Chihara, Kazuyuki

Kaneko, Yosuke

Nakamura, Hidenori

Qucosa

Diffusion study of multi-component gas adsorption in MSC5A
by chromatographic method: Diffusion study of multi-component gas adsorption in MSC5Aby chromatographic method

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 Diffusion Study of Multi-Component Gas Adsorption in MSC5A by Chromatographic Method  Kazuyuki Chihara, Hidenori Nakamura, Yosuke Kaneko  Department of Applied Chemistry, Meiji University, 1-1-1 Higashi-mita, Tama-ku, Kawasaki, Kanagawa, 214-8571, Japan, E-mail:chihara@isc.meiji.ac.jp   1. Introduction The combination of chromatographic method and moment analysis of the response peaks is one of the useful techniques to study adsorption equilibrium and adsorption rate [1]. Perturbation chromatography with the mixed multi component adsorbate gas carrier (two adsorbates) has been applied to several studies on adsorption [2][3]. In this work, perturbation chromatography with multi-component gas carrier (two adsorbates with inert gas) and non-equilibrium thermodynamics linear law was applied for discussion of the interference effect and the displacement effect (those are cross effects) on mass transfer in multi-component gas adsorption as previous study  for different gas mixture (He, N2, CH4) [4]. Moment analysis method and stop & go simulation method were utilized to obtain each mass transfer parameter of adsorbate gases. Dependency of micropore diffusion on amount adsorbed and correlation of micropore diffusion with chemical potential driving force for microporous adsorbent were discussed. Also, cross effects were discussed. Ruthven already emphasized the dependency of micropore diffusivity on amount adsorbed in single component adsorption [5]. Tondeur et al gave general background on multi-component perturbation chromatography for the first moment only [6].  2. Experimental method The apparatus was similar to a conventional gas chromatograph. Adsorbent particles were packed in a column. Carrier gas was a mixture of two or three components among He, CO2, CH4. Perturbation pulse was introduced into the carrier gas stream. Introduction of pulses was performed by 6-way valve. The pulse size was 1cc, which meant injection period was 1.4 sec. Then pulse response was detected by TCD cell. Output signal of TCD was transmitted to a personal computer through RS232C. This signal was also transmitted to the personal computer. Simulated chromatogram by a personal computer can be overlapped on experimental chromatogram shown in the monitor screen. Further, moment of pulse response, which is shown in the monitor screen, can be automatically calculated by the personal computer.  3. Result and Discussion Fig.1 shows an example of comparison of experimental chromatogram with simulated chromatogram for MSC5A to obtain Ksav for LDF model. Experimental conditions were 313 K, column pressure 5 atm, flow rate 25 cm/sec and He+CH4 mixed gas carrier with CH4 pulse. Here CH4 concentration in the carrier gas was changed 10, 30, 50, 70 and 90 %.   Fig.2 shows contribution of axial dispersion, external mass transfer, macropore diffusion and micropore diffusion in case of CH4 for MSC5A at 323 K. This figure 1The Open-Access Journal for the Basic Principles of Diffusion Theory, Experiment and Application© 2007, H. NakamuraDiffusion Fundamentals 6 (2007) 57.1 - 57.2 illustrated that mass transfer is controlled by micropore diffusion. Fig.3 shows the dependency of micropore diffusivity coefficient of CO2 with amount adsorbed at 303, 313 and 323 K for MSC5A. Fig.4 shows the correlation of micropore diffusivity of CO2 with chemical potential driving force at 303, 313 and 323 K for MSC5A. Proportional relation was obtained, which means that micropore diffusion is based on chemical potential driving force.    0%20%40%60%80%100%0 0.5 1 1.5 2 2.5 3 3.5 4 4.5Partial Pressure [atm]Mass transfer step M icroporeDiffusionMacroporeDiffusionExternalmasstransferAxialdispersion    2.E-083.E-084.E-085.E-086.E-087.E-088.E-089.E-080 50 100 150Amount adsorbed[cc/g]D[cm2 /sec]303K313K323K                               1.E-081.E-071.E-061 1Fig.2  Mass transfer steps of CH4on to MSC5A Fig. 1   Comparison of experimental  peaks with simulation 0D[cm2 /sec] 303K313K323Kδ lnP/δ lnQ   Fig.4  Correlation based on chemical potential driving force  Fig. 3   Dependency of micropore diffusivitycoefficient on the amount adsorbed   4. Conclusion This time, we cannot get good agreements between experimental chromatogram and simulated chromatogram, based on the modeling of Stop & Go method, in case of perturbation chromatography with mixed adsorbate gas carrier. And micropore diffusivities obtained were interpreted by chemical potential driving force consideration based on non-equilibrium thermodynamics law. Some possibility was shown for a cross-effect of micropore diffusion in multicomponent adsorption.  References [1] Kazuyuki Chihara, Motoyuki Suzuki and Kunitaro Kawazoe, “Adsorption Rate on Molecular Sieving Carbon by Chromatography,” AIChE J., 24, 237(1978). [2] Douglas M. Ruthven and Ravi Kumar, “A Chromatographic Study of the Diffusion of N2, CH4, and Binaly CH4-N2 Mixtures in 4A Molecular Sieve,” The Canadian Journal of chemical Engineering, 50, 342-348(1979). [3] Ravi Kumar, Robert C. Duncan and Douglas M. Ruthven, “A Chromatographic Study of Diffusion of Single Components and Binary Mixtures of Gases in 4A and 5A Zeolites,” The Canadian Journal of chemical Engineering, 60, 493-499(1982). [4] Chihara K. et al; “Study of Multicomponent Gas Adsorption into MSC5A by Chromatograph” Adsorption, 11, 249-253(2005). [5] Ruthven D.M,; “Principle of Adsorption and Adsorption Process” Wiley, 146 (1984). [6] Tondeur D. et al., “Multicompontnt  Adsorption Equilibria from Impulse Response Chromatography,” Chem. Eng. Science, 51(N15), 3781-3799(1996). 2

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Diffusion study of multi-component gas adsorption in MSC5A by chromatographic method: Diffusion study of multi-component gas adsorption in MSC5Aby chromatographic method

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