CO2/N2 Separation Using Cu-BTC, Uio-66 and MIL-53(Al) Metal Organic Frameworks

CO₂/N₂ Separation Using Cu-BTC, UIO-66 and MIL-53(Al) Metal Organic Frameworks

Satyannarayana Edubilli, Pradip Das, Sasidhar Gumma

Department of Chemical Engineering, Indian Institute of Technology Guwahati

Guwahati - 781039, Assam, India.

Email:  s.edubilli@iitg.ernet.in (S.Edubilli), pradip.das@iitg.ernet.in (Pradip.das), s.gumma@iitg.ernet.in (S. Gumma)

In recent years Metal Organic Frameworks (MOFs) have gained much attention for adsorptive separations due to their exceptional capacities, tunable pore Structures and ease of regenarability. MOF materials are being extensively studied in terms of equilibrium measurements, but for the practical application point of view, they have to be tested for their cyclic and thermal stabilities under process conditions.

In this presentation, the results of breakthrough and cyclic adsorption experiments for CO₂ / N₂ separation on different MOFs viz. Cu-BTC, Uio-66 and a flexible metal organic framework MIL-53(Al) will be reported. MOF powders are made into beads using PVA/H₂O as binder. Different ratios of MOF to binder were prepared and the binder content was optimized based on its strength and surface area. The adsorbent column was filled with MOF beads and this column was used for breakthrough as well as the cyclic PSA adsorption experiments. A mixture of 15% CO₂ in N₂ was used as the feed. During the experiments, the column pressure history, feed inlet flow rate, and column outlet flow rate are recorded using data acquisition system. The column outlet stream composition was analyzed using a Gas Chromatograph. The performance of a three step PSA cycle consisting of pressurization, feed and blowdown as well as cycles incorporating N₂ purge and CO₂ rinse steps will be reported. In a typical experiment about 10-12 grams of the adsorbent was used and the feed flow rate was about 200 cc/min. The adsorption step was carried out at about 1.3 bar, while desorption was done at 0.1 bar.

In addition to these results we also report, the effect of framework flexibility on the process performance. In our earlier work on MI-53(Al) we have reported that the pores of parent MIL-53(Al) into narrow pore (np) domain at ambient temperature in absence of guest molecules by manipulating its history [1]. Using this procedure, we have studied the performance of MIL-53 (Al) using both lp and np phased samples. Under the same experimental conditions, the observed CO₂ breakthrough times of lp and np phase materials are 180 and 510 seconds respectively.

References

 [1] P. Mishra, S. Edubilli, H. Uppara, B. Mandal and S. Gumma, Langmuir, 29, 12162-12167,2013