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DICAM Ph. D. Student Francesco M. Benedetti wins 2 Poster Awards at ICOM Meeting in San Francisco

At the recent ICOM Meeting (11th International Congress on Membranes and Membrane Processes) held in San Francisco, July 29-August 4 2017, the DICAM Ph. D Student Francesco M. Benedetti has been awarded with 2 poster prizes. Francesco is currently spending is research period abroad, at the Chemical Engineering Department of MIT, with Professor Zachary Smith

Francesco M. Benedetti is a PhD Student in his 2nd year, working on the fabrication, testing and modeling of Membranes for CO2 capture. Francesco has been awarded with 2 poster prizes at the recent ICOM meeting, 11th International Congress on Membranes and Membrane Processes, for the works:

 

1) E. Ricci, F.M. Benedetti, M.E. Dose, M.G. De Angelis, B.D. Freeman, D.R. Paul
Experimental determination and modelling of mixed gas CO2/CH4 sorption in HAB-6FDA polyamide precursor and corresponding thermally rearranged (TR) polymers
In collaboration with the University of Texas at Austin.


Abstract
Mixed gas sorption experiments allow to assess the interactions between gases during the permeation process and to gain a better fundamental understanding of the separation phenomenon, as well as to design with great detail a membrane separation process. We used a pressure decay technique to measure the mixed gas solubility of CO2 and CH4 at different compositions of the gas mixture in 3,3’-dihydroxy-4,4’-diamino-biphenyl (HAB) 2,2’-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), and its thermally rearranged
(TR) variants, up to 30 bar. These materials are of particular interest because of their optimal performance in CO2/CH4 separation.
Results showed that the solubility of both species in mixed gas conditions is lower than that of the pure gases at the same fugacity. However, CH4 is more affected by the presence of the second gas, while CO2 behaviour is barely altered. Therefore, the real solubility-selectivity is higher than the ideal value calculated from pure gas sorption data, similarly to what observed in other glassy materials like PTMSP and PIM-1.
The solubility of each component of the mixture was successfully modelled using the Non- Equilibrium Lattice Fluid (NELF) model, using only the pure component parameters and the binary interaction parameters retrieved from pure gas sorption. Thus, no further parameter needs to be determined from mixed gas sorption experiments. The availability and reliability of a modelling tool for mixed gas sorption, assessed for this system, is particularly promising because mixed gas experiments are very time-consuming.


2) F.M. Benedetti, A. Sardano, M. Minelli, M.G. De Angelis, M. Degli Esposti, P. Fabbri, G. Cucca, A. Pettinau
Mixed matrix membranes based on PPO with H2-selective fillers
In collaboration with Sotacarbo S.p.A.


Abstract
We fabricated robust mixed matrix membranes (MMMs) based on poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and two commercial molecular sieves: Zeolite 3A and ZIF-8. The membrane preparation was optimized to allow the formation of films up to 45wt% of filler. The permeation, diffusion and sorption of He (used as a model for H2), N2, CH4, CO2 were investigated at 35, 50, 65°C.
SEM images showed good adhesion between the polymer matrix and both fillers. The dispersion of the fillers was homogeneous, with some aggregates at high loadings. DSC analysis revealed that moisture is entrapped in PPO/Zeolite systems, removable with a high temperature treatment. Conversely, PPO/ZIF-8 films were fully hydrophobic and amorphous. Remarkable gas transport results were showed by PPO/ZIF-8 membranes, which revealed an increase of He permeability of around 800% with respect to the pure PPO and a He/CO2 selectivity which was 15% higher at 35°C. The diffusivity is inversely proportional to the kinetic diameter of the gas, thus MMMs behave as molecular sieves. Helium solubility increases by an order of magnitude for a 25 wt% ZIF-8 loading, while CO2 increases of around 30%. The effect of temperature further enables the gas separation properties, indeed both He permeability and He/CO2 selectivity increase sharply with increasing temperature. This aspect makes these materials even more interesting for industrial applications, which usually operate at temperature higher than the room temperature. The activation energy of the permeation and diffusion were evaluated, as well as their trend with filler content.

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