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Abstract Permeation measurements indicate that a SSZ-13 membrane exhibited significantly different adsorption behavior from SSZ-13 crystals. Both C 3 H 8 and n-C 4 H 10 adsorb to high loadings in SSZ-13 crystals, but they only have a small effect on CO 2 permeation through a SSZ-13 membrane at 293 K, indicating they do not adsorb in the SSZ-13 pores. Whereas 15% C 2 H 6 in the membrane feed decreased CO 2 permeance by 45%, 15% C 3 H 8 only decreased CO 2 permeance by 10%, even though C 3 H 8 adsorbs more strongly than C 2 H 6 in SSZ-13 crystals. Moreover, this 10% decrease is attributed to C 3 H 8 adsorption on the external surface of the membrane crystals because i-C 4 H 10 , which is significantly larger than SSZ-13 pores and thus does not adsorb in the pores, only decreased CO 2 permeance by 15%. The difference between SSZ-13 crystals and the SSZ-13 membrane is attributed to the presence of a diffusion barrier on the external surface of the membrane crystals. Thus, care should be taken in using adsorption measurements on zeolite powders to predict permeation behavior in zeolite membranes. Highlights • C 3 H 8 and n-C 4 H 10 did not adsorb in the pores of an SSZ-13 membrane even though they adsorbed in SSZ-13 crystal powders. • As a result, C 3 H 8 and n-C 4 H 10 reduced the CO 2 permeation through a SSZ-13 membrane much less than CH 4 and C 2 H 6. • CO 2 /C 3 H 8 separation selectivities greater than 104 were measured for the SSZ-13 membrane, indicating few defects. • Molecules too large to enter zeolite crystals can affect permeation through membranes by adsorbing on the external surface. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

When 0.65 mol% toluene was added to SAPO-34 membrane feeds (172-kPa feed pressure), the CO 2 and N 2 permeances decreased by approximately 50%, even though toluene is too large to diffuse into the SAPO-34 pores. Single-component adsorption isotherms for CO 2 and toluene were used to fit a dual-site Langmuir model to estimate external surface coverages. The lower CO 2 permeances qualitatively correlated with the reduced CO 2 surface coverages. Changes in permeances for 10-kPa feed pressures were also measured so that surface coverages could be estimated more accurately using ideal adsorbed solution theory. The estimated decreases in CO 2 coverages on the membrane surface due to competitively-adsorbed toluene reduced the trans-membrane CO 2 driving force and accounted for the observed decreases in permeance. [ABSTRACT FROM AUTHOR]

Single-component adsorption isotherms for CO2, CH4, C3H8, and H2O on SAPO-34, SSZ-13, and zeolite T were measured, and isosteric heats of adsorption were estimated. Long equilibration times were required for C3H8 adsorption in SAPO-34 and SSZ-13 because C3H8 diffuses slowly in these zeolites, but C3H8 isotherms were obtained quickly on zeolite T. Thus, when CO2 and C3H8 coadsorption loadings were measured by temperature-programmed desorption on SSZ-13, CO2 loadings were higher than C3H8 loadings at short times, whereas at long times, C3H8 loadings were higher as C3H8 displaced adsorbed CO2. In contrast, adsorption of CO2/C3H8 mixtures equilibrated quickly in zeolite T because of the fast C3H8 diffusion. These adsorption measurements may explain previously reported zeolite membrane behavior where C3H8 decreased CO2 permeances for SAPO-34, SSZ-13, and zeolite T membranes under most conditions, and steady state was only slowly obtained for SAPO-34 and SSZ-13 membranes in the presence of C3H8. [ABSTRACT FROM AUTHOR]

