Adeola F. Ojo

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.

AIPO4-based molecular sieves synthesized in the presence of di-n-propylamine: Are the structures related?

Aluminophosphate-based molecular sieves crystallize in the presence of many organic additives. To study the influence of this organic material on the resulting structure, the products of a series of syntheses involving the use of a single organic species, di- n -propylamine (DPA), were investigated. The systematic study of the effect of specific synthesis variables led to the preparation of AIPO 4 -11 (AEL), VPI-5 (VFI), AIPO 4 -H3 (APC), MAPO-39, CoAPO-43 (GIS), and MAPSO-46 (AFS). Each sample was characterized by X-ray powder diffraction, scanning electron microscopy (SEM), Guinier-Lenne photographs, and thermogravimetric analysis. SEM did not show any particular pattern of morphological similarity between the samples. A careful examination of the structures revealed that, although the structures are quite different from one another, all have straight channels with at least 8-ring pore openings. Those with one-dimensional channel systems were prepared from gels with a lower DPA:Al 2 O 3 ratio than those with three-dimensional ones. No cages are present in any of the structures synthesized.

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.

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.

Sorption Thermodynamics of Nitrogen and Oxygen on CaA Zeolite

Sorption thermodynamic quantities, i.e., isosteric sorption heat, standard entropy and stan- dard Gibbs free energy, of nitrogen and oxygen on CaA zeolite were studied using an isosteric sorption technique over entire concentration ranges from nearly zero to micropore saturation concentration. Monte Carlo molecular simulations were performed to calculate guest-host interactions and sorption heats for the two gases over certain pressure ranges. The experimental data and results of simulations were compared with literature data.

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.

03-O-05-Competitive role of sodium and potassium cations during hydrothermal zeolite crystallization from Na2O-K2O-Al2O3-SiO2-H2O gels

Publisher Summary This chapter discusses the competitive role of sodium and potassium cations during hydrothermal zeolite crystallization from Na 2 O-K 2 O-Al 2 O 3 -SiO 2 -H 2 O gels. It also describes the structure directing the roles of these alkali cations, the phase evolution of products, and the size and morphology of the crystals. Zeolites A, F, Q, X, and sodalite are synthesized hydrothermally from Na 2 O-K 2 O-Al 2 O 3 -SiO 2 -H 2 O gels. The crystallization processes are monitored as a function of the fraction of sodium cations in the sodium–potassium cation gel system. Pure phases are obtained in three distinct alkali composition ranges—namely, zeolite A is crystallized at Na 2 O/(Na 2 O+K 2 O) ∼ 0.9 to 1.0, zeolite X at Na 2 O/(Na 2 O+K 2 O) ∼ 0.7 to 0.8, and zeolite F at Na 2 O/(Na 2 O+K 2 O) ≤ 0.5.