TEOM - A UNIQUE TECHNIQUE FOR MEASURING ADSORPTION PROPERTIES - LIGHTALKANES IN SILICALITE-1

A new and fast technique, the tapered element oscillating microbalance , TEOM, has been applied to accurately measure adsorption in microporo us materials at conditions relevant for practical applications. With t his technique, the experimental data are not influenced by factors suc h as buoyancy and flow patterns, which are encountered with convention al gravimetric methods. The equilibrium adsorption of light alkanes, m ethane, ethane, propane, n-butane, and i-butane in silicalite-1 has be en investigated using the TEOM technique. Single-component adsorption isotherms are reported at temperatures in the range from 303 to 473 K and at pressures of up to 500 kPa. Either a conventional or a double L angmuir isotherm appropriately describes the equilibrium data. Thermod ynamic properties calculated from the isotherms are in excellent agree ment with literature data from other techniques. Isobaric and isotherm al experiments demonstrate that i-butane exhibits a two-step adsorptio n behavior. Based on geometry and entropy considerations, this behavio r is ascribed to first filling the intersections followed by filling t he channels of the silicalite-1 crystals, just the opposite of the beh avior of n-butane.