Energetic behavior of the pure silica ITQ-12 (ITW) zeolite under high pressure water intrusion

Abstract

Experimental water intrusion–extrusion isotherms were obtained at room temperature on pure silica ITW-type zeolites (ITQ-12 zeosil). The water intrusion is obtained by applying a high hydraulic pressure corresponding to the intrusion step. When the pressure is released, the water extrusion occurs at a similar pressure to that of the intrusion one. Therefore, the “ITW zeosil–water” system behaves like a spring and the phenomenon is reproducible over several cycles. Several characterization techniques have been performed before and after water intrusion–extrusion experiments in order to reveal the presence or the lack of defects after such experiments. Structural modifications at the long range order cannot be observed by XRD analysis after three water intrusion–extrusion cycles. However, solid state NMR spectroscopy provides evidence of the presence of Q₃ groups revealing the breaking of some siloxane bridges after the intrusion step. The “ITW zeosil–water” system can restore 100% of the stored energy corresponding to about 8 J g⁻¹.