Kinetics of hydrogen absorption and desorption in LaNi_5‐xAl_x slurries

Abstract

The kinetics of hydrogen absorption and desorption in LaNi4.Jl0,, LaNi4.,Alo., and LaNi,, suspended in cyclohexane and LaNi, in ethanol The phase transformation at the P/a boundary appears to be the rate-determining step. Alloys with higher aluminum contents produce a lower reaction rate constant.

Absorption of Hydrogen in LaNi4.75Al0.25/n-Octane Slurries

“…Snijder et al, 1993 The kinetics of hydrogen absorption and desorption in LaNi 5/cyclohexane, LaNi5/ethanol, LaNi4.9Al0.1/cyclohexane, and LaNi4.8Al0.2/cyclohexane systems have been investigated.…”

“…Additionally, such slurries are pumpable and can minimize the problems associated with powder migrations within the systems. A disadvantage is that the inert liquid brings additional masstransfer resistances between the gas and solid phases (Tung et al, 1986;Snijder et al, 1993;Kim et al, 1997c). Table 1 summarizes the previous efforts on metal hydride slurries.…”

“…In a metal hydride slurry, as diagrammed in Figure 1, the following mass-transfer steps may be involved for absorption (Reilly and Johnson, 1984;Snijder et al, 1993;Kim et al, 1997c):…”

Some Properties of LaNi5-xAlx Metal Alloys and the Diffusion Coefficient and Solubility of Hydrogen in Cyclohexane

“…The stirring was stopped after equilibrium between the gas and liquid phase had been established, and the pressure in the equilibrium cell and hydrogen storage vessel were recorded. With the measured pressures, temperature, amount of cyclohexane in the equilibrium cell, and gas volumes of the two vessels, the hydrogen solubility in cyclohexane were determined, expressed by mH, which is a solubility coefficient defined as (3) where CH~,, and CH*, are the hydrogen concentrations in the liquid phase and gas phase at equilibrium, respectively. Figure 7 shows the experimental results for the absorption of hydrogen in cyclohexane; the solubility has been presented as a Henry coefficient, K , which is directly related to the solubility coefficient according to K = m/(RT), with R = 8.314 Pa.m3.K-l.m01-~.…”

Solubility of Hydrogen in Aqueous Solutions of Sodium and Potassium Bicarbonate from 293 to 333 K

“…The value of the gas and liquid temperatures could be measured with an uncertainty of about 0.2 K. The solubility data for the sodium bicarbonate and sodium carbonate solutions were obtained in setup I (913 mL), whereas for the corresponding potassium salts setup II (548 mL) was applied. A more detailed description of both setups has been given elsewhere (Snijder et al, 1993).…”