Abstract: SAPO-34 membranes that have CO2/CH4 separation selectivities of ~100 at 295K and pressures up to 4.6MPa also show high molecular sieving separations of mixtures containing i-butane (0.50-nm kinetic diameter) or CF4 (0.47nm). The separation selectivities were 15,000–20,000 for CO2/i-butane from 295 to 420K, and 12,000–20,000 for CO2/CF4 for feed pressures up to 0.5MPa at 295K. These may be the highest gas-phase separation selectivities reported for zeolite membranes, and they are likely lower limits because of concentration polarization, leakage around O-rings, and i-butane diffusion through the silicone O-rings. The low defect concentration was also confirmed by spatial defect distributions measured with i-butane. Thus, less than 1% of the CH4 permeation during CO2/CH4 separations is through defects larger than 0.47nm. Isobutane, even though it is too large to adsorb in SAPO-34 pores (0.38-nm diameter), appeared to inhibit CO2 permeation by adsorbing on the external surface. These SAPO-34 membranes also separated H2/i-butane with lower limits on selectivities of 6000 at 295K and 10,000–14,000 at 423K, and they were also selective for He/CH4 separation (selectivity=20) and H2/CH4 separation (selectivity=35–45). In these separations, both He and H2 appear to speed up CH4 permeation, as expected from molecular simulations reported previously. Also, CH4 appears to slow diffusion of CO2, He, and H2. [Copyright &y& Elsevier]

Abstract: A technique to measure spatially resolved permeances through tubular membranes with a moveable mass spectrometer probe at the membrane surface is described. This technique was used to determine spatial permeance distributions for SAPO-34 zeolite membranes, alumina membrane supports, and a Vycor glass membrane. The distribution of local permeances provides more detailed information about membrane properties than global permeances. The CO2 and CH4 permeances of SAPO-34 membranes that had high permeances and selectivities at 4.6MPa were not spatially uniform across the membrane area. Membranes prepared using Al(OH)3 as the aluminum precursor had large regions that were nearly impermeable, whereas membranes prepared with Al(i-C3H7O)3 were more uniform, and thus had higher overall permeances. Scanning electron micrographs indicated that these differences in permeance were not due to differences in membrane thickness, and spatially uniform permeance distributions for alumina supports suggest that they were not due to non-uniformities in the supports. Defect locations in the SAPO-34 layers were detected using i-butane permeation, because i-butane is too large to enter the SAPO-34 pores, and the defect concentrations were low. These spatially resolved measurements indicate the potential to increase both CO2/CH4 selectivity and CO2 permeance, and help understand the factors that affect membranes properties. [Copyright &y& Elsevier]

Abstract: A MnO/NaOH based three-step thermochemical water splitting cycle was modified to improve the hydrolysis of α-NaMnO2 (sodium manganate) and to recover Mn(III) oxides for the high-temperature reduction step. Sodium manganate forms in the reaction of NaOH with MnO that releases hydrogen. The hydrolysis of α-NaMnO2 to manganese oxides and NaOH is incomplete even with a large excess of water and more than 10% sodium cannot be removed prior to the high-temperature reduction step. When mixed oxides of manganese with iron were used in the cycle, the NaOH recovery in the hydrolysis step improved from about 10% to 35% at NaOH concentrations above 1M. Only 60% sodium was removed at 0.5M from the mixed oxides whereas more than 80% can be recovered at the same NaOH concentration when only manganese oxides are used. A 10:1 Mn/Fe sample was cycled through all steps three times to confirm that multiple cycles are possible. The high-temperature reduction was carried out for 5h at 1773 K under vacuum and the conversion was about 65% after the 3rd cycle. Since sodium carryover into the high-temperature reduction cannot be avoided, even with the energy intensive hydrolysis step, a modified two-step cycle without low-temperature sodium recovery is proposed where α-NaMnO2 is reduced directly to MnO at 1773 K under vacuum. On a laboratory scale, about 60% of the sodium that volatilized at the high temperatures was trapped with a water-cooled cold finger and conversions were stable at about 35% after three completed cycles. [Copyright &y& Elsevier]

Gated ion diffusion is found widely in hydrophobic biological nanopores, upon changes in ligand binding, temperature, transmembrane voltage, and mechanical stress. Because water is the main media for ion diffusion in these hydrophobic biological pores, ion diffusion behavior through these nanochannels is expected to be influenced significantly when water wettability in hydrophobic biological nanopores is sensitive and changes upon small external changes. Here, we report for the first time that ion diffusion through highly hydrophobic nanopores (3 nm) showed a gated behavior due to change of water wettability on hydrophobic surface upon small temperature change or ultrasound. Dense carbon nanotube (CNT) membranes with both 3-nm CNTs and 3-nm interstitial pores were prepared by a solvent evaporation process and used as a model system to investigate ion diffusion behavior. Ion diffusion through these membranes exhibited a gated behavior. The ion flux was turned on and off, apparently because the water wettability of CNTs changed. At 298 K, ion diffusion through dense CNT membranes stopped after a few hours, but it dramatically increased when the temperature was increased 20 K or the membrane was subjected to ultrasound. Likewise, water adsorption on dense CNT membranes increased dramatically at a water activity of 0.53 when the temperature increased from 293 to 306 K, indicating capillary condensation. Water adsorption isotherms of dense CNT membranes suggest that the adsorbed water forms a discontinuous phase at 293 K, but it probably forms a continuous layer, probably in the interstitial CNT regions, at higher temperatures. When the ion diffusion channel was opened by a temperature increase or ultrasound, ions diffused through the CNT membranes at a rate similar to bulk diffusion in water. This finding may have implications for using CNT membrane for desalination and water treatment. [ABSTRACT FROM AUTHOR]

