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The energetic performances of pure silica ITH-type zeolites were studied by high pressure intrusion–extrusion in water and LiCl aqueous solutions at different concentrations. When pure water was intruded, a bumper behavior was exhibited with an intrusion pressure of 82 MPa and an absorbed energy of 6.6 J g−1. Changing the intruded liquid from water to LiCl aqueous solutions, an increase of the intrusion pressure was observed with 119, 175 and 280 MPa for 5 M, 10 M and 20 M LiCl aqueous solutions, respectively. The energy that the latter system could absorb (30.8 J g−1) was among the highest ever reported. A change in the behavior with LiCl concentration was also observed. The “ITH-type zeosil–20 M LiCl solution” system demonstrated a combination of bumper and shock-absorber behaviors, whereas a bumper behavior was displayed for water and the other LiCl aqueous solutions. All the zeolite samples were characterized before and after intrusion–extrusion experiments (XRD, SEM, N2 adsorption–desorption, TG and NMR analysis) in order to understand the influence of LiCl concentration on the “zeosil–liquid” system behavior. [ABSTRACT FROM AUTHOR]

In order to study the energetic performances of different “pure silica chabazite–LiCl aqueous solution” systems, intrusion–extrusion experiments were performed under high pressure. Depending on the LiCl concentration in the aqueous medium (0 M, 5 M, 10 M, 20 M), an increase of the stored (4.4, 9.9, 13.5, 24.3 J g−1) and restored (2.6, 8.1, 11.8, 20.5 J g−1) energies are observed. Therefore, compared to the “pure silica CHA–H2O” system, the stored energy is increased by 5.5 times for the “pure silica CHA–20 M LiCl” one. The zeolite samples were characterized (XRD, TG, NMR spectroscopy, N2 adsorption and SEM) before and after the intrusion–extrusion process in order to better understand the influence of the LiCl concentration on the system behavior. [ABSTRACT FROM AUTHOR]

Abstract: Four pure silica zeolites, chabazite (CHA-structure type) and SSZ-23 (STT-structure type) with cage-like structure and silicalite-1 (MFI-structure type) and beta (∗BEA-structure type) with channel structure, were synthesized and fully characterized. Their sorption properties were examined using gravimetric method combined with Grand Canonical Monte Carlo simulations (GCMC). Of particular interest is the large difference in the adsorption rates of n-hexane, p-xylene and acetone observed for these zeosils at 25, 75 and 150°C. As expected, in most cases, a decrease in the adsorption capacity is observed with increasing the molar volume of the used probe molecule and the temperature. An exception is observed for the pure silica CHA-type zeolite due to its small pore size which prevents molecules from entering its porosity. However, at higher temperature, the window size widens slightly and allows n-hexane and acetone, which have kinetic diameter close to the pore opening, to enter easily in chabazite. As a result, for this zeosil, an increase in the adsorption capacity compared to that obtained at 25°C is observed. All these zeosils are promising for technological uses in car exhaust gas decontamination. [Copyright &y& Elsevier]