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Al2O3 Membranes (al2o3 + membrane)
Selected AbstractsMultilayer Amorphous-Si-B-C-N/,-Al2O3/,-Al2O3 Membranes for Hydrogen Purification,,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Ravi Mohan Prasad Abstract The hydrogen and carbon monoxide separation is an important step in the hydrogen production process. If H2 can be selectively removed from the product side during hydrogen production in membrane reactors, then it would be possible to achieve complete CO conversion in a single-step under high temperature conditions. In the present work, the multilayer amorphous-Si-B-C-N/,-Al2O3/,-Al2O3 membranes with gradient porosity have been realized and assessed with respect to the thermal stability, geometry of pore space and H2/CO permeance. The ,-Al2O3 support has a bimodal pore-size distribution of about 0.64 and 0.045 µm being macroporous and the intermediate ,-Al2O3 layer,deposited from boehmite colloidal dispersion,has an average pore-size of 8,nm being mesoporous. The results obtained by the N2 -adsorption method indicate a decrease in the volume of micropores,0.35 vs. 0.75,cm3,g,1,and a smaller pore size ,6.8 vs. 7.4 Å,in membranes with the intermediate mesoporous ,-Al2O3 layer if compared to those without. The three times Si-B-C-N coated multilayer membranes show higher H2/CO permselectivities of about 10.5 and the H2 permeance of about 1.05,×,10,8 mol m,2 s,1 Pa,1. If compared to the state of the art of microporous membranes, the multilayer Si-B-C-N/,-Al2O3/,-Al2O3 membranes are appeared to be interesting candidates for hydrogen separation because of their tunable nature and high-temperature and high-pressure stability. [source] Effect of metal-support interface on hydrogen permeation through palladium membranesAICHE JOURNAL, Issue 3 2009Ke Zhang Abstract Thin palladium membranes of different thicknesses were prepared on sol-gel derived mesoporous ,-alumina/,-alumina and yttria-stabilized zirconia/,-alumina supports by a method combining sputter deposition and electroless plating. The effect of metal-support interface on hydrogen transport permeation properties was investigated by comparing hydrogen permeation data for these membranes measured under different conditions. Hydrogen permeation fluxes for the Pd/,-Al2O3/,-Al2O3 membranes are significantly smaller than those for the Pd/YSZ/,-Al2O3 membranes under similar conditions. As the palladium membrane thickness increases, the difference in permeation fluxes between these two groups of membranes decreases and the pressure exponent for permeation flux approaches 0.5 from 1. Analysis of the permeation data with a permeation model shows that both groups of membranes have similar hydrogen permeability for bulk diffusion, but the Pd/,-Al2O3/,-Al2O3 membranes exhibit a much lower surface reaction rate constant with higher activation energy, due possibly to the formation of Pd-Al alloy, than the Pd/YSZ/,-Al2O3 membranes. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Donor/Conductor/Acceptor Triads Spatially Organized on the Micrometer-Length Scale: An Alternative Approach to Photovoltaic CellsCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2007Francesc Abstract We have used porous anodised Al2O3 membranes as inert matrix for constructing and organizing spatially ternary donor/conductor/acceptor (DCA) systems exhibiting photovoltaic cell activity on the micrometric-length scale. These DCA triads were built stepwise by first growing a conducting polymer inside the membrane pores, thus forming nanorods that completely fill the internal pore space of the membrane. Then, an electron donor and an electron acceptor were adsorbed one on each side of the membrane, so that they were separated by a distance equal to the membrane thickness (ca. 60,,m), but electronically connected through the conductive polymer. When this device was placed between two electrodes and irradiated with visible light, electrons jumped from the donor molecule, crossed the membrane from side to side through the conductive polymer (a journey of about 60,,m!) until they finally reach the acceptor molecule. In so doing, an electric voltage was generated between the two electrodes, capable of maintaining an electric current flow from the membrane to an external circuit. Our DCA device constitutes the proof of a novel concept of photovoltaic cells, since it is based on the spatial organization at the micrometric scale of complementary, but not covalently linked, electron-donor and electron-acceptor organic species. Thus, our cell is based in translating photoinduced electron transfer between donors and acceptors, which is known to occur at the molecular nanometric scale, to the micrometric range in a spatially organised system. In addition our cell does not need the use of liquid electrolytes in order to operate, which is one of the main drawbacks in dye-sensitised solar cells. [source] | ||||||||||