The Experts below are selected from a list of 3648 Experts worldwide ranked by ideXlab platform
William J. Koros - One of the best experts on this subject based on the ideXlab platform.
-
Composite Carbon Molecular Sieve Hollow Fiber Membranes: Resisting Support Densification via Silica Particle Stabilization
Industrial & Engineering Chemistry Research, 2018Co-Authors: Chen Zhang, Kuang Zhang, Yuhe Cao, William J. KorosAbstract:Resisting densification of hollow fiber support layers under high-temperature pyrolysis is critical to form Carbon Molecular Sieve hollow fiber membranes with thin separation layer and attractive productivity. In this paper, a new silica particle stabilization approach is introduced to form thin-skinned composite Carbon Molecular Sieve hollow fiber membranes with excellent resistance to support layer densification. By dispersing small-sized silica particles with low bulk density in the support layer of polymer precursor hollow fibers, composite Carbon Molecular Sieve hollow fiber membranes were formed with highly porous supports. The composite Carbon Molecular Sieve hollow fiber membranes showed very attractive selectivities and productivities higher than those of monolithic asymmetric Carbon Molecular Sieve hollow fiber membranes formed by the standard sol–gel support stabilization technique.
-
iron containing Carbon Molecular Sieve membranes for advanced olefin paraffin separations
Journal of Membrane Science, 2018Co-Authors: Yuhan Chu, Marcos V Martinez, Mark K Brayden, David F Yancey, William J. KorosAbstract:Abstract In this work, Carbon Molecular Sieve (CMS) dense film membranes derived from 6FDA-DAM:DABA (3:2) polyimide precursor were studied for separation of mixed olefins (C2H4 and C3H6) from paraffins (C2H6 and C3H8). Olefin-selective CMS membranes with high performance can be made by pyrolysis of metal-containing polymeric precursors. Pyrolyzed at 550 °C with a fast ramp rate, CMS membranes with integrated Fe2+ (2.2 wt% in the precursor) showed 19% higher C2H4/C2H6 and 11% higher C3H6/C3H8 sorption selectivity than that of the neat CMS membrane. Additional investigations with a quaternary mixture feed (C2 and C3 hydroCarbons) show that C2H4 permeability above 10 Barrers with C2H4/C2H6 permselectivity near 11 were achieved for the 3.2 wt% Fe loading case. Although Fe incorporation did not appear to promote C3H6/C2H6 permselectivity, Fe is useful to improve C2 pair olefin/paraffin separation. Deconvolution of the C2H4/C2H6 permselectivity for our more extensively studied 2.2 wt% loading case was also revealing. While both sorption and diffusion selectivity increased due to the Fe incorporation, a larger influence is seen on the diffusion selectivity versus the sorption selectivity. Hypotheses to explain this surprising outcome are offered to guide future work.
-
purification of aggressive supercritical natural gas using Carbon Molecular Sieve hollow fiber membranes
Industrial & Engineering Chemistry Research, 2017Co-Authors: Chen Zhang, Graham B Wenz, Jason P. Williams, Joseph M. Mayne, Gongping Liu, William J. KorosAbstract:In this paper, we describe polyimide-derived Carbon Molecular Sieve (CMS) hollow fiber membranes with CO2/CH4 separation factors ∼60 under a supercritical (1800 psia) natural gas feed comprising 50% CO2 and 500 ppm highly condensable C7 hydroCarbons. Long-term tests extending for 200 h proved membrane stability. Temperatures ranging from −50 to 100 °C were also tested, and the membrane showed attractive performance under the diverse conditions studied. With attractive and stable separation performance, the CMS hollow fiber membranes studied in this work can potentially enable next-generation CO2 removal processes for challenging natural gas feeds.