Abstract: Adsorption of i-butane, p-xylene, and benzene shrinks the size of MFI crystals in polycrystalline MFI membranes at room temperature. The crystal shrinkage, which is over different loading ranges for the three molecules, increases the sizes of the defects (gaps between the crystals). Two membranes, one with 90% of its helium flux through defects, and one with 9% were studied in detail. For the membrane with 90% of its helium flow through defects, the flux through the defects increased by as much as 44%, depending on the permeating molecule. The defect sizes increased for p-xylene loadings below 4molec./u.c. and for i-butane loading between 3 and 8molec./u.c. At higher loadings (7molec./u.c. for p-xylene and 9molec./u.c. for i-butane) p-xylene and i-butane expanded MFI crystals and shrank the defect sizes so that the helium flow through defects decreased by as much as two orders of magnitude. Benzene did not significantly change the flux through defects at loadings below 8molec./u.c. Near a loading of 8benzenemolec./u.c. the flux through the defects increased by approximately 18% for one membrane. [Copyright &y& Elsevier]

Abstract: Separation of CO2/CH4 mixtures through tubular SAPO-34 membranes with high permeances was strongly affected by concentration polarization at feed pressures above about 1MPa. The faster-permeating CO2 was depleted near the membrane surface because it could not diffuse fast enough from the bulk phase. Concentration polarization increased as pressure increased at constant feed rates because fluxes through the membranes increased, gas diffusivities decreased, and the velocity across the membrane decreased because gas densities increased. The CO2/CH4 selectivity, at 298K and a feed pressure of 5.8MPa, increased by about 160% and the CO2 flux increased by about 80% when Teflon spacers were inserted inside the membrane tube and the feed flow rate was increased by a factor of three. The spacers and the increased feed rate increased the gas velocity and decreased the diffusion distance from the bulk phase to the membrane surface, and thus they decreased the polarization boundary layer. The spacers did not affect separations at low pressures, where gas velocities and diffusivities were higher and fluxes were lower. [Copyright &y& Elsevier]

Abstract: Two polycrystalline MFI membranes with significant flow through defects (non-zeolitic pores that are gaps between the crystals) are shown to have high ideal and mixture selectivities. The membranes were characterized at room temperature by permporosimetry, pervaporation, separations, and single-gas permeation. These measurements indicate that one membrane (B-ZSM-5) had a relatively large number of smaller defects, whereas the second membrane (silicalite-1) had a smaller number of somewhat larger defects. The relative contributions of these defects to the overall flux changed dramatically in the presence of n-alkanes and SF6. These molecules caused adsorption-induced expansion of the crystals, and this expansion shrank the defect sizes and thus changed the membrane permeation characteristics. The B-ZSM-5 membrane had 90% of its helium flux through defects at room temperature, but it had a H 2 /SF 6 ideal selectivity as high as 260 because of SF 6 -induced swelling that stopped 99% of the flux through the defects. In contrast, the silicalite-1 membrane had only 9% of its helium flux through defects, but the defects were large enough that crystal swelling only decreased the flux through them by 30%. Thus its selectivities were lower. These studies show that n-hexane, n-pentane, n-butane, n-propane, and SF6 swell MFI crystals when they adsorb, but benzene and CO2 do not. The changes in membrane microstructure due to crystal expansion not only significantly affect membrane separation ability, but also have implications on how to select appropriate characterization techniques for evaluating MFI membrane quality. [Copyright &y& Elsevier]

