(354j) Understanding Facilitated Transport of Hydrogen in Polybenzimidazole Containing Palladium Nanoparticles Using an Integrated Experimental and Modeling Approach

Membrane
technology is an energy-efficient and low-cost approach for pre-combustion CO₂
capture and H₂ purification in the integrated gasification combined
cycle (IGCC) processes. Conventional membranes are based on rigid polymers with
strong size sieving ability, such as
poly[2,2’-(m-phenylene)-5,5’-bisbenzimidazole] (PBI) that provides high H₂/CO₂
diffusion selectivity. In this study, we demonstrate enhanced H₂
sorption and diffusion in PBI films with embedded palladium (Pd) nanoparticles,
which have strong affinity towards H₂. Pd nanoparticles with uniform
diameters of 6 - 8 nm are prepared via a hot-injection colloidal synthesis. The
loading of Pd nanoparticles in PBI increases H₂ sorption by almost
1,000 times, and at high Pd loadings, the Pd nanoparticles may form fast
channels allowing the H₂ molecules to jump from one particle to
another and thus increasing the effective H₂ diffusivity.  For
example, adding 70 wt.% Pd in PBI increases H₂ permeability from 25
to 70 Barrers, and H₂/CO₂ selectivity from 13 to 29 at
150 °C. Such performance is above the Robeson’s upper bound for H₂/CO₂
separation, demonstrating the potential of these new materials for industrial H₂/CO₂
separation. The gas transport in these PBI-Pd nanocomposites is being modeled using
computational fluid dynamics (CFD)  to elucidate the mechanisms for the facilitated
H₂ transport. This presentation will also discuss the visualized microstructure
of the nanocomposites and provide a unified view of the H₂ and CO₂
transport in the nanocomposites using an integrated experimental and simulation
approach.