Pierre Billemont

ADSORPTION OF CARBON DIOXIDE, METHANE, AND THEIR MIXTURES IN POROUS CARBONS: EFFECT OF SURFACE CHEMISTRY, WATER CONTENT, AND PORE DISORDER

The adsorption of carbon dioxide, methane, and their mixtures in nanoporous carbons in the presence of water is studied using experiments and molecular simulations. Both the experimental and numerical samples contain polar groups that account for their partially hydrophilicity. For small amounts of adsorbed water, although the shape of the adsorption isotherms remain similar, both the molecular simulations and experiments show a slight decrease in the CO2 and CH4 adsorption amounts. For large amounts of adsorbed water, the experimental data suggest the formation of methane or carbon dioxide clathrates in agreement with previous work. In contrast, the molecular simulations do not account for the formation of such clathrates. Another important difference between the simulated and experimental data concerns the number of water molecules that desorb upon increasing the pressure of carbon dioxide and methane. Although the experimental data indicate that water remains adsorbed upon carbon dioxide and methane adsorption, the molecular simulations suggest that 40 to 75% of the initial amount of adsorbed water desorbs with carbon dioxide or methane pressure. Such discrepancies show that differences between the simulated and experimental samples are crucial to account for the rich phase behavior of confined water-gas systems. Our simulations for carbon dioxide-methane coadsorption in the presence of water suggest that the pore filling is not affected by the presence of water and that adsorbed solution theory can be applied for pressures as high as 15 MPa.

An experimental and molecular simulation study of the adsorption of carbon dioxide and methane in nanoporous carbons in the presence of water.

The adsorption of carbon dioxide and methane in nanoporous carbons in the presence of water is studied using experiments and molecular simulations. For all amounts of adsorbed water molecules, the adsorption isotherms for carbon dioxide and methane resemble those obtained for pure fluids. The pore filling mechanism does not seem to be affected by the presence of the water molecules. Moreover, the pressure at which the maximum adsorbed amount of methane or carbon dioxide is reached is nearly insensitive to the loading of preadsorbed water molecules. In contrast, the adsorbed amount of methane or carbon dioxide decreases linearly with the number of guest water molecules. Typical molecular configurations obtained using molecular simulation indicate that the water molecules form isolated clusters within the host porous carbon due to the nonfavorable interaction between carbon dioxide or methane and water.

MIL-91(Ti), a small pore metal–organic framework which fulfils several criteria: an upscaled green synthesis, excellent water stability, high CO2 selectivity and fast CO2 transport

A multidisciplinary approach combining advanced experimental and modelling tools was undertaken to characterize the promises of a small-pore type Ti-based metal–organic framework, MIL-91(Ti) for CO2 capture. This material was prepared using two synthesis strategies, i.e. under hydrothermal conditions and under reflux, and its single component adsorption behaviour with respect to CO2, CH4 and N2 was first revealed by gravimetry measurements. This hydrophilic and highly water stable MOF is characterized by a relatively high CO2 adsorption enthalpy. Molecular simulations combined with in situ powder X-ray diffraction evidenced that this is due to the combined interaction of this probe with N–H and P–O groups in the phosphonate linker. High CO2 selectivities in the presence of either N2 or CH4 were also predicted and confirmed by co-adsorption measurements. The possibility to prepare this sample under reflux represents an environmentally friendly route which can easily be upscaled. This green synthesis route, excellent water stability, high selectivities and relatively fast transport kinetics of CO2 are significant points rendering this sample of utmost interest for CO2 capture.

Design of salt–metal organic framework composites for seasonal heat storage applications

Porous materials are recognized as very promising materials for water-sorption-based energy storage and transformation. This study presents the first attempt to use Metal Organic Frameworks (MOFs) as host matrices of salts for the preparation of composite sorbents for seasonal heat storage. We have considered six water stable MOFs (i.e. MIL-127(Fe), MIL-100(Fe), MIL-101(Cr), UiO-66(Zr)–NH2, MIL-125(Ti)–NH2 and MIL-160(Al)) differing in their crystalline structure, hydrophilic–hydrophobic balance, pore size/shape and pore volume. The successful encapsulation of CaCl2 in the pores of MOFs leads to two series of MOFs–CaCl2 composites whose salt content could be finely tuned depending on the pore volume of MOFs and the synthesis conditions. These materials were fully characterized by combining multiple techniques (i.e. powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, X-ray energy-dispersive spectrometry elemental mapping, N2 sorption and elemental analysis). The water sorption properties of these composites were studied under conditions of a solar heat storage system (i.e. adsorption at 30 °C, desorption at 80 °C, both steps at a water vapour pressure of 12.5 mbar) in comparison to the parent MOFs. We analyze how the physico-chemical and structural properties of these host matrices impact the energy density of composite sorbents. We show that two mesoporous MOFs–CaCl2 composites (i.e. MIL-100(Fe)/CaCl2 and MIL-101(Cr)/CaCl2) with the highest salt loading (46 and 62 wt% respectively) exhibit very high energy storage capacities (up to 310 kW h m−3 (485 W h kg−1)) outperforming the best composites or physical sorbents reported so far together with very little loss upon adsorption–desorption cycling and high chemical stability upon ageing (up to 18 months).

Correction to: A reference high-pressure CO2 adsorption isotherm for ammonium ZSM-5 zeolite: results of an interlaboratory study

The original version of this article was published open access. Unfortunately, due to a technical issue, the copyright holder name in the online version (HTML and XML) is incorrectly published as “Springer Science+Business Media, LLC, part of Springer Nature 2018”. Instead, it should be “The Author(s) 2018”.