Abstract: The hydrolysis of zinc powder was studied in an aerosol to determine if high conversions are feasible at short residence times and high dispersions. This reaction is the low temperature hydrogen formation step in a two step zinc/zinc oxide based thermo-chemical cycle for water splitting using solar energy. Zinc particles with an average size of 158nm were reacted with water vapor to form hydrogen and zinc oxide in an aerosol flow tube reactor at ambient pressure (82kPa) between 653 and 813K and a water concentration of 3%. The highest conversion observed in the flow system was about 24% at 813K and a gas residence time of . Non-isothermal thermogravimetric analysis (TGA) indicated that complete conversion of zinc to zinc oxide could be achieved for longer residence times. An activation energy of was calculated from the TGA experiments using a model-free isoconversional method. Standard reaction models did not describe the data so an empirical order of reaction rate law was used instead. Reaction rates in the aerosol flow reactor were higher than those calculated from the TGA measurements, likely due to lower mass and heat transfer resistances in the aerosol. [Copyright &y& Elsevier]

Examines the usability of tunable laser spectroscopy to detect trace moisture in ultra-high purity gases. Reason for the popularity of Fourier transform infrared spectroscopy as a method for trace moisture detection; Response rate of the instrument in nitrogen analysis; Factor affecting the discrepancy in instruments readings and the true moisture content.

The control of water vapor (moisture) contamination in process gases is critical to the successful manufacture of semiconductor devices. As specified moisture levels have become more stringent, there is a growing demand for more sensitive analytical methods. Instrumental methods currently being used or in development for measuring trace moisture at ppbv levels include Fourier transform infrared spectroscopy, tunable diode laser absorption spectroscopy, cavity ringdown spectroscopy, intracavity laser spectroscopy, electron impact ionization mass spectrometry, and atmospheric pressure ionization mass spectrometry. In addition, sensor-based technologies such as oscillating quartz crystal microbalances, and chilled mirror-, capacitor-, and electrolytic-based hygrometers operate in this regime. These approaches are presented and reviewed. As the success of each trace moisture method is dependent on the degree to which the different process gases interfere with the measurement process, important process gas applications of the techniques are highlighted. Advantages and disadvantages as well as future developments and trends are also presented. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The reliability of a newly engineered palladium membrane diffuser for hydrogen purification has been investigated. The purifier was exposed to operating conditions that cause high failure rates in other currently available commercial designs. Stress tests include repeated power outages, and rapidly increasing and decreasing flow rates. Helium leak tests confirmed that the membranes maintained their integrity under these conditions. Atmospheric pressure ionization mass spectrometry (APIMS) verified sub-ppb efficiency of the purifier for impurity removal. Flow rate measurements as a function of pressure gradient and membrane temperature indicated that the flux across the membrane was not limited by external mass transfer resistance and followed basic laws of diffusion. [Copyright &y& Elsevier]

Each of the elements of a gas distribution system potentially is a source of contamination in film growth reactors. A detailed technical understanding of the origin and properties of the most common contaminants, their fluctuations and their interaction with the different elements in the delivery system are essential to provide consistent high gas purity for device growth. Governing processes in the gas source, the delivery system, and purifiers were addressed with selected examples, along with approaches for integrated solutions. The examples include impurity fluctuation in NH3 as a function of the method of delivery, moisture outgassing from particle filters as a function of filter material and matrix gas, and low-level breakthrough in packed bed adsorbent-based purifiers as a result of transport and reaction rate limitations. [Copyright &y& Elsevier]

Defect-free, microporous Al2O3/SAPO-34 zeolite composite membranes were prepared by coating hydrothermally grown zeolite membranes with microporous alumina using molecular layer deposition. These inorganic composite membranes are highly efficient for H2 separation: their highest H2/N2 mixture selectivity was 1040, in contrast with selectivities of 8 for SAPO-34 membranes. The composite membranes were selective for H2 for temperatures up to at least 473 K and feed pressures up to at least 1.5 MPa; at 473 K and 1.5 MPa, the H2/N2 separation selectivity was 750. The H2/CO2 separation selectivity was lower than the H2/N2 selectivity and decreased slightly with increasing pressure; the selectivity was 20 at 473 K and 1.5 MPa. The high H2 selectivity resulted either because most of the pores in the Al2O3 layer were slightly smaller than 0.36 nm (the kinetic diameter of N2) or because the Al2O3 layer slightly narrowed the SAPO-34 pore entrance. These composite membranes may represent a new class of inorganic membranes for gas separation. [ABSTRACT FROM AUTHOR]

Describes the capabilities of automated gas monitoring/purification system that detects unacceptable contaminant intrusions and interrupts or bypasses gas flow into the purifier. Two beta versions of the system; System configuration; Typical oxygen concentrations in the house nitrogen supply measured at the point of use.

