Towards polymer grade ethylene production with Cu-BTC: gas-phase SMB versus PSA

Abstract

The recovery of ethylene as a product from ethylene/ethane mixtures by adsorptive processes has been attracting great interest due to the high operating and capital costs of the cryogenic distillation traditionally practiced. This search for novel economical ways to separate olefins from paraffins by adsorptive processes has motivated the appearance of improved materials. The trend of developing new materials, such as metal–organic frameworks (MOF) and the challenge of improving the existing technologies, such as pressure swing adsorption (PSA) and simulated moving bed (SMB) leave the horizon open for new alternatives. In the present work, PSA and SMB in gas phase were tested to produce ethylene at high purity on Cu-BTC MOF in beads form. For the first time, the olefin/paraffin separation by SMB technology, using a MOF as adsorbent, was achieved. Both technologies were successfully implemented experimentally and simulated. In the best cycle performed by VPSA for the 20/80 ethane/ethylene feed composition, the ethylene was obtained with a purity of 98.0% at a recovery of 70.2% and a productivity per unit mass of stationary phase of 1.55 molC2 h−1 kg−1adsorbent. Additionally, for the 50/50 ethane/ethylene mixture only 43.2% of the ethylene is recovered at a purity of 95.4% and a productivity of 0.52 molC2 h−1 kg−1adsorbent. In the two cycles performed by SMB, to separate 39/61 ethane/ethylene mixture, ethylene was obtained with a purity of 95%, a recovery above 90% and productivity between 0.50 and 0.66 molC2 h−1 kg−1adsorbent. All the experiments were well predicted by the axial dispersion flow model with the LDF approximation.