Abstract
Porous materials have widespread industrial applications in adsorption and catalysis, but experimental studies providing atomistic data regarding gas-sorbent interactions under application-relevant conditions are limited. Current analytical methods give information about either the crystal structure or the macroscopic kinetics involved in these processes, but not their interplay. The development of a new combination of stroboscopic, isotope-contrasted neutron total scattering and steady-state isotopic transient kinetic analysis provides insight into both areas. An advanced data reduction procedure was developed to isolate the differential isotope signal from the stroboscopic neutron diffraction. These data, combined with measurement of adsorption isotherms and theoretical considerations from Grand Canonical Monte Carlo simulation, enabled the location of a heterogeneous distribution of nitrogen adsorption sites in calcium exchanged zeolite X under operational conditions (1 atm, 300 K). The nitrogen is found to adsorb primarily at Ca site II, drawing the associated Ca atoms further out into the cage structure. This approach has great potential for the investigation of gas sorption, separation, and catalysis processes in process-relevant conditions.
| Original language | English |
|---|---|
| Pages (from-to) | 296-302 |
| Number of pages | 7 |
| Journal | Chemistry of Materials |
| Volume | 30 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 9 2018 |
Funding
This work was primarily supported under the Department of Energy’s Office of Basic Energy Sciences and the Laboratory Directed Research and Development (LDRD) Program at Oak Ridge National Laboratory (LDRD Seed No. 7735). The presented analysis of neutron powder diffraction data was funded by the BES Early Career Award, Exploiting Small Signatures: Quantifying Nanoscale Structure and Behavior KC04062, under Contract No. DE-AC05-00OR22725. The data were measured on the Nanoscale-Ordered Materials Diffractometer (NOMAD) instrument at the Spallation Neutron Source at ORNL. Some samples were prepared and additional characterization was performed at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. K.V.L. and P.M.F. would like to acknowledge funding by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through DOE Cooperative Agreement No. DE-NA0001982.