Formulations of human papillomavirus (HPV) 16, 18, and 31 L1 capsomere protein antigens were spray dried to obtain glassy microspheres that were then coated by atomic layer deposition (ALD) with nanometer-thin protective layers of alumina. Spray-drying was used to formulate human papillomavirus (HPV) 16, 18, and 31 L1 capsomere protein antigens within glassy microspheres to which nanoscopic protective layers of alumina were applied using ALD. Suspensions of alumina-coated, capsomere-containing microparticles were administered in a single dose to mice. ALD-deposited alumina coatings provided thermostability and a delayed in vivo release of capsomere antigens, incorporating both a prime and a boost dose in one injection. Total serotype-specific antibody titers as well as neutralizing titers determined from pseudovirus infectivity assays were unaffected by incubation of the ALD-coated vaccines for at 4, 50, or 70 °C for three months prior to administration. In addition, even after incubation for three months at 70 °C, single doses of ALD-coated vaccines produced both higher total antibody responses and higher neutralizing responses than control immunizations that used two doses of conventional liquid formulations stored at 4 °C. [ABSTRACT FROM AUTHOR]

Especially in developing countries, the impact of vaccines can be limited by logistical obstacles associated with multiple dose regimens, pathogen variants, and challenges imposed by requirements for maintaining vaccines at low temperatures during shipping and storage. Thus, there is a need for vaccines that can be flexibly modified to address evolving pathogen landscapes, are stable outside of narrow "cold-chain" temperatures and require administration of only single doses. Here we demonstrate in proof-of-concept studies a vaccine platform that addresses these impediments to more widespread use of vaccines. The platform relies on bacteriophage-derived phage-like-particles (PLPs) that utilize a "plug-and-play" antigen delivery system that allows for fast, easy alteration of antigens on the surface of the PLPs. Thermostability of PLP-based vaccines can be achieved by embedding the PLPs within glassy particles produced by spray drying, and nanoscopic aluminum oxide layers applied using atomic layer deposition (ALD) can serve to control release of antigen in vivo, yielding vaccine formulations that elicit strong immune responses after administration of single doses. Bacteriophage λ was stabilized by spray drying to form powders that were incubated at 37 °C for up to a year without loss of infectious activity. PLPs derived from bacteriophage λ were expressed and purified from E. coli cultures, and an in vitro conjugation strategy was used to decorate specific PLP surface sites with T4-lysozyme, a model vaccine antigen. The resulting T4-lysozyme:PLP complexes (Lys-PLPs) were embedded in glassy dry powders formed by spray drying and coated with nanometer-thick layers of alumina deposited by ALD in a fluidized bed reactor. Alumina-coated Lys-PLP vaccines were stable for a least a month at 50 °C, and single doses of the alumina-coated vaccines elicited immune responses that were indistinguishable from responses generated by conventional two-dose, prime-and-boost dosing regimens of alum-adjuvanted Lys-PLP vaccines. [ABSTRACT FROM AUTHOR]

Following removal of coordinated CH³CN, the resulting complexes [AgI(2,2'-bipyridine)][BF4] (1) and [AgI(6,6'-dimethyl-2,2'-bipyridine)][OTf] (2) show ethene/ ethane sorption selectivities of 390 and 340, respectively, and corresponding ethene sorption capacities of 2.38 and 2.18 mmolg-1 when tested at an applied gas pressure of 90 kPa and a temperature of (20±1) °C. These ethene/ethane selectivities are 13 times higher than those reported for known solid sorbents for ethene/ethane separation. For 2, ethene sorption reached 90% of equilibrium capacity within 15 minutes, and this equilibrium capacity was maintained over the three sorption/desorption cycles tested. The rates of ethene sorption were also measured. To our knowledge, these are the first complexes, designed for olefin/paraffin separations, which have open silver(I) sites. The high selectivities arise from these open silver(I) sites and the relatively low molecular surface areas of the complexes. [ABSTRACT FROM AUTHOR]

