Abstract
A vast source of methane is found in gas hydrate deposits, which form naturally dispersed throughout ocean sediments and arctic permafrost. Methane may be obtained from hydrates by exchange with hydrocarbon byproduct carbon dioxide. It is imperative for the development of safe methane extraction and carbon dioxide sequestration to understand how methane and carbon dioxide co-occupy the same hydrate structure. Pair distribution functions (PDFs) provide atomic-scale structural insight into intermolecular interactions in methane and carbon dioxide hydrates. We present experimental neutron PDFs of methane, carbon dioxide and mixed methane-carbon dioxide hydrates at 10 K analyzed with complementing classical molecular dynamics simulations and Reverse Monte Carlo fitting. Mixed hydrate, which forms during the exchange process, is more locally disordered than methane or carbon dioxide hydrates. The behavior of mixed gas species cannot be interpolated from properties of pure compounds, and PDF measurements provide important understanding of how the guest composition impacts overall order in the hydrate structure.
| Original language | English |
|---|---|
| Article number | 6 |
| Journal | Communications Chemistry |
| Volume | 4 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 2021 |
Funding
B.R.C. received partial support from the University of Tennessee Chancellor’s Fellowship program and the Center for Materials Processing, a Tennessee Higher Education Commission (THEC) Center of Excellence. Part of this research was sponsored by the Office of Science Graduate Student Research (SCGSR) program, administered by the Oak Ridge Institute for Science and Education for DOE. Research at the Spallation Neutron Source (SNS), a US Department of Energy (DOE) Office of Science User Facility operated by Oak Ridge National Laboratory (ORNL), was sponsored by the DOE Office of Basic Energy Sciences. The ICE-MAN software suite used for this work was funded by the ORNL Laboratory Directed Research and Development program. We thank Dayton Kizzire from University of Tennessee, Knoxville, for assisting with the neutron total scattering data collection at the SNS and Jared Floyd for assistance in sample synthesis.
| Funders | Funder number |
|---|---|
| ORNL Laboratory Research and Development Program | |
| Office of Science Graduate Student Research | |
| SCGSR | |
| U.S. Department of Energy | |
| Office of Science | |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | |
| Oak Ridge Institute for Science and Education | |
| University of Tennessee | |
| Tennessee Higher Education Commission |
