Preparation and gas permeability of the surface-modified porous Al2O3 ceramic filter for CO2 gas separation

• Pore sizes of the obtained Al2O3 filters were about 760 or 74 nm.
• The filter with 760 nm pores showed no N2/CO2 gas selectivity.
• The maximum selectivity of the filter with 74 nm pores was 1.47 at 0.01 MPa.
• N2 gas permeability of the filter was 8.5 × 10−10 kmol·m·m−2·s−1·kPa−1.

Al2O3 filters for CO2 gas separation were prepared by slip casting method. Average pore size and porosity of the obtained Al2O3 filters were about 74 nm and 40%, respectively. To evaluate the pore size effect, the Al2O3 filters having average pore size of 760 nm were also prepared. FE-SEM micrographs show fine new crystals on the pore surface. They were synthesized by hydrothermal treatment, and were identified to AlOOH by XRD and XPS. Both gas selectivity of the filter having larger pore size were about 1, which indicated that this filter has no gas separation capability. In contrast, the gas selectivity of the Al2O3 filter with 74 nm pores became about 1.47 at 0.01 MPa. The N2/CO2 gas selectivity was improved by controlling the pore size and the chemical properties of a pore surface precisely and by setting an appropriate gas permeation pressure.