Following removal of coordinated CH3CN, the resulting complexes [AgI(2,2'-bipyridine)][BF4] (1) and [AgI(6,6'-dimethyl-2,2'-bipyridine)][OTf] (2) show ethene/ ethane sorption selectivities of 390 and 340, respectively, and corresponding ethene sorption capacities of 2.38 and 2.18 mmolg-1 when tested at an applied gas pressure of 90 kPa and a temperature of (20±1) °C. These ethene/ethane selectivities are 13 times higher than those reported for known solid sorbents for ethene/ethane separation. For 2, ethene sorption reached 90% of equilibrium capacity within 15 minutes, and this equilibrium capacity was maintained over the three sorption/desorption cycles tested. The rates of ethene sorption were also measured. To our knowledge, these are the first complexes, designed for olefin/paraffin separations, which have open silver(I) sites. The high selectivities arise from these open silver(I) sites and the relatively low molecular surface areas of the complexes. [ABSTRACT FROM AUTHOR]

Abstract: Previously, SAPO-34 membranes prepared using aluminum isopropoxide (Al(O–i–Pr)3) and two templates (tetraethylammoniumhydroxide (TEAOH); dipropylamine (DPA)) were shown to separate CO2/CH4 mixtures with high fluxes at high pressures and room temperature. In this study, the synthesis was simplified, made safer, and modified to create less toxic waste by using only one template (TEAOH), but at twice the concentration, and Al(OH)3 instead of Al(O–i–Pr)3. However, some membranes prepared with the new procedure had low fluxes because they had impermeable regions. The impermeable regions were determined to be due to synthesis gel that remained in the support following a 15-min, post-synthesis rinse with water. Rinsing the membranes for at least 24h in deionized water before calcination removed most of the residual gel and formed spatially-uniform membranes with high permeances (maximum of 1.2×10−6 mol/(m2 sPa)) and high CO2/CH4 separation selectivities (70) for 46-bar feed pressure. Additional benefits of these changes in membrane preparation include a 200-K increase in the temperature at which template could be removed, increased stability of calcined membranes contacted with liquid water, and better long-term stability during storage. [Copyright &y& Elsevier]

Abstract: SAPO-34 zeolite membrane synthesis was scaled up by preparing membranes on seven-channel monolith alumina supports. These monoliths have CO2 permeances and CO2/CH4 separations selectivities at 4.6MPa feed pressure that were similar to SAPO-34 membranes on single channel supports. They also exhibited the same pressure dependence. SAPO-34 membrane preparation was improved by adding SAPO-34 seed crystals to the synthesis gel instead of placing seeds on the support surface. Membranes prepared by seeded-gel synthesis had higher CO2 permeances, higher CO2/CH4 separation selectivities, and smaller standard deviations for these values. Using seeded-gel synthesis also decreased the number of synthesis steps, but increased the amount of seeds needed by two orders of magnitude. [Copyright &y& Elsevier]

Abstract: SAPO-34 membranes had 95–100% higher CO2 permeances and 9–17% lower CO2/CH4 separation selectivities when their structure-directing templates were removed at 673K in flowing N2 or under vacuum instead of in flowing air. The average CO2 permeance was 8.2±2×10−7 mol/(m2 sPa) during CO2/CH4 separations at 4.6MPa feed pressure for five membranes whose templates were removed under vacuum. The average CO2/CH4 separation selectivity was 55±6. Membranes heated in N2 or under vacuum were white in color, whereas those heated in air were darker. Membrane preparation was reproducible. Temperature-programmed desorption (TPD) and oxidation (TPO) of SAPO-34 crystals showed that more of the templates decomposed and were removed at lower temperature in inert gas than in air or oxygen. Over 90% of the templates were removed by 773K during TPD in helium, and ethylene was the main decomposition product. In contrast, only 70% of the templates were removed by 773K during TPO in air or oxygen, and CO2 and water were the major products When the SAPO-34 crystals were heated in air or oxygen, some of the template, before it decomposed to form ethylene, was oxidized to more stable compounds that were only removed at higher temperatures. [Copyright &y& Elsevier]

