Separation of Hydrogen from Carbon Dioxide through Porous Ceramics

Abstract

The gas permeability of α-alumina, yttria-stabilized zirconia (YSZ), and silicon carbide porous ceramics toward H2, CO2, and H2–CO2 mixtures were investigated at room temperature. The permeation of H2 and CO2 single gases occurred above a critical pressure gradient, which was smaller for H2 gas than for CO2 gas. When the Knudsen number (λ/r ratio, λ: molecular mean free path, r: pore radius) of a single gas was larger than unity, Knudsen flow became the dominant gas transportation process. The H2 fraction for the mixed gas of (20%–80%) H2–(80%–20%) CO2 through porous Al2O3, YSZ, and SiC approached unity with decreasing pressure gradient. The high fraction of H2 gas was closely related to the difference in the critical pressure gradient values of H2 and CO2 single gas, the inlet mixed gas composition, and the gas flow mechanism of the mixed gas. Moisture in the atmosphere adsorbed easily on the porous ceramics and affected the critical pressure gradient, leading to the increased selectivity of H2 gas.

Process intensification for generating and decomposing formic acid, a liquid hydrogen carrier

“…H 2 separation: As expected [19], the nanoporous filter did not separate a dry stream of H 2 and CO 2 . It exhibited only a slight separation, Sf = (CO 2,out /H 2,out )/ (CO 2,in /H 2,in ), when fed with gases that had bubbled through water at room temperature (Table 5).…”

“…Given that the dehydrogenation reaction produces the H 2 and CO 2 at elevated pressure, we first thought to try to enrich the product stream in H 2 through the use of a nanoporous membrane that exploited the difference in rates of Knudsen diffusion of the two gases [19]. We used a 20 nm, nanoporous, titania-coated metal filter from Graver Technologies [20].…”

Hydrogen gas distribution in organs after inhalation: Real-time monitoring of tissue hydrogen concentration in rat

“…For example, C max can only be determined by continuous monitoring, since it is not known when the hydrogen concentration will reach a maximum in a certain organ/tissue. It is also important to underline that the hydrogen rapidly diffuses and can penetrate even glass containers 23 , therefore, it should be administered continuously and its concentration should be measured in vivo , not via sampled tissues, to obtain accurate saturation measurements 9 . Moreover, the administration methods should be also considered, since the hydrogen can be introduced and distributed throughout the body by both gaseous diffusion and blood flow.…”