-mixed matrixed membranes (POC-MMM) at 25 °C and pressures up to 1 bar. At 1 bar and 25 °C, C3H8, C3H6 adsorption capacities reached 2.77 and 2.65 mmol/g over POC-MMM, respectively, while CO2, CH4, CO, N2 and H2 adsorption capacities of 1.48, 0.84, 0.33, 0.11, and 0.068 mmol/g, respectively. Furthermore, stable CMS membrane was formed by pyrolysis of POC-MMMs under an inert argon atmosphere at 1 atm. To test the gas transport properties of CMS-derived POC/MMM, a lab-scale hollow fiber module with two-five fibers was constructed. The results of longer-term operation of synthesized CMS membrane that was continuously operated for 264 h (10 days) with an equimolar binary H2/CO2, CH4/CO2 and C3H6/C3H8 feed at 25°C and 1 bar feed pressure. The modification yielded promising results in the reduction of physical aging of CMS membranes. 

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3. Nanostructured molybdenum carbide on biochar for CO2 reforming of CH4

   Li, Rui (January 2018, Fuel)

   A simple procedure was developed to synthesize molybdenum carbide nanoparticles (Mo2C/BC) by carburization of molybdate salts supported on the biochar from pyrolysis of biomass without using extra carbon source or reducing gas. The molybdenum carbide formation procedure investigated by in-situ XRD and TGA-MS indicated that the phase transitions followed the path of (NH4)6Mo7O24·4H2O → (NH4)2Mo3O10 → (NH4)2Mo14O42 → Mo8O23 → Mo4O11 → MoO2 → Mo2C. The volatile gases CO, H2, and CH4 evolved from biochar and the biochar solid carbon participated in the reduction of molybdenum species, while the biochar and CH4 served as carbon sources for the carburization. Temperature programmed surface reactions of Mo2C/BC indicated that CH4 dissociated as CH4 ⇋ C∗ + 2H2 on the catalyst surface, and CO2 reacted as CO2 + C∗ ⇋ 2CO+ ∗ due to oxidation of Mo2C. Both experiment data and thermodynamic analysis for the study of operation conditions of CO2 reforming of CH4 clearly demonstrated that the yields of H2 and CO increased with the increased temperature and the reasonable conversions should be performed at 850 °C, at which both CH4 and CO2 conversions were higher than 80%. 

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4. Experimental Investigation of the Combustion Properties of an Average Thermal Runaway Gas Mixture from Li-Ion Batteries.

   Olivier Mathieu, Claire M. (February 2022, Energy fuels)

   To assess the fire hazard associated with venting gases coming from a lithium-ion battery during a thermal runaway, a mixture representative of such venting gas was determined by averaging 40 gas compositions presented in the literature. The final mixture is composed of C3H8, C2H6, C2H4, CH4, H2, CO, and CO2. The combustion properties of this mixture were determined using various combustion devices: shock tubes for ignition delay time measurements in air and for H2O time histories in very dilute mixtures (99% Ar), as well as a closed bomb to measure the laminar flame speeds. Experiments were performed at around atmospheric pressure and for several equivalence ratios in all cases. Several detailed kinetics models from the literature were assessed against the data generated with this very complex mixture, and it was found that modern detailed kinetics mechanisms were capable of appropriately predicting the combustion properties of thermal runaway gases from a battery in most cases, with the NUIGMech 1.1 model being the most accurate. A numerical analysis was conducted with the two most modern models to explain the results and highlight the most important reactions. 

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5. Experimental Investigation of the Combustion Properties of an Average Thermal Runaway Gas Mixture from Li-Ion Batteries

   Olivier Mathieu, Claire M. (February 2022, Energy fuels)

   To assess the fire hazard associated with venting gases coming from a lithium-ion battery during a thermal runaway, a mixture representative of such venting gas was determined by averaging 40 gas compositions presented in the literature. The final mixture is composed of C3H8, C2H6, C2H4, CH4, H2, CO, and CO2. The combustion properties of this mixture were determined using various combustion devices: shock tubes for ignition delay time measurements in air and for H2O time histories in very dilute mixtures (99% Ar), as well as a closed bomb to measure the laminar flame speeds. Experiments were performed at around atmospheric pressure and for several equivalence ratios in all cases. Several detailed kinetics models from the literature were assessed against the data generated with this very complex mixture, and it was found that modern detailed kinetics mechanisms were capable of appropriately predicting the combustion properties of thermal runaway gases from a battery in most cases, with the NUIGMech 1.1 model being the most accurate. A numerical analysis was conducted with the two most modern models to explain the results and highlight the most important reactions. 

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