The trinuclear copper(I) pyrazolate complex [Cu3] rearranges to the dinuclear analogue [Cu2⋅(C2H4)2] when exposed to ethylene gas. Remarkably, the [Cu3]↔[Cu2⋅(C2H4)2] rearrangement occurs reversibly in the solid state. Furthermore, this transformation emulates solution chemistry. The bond‐making and breaking processes associated with the rearrangement in the solid‐state result in an observed heat of adsorption (−13±1 kJ mol−1 per Cu–C2H4 interaction) significantly lower than other Cu–C2H4 interactions (≥−24 kJ mol−1). The low overall heat of adsorption, "step" isotherms, high ethylene capacity (2.76 mmol g−1; 7.6 wt % at 293 K), and high ethylene/ethane selectivity (136:1 at 293 K) make [Cu3] an interesting basis for the rational design of materials for low‐energy ethylene/ethane separations. Three's a crowd: A polyfluorinated, trinuclear copper complex absorbs ethylene and undergoes a major structural rearrangement leading to a dinuclear copper–ethylene complex. Upon removal of ethylene it reverts back to the trinuclear species. This process occurs both in solution and in the solid state. [ABSTRACT FROM AUTHOR]

The trinuclear copper(I) pyrazolate complex [Cu3] rearranges to the dinuclear analogue [Cu2⋅(C2H4)2] when exposed to ethylene gas. Remarkably, the [Cu3]↔[Cu2⋅(C2H4)2] rearrangement occurs reversibly in the solid state. Furthermore, this transformation emulates solution chemistry. The bond‐making and breaking processes associated with the rearrangement in the solid‐state result in an observed heat of adsorption (−13±1 kJ mol−1 per Cu–C2H4 interaction) significantly lower than other Cu–C2H4 interactions (≥−24 kJ mol−1). The low overall heat of adsorption, "step" isotherms, high ethylene capacity (2.76 mmol g−1; 7.6 wt % at 293 K), and high ethylene/ethane selectivity (136:1 at 293 K) make [Cu3] an interesting basis for the rational design of materials for low‐energy ethylene/ethane separations. [ABSTRACT FROM AUTHOR]

Adding propane or n-butane in low concentrations to a H 2 /N 2 feed increases the H 2 /N 2 separation selectivity in SAPO-34 membranes by decreasing the N 2 permeance more than the H 2 permeance. More than two days were required to reach steady state because propane and n-butane diffuse slowly into the zeolite pores, but they adsorb strongly and thus decrease H 2 and N 2 loadings. Although the loading of the more-weakly adsorbed H 2 is expected to decrease more, the N 2 permeance decreased more than the H 2 permeance apparently because the diffusivity of the larger N 2 molecule decreased more. Propane more than doubled the H 2 /N 2 selectivity at 298 K, but its effect on selectivity decreased as the temperature increased because the propane loading in the SAPO-34 pores decreased. Ethane also decreased H 2 and N 2 permeances, but it did not change H 2 /N 2 selectivity. As with propane, ethane decreased H 2 loadings more than N 2 loadings, and decreased N 2 diffusivity more than H 2 diffusivity. However, the smaller ethane had less effect on the N 2 diffusivity than did propane, so the net effect was that the selectivity did not change. The effects of alkane adsorption in SAPO-34 membranes were reversed when the alkanes were removed from the feed. [ABSTRACT FROM AUTHOR]

A wide range of inorganic nanostructures have been used as photocatalysts for generating H2. To increase activity, Z-scheme photocatalytic systems have been implemented that use multiple types of photoactive materials and electron mediators. Optimal catalysis has previously been obtained by interfacing different materials through aggregation or epitaxial nucleation, all of which lowers the accessible active surface area. DNA has now been used as a structure-directing agent to organize TiO2 and CdS nanocrystals. A significant increase in H2 production compared to CdS or TiO2 alone was thus observed directly in solution with no sacrificial donors or applied bias. The inclusion of benzoquinone (BQ) equidistant between the TiO2 and CdS through DNA assembly further increased H2 production. While the use of a second quinone in conjunction with BQ showed no more improvement, its location within the Z-scheme was found to strongly influence catalysis. [ABSTRACT FROM AUTHOR]

