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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 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]

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]

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]

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]