Hybrid MIL-101(Cr)@MIL-53(Al) composite for carbon dioxide capture from biogas

Armin Taheri; Ensieh Ganji Babakhani; Jafar Towfighi Darian; Saeed Pakseresht

doi:10.1039/c8ra10619c

Hybrid MIL-101(Cr)@MIL-53(Al) composite for carbon dioxide capture from biogas

RSC Adv. 2019 May 14;9(26):15141-15150. doi: 10.1039/c8ra10619c. eCollection 2019 May 9.

Authors

Armin Taheri¹, Ensieh Ganji Babakhani², Jafar Towfighi Darian², Saeed Pakseresht³

Affiliations

¹ Young Researchers and Elites Club, Science and Research Branch, Islamic Azad University Tehran Iran armin.taheri@gmail.com armin_taheri@alum.sharif.edu.
² Gas Department, Research Institute of Petroleum Industry (RIPI) Tehran Iran.
³ Research & Technology Directorate of National Iranian Gas Company Iran.

Abstract

In this study, hybrids of nanoporous MIL-101(Cr) and MIL-53(Al) were synthesized using a hydrothermal method for various time periods, ranging from 8 to 40 h. The prepared materials were characterized by powder X-ray diffraction (PXRD) and elemental analysis, and their specific surface areas were measured by N₂ sorption at 77 K using the Brunauer-Emmett-Teller (BET) method. To investigate the practical application of these materials, the pure carbon dioxide and methane adsorption capacities of the samples were determined using the volumetric method. The Langmuir model was used to fit the CO₂ and CH₄ isotherms. Extended Langmuir (EL) equations and the ideal adsorbed solution theory (IAST) models were used to obtain the CO₂/CH₄ selectivity. The sample with the highest BET specific surface area was selected as a candidate for further investigations. The thermal stability of the selected sample was investigated by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) was used to characterize the sample morphology. XRD results showed that the sample synthesized over the shortest time corresponded to MIL-101(Cr), while the sample synthesized over the longest time was in agreement with MIL-53(Al). Samples synthesized for time periods between these two limits were assumed to be composites of both MIL-53(Al) and MIL-101(Cr). TGA results indicated that the hybrid materials were thermally stable at temperatures about 100 °C higher than for pure MIL-101(Cr). The BET specific surface area (1746 m² g^-1) and CO₂ adsorption capacity (16 mmol g^-1) of the selected hybrid sample were about 50% and 35% higher, respectively, compared with those of pure MIL-53(Al), but 30% and 20% lower, respectively, compared with those of pure MIL-101(Cr). Binary adsorption modeling showed the high selectivity of the MIL-101(Cr) and MIL-53(Al) hybrid material for CO₂ with a minimum separation factor of about 60 at 298 K. This value was much higher than those reported previously and those observed in this work for the original MIL-101(Cr) or MIL-53(Al). These results demonstrated that the hybrid of MIL-101(Cr) and MIL-53(Al) was a promising material for selective CO₂ capture from natural and biogas.