-
Carbon Molecular Sieve structure development and membrane performance relationships
Carbon, 2017Co-Authors: Meha Rungta, Graham B Wenz, Chen Zhang, Liren Xu, Wulin Qiu, Jason S Adams, William J. KorosAbstract:Abstract Characterization techniques beyond microscopy, scattering and spectroscopy approaches are needed to understand and improve sub-angstrom discrimination between penetrants in Carbon Molecular Sieve (CMS) membranes. Here we use a method based on Molecular scale gas diffusion probes to understand relevant membrane properties at the required level of detail. We further use this method to consider hypotheses about the evolution of structure responsible for fundamental properties of CMS materials derived from a high performance CMS precursor polymer, 6FDA:BPDA-DAM. While 6FDA:BPDA-DAM derived CMS membranes display a ∼230% improvement in CO2 permeability when compared to Matrimid® derived CMS formed under the same conditions, the CO2/CH4 diffusional selectivity for these two materials are very similar at 35 and 38.5, respectively. These results indicate a non-trivial connection between CMS precursor material structure and resulting performance. Linking hypotheses about structural changes likely to occur during pyrolysis with the probe data provides insights regarding transformation of the random coil polyimide into ultra-rigid CMS, with exquisite size and shape diffusion selectivity. The results provide a framework for understanding and tuning properties of this special class of materials with important technological advantages in energy-intensive gas separations.
-
Purification of Aggressive Supercritical Natural Gas Using Carbon Molecular Sieve Hollow Fiber Membranes
2017Co-Authors: Chen Zhang, Graham B Wenz, Jason P. Williams, Joseph M. Mayne, Gongping Liu, William J. KorosAbstract:In this paper, we describe polyimide-derived Carbon Molecular Sieve (CMS) hollow fiber membranes with CO2/CH4 separation factors ∼60 under a supercritical (1800 psia) natural gas feed comprising 50% CO2 and 500 ppm highly condensable C7 hydroCarbons. Long-term tests extending for 200 h proved membrane stability. Temperatures ranging from −50 to 100 °C were also tested, and the membrane showed attractive performance under the diverse conditions studied. With attractive and stable separation performance, the CMS hollow fiber membranes studied in this work can potentially enable next-generation CO2 removal processes for challenging natural gas feeds
Adélio Mendes - One of the best experts on this subject based on the ideXlab platform.
-
Preparation of Carbon Molecular Sieve membranes from an optimized ionic liquid-regenerated cellulose precursor
Journal of Membrane Science, 2019Co-Authors: Sandra C. Rodrigues, Fernão D. Magalhães, Márcia Andrade, Jamie Moffat, Adélio MendesAbstract:Abstract Novel Carbon Molecular Sieve membranes with high separation performance and stability in the presence of humidified streams were prepared from an optimized ionic liquid-regenerated cellulose precursor, in a single Carbonization step. Membranes prepared at two different Carbonization end temperatures (550 °C and 600 °C) were analyzed through scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, Carbon dioxide adsorption and permeation experiments. The prepared membranes exhibited uniform thickness of approximately 20 µm and a well-developed microporous structure. The permeation performance of these Carbon Molecular Sieve membranes was above the Robeson upper bound curve for polymeric membranes. In particular, the membrane prepared at 550 °C end temperature exhibited permeability to oxygen of 5.16 barrer and O2/N2 ideal selectivity of 32.3 and permeability to helium of 126 barrer and He/N2 ideal selectivity of 788; besides, permeation experiments performed in the presence of ca. 80% relative humidity showed that humidity does not originate pore blockage. These results open the door for the preparation of tailor made precursors that originate Carbon Molecular Sieve membranes with extraordinary separation performances, mechanical resistance and stability.
-
Preparation of Carbon Molecular Sieve membranes from an optimized ionic liquid-regenerated cellulose precursor
'Elsevier BV', 2019Co-Authors: Sandra C. Rodrigues, Fernão D. Magalhães, Márcia Andrade, Jamie Moffat, Adélio MendesAbstract:Novel Carbon Molecular Sieve membranes with high separation performance and stability in the presence of humidified streams were prepared from an optimized ionic liquid-regenerated cellulose precursor, in a single Carbonization step. Membranes prepared at two different Carbonization end temperatures (550 degrees C and 600 degrees C) were analyzed through scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, Carbon dioxide adsorption and permeation experiments. The prepared membranes exhibited uniform thickness of approximately 20 mu m and a well-developed microporous structure. The permeation performance of these Carbon Molecular Sieve membranes was above the Robeson upper bound curve for polymeric membranes. In particular, the membrane prepared at 550 degrees C end temperature exhibited permeability to oxygen of 5.16 barrer and O-2/N-2 ideal selectivity of 32.3 and permeability to helium of 126 barrer and He/N-2 ideal selectivity of 788; besides, permeation experiments performed in the presence of ca. 80% relative humidity showed that humidity does not originate pore blockage. These results open the door for the preparation of tailor made precursors that originate Carbon Molecular Sieve membranes with extraordinary separation performances, mechanical resistance and stability
-
composite phenolic resin based Carbon Molecular Sieve membranes for gas separation
Carbon, 2011Co-Authors: Miguel A Teixeira, M C Campo, Margot A. Llosa Tanco, David Pacheco A Tanaka, Cesar Magen, Adélio MendesAbstract:Abstract Composite Carbon Molecular Sieve membranes (c-CMSM) were prepared from phenolic resin loaded with boehmite by a single dipping–drying–pyrolysis step. The composite membrane was analyzed by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, mercury porosimetry, CO 2 adsorption and permeation experiments. It was produced a 2 μm thick composite uniform layer on top of a α-Al 2 O 3 support. The composite top layer exhibited nanowires of Al 2 O 3 1–2 nm thick and 10–30 nm long well dispersed in a microporous Carbon matrix. The micropores network accounted for 63% of the total pore volume (DR isotherm). The c-CMSM exhibited ideal O 2 /N 2 and C 3 H 6 /C 3 H 8 permselectivities of 5 and 15, respectively. The performance of the c-CMSM for pair C 3 H 6 /C 3 H 8 was above the upper bound curve for polymeric membranes, making it a promising vehicle for olefin purification.
