Frank R. Fitch

Metallo-organic molecular sieve for gas separation and purification

Abstract An improved synthesis process was developed for large-scale production of a highly porous material, [Cu 3 (BTC) 2 (H 2 O) x ] n , i.e., polymeric copper(II) benzene-1,3,5-tricarboxylate with molecular-sieve character, denoted as Cu-BTC, where BTC denotes benzene-1,3,5-tricarboxylate. A series of sorption properties for nitrogen, oxygen, carbon monoxide, carbon dioxide, nitrous oxide, methane, ethylene, ethane, n -dodecane, and water were studied. A detailed investigation of sorption thermodynamics was performed for carbon dioxide by a sorption-isosteric method. The experimental results show that Cu-BTC can be used for separation of gas mixtures such as carbon dioxide–carbon monoxide, carbon dioxide–methane and ethylene–ethane mixtures. In addition, air can be purified effectively from carbon dioxide, nitrous oxide, high-molecular weight hydrocarbons and moisture.

Adsorptive separation of nitrogen from other gases

Type X zeolites whose charge-compensating cations are composed of 95 to 50% lithium ions, 4 to 50% of one or more of aluminum, cerium, lanthanum and mixed lanthanides and 0 to 15% of other ions. The zeolites preferentially adsorb nitrogen from gas mixtures.

Thermodynamics of nitrogen and oxygen sorption on zeolites LiLSX and CaA

Sorption thermodynamics of nitrogen, N2, and oxygen, O2, on zeolites LiLSX and CaA were investigated using an isosteric sorption technique [Stud. Surf. Sci. Catal. 83 (1994) 209; Micropor. Mesopor. Mater. 22 (1998) 237] and molecular simulation. The sorption thermodynamic quantities, i.e., isosteric sorption heat, standard sorption entropy and standard Gibbs free sorption energy, were obtained over entire sorption phase concentration ranges from nearly zero to micropore saturation concentration. The differences in these thermodynamic quantities for the two zeolites of different structures and cation compositions were discussed, and these experimental data were compared with the results from molecular simulation. The advantages of LiLSX over CaA as sorbents for air separation were quantified.

Mössbauer spectroscopy of partially ferrous exchanged zeolite L. Part 1 Dehydration/hydration studies

The effect of progressive dehydration on the Mossbauer spectrum of (Fe, K)-L zeolite has been studied. Ferrous ions, originally located in site D, have been shown to migrate into sites A and E on dehydration at elevated temperatures. On subsequent progressive resorption of water into dehydrated (Fe, K)-L the ferrous ions in site E migrate back into site D before finally becoming only loosely associated with the framework on saturation. The ions in site A remain in this site on rehydration but an expansion of the framework degrades the Mossbauer spectrum at high water contents.

SYNTHESIS OF MICROPOROUS ZIRCONOSILICATES CONTAINING ZRO6 OCTAHEDRA AND SIO4 TETRAHEDRA

Three novel crystalline zirconosilicate molecular sieves, analogous to elpidite, umbite and gaidonnayite minerals, containing zirconium in octahedral coordination and silicon in tetrahedral coordination are synthesized.

Mössbauer emission studies of zeolite A. Part 1 — Effect of dehydration on 57Co2+ doped Na+ and Co2+ exchanged zeolite A

57 Co 2+ ions have been exchanged into zeolite A. Even at ppm concentrations Co 2+ ions were found to be located only in the sodalite window site (site I) with trigonal coordination to lattice oxygens. The temperature dependence of the Mossbauer parameters was measured in the range 77 to 573 K from which the Debye temperature and source recoil free fractions, f s , for Co 2+ ions located in site I were derived.

Mössbauer spectroscopy of ferrous exchanged zeolite L. Part 2. Study of various adsorbates

In a previous paper it was shown that the ferrous ions in dehydrated (Fe, K)-L zeolite are located in sites A and E of this framework. In this paper, the effect of the sorption of ethanol, propan-2-ol, 2-methyl propan-2-ol, methyl cyanide and triethylamine on the Mossbauer spectrum of these two ferrous species has been studied. The low quadrupole split doublet which arises from ferrous ions in square planar coordination with four lattice oxygens in site E is progressively reduced in intensity when most of the above sorbates are titrated into the zeolite with the corresponding formation of a wide quadrupole split doublet due to ferrous ions in site D coordinated to framework oxygens and one sorbate molecule. Although the ferrous cations in site A are inaccessible to sorbate molecules sorption of the above sorbates has been shown to affect the Mossbauer parameters of this ferrous species. The effect of outgassing the zeolite saturated with the above sorbates at various temperatures has been determined from the Mossbauer spectra of these outgassed samples.

Mössbauer emission studies of zeolite A Part II — The adsorption of water, methanol and ethanol in 57Co2+ doped Na+ and Co2+ exchanged zeolite A

The nature of the complexes formed between water, methanol, and ethanol molecules and the Co 2+ cations in 57 Co 2+ doped Na-A are discussed. A large anomalous ferric component was observed in the spectra of the water complexed sources, but not with the alcohol complexed sources. This ferric component arose from the radiolysis of the complexed water molecules in the electron capture decay process of 57 Co.

Sorption equilibia of nitrogen and oxygen on Li, Re-LSX zeolite for oxygen PVSA processes

Abstract Fundamental features of sorption thermodynamics for nitrogen, N 2 , and oxygen, O 2 , as obtained by the Sorption-isosteric Method and by Grand-canonical Monte Carlo simulations using the Accelerys Cerius software package together with the Cation-locator module, are described for a BOC proprietary lithium and trivalent-ion exchanged zeolite sorbent, Li, RELSX, for O 2 -PVSA processes. Structure-property relationship are detailed for intracrystalline centers and heats of sorption. The results are supported by TOF-SIMS data for ion distributions over related zeolite-composite geometries. Several basic sorption properties are compared between the homologous low-silicon type-X zeolite modifications Li, RELSX and LiLSX.

Monte Carlo simulation of the temperature dependence of adsorption of nitrogen and oxygen by LiLSX zeolite

Grand canonical Monte Carlo simulation of adsorption of nitrogen and oxygen was carried out on the LiLSX zeolite structure, and the results are compared with experimental adsorption data. The influence of temperature on the differential adsorption enthalpies, adsorption capacities, and N 2 /O 2 selectivities is discussed.