To improve CO2 permselectivity, a modified silica membrane was prepared by chemical vapor deposition with tetraethoxysilane(TEOS)-ethanol-water, and TEOS-ethanol-water-HCI solution at 300-600℃. The silica was effectively deposited in the mesopores of a γ-alumina film coated on a porous α-alumina tube by evacuating the reactants through the porous wall. In this membrane, CO2 interacts, to some extent, with the pore wall, and CO2/N2 selectivity then exceeds the value of the Knudsen diffusion mechanism, while the membrane derived from TEOS alone has no CO2 selectivity. The silica membrane prepared from TEOS-ethanol-water-HC1 solution showed that CO2 permeance was 2.5×10-7㏖/s-1. m-2. Pa-1 at 30℃ and CO2/N2 selectivity was approximately 3. The CO2 permeance and selectivity was improved by enlarging the surface diffusion with modification of chemical affinity of the silica pores.

For effective CO2 separation using pore size controlled membrane, silica was deposited in the mesopores of a γ-alumina film by chemical vapor deposition of tetraethoxysilane (TEOS) and phenyl-substituted ethoxysilanes at 773-873K. The membranes prepared with phenyl-substituted ethoxysilanes were calcined to remove the phenyl group and control the pore size. The gas permselectivity of prepared membranes was evaluated by using H2, CO2, N2, CH4 and C3H8 single component and a mixture of CO2 and N2. The membranes produced using TEOS contained micropores having permselectivity only to hydrogen, but the phenyl-substituted ethoxysilane derived membranes possessed micropores which are recognizable molecules of CO2, N2 and CH4. In the diphenyldiethoxysilane-derived membrane, the CO2 permeance and selectivity of CO2/CH4 were 10-6 ㎥(STP)·m-2·s-1·kPa-1 and 11, respectively. Therefore, the use of phenyl-substituted ethoxysilane was effective in controlling micropore size for CO2 separation.

When we conduct environmental impact assessment, main contents consist of summary, project outline, environmental conditions, environmental impacts due to the project, mitigation devices, and alternative measures of harmful impact on environment. In this paper, to understand how they really conduct air quality impact assessment and prediction and examine their effectiveness, we considered the provisions and actual case of environmental impact assessment in Korea with that in Japan. As a result, we propose a method of improving air quality impact assessment and prediction, such as reflection of the result in environmental impact assessment, detailed assessment focused on relatively important environmental impact elements, field measurement investigation over four season and seven sucessive days, the uniformity of units, the proper model development to predict environmental concentration and a biennial environmental impact assessment for ex post management.