Gas separation using sol–gel derived microporous zirconia membranes with high hydrothermal stability

A microporous zirconia membrane with hydrogen permeance about 5 × 10− 8 mol·m− 2·s− 1·Pa− 1, H2/CO2 permselectivity of ca. 14, and excellent hydrothermal stability under steam pressure of 100 kPa was fabricated via polymeric sol–gel process. The effect of calcination temperature on single gas permeance of sol–gel derived zirconia membranes was investigated. Zirconia membranes calcined at 350 °C and 400 °C showed similar single gas permeance, with permselectivities of hydrogen towards other gases, such as oxygen, nitrogen, methane, and sulfur hexafluoride, around Knudsen values. A much lower CO2 permeance (3.7 × 10− 9 mol·m− 2·s− 1·Pa− 1) was observed due to the interaction between CO2 molecules and pore wall of membrane. Higher calcination temperature, 500 °C, led to the formation of mesoporous structure and, hence, the membrane lost its molecular sieving property towards hydrogen and carbon dioxide. The stability of zirconia membrane in the presence of hot steam was also investigated. Exposed to 100 kPa steam for 400 h, the membrane performance kept unchanged in comparison with freshly prepared one, with hydrogen and carbon dioxide permeances of 4.7 × 10− 8 and ~ 3 × 10− 9 mol·m− 2·s− 1·Pa− 1, respectively. Both H2 and CO2 permeances of the zirconia membrane decreased with exposure time to 100 kPa steam. With a total exposure time of 1250 h, the membrane presented hydrogen permeance of 2.4 × 10− 8 mol·m− 2·s− 1·Pa− 1 and H2/CO2 permselectivity of 28, indicating that the membrane retains its microporous structure.

Microporous zirconia membranes with good H2/CO2 permselectivity and excellent hydrothermal stability were prepared. The H2/CO2 permselectivity and H2 permeance of zirconia membrane were 14 and 5 × 10− 8 mol·m− 2·s− 1·Pa− 1, respectively. After a small rise during the first 49 h exposure to 100 kPa steam, both H2 and CO2 permeances decreased during steam treatment, reducing to 2.4 × 10− 8 and 9 × 10− 10 mol·m− 2·s− 1·Pa− 1, respectively, after a total exposure time of 1250 h, while the H2/CO2 permselectivity increased to 27.4. The results indicate that zirconia membranes may find potential use in gas separation processes.Figure optionsDownload as PowerPoint slide