A wide range of inorganic nanostructures have been used as photocatalysts for generating H2. To increase activity, Z-scheme photocatalytic systems have been implemented that use multiple types of photoactive materials and electron mediators. Optimal catalysis has previously been obtained by interfacing different materials through aggregation or epitaxial nucleation, all of which lowers the accessible active surface area. DNA has now been used as a structure-directing agent to organize TiO2 and CdS nanocrystals. A significant increase in H2 production compared to CdS or TiO2 alone was thus observed directly in solution with no sacrificial donors or applied bias. The inclusion of benzoquinone (BQ) equidistant between the TiO2 and CdS through DNA assembly further increased H2 production. While the use of a second quinone in conjunction with BQ showed no more improvement, its location within the Z-scheme was found to strongly influence catalysis. [ABSTRACT FROM AUTHOR]

Two types of CHA zeolite membranes (SAPO-34, SSZ-13) were used for CO 2 /CH 4 , N 2 /CH 4 , and CO 2 /i-butane separations at both low (270 and 350 kPa) and high (1.73 MPa) pressures. The SSZ-13 membranes were more selective, with CO 2 /CH 4 separation selectivities as high as 280 and N 2 /CH 4 separation selectivities of 12 at 270 kPa feed pressure. For both types of membranes, selectivities and permeances decreased as the feed pressure increased. The CO 2 /i-butane separation selectivities were greater than 500,000 for SAPO-34 membranes, indicating extremely low densities of defects because i-butane is too large to enter the CHA pores. The CO 2 /i-butane selectivities were smaller for SSZ-13 membranes (2,800–20,000), in part because the SSZ-13 layer was on the outside of the porous mullite tubes and sealing the membrane on the zeolite surface was more difficult than for the SAPO-34 membranes that were grown on the inside of glazed alumina tubes. Propane, in feed concentrations from 1 to 9%, significantly influenced separations by decreasing permeances in most cases. The effect was larger for N 2 /CH 4 than for CO 2 /CH 4 mixtures, apparently because the more strongly-adsorbing CO 2 competes better than N 2 with propane for adsorption sites. Although propane caused permeances to decrease significantly over time, selectivities decreased much less. Propane decreased permeances more for SAPO-34 membranes than for SSZ-13 membranes at 350 kPa, and at high pressure propane even increased CO 2 permeances and decreased CH 4 permeances in SSZ-13 membranes, thus significantly increasing CO 2 /CH 4 selectivities. Propane permeances reached steady state relatively quickly because its permeation was mostly through defects, but CO 2 , N 2 , and CH 4 permeances did not stabilize in the presence of propane, even after seven days. The effects of propane were reversible when it was removed from the feed and the membranes were heated. [ABSTRACT FROM AUTHOR]

Abstract: The CO2/CH4 separation selectivity of SAPO-34 membranes increased by 20–150% after soaking them in 1–2% aqueous β-cyclodextrin (CD) solution and drying them at 473K. The percentage increase was higher at higher pressures, and the selectivities increased more for membranes with more defects. The CD decreased the CO2 fluxes at high pressures by about 10–20%, whereas CH4 fluxes decreased by 30–60%. The flux of CF4, which is too large to enter the SAPO-34 pores and thus only permeates through defects, decreased 80% for one membrane (5.7MPa feed pressure) after CD deposition; this confirmed that defects were effectively blocked. Even before CD exposure, the CF4 permeance at 2.8MPa was only 0.25% of the CO2 mixture permeance for that membrane. Permporometry also showed that CD blocked defects; the maximum defect size decreased from greater than 30nm to less than 20nm. About 91% of the overall defect area in the original membrane was from defects smaller than 8nm, whereas 99% was for defects smaller than 2nm after CD deposition. The membrane separation performance did not change during 3 days of continuous measurements, nor did it change after long term storage at 473K in air. [Copyright &y& Elsevier]

Abstract: High flux SAPO-34 membranes on porous, tubular stainless steel supports with CO2/CH4 separation selectivities greater than 200 were scaled up from 5cm length to 25cm (a factor of 7.5 increase in membrane area). The preparation of the 25-cm membranes required a more dilute synthesis gel and shorter crystallization times to avoid excess build-up of zeolite crystals at the bottom of the membrane tubes. These changes yielded 25-cm membranes with similar permeances and selectivities to those of the 5-cm membranes. Aluminum sources, gel compositions, and synthesis procedures were systematically investigated to lower the membrane cost, optimize the separation performance, and obtain good reproducibility. The CO2 permeances of the 25-cm membranes were approximately 5×10−7 mol/(m2 sPa) at 295K for a feed pressure of 138kPa and a 50/50 feed. [Copyright &y& Elsevier]