Experimental Quantification of Gas Dispersion in 3D-Printed Logpile Structures Using a Noninvasive Infrared Transmission Technique.

3D-printed catalyst structures have the potential to broaden reactor operating windows. However, the hydrodynamic aspects associated with these novel catalyst structures have not yet been quantified in detail. This work applies a recently introduced noninvasive, instantaneous, whole-field concentration measurement technique based on infrared transmission to quantify the rate of transverse gas dispersion in 3D-printed logpile structures. Twenty-two structural variations have been investigated at various operating conditions, and the measured transverse gas dispersion has been correlated to the Péclet number and the structures' porosity and feature size. It is shown that staggered configurations of these logpile structures offer significantly more tunability of the dispersion behavior compared to straight structures. The proposed correlations can be used to facilitate considerations of reactor design and operating windows.

On the Potential of Gallium- and Indium-Based Liquid Metal Membranes for Hydrogen Separation.

The concept of liquid metal membranes for hydrogen separation, based on gallium or indium, was recently introduced as an alternative to conventional palladium-based membranes. The potential of this class of gas separation materials was mainly attributed to the promise of higher hydrogen diffusivity. The postulated improvements are only beneficial to the flux if diffusion through the membrane is the rate-determining step in the permeation sequence. Whilst this is a valid assumption for hydrogen transport through palladium-based membranes, the relatively low adsorption energy of hydrogen on both liquid metals suggests that other phenomena may be relevant. In the current study, a microkinetic modeling approach is used to enable simulations based on a five-step permeation mechanism. The calculation results show that for the liquid metal membranes, the flux is limited by the dissociative adsorption over a large temperature range, and that the membrane flux is expected to be orders of magnitude lower compared to the membrane flux through pure palladium membranes. Even when accounting for the lower cost of the liquid metals compared to palladium, the latter still outperforms both gallium and indium in all realistic scenarios, in part due to the practical difficulties associated with making liquid metal thin films.