Liquid pressure, drying methods

The vacuum drying methods take advantage of the greater vapor pressure of water in the liquid phase in contrast to the lower vapor pressure of ice or water at its melting point (4) vapor pressure of H20 at 0°C = 4.6 mm vapor pressure of H20 at 4.4°C = 6.3 mm (potential efficiency increase of 37%) vapor pressure of H20 at 10°C = 9.2 mm (potential efficiency increase of 100% ). 

Among all solvent-replacement supercritical drying methods, organic solvent-replacement supercritical drying has limitations of poor safety due to its high temperature and pressure operation in addition its equipment and operation costs are high. As for liquid carbon dioxide-replacement supercritical... 

Stability of phase boundaries depends on the surface tension. Surface tension in a supercritical fluid system is of major importance for drying, surfactant efficacy, and extraction. The surface tension of a gas increases with pressure and approaches zero at the critical point while the surface tension of liquid decreases with pressure resulting in dissolution of supercritical components in the liquid phase. The methods useful in correlating surface tension include Macleod-Sugden correlation and corresponding states theory. ... 

Methods have been developed by which the porous network structure is retained upon drying, the most important being drying with supercritical fluids and the so-called ambient-pressure drying, where formation of Si—O—Si bridges is prevented by hydrophobization of the pore walls. The obtained materials are called aerogels (because the pore liquid is replaced by air) [17] and will be treated in Qiapter 18. 

Importantly, ionic liquids show excellent properties on the adsorption of microwave. The combination of microwave-assisted synthesis and ionothermal synthesis opens up an efficient and safe route to prepare zeolite materials [60]. Tian and coworkers reported the microwave-assisted ionothermal synthesis of AlPO-ll using [EmimJBr [61]. Silicon element was also successfully introduced to the framework forming SAPO-11 with potential catalytic applications. In addition, Yan and coworkers developed the ambient pressure synthesis method for silicate zeolites by combining the advantages of ionothermal synthesis, dry-gel conversion, and microwave irradiation [62]. With the assistance of microwave-assisted synthesis, the safe and fast process of ionothermal synthesis has shown to be a promising synthetic route for a variety of zeolite structures. 

Cai R, Liu Y Gu S, Yan Y. Ambient pressure dry-gel conversion method for zeohte MFI synthesis using ionic liquid and microwave heating. J Am Chem Soc 2010 132 12776-7. 

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