Adsorption isotherms and ideal selectivities of hydrogen sulfide and carbon dioxide over methane for the Si-CHA zeolite:
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Adsorption isotherms and ideal selectivities of hydrogen sulfide and carbon dioxide over methane for the Si-CHA zeolite: comparison of carbon dioxide and methane adsorption with the all-silica DD3R zeolite Hafez Maghsoudi • Mohammad Soltanieh • Hamidreza Bozorgzadeh • Ali Mohamadalizadeh
Received: 31 August 2012 / Accepted: 21 February 2013 Ó Springer Science+Business Media New York 2013
Abstract Adsorption isotherms of H2S, CO2, and CH4 on the Si-CHA zeolite were measured over pressure range of 0–190 kPa and temperatures of 298, 323, and 348 K. Acid gases adsorption isotherms on this type of zeolite are reported for the first time. The isotherms follow a typical Type-I shape according to the Brunauer classification. Both Langmuir and Toth isotherms describe well the adsorption isotherms of methane and acid gases over the experimental conditions tested. At room temperature and pressure of 100 kPa, the amount of CO2 adsorption for Si-CHA zeolite is 29 % greater than that reported elsewhere (van den Bergh et al. J Mem Sci 316:35–45 (2008); Surf Sci Catal 170:1021–1027 (2007)) for the pure silica DD3R zeolite while the amounts of CH4 adsorption are reasonably the same. Si-CHA zeolite showed high ideal selectivities for acid gases over methane at 100 kPa (6.15 for H2S and 4.06 for CO2 at 298 K). Furthermore, H2S adsorption mechanism was found to be physical, and hence, Si-CHA can be utilized in pressure swing adsorption processes. Due to higher amount of carbon dioxide adsorbed and lower heats of adsorption as well as three dimensional channels of Si-CHA pore structure, this zeolite can remove acid gases from methane in a kinetic based process such as zeolite membrane.
H. Maghsoudi M. Soltanieh (&) Department of Chemical and Petroleum Engineering, Sharif University of Technology, Azadi Avenue, P.O. Box 11155-9496, Tehran, Iran e-mail: [email protected] H. Bozorgzadeh A. Mohamadalizadeh Gas Research Division, Research Institute of Petroleum Industry (RIPI), West Boulevard, Azadi Sport Complex, Tehran, Iran
Keywords Adsorption Zeolite Pure silica chabazite (Si-CHA) Acid gas Natural gas sweetening List of symbols b Affinity parameter of Langmuir or Toth isotherm (kPa-1) b? Affinity parameter of Langmuir or Toth isotherm at infinite temperature (kPa-1) Cls Saturation adsorption capacity of adsorbent (mol kg-1) Cl Amount adsorbed (mol kg-1) p Pressure (kPa) Qst Isosteric heat of adsorption (kJ mol-1) Q Isosteric heat of adsorption for Langmuir isotherm in Eq. 3 (kJ mol-1) R Universal gas constant (kJ K-1 mol-1) r Correlation coefficient T Temperature (K) T0 Reference temperature (K) t Heterogeneity parameter in Toth isotherm t0 Heterogeneity parameter at the reference temperature (T0) h Fractional amount adsorbed a Adjustable parameter in Eq. 4
1 Introduction Removal of acid gases (H2S, CO2) impurities from gas streams is of importance for the chemical industries, as industrial processes such as purification of natural gas and sweetening of gas streams in petrochemical plants should be carried out in ac
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