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Zeolite ZSM-5 has been synthesized using natural mordenite sourced from the San José-Los Escullos-Cabo de Gata deposit in southeast of Spain. The final pure ZSM-5 was achieved without the need of calcination of the natural mordenite through an inter-zeolite transformation being the adjustment of the Si/Al ratio the key factor. The Si/Al ratio of the natural mordenite was modified through two main methods: (i) dealumination under acidic conditions and (ii) the addition of an extra silica source. Dealumination process adds the advantage of eliminating the impurities present in the initial natural mordenite. ZSM-5 with over 88 % crystallinity was produced under hydrothermal synthesis conditions at 190 °C for 48 h using NH 4 OH as the alkalinity source with coffin shape particles showing short b -axis ranging from 90 to 200 nm. Similarly, ZSM-5 with over 78 % crystallinity was obtained with NaOH as the alkalinity source at 190 °C for 48 h, however, the particles are irregular-shaped of around 160–260 nm in size. In the second approach, despite the presence of impurities of Fe, highly crystalline (over 100 % crystallinity) ZSM-5 is produced, once again with well-shaped coffin shaped crystals using NH 4 OH yet larger, with a b -axis ranging from 200 to 300 nm and irregular shaped ZSM-5 using NaOH. [Display omitted] • ZSM-5 is synthesized via inter-zeolite transformation from natural mordenite from Spain. • The mordenite can be used raw or dealuminated yielding both highly crystalline ZSM-5. • Highly crystalline ZSM-5 can be synthesized using NaOH or NH 4 OH as alkalinity source at 190 °C for 48 h or 120 °C for 5 days. • Highly crystalline ZSM-5 with uniformly distributed coffin-shaped crystals are obtained. [ABSTRACT FROM AUTHOR]

Abstract: This work reviews the use of pyrrole, chloroform, methanol, as well as methoxy and nitrosonium groups generated ‘in situ’, as infrared and NMR probe molecules to characterize zeolites basicity. The main results reported in the bibliography about the correlation of the spectroscopic properties of the adsorbed molecule with the framework basicity, the host–guest interactions, and the limitations in the use of these molecules as probes for zeolite basicity are discussed. Special attention is paid to the results reported for the adsorption of pyrrole and halocarbons, most specially CHCl3 and CHClF2 over alkali-exchanged FAU-type zeolites using IR and NMR spectroscopies. [Copyright &y& Elsevier]

Examines the nature of adsorption sites of pyrrole in alkali-exchanged zeolite y by nuclear magnetic resonance. Displacement of cations toward the supercage to bind with guest molecules; Analysis by nuclear magnetic resonance showing cation-pyrrole complexes; Determination on the parameters of quadripolar.

Abstract: For the first time, the synthesis of Sn–zeolites starting from SiO2–SnO2 xerogels is described. The influence of several synthesis parameters in the physico–chemical properties of the xerogels and the zeolites subsequently generated has been investigated. Two different tin sources were assayed in the synthesis of xerogels (anhydrous SnCl4 and SnCl4 ·5H2O) as well as two gelation agents (NH3 and TPAOH). Though both bases led SiO2–SnO2 xerogels mainly showing tetrahedrally coordinated tin centres, regardless the tin source, only TPAOH derived materials were easily transformed into MFI-type zeolites showing tin incorporation. On the other hand, NH3 gelified xerogels were difficult to crystallize, being this fact attributed to the retention of NH3 species in the xerogels because of the tin Lewis acidity, avoiding its inclusion in the zeolite crystalline framework. Studies on the crystallization time and temperature allowed to optimize the transformation of TPAOH gelified SiO2–SnO2 xerogels into tin-containing MFI zeolites showing isomorphically incorporated tin centres. The so-obtained materials were compared with conventionally synthesized SnS-1 zeolite showing better quality in terms of tin incorporation. [Copyright &y& Elsevier]

The large-pore zeolite omega (SiAl = 3.1) has been treated with solutions of the surfactant hexadecyltrimethylammonium (CTA) in aqueous ammonia in order to generate intracrystalline mesoporosity. For this purpose, the as-made sample was calcined, transformed in the acid form by ion exchange with ammonium chloride solution followed by calcination, and the resulting acid form subsequently treated with steam at 620 ºC to partially dealuminate the framework. The samples were characterized by XRD, N 2 adsorption, TGA, SEM, 29Si and 27Al MAS NMR, pyridine adsorption for acidity determination, and tested in the isomerization/disproportionation of m -xylene. It has been found that partial dealumination of the framework (Si/Al ∼ 7.3) followed by mild acid leaching (HCl = 0.3 M) to remove only the extraframework aluminium species is required for CTA to generate intracrystalline mesopores with a narrow pore diameter of 4 nm. The CTA treatment is ineffective when applied to the acid form (Si/Al ∼ 5.7) or the steamed sample before acid leaching. The concentration of strong acid sites and the average acid strength of the CTA samples are lower than those of the steamed/acid leached sample, which suggests the presence of weak acid sites located at the mesopores. The mesopores greatly enhanced the catalytic activity in the m -xylene conversion by decreasing diffusional constraints. However, the selectivity to the bulky trimethylbenzenes is not improved by the CTA treatment, which suggests that the reaction mainly takes place at the strong acid sites located at the micropores. [Display omitted] • Extraframework Al can be removed from steamed zeolite omega by mild acid leaching. • Basic treatment with the surfactant CTA generates mesoporosity in acid-leached omega. • CTA-treated samples had lower acid strength than parent dealuminated omega. • Mesoporosity strongly enhanced the activity in m -xylene transformation. • m -xylene transformation mostly takes place at the micropores. [ABSTRACT FROM AUTHOR]