Separation characteristics of tetrapropylammoniumbromide templating silica/alumina composite membrane in CO2/N-2, CO2/H-2 and CH4/H-2 systems

JH Moon, HW Ahn, SH Hyun, CH Lee*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Nanoporous silica membrane without any pinholes and cracks was synthesized by organic templating method. The tetrapropylammoniumbromide (TPABr)-templating silica sols were coated on tubular alumina composite support (gamma-Al2O3/alpha-Al2O3 composite) by dip coating and then heat-treated at 550degreesC. By using the prepared TPABr templating silica/alumina composite membrane, adsorption and membrane transport experiments were performed on the CO2/N-2, CO2/H-2 and CH4/H-2 systems. Adsorption and permeation by using single gas and binary mixtures were measured in order to examine the transport mechanism in the membrane. In the single gas systems, adsorption characteristics on the alpha-Al2O3 support and nanoporous unsupport (TPABr templating SiO2/gamma-Al2O3 composite layer without alpha-Al2O3 support) were investigated at 20-40degreesC conditions and 0.0-1.0 atm pressure range. The experimental adsorption equilibrium was well fitted with Langmuir or/and Langmuir-Freundlich isotherm models. The alpha-Al2O3 support had a little adsorption capacity compared to the unsupport which had relatively larger adsorption capacity for CO2 and CH4. While the adsorption rates in the unsupport showed in the order of H-2>CO2>N-2>CH4 at low pressure range, the permeate flux in the membrane was in the order of H(2)much greater thanN(2)>CH4>CO2. Separation properties of the unsupport could be confirmed by the separation experiments of adsorbable/non-adsorbable mixed gases, such as CO2/H-2 and CH4/H-2 systems. Although light and non-adsorbable molecules, such as H-2, showed the highest permeation in the single gas permeate experiments, heavier and strongly adsorbable molecules, such as CO2, and CH4, showed a higher separation factor (CO2/H-2=5-7, CH4/H-2=4-9). These results might be caused by the surface diffusion or/and blocking effects of adsorbed molecules in the unsupport. And these results could be explained by surface diffusion.

Original languageEnglish
Pages (from-to)477-487
Number of pages11
JournalKorean Journal of Chemical Engineering
Issue number2
Publication statusPublished - Mar 2004


  • surface diffusion
  • knudsen diffusion
  • blocking effect
  • silica membrane
  • adsorption
  • TPABr
  • templating method
  • separation factor

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