A Porous Copper Metal Organic Framework with Highly Nucleophilic Amine Links for CO2 Gas Separation from Biogas

A porous copper metal organic framework with highly
nucleophilic amine links for CO₂ gas separation from biogas

Kritika  Narang¹, Andreas
Kaiser ², Farid
Akhtar ^1*

¹Luleå University of Technology, Luleå 97187, Sweden

² Technical University of Denmark

*: corresponding author, email: farid.akhtar@ltu.se

The rising interest in using biogas as an energy fuel
has lowered the consumption of fossil fuel and inclined the environment toward
sustainability. Despite having low CO₂ emissions during the
combustion of biogas, it still involves a significant challenge to remove the existing
impurities in the biogas using the most efficient technology before becoming a
substantial fuel for the industries.  Biogas consist of ~ 40 mol% of CO₂
depending upon the substrate and conditions of the digester used during
production [1]. This CO₂ is the major undesirable
component for the energy recovery of the biogas as it lowers the calorific
value of the fuel. Adsorption driven materials have set a benchmark in CO₂
separation in the biogas upgrading process [2,3]. Wide variety of adsorbents has been studied for
their separation performances and energy consumption to procure efficient, energy-saving
and environmentally benign separation processes [4]. MOFs (Metal-organic frameworks) are porous materials,
which has gained attention in the past two decades and has widespread potential
applications in gas separation and purification technology. MOFs offer unique properties
such as high surface area, tunable pore size and easy tailoring of chemical
functionalities.

In this research, we report a copper MOF synthesized using
a facile solvothermal synthesis. The Cu-MOF crystals were of cuboid-shaped of 300-500
nm in size and demonstrated a BET surface area of 756 m²/g. The Cu-MOF
showed carbon dioxide uptake capacity of 2.1 mmol/g at 273K and 100 kPa and 1.8
mmol/g at 293 K and 100 kPa. The gravimetric high-pressure adsorption was
carried out for both CO₂ and CH₄ gases at 10 bar. The Cu-MOF
showed 3.7 mmol/g uptake of CO₂ and 2.5 mmol/g for CH₄ at
10 bar and 293 K. The isosteric heat of adsorption (Q_st) using Van’t
Hoff equation was 18 kJ/mole for CO₂ adsorption, which describes the
low energy penalty for the regeneration cycles. To investigate the CO₂ separation
performance from CH₄, the Cu-MOF powders were structured into mechanically
strong hierarchically porous pellets and breakthrough adsorption and desorption
cycles were measured. The breakthrough data was used to obtain mass transfer
coefficient and diffusivities value.

References

[1] I Angelidaki, L Treu, P
Tsapekos, G Luo, S Campanaro, H Wenzel, et al., Biogas upgrading and
utilization: Current status and perspectives, Biotechnology Advances. 36 (2018)
452-466.

[2] S Chaemchuen, NA Kabir, K
Zhou, F Verpoort. Metal-organic frameworks for upgrading biogas via CO2
adsorption to biogas green energy, Chem.Soc.Rev. 42 (2013) 9304-9332.

[3] B Yuan, X Wu, Y Chen, J Huang, H Luo, S Deng. Adsorption of CO2, CH4, and N2 on Ordered
mesoporous carbon: Approach for greenhouse gases capture and biogas upgrading,
Environ.Sci.Technol. 47 (2013) 5474-5480.

[4] K Zhou, S Chaemchuen, F Verpoort. Alternative materials
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