Jin Wai Goh, Yoona Choung, Aloysius Davin OetomoSchool of Chemical & Biomolecular Engineering, Georgia Institute of Technology

Linearization of Adsorption Models

Methods & Theories 

Introduction• CO2 and CH4 are most common greenhouse gases emitted.

• Adsorbing using zeolites and activated carbons, but cost of regeneration process is expensive.

• Turn towards metal-organic frameworks (MOFs), particularly MIL-100(Cr) and MIL-101(Cr)

• Extremely high surface areas• Crystalline open structure• Tunable pore size• Catalysis, gas storage, liquid-phase separation

References 1. Llewellyn, P.L.; Bourrelly, S.; Serre, C.; Vimont, A.; Daturi, M.; Hamon, L.; De Weireld, G.; Chang, J.S.;

Hong, D.Y.; Kyu Hwang, Y.; Hwa Jhung, S. High Uptakes of CO2 and CH4 in Mesoporous Metal–Organic Frameworks MIL-100 and MIL-101. Langmuir, 2008, 24(14), pp.7245-7250.

2. Dada, A.O.; Olalekan, A.P.; Olatunya, A.M.; Dada, O. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms studies of equilibrium sorption of Zn2+ unto phosphoric acid modified rice husk. Journal of Applied Chemistry, 2012, 3(1), 38-45.

3. Temkin, M.I.; Pyzhev, V. Kinetics of ammonia synthesis on promoted iron catalysts. Acta physiochim. URSS, 1940, 12(3), 327-356.

4. Aharoni, C.; Ungarish, M. Kinetics of activated chemisorption. Part 2.—Theoretical models. Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 1977, 73, 456-464.

5. Munusamy, K.; Sethia, G.; Patil, D.V.; Rallapalli, P.B.S.; Somani, R.S.; Bajaj, H.C. Sorption of carbon dioxide, methane, nitrogen and carbon monoxide on MIL-101 (Cr): volumetric measurements and dynamic adsorption studies. Chemical engineering journal, 2012, 195, 359-368.

6. Ruthven, D.M. Principles of adsorption and adsorption processes. John Wiley & Sons, 1984.7. Zhang, Y.; Su, W.; Sun, Y.; Liu, J.; Liu, X.; Wang, X. Adsorption Equilibrium of N2, CH4, and CO2 on

MIL-101. Journal of Chemical & Engineering Data, 2015, 60(10), 2951-2957.

Results

Conclusions

Adsorption Isotherm Parametersof CH4 and CO2 on MIL-100 and MIL-101

n=1 n=3∆H(kJ/mol) 21.77 20.386

• Langmuir, Freundlich, and Temkin models described the adsorption of CO2 and CH4 on MIL-100(Cr) and MIL-101(Cr) relatively well (R2 > 0.97).

• The Langmuir model had the smallest distribution of deviation of the linearized experimental loading to the fitted loading over the adsorption pressure.

• The uniform isosteric heat of adsorption supported the Langmuir model, which assumed constant amount of energy of adsorption.

• The adsorption of CH4 and CO2 on MIL-100 and MIL-101 are monolayer adsorption.

• In the Langmuir model, the synthesis method of MIL-101 has a greater effect on the max loading parameter than the adsorption constant.

Langmuir Isotherm ParametersCH4 CO2

MIL-100

MIL-101

MIL-100

MIL-101

nm (mmol/g) 13.32 23.92 21.65 51.55

K (MPa-1) 0.3103 0.2072 0.7086 0.2891

R2 0.9944 0.9990 0.9907 0.9964

Freundlich Isotherm ParametersCH4 CO2

MIL-100

MIL-101

MIL-100

MIL-101

K 2.844 3.976 7.737 11.09m 1.460 1.434 1.870 1.566R2 0.9872 0.9888 0.9795 0.9718

Temkin Isotherm ParametersCH4 CO2

MIL-100

MIL-101

MIL-100

MIL-101

bT 837.1 514.6 490.6 236.7

AT 3.327 2.496 6.149 3.379

R2 0.9539 0.9678 0.9886 0.9833

Literature Langmuir Isotherm Parameters7

CH4 CO2

MIL-101 MIL-101nm (mmol/g) 8.708 22.91

K (MPa-1) 0.257 0.349