Masanao Kato

Determination of the ordered distribution of aluminum atoms in zeolitic frameworks. Part I

A new method was developed to determine the ordered distribution of Al atoms in a zeolitic framework by combining X-ray structural and 29Si MAS n.m.r. data. The configuration of Al atoms sought must give populations of 29Si(OSi)4−n(OAl)n′ with n = 0 ∼ 4, which are very close to the observed. The procedure consists of two steps. First, a configuration in an ideal (stoichiometric and disorder-free) crystal is determined by using connectivity relations between T sites (sites occupied by Si or Al atom). Then, the configuration is modified by introducing disorders so as to give the desired population spectrum. The method was applied successfully to ZK19, synthetic counterpart of phillipsite, and mined chabazite.

Thin Films of (BEDT-TTF)2Cu(NCS)2 Prepared by an Electrodeposition Method*

Thin films of (BEDT-TTF)2Cu(NCS)2 are prepared by the electrochemical oxidation of BEDT-TTF at a large current density. The films are composed of numerous platelets, which are set on edge and loosely packed on the anodes. The X-ray diffraction suggests that the product contains both amorphous regions and κ-type and other crystals. The ESR and conductivity are discussed in terms of the presence of amorphous regions.

Synthetic clinoptilolite and distribution of aluminum atoms in the framework of HEU type zeolites

Pure (K, Na)-clinoptilolite was crystallized in good reproducibility without seed crystals. Ordered Al distributions in frameworks of synthehized and natural clinoptilolite and natural heulandite, which are isostructural framework, were also analyzed. It was found that Al atoms in clinoptilolite were condensed in T 1 and T 2 sites with space group P2/c. On the other hand, Al atoms in heulandite were distributed in T 1 , T 2 , T 3 , and T 4 sites with space group P2 1 , which violates against the 2 Al/5 ring avoidance rule.

Effects of Structural Disorder on the Generation of Acidic Sites in Zeolite L

Acidic properties of zeolite L were observed to correlate well with its structural disorders. The 29 Si-MAS-NMR spectrum of zeolite L having a Si/Al ratio different from 3 revealed that Al distribution deviated from the ideal and suggested the presence of six different boat-shaped 8-ring patterns. Differential molar heats of adsorption of ammonia changed step-wise with the adsorbed amount, which reflects the difference in the acid strength of protons located in structurally different 8-rings.

Adsorption potential and the mutual interaction potential between adsorbates: Rare gases in the pore of ferrierite

Abstract A method has been developed to determine values of parameters contained in a Lennard—Jones 6–12 potential. This method was applied to the determination of the pair potential function between a rare gas atom and a lattice oxygen of a zeolite, and the adsorption potential was subsequently calculated. The calculated potentials agree with experimental results if the three-body interactions are taken into account. The mutual interaction potentials between the ad-atoms and the second virial coefficient of the adsorbed gas were also calculated. The results show that the depth of potential curves decrease sharply if the three-body interaction and a weak electric field are taken into account and that the depth becomes one-third of the depth of the pair interaction potential in the case of Xe, while it is about 60% in the case of Ar. It is concluded that three-body interactions are a very important factor in the physical adsorption of gas on zeolites.

Avoidance of 2 Al atoms in a 5-ring a new rule complementing the Loewenstein's rule

A new rule is proposed which restricts the distribution of Al atoms in zeolitic frameworks complementing the Loewensteins rule. The new rule shows that any 5-ring in a siliceous zeolitic framework can not contain two Al atoms, and is applied to determine the lowest limit of Si/Al ratio in these zeolites.