-
Carbon Molecular Sieve membranes from cellophane paper
Journal of Membrane Science, 2010Co-Authors: M C Campo, Fernão D. Magalhães, Adélio MendesAbstract:Abstract Carbon Molecular Sieve membranes (CMSM) were successfully prepared from cellophane paper by one single pyrolysis step. The influence of pyrolysis parameters on the membranes’ structure, morphology and performance was examined through scanning electron microscopy, X-ray microanalysis, X-ray diffraction and monocomponent permeation experiments towards He, H 2 , Ar, N 2 , CO 2 , O 2 , CH 4 and water vapor at 29.5 °C. The permeabilities reached a maximum for CMSM heated up to 550 °C, without significantly compromising selectivities. The soaking time at this temperature led to pore closing and, consequently, decrease in permeability and an enhancement in selectivity. These membranes were also considerably permeable to water vapor (1000 barrer), and very selective concerning H 2 O/CH 4 ( α = 921–7518) and H 2 O/N 2 ( α = 364–9936) separations. No aging effects were observed due to oxygen or water vapor exposure. The permselectivity of CMSM prepared up to 550 °C overtook the Robeson bound for polymeric membranes, especially regarding ideal selectivities of pairs O 2 /N 2 ( α = 13–18), H 2 /N 2 , H 2 /O 2 , H 2 /CH 4 and H 2 /CO 2 . Therefore, they might be considered in relevant industrial applications such as separation of nitrogen from air and recovery of hydrogen from synthesis gas.
-
Aging study of Carbon Molecular Sieve membranes
Journal of Membrane Science, 2007Co-Authors: S. Lagorsse, Fernão D. Magalhães, Adélio MendesAbstract:Further insight into the impact of air and humidity exposure on Carbon Molecular Sieve membranes (CMSM) is provided. A CMSM was exposed to water vapor and to different dry environments (air, oxygen, nitrogen, propylene, etc.) for several months and the performance stability with time was analyzed periodically. In an effort to better understand the effect of oxygen on the fresh CMSM, regeneration at high temperature, used to remove some oxygen surface groups, was conducted 1 year after fabrication. The impact of oxygen removal from the surface on adsorption equilibrium, kinetic transport and pore structure is considered. Membrane aging as a result of oxygen adsorption was investigated on the heat-treated sample. This is the first time that oxygen chemisorption uptake rates have been measured on CMSM. Passivation methods and regeneration procedures on CMSM are also discussed.
Kumar Varoon Agrawal - One of the best experts on this subject based on the ideXlab platform.
-
Ultrathin Carbon Molecular Sieve Films and Room-Temperature Oxygen Functionalization for Gas-Sieving.
ACS applied materials & interfaces, 2019Co-Authors: Shiqi Huang, Luis Francisco Villalobos, Deepu J. Babu, Andreas Züttel, Kumar Varoon AgrawalAbstract:Inorganic membranes based on Carbon Molecular Sieve (CMS) films hosting slit-like pores can yield high Molecular selectivity with a sub-angstrom resolution in Molecular differentiation and therefor...
