Showing papers in "Zeolites in 1985"

TL;DR: In this article, molecular statistical calculations of the thermodynamic characteristics of adsorption by silicalite at very low coverages using the atom-atom approximation for the potential energy of intermolecular interaction were carried out.

TL;DR: In this paper, a review is given on the possibilities of various nuclear magnetic resonance techniques which have been applied up till now to study quantitatively the acidity of zeolites and related catalysts.

TL;DR: In this article, molecular orbital calculations were performed on two types of pentameric model clusters with geometry derived from the known structure of zeolite ZSM-5, and the average acid strength of isolated aluminium sites was found to be comparable to that of paired Al-sites.

TL;DR: In this article, the structure of ZSM-12, a high-silica zeolite, was determined by analysis of electron and X-ray powder diffraction data combined with model building.

TL;DR: In this article, an e.s.r.-study was carried out on Cu 2+cation location in copper-exchanged H- and Na-forms of mordenite and ZSM-5.

TL;DR: In this article, the effect of hydration and dehydration on the coordination of boron in H-Boralite is investigated by 11B magic angle spinning n.m.r.

TL;DR: ZSM-22 as discussed by the authors, an orthorhombic high silica zeolite (Cmcm, a = 13.86 ± 0.03A, b = 17.41± 0.04A, and c = 5.5 × 4.5 A), has a framework consisting of 5-, 6- and 10-rings.

TL;DR: In this paper, single crystals of ZSM-5 of up to 280 μm were synthesized and an X-ray structure analysis was performed on one such crystal, and precise atomic positions and an R -factor of 0.0965 were measured.

TL;DR: In this article, a disordered structure consisting of ferrierite sheets linked via bridging oxygens located on mirror planes is proposed for this material, characterized by ten-ring noninterpenetrating linear channels whose ideal dimensions are 5.3 × 5.6 A.

TL;DR: In this paper, the pulsed field gradient technique is applied to measure the intracrystalline self-diffusion coefficients of benzene, toluene and ortho-, meta- and para-xylene in NaX type zeolites with ratios Si Al = 1.2 and 1.8 in dependence on the sorbate concentration and the temperature.

TL;DR: In this article, the 29Si MAS n.m.r. spectra of highly dealuminated zeolites are shown to exhibit separate Si(OAl) resonances due to crystallographically inequivalent lattice sites.

TL;DR: ZSM-23 as discussed by the authors is a high-silica zeolite with lattice parameters of: a = 5.01 ± 0.02A, b = 21.52± 0.04A, and c = 11.13 ± 1.03A.

TL;DR: In this article, an empirical correlation between chemical shift and mean AlO4OP bond angle has been found for the dense AlPO4 phases, both the 31P and the corrected 27Al chemical shift values suggest a mean angle of 150°.

TL;DR: In this article, a mathematical model based on the population balance method is developed for hydrothermal molecular sieve zeolite synthesis, where the material balances for the amorphous, fluid and crystalline phases are based on conservation of unit cells in the three phases.

TL;DR: In this paper, various attempts to model the hydrothermal molecular sieve zeolite synthesis process are summarized, divided into several groups: empirical, reaction engineering, particulate-based, and combinations of those.

TL;DR: In this paper, the authors studied the factors influencing metastability and crystallite morphology in the hydrothermal synthesis of EU-1 and EU-2 in the sodium, ammonium and hexamethonium (Na, NH 4, HM) cation systems.

TL;DR: In this paper, the synthesis of zeolite ZSM-5 with boron instead of aluminium atoms in the framework is described, and a product containing 1.5% by mass B 2 O 3 and only 0.013% by Mass Al 2 O 4 was obtained.

TL;DR: In this paper, the properties of the aluminosilicate gels formed as intermediates from reactant mixtures of equal overall composition in zeolite NaA synthesis depend highly on the chemical composition of the starting silicate and aluminate solutions.

TL;DR: In this paper, the crystallization of high SiO2/Al2O3 zeolites was examined in the presence of α, ω-diamines at pH < 12.

TL;DR: In this article, the relationship between the aluminium-sodium content and the high Si Al region was investigated for the case of zeolites and it was shown that the crystallographic orthorhombic-monoclinic transformation takes place for high SiAl ratio samples, while the orthor hombic symmetry is retained for dry air calcined samples characterized by low Si Al ratios.

TL;DR: In this paper, the extent of aromatization and the distribution of aromatic hydrocarbons in the conversion of methanol and ethanol on H-ZSM-5 have been found to be strongly dependent on the Si Al ratio and the degree of H-exchange of the zeolite.

TL;DR: In this paper, the physicochemical properties of Na SPM, Na LPM, and Na H forms of variously modified SPM and LPM have been studied and a model of formation of these defects is proposed on the basis of the synthesis conditions.

TL;DR: The decomposition of TPA in NaZSM-5 zeolites, the localization of OH groups and acid properties of zeolite were studied by i.r. spectroscopy as discussed by the authors.

TL;DR: Using high-speed X-ray powder diffraction methods, the influence of the temperature and the adsorption of benzene molecules on the location of K, Ca and Sr ions in Y-type zeolites was investigated as mentioned in this paper.

TL;DR: In this paper, the use of weak bases as probe molecules, to study ZSM-5 acid sites, was evaluated by thermogravimetric analysis and thermal desorption/mass spectrometry.

TL;DR: In this article, a sodium gallosilicate zeolite with the sodalite structure was synthesized from the silica-rich starting gel, which has a very low SiO 2 to Ga 2 O 3 molar ratio (less than 1.0).

TL;DR: In this article, the 5-1, mordenite group of zeolites (bikitaite (B), dachiardite (D), epistilbite (E), ferrierite (F) and M) were examined by electron diffraction and microscopy in order to detect and characterize structural faults in the crystals.

TL;DR: In this article, the process of aggregation of benzene molecules chemisorbed on a NaY zeolite was studied with small angle neutron scattering, and it was shown that at low coverage, i.e., one molecule per supercage, the hydrocarbon is dispersed in the network, each molecule being fixed on a cationic site.

TL;DR: Based on room and low temperature vibrational spectra, and the structure of faujasite type zeolites, the optical modes were classified and energetically described in this article.

TL;DR: In this article, a neutron study of a single crystal of thomsonite (Na(Ca,Sr) 2 Al 5 Si 5 O 20.6H 2 O at 293K yielded a final agreement factor of R (F 2 ) = 0.048 for conventional anisotropic refinement using 4626 diffraction intensities from the Brookhaven National Laboratory high-flux beam reactor.