High-Pressure Water Intrusion Investigation of Pure Silica RUB-41 and S-SOD Zeolite Materials

The energetic performance of two microporous siliceous materials, RUB-41 (RRO structure type) and S-SOD (SOD structure type) possessing medium-sized and very small pore openings, respectively, were studied using high-pressure water intrusion−extrusion experiments at room temperature. The pressure−volume diagrams of the RUB-41 material indicate a partly reversible phenomenon showing a slight hysteresis at the extrusion stage, which reveals that the water− RUB-41 system displays a shock-absorber behavior. Moreover, a shift toward the low pressure range was detected between the first cycle of water intrusion and the second one, indicating the creation of new defect sites in the inorganic framework after the intrusion process. Several investigations, mainly by 29 Si solid-state NMR spectroscopy, confirm this observation. For the S-SOD material, no water intrusion was observed after three water intrusion−extrusion cycles. The highly hydrophobic character of the S-SOD material with its small pore opening or the value of the capillary pressure, which exceeds that tolerated by the instrument, are probably the two reasons for this result.