-
Ultrathin Carbon Molecular Sieve Films and Room-Temperature Oxygen Functionalization for Gas-Sieving
ACS Applied Materials & Interfaces, 2019Co-Authors: Shiqi Huang, Luis Francisco Villalobos, Deepu J. Babu, Andreas Züttel, Guangwei He, Mo Li, Kumar Varoon AgrawalAbstract:Inorganic membranes based on Carbon Molecular Sieve (CMS) films hosting slit-like pores can yield high Molecular selectivity with a sub-angstrom resolution in Molecular differentiation and therefore are highly attractive for energy-efficient separations. However, the selective layer thickness of the state-of-the-art CMS membranes for gas separation is more than 1 μm, yielding low gas permeance. Also, there is no room-temperature functionalization route for the modification of the pore-size-distribution of CMS to increase the Molecular selectivity. In this context, we report two novel fabrication routes, namely, transfer and masking techniques, leading to CMS films with thicknesses as small as 100 nm, yielding attractive gas-sieving performances with H2 permeance reaching up to 3060 gas permeation unit (GPU). Further, a rapid and highly tunable room-temperature ozone treatment-based postsynthetic modification is reported, shrinking the electron density gap in the nanopores by a fraction of an angstrom and ...
Jayesh J. Nair - One of the best experts on this subject based on the ideXlab platform.
-
Selectivity engineering in the nitration of chlorobenzene using eclectically engineered sulfated zirconia and Carbon Molecular Sieve catalysts
Catalysis Letters, 1999Co-Authors: Ganapati D. Yadav, Jayesh J. NairAbstract:Selective synthesis of the para‐nitro derivative from chlorobenzene by using nitric acid over an eclectically engineered sulfated zirconia Carbon Molecular Sieve catalyst is reported. The p : o ratio in chlorobenzene nitration was found to be very high with eclectically engineered sulfated zirconia and Carbon Molecular Sieve catalyst.
-
Novelties of eclectically engineered sulfated zirconia and Carbon Molecular Sieve catalysts in cyclisation of citronellal to isopulegol
Chemical Communications, 1998Co-Authors: Ganapati D. Yadav, Jayesh J. NairAbstract:Sulfated zirconia (S-ZrO2) is a well-known solid superacid catalyst used in various reactions of commercial importance such as isomerisation, alkylation and acylation, nitration, etc. The selectivity towards the formation of isopulegol, a potential intermediate in the synthesis of menthol, can be drastically increased by using Carbon Molecular Sieve (CMS) with S-ZrO2.
Shiqi Huang - One of the best experts on this subject based on the ideXlab platform.
-
Ultrathin Carbon Molecular Sieve Films and Room-Temperature Oxygen Functionalization for Gas-Sieving.
ACS applied materials & interfaces, 2019Co-Authors: Shiqi Huang, Luis Francisco Villalobos, Deepu J. Babu, Andreas Züttel, Kumar Varoon AgrawalAbstract:Inorganic membranes based on Carbon Molecular Sieve (CMS) films hosting slit-like pores can yield high Molecular selectivity with a sub-angstrom resolution in Molecular differentiation and therefor...
-
Ultrathin Carbon Molecular Sieve Films and Room-Temperature Oxygen Functionalization for Gas-Sieving
ACS Applied Materials & Interfaces, 2019Co-Authors: Shiqi Huang, Luis Francisco Villalobos, Deepu J. Babu, Andreas Züttel, Guangwei He, Mo Li, Kumar Varoon AgrawalAbstract:Inorganic membranes based on Carbon Molecular Sieve (CMS) films hosting slit-like pores can yield high Molecular selectivity with a sub-angstrom resolution in Molecular differentiation and therefore are highly attractive for energy-efficient separations. However, the selective layer thickness of the state-of-the-art CMS membranes for gas separation is more than 1 μm, yielding low gas permeance. Also, there is no room-temperature functionalization route for the modification of the pore-size-distribution of CMS to increase the Molecular selectivity. In this context, we report two novel fabrication routes, namely, transfer and masking techniques, leading to CMS films with thicknesses as small as 100 nm, yielding attractive gas-sieving performances with H2 permeance reaching up to 3060 gas permeation unit (GPU). Further, a rapid and highly tunable room-temperature ozone treatment-based postsynthetic modification is reported, shrinking the electron density gap in the nanopores by a fraction of an angstrom and ...