Selective adsorption of unsaturated linear C4 molecules on the all-silica DD3R

Abstract

The adsorption of but-1-ene, buta-1,3-diene, cis-but-2-ene and trans-but-2-ene on the all-silica DD3R has been investigated using a tapered element oscillating microbalance (TEOM). The single-component adsorption isotherms of buta-1,3-diene and trans-but-2-ene are reported for the first time at temperatures in the range from 303 to 473 K and at pressures up to 1.5×10⁵ Pa. The Langmuir isotherm appropriately describes their equilibrium data of adsorption on the all-silica DD3R. The analysis of thermodynamic properties such as isosteric heat and entropy of adsorption indicates that the adsorbent is energetically uniform. Transient experiments reveal that the 8-ring windows of the all-silica DD3R are accessible to buta-1,3-diene and trans-but-2-ene molecules, while they exclude but-1-ene and cis-but-2-ene molecules. High adsorption selectivities suggest that the all-silica DD3R might be an effective adsorbent for the separation or purification of C₄ mixtures.