Processing of Microporous VPI-5 molecular sieve by using supercritical CO2: stability and adsorption properties

GARCÍA-CARMONA, M. A. FANOVICH, J. LLIBRE, R. RODRÍGUEZ-CLEMENTE, C. DOMINGO

MICROPOROUS AND MESOPOROUS MATERIALS

Elsevier

Año: 2002 p. 127 - 137

1387-1811

The stability and adsorption behavior of the microporous molecular sieve VPI-5, an AlPO4 hydrate phase, processed using supercritical carbon dioxide (SCCO2) as a solvent, were explored. Di.erent thermal treatments up to 373 K were carried out on samples of VPI-5 previously treated with methanol, ethanol or 2-propanol. The thermally treated samples were characterized by X-ray diffraction and low-temperature N2 adsorption. VPI-5 was completely transformed to AlPO4-8 when it was heated up to 373 K in ambient air. By previously shaking VPI-5 samples with methanol the transformation was partially avoided. Additionally, when the thermal treatment was carried out in an SCCO2  atmosphere, the VPI-5 structure was preserved. VPI-5 was charged with low molecular weight organic compounds using a high-pressure apparatus and employing SCCO2 as a solvent. The adsorption behavior of either a pure solute or a mixture of two solutes into the channels of VPI-5 was studied as a function of time, pressure and temperature of adsorption. A significant time-, pressure- and temperature-dependence for the absorbed amount was found.