Hybrid organosilica membranes have become attractive for industrial applications because of high performance and long-term stability. This work investigated the influence of water vapor on CO2 gas permeation through the hybrid membranes. Two types of organoalkoxysilanes, bis­(triethoxysilyl)­ethane (BTESE) and bis­(triethoxysilyl)octane (BTESO), were used as precursors to prepare membranes via the sol–gel method. The two membranes showed distinct properties of porosity and water affinity because of the differences in the bridging methylene numbers between the two Si atoms. Under dry conditions, the BTESE and BTESO membranes showed CO2 permeances as high as 7.66 × 10–7 and 6.63 × 10–7 mol m–2 s–1 Pa–1 with CO2/N2 selectivities of 36.1 and 12.6 at 40 °C, respectively. In the presence of water vapor, CO2 permeance was decreased for both membranes, but the effect of water vapor on CO2 permeation was slighter for BTESO membranes than it was for BTESE membranes because of more hydrophobicity and denser structures with a longer linking-bridge group. The hybrid organosilica membranes both showed good reproducibility and stability in water vapor.

Organosilica membranes are a type of novel materials derived from organoalkoxysilane precursors. These membranes have tunable networks, functional properties and excellent hydrothermal stability that allow them to maintain high levels of separation performance for extend periods of time in either a gas-phase with steam or a liquid-phase under high temperature. These attributes make them outperform pure silica membranes. In this review, types of precursors, preparation method, and synthesis factors for the construction of organosilica membranes are covered. The effects that these factors exert on characteristics and performance of these membranes are also discussed. The incorporation of metals, alkoxysilanes, or other functional materials into organosilica membranes is an effective and simple way to improve their hydrothermal stability and achieve preferable chemical properties. These hybrid organosilica membranes have demonstrated effective performance in gas and liquid-phase separation.

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Polyhedral oligomeric silsesquioxane (POSS) is a promising nanofiller with a cubic inorganic framework and optional organic functional groups. In this work, organosilica− POSS mixed matrix membranes were successfully prepared via the incorporation of octabenzamidopropyl-POSS into 1,2bis(triethoxysilyl)ethane (BTESE)-derived matrix for gas separation. The BTESE−POSS composites showed stable structures up to 400 °C, and the POSS could be loaded within a wide range of contents by adjusting the concentrations in mixed solutions. In the gas separation, the effects of POSS content and operating temperature were investigated. As POSS content increased, the selectivities for H 2 /N 2 were enhanced. The highest H 2 /N 2 selectivity of 52.1 was obtained for BTESE−POSS (50.0%) composite membrane, which amounted to an increase of 160% over that of pure BTESE membrane at 100 °C. The apparent activation energy for gas permeation through these composite membranes became higher than that of pure BTESE membrane, which indicated a smaller pore size obtained by the addition of POSS. The permeances of He and H 2 for BTESE−POSS mixed matrix membranes were well predicted by the n = 1 Maxwell−Wagner−Sillar model, suggesting that small gases permeated a stack of oblate ellipsoidal layers of these membranes with parallel transport to the pressure gradient.

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A heat pump is applied in pressure-swing distillation (PSD) for separating an isobutanol/isobutyl acetate mixture in this paper. To ensure dry compression and prevent compressor damage, a preheater is added before the compressor based on the dry fluid property of the isobutanol/isobutyl acetate mixture. In addition, the optimal preheated temperature of the overhead vapor stream may further improve the performance of the heat pump-assisted PSD process. Through optimization and analysis, the optimum superheat values of overhead vapor streams from two columns are 12 and 8.4 °C, respectively. The coefficients of performance of heat pumps achieve maximum values of 17.18 and 20, and the total annual cost of the process is minimum. Moreover, a heat exchanger network (HEN) is applied in the heat pump with preheater-assisted PSD (HPPSD) to reduce the use of steam in preheaters. Compared with the conventional PSD, the total annual costs, energy consumption, and CO2 emission of the HPPSD-HEN process are decreased by 69.8, 83.99, and 79.58%, respectively.