Absorption/desorption

When acetylene is recovered, absorption—desorption towers are used. In the first tower, acetylene is absorbed in acetone, dimethylformarnide, or methylpyroUidinone (66,67). In the second tower, absorbed ethylene and ethane are rejected. In the third tower, acetylene is desorbed. Since acetylene decomposition can result at certain conditions of temperature, pressure, and composition, for safety reasons, the design of this unit is critical. The handling of pure acetylene streams requires specific design considerations such as the use of flame arrestors. 

Porosity and surface area are routinely measured by nitrogen absorption-desorption, mercury intrusion, and low-angle X ray. The electron microscope (EM) provides direct visual evidence of pore size and pore-size distribution. Thus, a combination of EM and conventional methods of pore-size measurement should provide reliable information on the pore structure of polymers. 

The effective interfacial area is used in mass transfer studies as an undivided part of individual and overall coefficients when it is difficult to separate and determine the effective area. The work of Shulman et.al.,65 presents a well organized evaluation of other work in addition to their own. One of the difficulties in correlating tower packing performance lies in obtaining the correct values for the effective interfacial areas of the packing on which the actual absorption, desorption, chemical reaction, etc. are completed. Figures 9-47 A, B, C, D, E, F, G present a correlation for Avater flow based on the ammonia-water data of Fellinger [27] and are valid for absorption work. 

All AB, alloys are very brittle and are pulverized to fine particles in the hydrid-ing-dehydriding process (see Sec. 7.2.1). Thus electrodes must be designed to accommodate fine powders as the active material. There are several methods of electrode fabrication Sakai et al [35] pulverize the alloy by subjecting it to several hydrogen absorption-desorption cycles, before coating the resulting particles with Ni by chemical plating. The powder is mixed with a Teflon dispersion to obtain a paste which is finally roller-pressed to a sheet and then hot-pressed to an expanded nickel mesh. The fabrication of a simple paste electrode suitable for laboratory studies is reported by Petrov et al. [37],... 

Fig. 10. Coefficient of H atom recombination on Ni-Cu alloy catalysts as a function of the alloy composition, at 20°C. A, on Ni-Cu foils (59), O, on Ni-Cu evaporated films af ter their previous homogenization at 400°C (65,65a) d, on Ni-Cu foils after a multiple hydrogen absorption-desorption treatment (64a).

Fig. 11. X-ray diffraction pattern of a Ni99Cul alloy partially transformed into its (3-hydride (0 NiCuH) before (a) and after (b) hydride decomposition. Arrows point to the diffraction peaks representing the rich in copper alloy phsae desegregated from the initial alloy after a multiple hydrogen absorption-desorption treatment. After Palczew-ska and Majchrzak (48).

Moreover, the absorption-desorption hydrogen by a metal, able to form the hydride phase, leads to a cracking of metal crystallites (9, 4 )i the disclosure of new crystal planes, and increasing disintegration—the whole set of phenomena resulting in an enhancement of catalytic activity. 

Surfactants have a unique long-chain molecular structure composed of a hydrophilic head and hydrophobic tail. Based on the nature of the hydrophilic part surfactants are generally categorized as anionic, non-ionic, cationic, and zwitter-ionic. They all have a natural tendency to adsorb at surfaces and interfaces when added in low concentration in water. Surfactant absorption/desorption at the vapor-liquid interface alters the surface tension, which decreases continually with increasing concentrations until the critical micelle concentration (CMC), at which micelles (colloid-sized clusters or aggregates of monomers) start to form is reached (Manglik et al. 2001 Hetsroni et al. 2003c). 

Gas absorption/desorption, stripping, scrubbing Humidification and water cooling Dehumidification and air conditioning Drying Adsorption... 

Fig. 7.10 Ni Mossbauer spectra of LaNi5 samples after various treatments (a) no hydrogen exposure, (b) activated in hydrogen, (c) after 1,584 thermally induced absorption-desorption cycles, as described in the text. The solid lines are least-squares fits to a single Lorentzian in (a) and (b). (c) was fitted with a single Lorentzian (representing nonmagnetic nickel atoms) and a 12-line hyperfine spectrum (from [20])...

