A New Method for the Determination of Low Coverage Adsorption Heats for Zeolite-VOC Systems

International audienceThe adsorption of the acid gas H2S has been explored in both MIL-47(V) and MIL-53(Cr) porous metal organic frameworks (MOFs) by combining infrared measurements and molecular simulations. It is shown that while the MIL-47(V) structure remains rigid upon H2S adsorption up to a pressure of 1.8 MPa, the MIL-53(Cr) solid initially present in the large pore form (LP) switches to its narrow pore version (NP) at very low pressure before undergoing a second structural transition from the NP to the LP versions at higher pressure. Such structural transitions further explain the different shape of the adsorption isotherms for both MILs. A further step consists of providing some insights into the microscopic arrangements of the adsorbate molecules within the pores of the MILs. At the initial stage of adsorption, the H2S molecules mainly form hydrogen bonded species, either as hydrogen donor (in MIL-47 V) or hydrogen-acceptor (in MIL-53Cr) with the mu(2)-O and mu(2)-OH groups, respectively, present at the MOF surfaces. At higher pressure (1.8 MPa), the adsorbates are preferentially arranged within the channel in order to form dimers with a high orientational disorder. Both experimental and simulated adsorption enthalpies for H2S decrease in the following sequence: MIL-53(Cr) NP > MIL-47(V) > MIL-53(Cr) LP. The conclusions drawn from this work are then discussed considering the use of such materials for the CH4/H2S separation by means of Pressure Swing Adsorption

show abstract

“…The isosteric heats of adsorption have been determined for all MILs following the procedure previously described …”

Section: Methodsmentioning

confidence: 99%

Molecular Insight into the Adsorption of H₂S in the Flexible MIL-53(Cr) and Rigid MIL-47(V) MOFs: Infrared Spectroscopy Combined to Molecular Simulations

et al. 2011

Self Cite

View full text Add to dashboard Cite

show abstract

“…In addition, toluene is a typical VOC (volatile organic compound), and removal of it from the atmosphere by catalytic combustion or adsorption is being attempted widely. Also from this viewpoint, the adsorption behavior is being studied. ,, …”

Section: Introductionmentioning

confidence: 99%

“…Also from this viewpoint, the adsorption behavior is being studied. 23,32,42 One purpose of this study is development of a quantitative analysis method based on TPD of toluene to contribute to these fields, where most of the above studies have utilized TPD of aromatic hydrocarbons only qualitatively.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Toluene Adsorption on Na-Form Zeolite with a Temperature-Programmed Desorption Method

et al. 2006

View full text Add to dashboard Cite

Temperature-programmed desorption (TPD) of toluene was carried out on various zeolites, and theoretically analyzed to determine thermodynamic parameters. The TPD process was identified as the case of equilibrium control, showing that the analytical method, the same as that for ammonia TPD, can be applied to the toluene TPD to calculate the adsorption heat. It was observed that approximately one toluene molecule was adsorbed on one Na + cation for MFI and BEA. The heat of toluene adsorption on Na + was MOR > MFI > BEA > FAU, similar to the heat of ammonia adsorption on the corresponding H-form zeolite. A linear relationship was observed between both adsorption heats. It suggests that the adsorption of toluene on Na + is controlled by the electron-withdrawing nature of the ion exchange site, as well as the Brønsted acid strength of the H-form zeolite.

show abstract

“…In such a situation, obtaining an isotherm at concentrations of interest will be difficult, if not impossible . If the VOC uptake is high this problem will be more pronounced; it can however be overcome by using a flow-through type gravimetric experiment as explained elsewhere in the literature . In this work we implement a flow-through gravimetric technique using a simple TGA setup.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Dichloromethane on Activated Carbon

2009

View full text Add to dashboard Cite

Adsorption is an economical option for the removal of volatile organic compounds (VOCs) from effluent streams of various industries. Its feasibility depends on the equilibrium and kinetics of the adsorption process. A conventional apparatus for the measurement of adsorption equilibria and kinetics needs dedicated equipment which may not be readily available in all laboratories. To overcome this limitation, in this work adsorption equilibrium of a VOC, namely, dichloromethane, was measured on activated carbon by a flow-through gravimetric technique using a thermogravimetric analyzer (TGA, an instrument readily available in most laboratories). Moreover, in a flow-through measurement technique the concentration of the VOC in the gas phase can be accurately controlled. The measurements were performed at three different temperatures, namely, (303.15, 318.15, and 353.15) K. The results were comparable to already available data for the adsorption of dicholoromethane on activated carbon. A virial form of isotherm best describes the isotherm behavior. The limiting enthalpy of adsorption was around −41 kJ·mol−1.

show abstract

A New Method for the Determination of Low Coverage Adsorption Heats for Zeolite-VOC Systems

Cited by 3 publications

References 4 publications

Molecular Insight into the Adsorption of H₂S in the Flexible MIL-53(Cr) and Rigid MIL-47(V) MOFs: Infrared Spectroscopy Combined to Molecular Simulations

Molecular Insight into the Adsorption of H₂S in the Flexible MIL-53(Cr) and Rigid MIL-47(V) MOFs: Infrared Spectroscopy Combined to Molecular Simulations

Analysis of Toluene Adsorption on Na-Form Zeolite with a Temperature-Programmed Desorption Method

Adsorption of Dichloromethane on Activated Carbon

Contact Info

Product

Resources

About

A New Method for the Determination of Low Coverage Adsorption Heats for Zeolite-VOC Systems

Cited by 3 publications

References 4 publications

Molecular Insight into the Adsorption of H2S in the Flexible MIL-53(Cr) and Rigid MIL-47(V) MOFs: Infrared Spectroscopy Combined to Molecular Simulations

Molecular Insight into the Adsorption of H2S in the Flexible MIL-53(Cr) and Rigid MIL-47(V) MOFs: Infrared Spectroscopy Combined to Molecular Simulations

Analysis of Toluene Adsorption on Na-Form Zeolite with a Temperature-Programmed Desorption Method

Adsorption of Dichloromethane on Activated Carbon

Contact Info

Product

Resources

About

Molecular Insight into the Adsorption of H₂S in the Flexible MIL-53(Cr) and Rigid MIL-47(V) MOFs: Infrared Spectroscopy Combined to Molecular Simulations

Molecular Insight into the Adsorption of H₂S in the Flexible MIL-53(Cr) and Rigid MIL-47(V) MOFs: Infrared Spectroscopy Combined to Molecular Simulations