High flux zeolite X membranes

Abstract

Methanol synthesis from synthesis gas is equilibrium limited and selective removal of products could improve the process. In the present work, zeolite X membranes with a film thickness of about 1 μm were evaluated for this separation. A maximum methanol/carbon dioxide separation factor of about 140 and a maximum methanol/hydrogen separation factor of about 8 were observed in the temperature range of 50–100 °C. In the same temperature range, the maximum water/carbon dioxide and water/hydrogen separation factors were about 250 and 15, respectively. The membranes were also evaluated for room temperature drying of synthesis gas and natural gas. The observed water/carbon dioxide separation factors were 482 and 252 for carbon dioxide/hydrogen/water and carbon dioxide/methane/water feed mixtures, respectively. In all separation experiments performed in the present work, the observed water and methanol permeances were very high. The water permeance was in the range of (15–24) × 10 −7 mol m −2 s −1 Pa −1 for all evaluated feed mixtures and temperatures, while the methanol permeance in the methanol/synthesis gas feed mixture was (12–14) × 10 −7 mol m −2 s −1 Pa −1 in the temperature range of 100–150 °C. To the best knowledge of the authors, the observed methanol and water permeances are several times higher than previously reported in the open literature for gas phase separations using FAU membranes. In summary, the membranes were found to be selective for the most polar components in a feed mixture, and the observed permeances were high.