화학공학소재연구정보센터
홈 로그인 로그아웃 연락처 사이트맵
HWAHAK KONGHAK, Vol.36, No.2, 169-178, April, 1998
Export Citation
제올라이트 Ca-X에서 N2, CH4 및 CO2의 확산기구
Diffusion Mechanism of N2, CH4 and CO2 in Pelletized Zeolite Ca-X
안형웅, 박명규, 박두선, 이창하
초록
Ca로 이온 교환된 성형 제올라이트 X에 대한 N2, CH4 및 CO2 기체의 확산기구를 압력범위 0-1 atm와 온도 범위 273-293 K에서 연구하였다. 중량법에 의해 실험적으로 얻은 uptake curve로부터 등온흡착속도모형과 비등온흡착속도모형을 이용하여 확산계수를 얻었으며, 수학 모형으로부터 흡착속도에 미치는 홉착열의 영향을 살펴보았다. 저압에서는 흡착거동이 등온과정에 가까웠으나, 압력이 증가함에 따라 흡착열의 영향으로 인해 비등온거동을 나타내었다. 성형 제올라이트 Ca-X에서 N2, CH4 및 CO2의 흡착속도는 대기공내의 율속단계로 나타났다. 저온과 저압 조건에서 N2와 CH4는 대기공 확산에 있어 Knudsen확산이 지배적인 반면, 온도 증가와 압력 증가에 따라 대기공 확산의 지배기구는 Knudsen확산과 분자확산의 전이영역으로 이동하였다. 그러나 CO2는 모든 온도에서 압력증가에 따라 Knudsen확산에서 분자확산으로 전이되는 현상을 보였다. 대기공에서 N2, CH4 및 CO2의 유효확산계수는 압력과 온도에 대한 의존성을 보였다.
Diffusion mechanism of N2, CH4 and CO2 in pelletized zeolite Ca-X was studied theoretically and experimentally in the range of 0-1.0 atm and 273-293 K. Using the isothermal and nonisothermal adsorption rate models, diffusion coefficients were obtained from the experimental uptake curves through a gravimetric method. The effect of heat of adsorption on the adsorption rate was also investigated using these mathematical models. The diffusion showed the tendency of an isothermal behavior in the range of low pressures, but showed a nonisothermal behavior with an increase of pressure due to the effect of heat of adsorption. The adsorption rates of N2, CH4 and CO2 in pelletized zeolite Ca-X were controlled by the macropore diffusion. In the case of N2 and CH4 at low temperature and pressure, Knudsen diffusion was dominant in the effective macropore diffusion, while the controlling mechanism of the effective macropore diffusion was moved to the transition region of Knudsen diffusion and a molecular diffusion with an increase of temperature and pressure. In the case of CO2, however, the diffusion rate control in the effective macropore diffusion showed a transition from Knudsen diffusion to a molecular diffusion with an increase of pressure. Furthermore, the effective diffusion coefficients in the macropore showed dependences on both pressure and temperature.
Keywords:Zeolite Ca-X;Nonisothermal Adsorption Rate Model;Effective Macropore Diffusion
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