1. Structural Evolution of CO2-Filled Pure Silica LTA Zeolite under High-Pressure High-Temperature Conditions
- Author
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Universitat Politècnica de València. Instituto Universitario Mixto de Tecnología Química - Institut Universitari Mixt de Tecnologia Química, U.S. Department of Energy, National Science Foundation, EEUU, Ministerio de Economía y Competitividad, Santamaria-Perez, David, Marqueño, Tomás, MacLeod, Simon, Ruiz-Fuertes, Javier, Daisenberger, Dominik, Chulia-Jordan, Raquel, Errandonea, Daniel, Jorda Moret, Jose Luis, Rey Garcia, Fernando, McGuire, Chris, Mahkluf, Adam, Kavner, Abby, Popescu, Catalin, Universitat Politècnica de València. Instituto Universitario Mixto de Tecnología Química - Institut Universitari Mixt de Tecnologia Química, U.S. Department of Energy, National Science Foundation, EEUU, Ministerio de Economía y Competitividad, Santamaria-Perez, David, Marqueño, Tomás, MacLeod, Simon, Ruiz-Fuertes, Javier, Daisenberger, Dominik, Chulia-Jordan, Raquel, Errandonea, Daniel, Jorda Moret, Jose Luis, Rey Garcia, Fernando, McGuire, Chris, Mahkluf, Adam, Kavner, Abby, and Popescu, Catalin
- Abstract
[EN] The crystal structure of CO2-filled pure-SiO2 LTA zeolite has been studied at high pressures and temperatures using synchrotron-based X-ray powder diffraction. Its structure consists of 13 CO2 guest molecules, 12 of them accommodated in the large alpha-cages and one in the beta-cages, giving a SiO2/CO2 stoichiometric ratio smaller than 2. The structure remains stable under pressure up to 20 GPa with a slight pressure-dependent rhombohedral distortion, indicating that pressure-induced amorphization is prevented by the insertion of guest species in this open framework. The ambient temperature lattice compressibility has been determined. In situ high-pressure resistive-heating experiments up to 750 K allow us to estimate the thermal expansivity at P approximate to 5 GPa. Our data confirm that the insertion of CO2 reverses the negative thermal expansion of the empty zeolite structure. No evidence of any chemical reaction was observed. The possibility of synthesizing a silicon carbonate at high temperatures and higher pressures is discussed in terms of the evolution of C-O and Si-O distances between molecular and framework atoms.
- Published
- 2017