Uncommon adsorption isotherm of methanol on a hydrophobic Y-zeolite

The physisorption of methanol vapor on a dealuminated, commercial Y type ze olite (CBV-901) at temperatures from 0 to 80 degreesC, produces a rare Type V adsorption isotherm. In contrast to some microporous carbons and AIPO(4) -5 derivatives that give Type V isotherms only with water, CBV-901 barely a dsorbs water at p/p(o) < 0.7 relative pressures. Micropore filling with met hanol takes place near p/p(o) approximate to 0.2, which is unusually low fo r Type V isotherms. To our knowledge, such isotherms have not been reported over zeolites before. Pore size measurements and grand canonical Monte Car lo molecular simulation experiments indicate that the selective micropore c ondensation of methanol is intimately associated with the micropore structu re and the force field of the dealuminated Y-zeolite. Mesopores or lattice defects including silanol groups and detached crystal fragments play a seco ndary role in shaping the methanol isotherms. The unique combination of hig h adsorption capacity and low relative pressures both for adsorption and re generation is desirable for various applications including pressure swing s eparations, air pollution abatement, and adsorptive heat pumps.