Hydrogen separation characteristics

As can be seen from Table 1, the starting membrane exhibits almost pure Knudsen separation characteristics, as can be expected from a state-of-the-art mesoporous y-alumina membrane. The ideal Knudsen permselectivities are H2 N2=3.74, He N2=2.65, H2 CC>2=4.69, which are in agreement with the measured permselectivities. After 43 minutes of CVI in experiment num-ber 1, the hydrogen permeance had decreased to 4.0 10 mol/m sPa, but the permselectivity towards nitrogen had increased to 43, which is far above the Knudsen value. 

Sakurai, M., Nakajima, H., Onuki, K., and Shimizu, S., Investigation of two liquid phase separation characteristics on the iodine-sulfur thermochemical hydrogen production process. International Journal of Hydrogen Energy, 25, 605-611, 2000. 

E. Kikuchi and S. Uemiya, Preparation of supported thin palladium-silver alloy membranes and their characteristics for hydrogen separation. Gas Sep. Purif. 5 261 (1991). 

In the 1960s, two direct coal liquefaction processes were under development in the U.S. the Exxon Donor Solvent (EDS) process and the H-Coal process. The distinguishing feature of the EDS process was a separate solvent hydrogenation step to carefully control the hydrogen donor characteristics of the solvent. The most important feature of the H-Coal process was the emulated bed reactor in the process. 

In contrast to polypeptides that have many possible conformations, poly(hexyl isocynate) is known to have a stiff rodlike helical conformation in the solid state and in a wide range of solvents, which is responsible for the formation of a nematic liquid crystalline phase.45-47 The inherent chain stiffness of this polymer is primarily determined by chemical structure rather than by intramolecular hydrogen bonding. This results in a greater stability in the stiff rodlike characteristics in the solution as compared to polypeptides. The lyotropic liquid crystalline behavior in a number of different solvents was extensively studied by Aharoni et al.48-50 In contrast to homopolymers, interesting new supramolecular structures can be expected if a flexible block is connected to the rigid polyisocyanate block (rod—coil copolymers) because the molecule imparts both microphase separation characteristics of the blocks and a tendency of rod segments to form anisotropic order. 

M. Sakurai, H. Nakajima, K. Onuki and S. Shimizu, Investigation of 2 liquid phase separation characteristic on the iodine-sulfur thermochemical hydrogen production. Int. J. Hydrogen Energy 25, 605-611 (2000). 

In practice, the negative electrode assumes a mixed-potential condition, with some portions of the surface supporting oxygen reduction and others continuing to generate hydrogen gas, as shown in Fig. 9.2. This is a balanced, delicate condition, and small changes in saturation levels or choices of separator characteristics can... 

To compete successfully with conventional hydrogen separation technologies, such as pressure swing adsorption or polymer membranes, or to be used in a membrane reactor successfully, palladium membranes must possess the following characteristics [4] ... 

These derivatizations have not been used extensively since the catalysts are generally strong acids that would isomerize CLA. Furthermore, the separation characteristics of these esters, and the method of how the results of esters are integrated with the FAME results, have not been as well documented. Alternatively, some researchers have used a combination of GC columns the total FAME were analyzed on a shorter Carbowax type GC column (25 m), followed by resolution of the 18 1 to 18 3 isomers using a 100 m polar column operated at different isothermal conditions from 170 to 190°C (33,89,91,104,118). Isothermal temperatures between 170 and 190°C maybe appropriate for the analysis of partially hydrogenated fats (100) and specific regions of the milk FA profile, but not for the complete analysis of dairy fats that contain short-chain FA (15,34). In fact the new AOCS official method forTFA analysis (method Ce lh-05) recommends isothermal operation at 180°C, but this method is not suitable for ruminant fats (67). 

Maher, G.C., Poulidi, D., Thursfield, A., Pascual, M.J., Jurado, J.R., and Metcalfe, I.S. (2010) Hydrogen permeation characteristics of a SrCeOa-based ceramic separation membrane thermal, aging and surfece-modification effects. Solid State Ionics, 181, 230-235. 

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