Influence of Packing On Gas Diffusion in Samaria Aerogel Catalyst By Diffusion NMR

Recent investigations have shown that different macroscopic catalyst packings made from the same material can lead to very different catalytic performance for catalytic processes involving small gas molecules. These observations can be attributed to an influence of diffusion of reactant and product species on the catalytic performance.  In this work, a pulsed field gradient (PFG) NMR technique employing a high magnetic field of 17.6 T was used to study self-diffusion of carbon dioxide in alumina stabilized samaria aerogel, a promising porous catalyst for gas-phase reactions. Such rare-earth aerogels exhibit high porosity and surface area with active sites directly integrated into the pore framework. PFG NMR diffusion studies were performed with the catalyst formed into the following two types of samples: macroscopic monoliths and beds of particles with sizes around 200 µm. The behaviour of CO₂ self-diffusion will be presented and discussed for both types of packings at different CO₂ loading pressures.