ISSN:
1573-9171
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Conclusions 1. A new variety of regular intracrystalline structure has been found, which forms during the dealumination and hot vapor stabilization of the faujasite structure of zeolite. The mechanism of formation and the nature of the distribution of this pore structure is discussed. 2. From the isotherms and heats of adsorption of benzene and n-pentane vapor the principal structural features of ultrastable dealuminized Y zeolite have been determined: micropore volume Wo=0.18 cm3/g; overall specific surface of mesopores and macropores, determined by various methods, s+170 m2/g; distribution of mesopore volume by radius with rmax+25 Å and line half-width ∼1 Å. 3. The mesopore structure is resistant to mechanical treatment up to at least 200 bar; i.e., it contains practically no slitlike pores, but consists of channels uniformly distributed in the crystal, with average diameter ∼2a and in part ∼6a (wherea is the diameter of the unit cell of the zeolite crystal). 4. Benzene molecules are sensitive to the surface hydroxyl groups of the mesopores and macropores; i.e., at incomplete dehydroxylation of US-Ex zeolite the isotherms and heats of adsorption decrease from 200 to 430°. Removal of cations from the adsorbing faujasite voids causes an abrupt decrease in the differential heat of adsorption of benzene. According to the entropy diagram the mobility of the adsorbate molecules increases substantially in comparison with the starting type Y zeolite, but it remains lower than in a liquid.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00948609
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