Hodjati, S., Petit, C., Pitchon, V. et al. (2000) Absorption/Desorption of NOx Process on Perovskites Nature and Stability of the Species formed on BaSn03, Appl. Catal. B Environ., 27, 117. 

Fig. 1.6. Thin layer cell for in situ IR absorption-desorption measurements based in a model proposed by Seki et al. [32]. WE = working electrode, W = window, L=lead, M = micrometer screw, S = steel spring, SM = simmer gasket.

They also found that Dawson HP2W is more active than Keggin HP As and attributed the higher activity to the fact that Dawson HP2W has a less rigid structure and weaker acidity than Keggin HPW, which gives rise to a faster absorption - desorption rate of polar solvents in the pseudo-liquid phase of the HPA. 

Hydrogen absorption/desorption characteristics of magnesium-nickel alloy containing 23 atomic% Ni. (Reproduced with permission from Schwarz, R.B., Storage of hydrogen in powders with nanosized crystalline domains, Mater. Res. Bull., 24, 40, 1999, available at http //www.wtec.org/loyola/nano/US.Review/04 06.htm, May 2007.)... 

Nathwani, J.S., Philip, C.R. (1977) Absorption-desorption of selected hydrocarbons in crude oils on soils. Chemosphere 6, 157-162. 

Upon selective absorption of analyte molecules from the ambient environment, the zeolite thin film increases its refractive index. Correspondingly, release of adsorbed molecules from the zeolite pore results in the decrease of its refractive index. The absorption/desorption of molecules depends on the molecule concentration in the environment to be monitored. Therefore, monitoring of the refractive index change induced phase shift in the interference spectrum can detect the presence and amount of the target analyte existing in the environment. 

However, an interpretation of this experiment is not straightforward in view of the experimental conditions, which imply a monolayer on the substrate surface covered by the solution of molecules. Cis-trans isomerization for an observed molecule is supposed to promote desorption, so that a pattern change includes absorption-desorption equilibria. It would be important therefore, to observe a light induced change of a 2D pattern only for adsorbed molecules. This is, indeed, possible for C9(DIA)C8ISA... 

The Kelvin Probe technique allows measurement of the Work Function of a given surface, not only in stationary conditions but also during absorption - desorption processes. 

Absorption characteristics, of hydrogenated amorphous silicon films, 22 133-134 Absorption coefficients, 23 126 Absorption-desorption towers, 10 614 Absorption maxima, vinylene shifts of,... 

Absorption - desorption - N-octanol/water coefficient - Henry constant - Biodegradation and/or abiotic degr. disappearance coef. - Bioaccumulation - Aquatic Ecotox Fish 24 to 96 hours Daphnia 24 to 48 hours - Air/soil/sediment Ecotox ... 

The Li-Mg-B-N-H structure possesses storage capacity of more than 10 wt.% at around 150-200 "C. However, the reversibility of the hydrogen sorption characteristics was determined using pressure-composition isotherms as shown in Figure 6. From this study, we found reversible hydrogen absorption-desorption behavior (-3-4 wt.%) of the new complex hydride Li-Mg-B-N-H. The improvement in temperature and reversible hydrogen storage capacity were unaffected even after ten... 

Sorensen titration analy chem Titration with one of the Sorensen hydrogen-ion-concentration indicators. sor-an-san tT.tra-shon sorption phys chem A general term used to encompass the processes of adsorption, absorption, desorption, ion exchange, ion exclusion, ion retardation, chemisorption, and dialysis. sorp-shan )... 

Tsuzuki, K., Eiki, H., Inoue, N., Sagara, A., Noda, N., Hirohata, Y, Hino T. 1999. Hydrogen absorption/desorption behavior with oxygen contaminated boron film. J Nuclear Mat 266-269 247-250. 

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