Various metal-β zeolites have been synthesized under similar ion-exchange conditions. During the exchange process, the nature and acid strength of the used cations modified the composition and textural properties as well as the Brönsted and Lewis acidity of the final materials. Zeolites exchanged with divalent cations showed a clear decrease of their surface Brönsted acidity and an increase of ...

1. Introduction Measuring diffusion in zeolites is a long-lasting challenge. For more than 70 years many efforts have been made to determine the diffusion coefficient of host molecules in the porous framework of zeolites [1]. Actually the different techniques, which were applied, observed different processes and provided dissenting diffusion coefficients. Precisely, there are methods observing ...

The poor hydrothermal stability of germanosilicate zeolites greatly retards their industrial application. Herein, we present a direct synthesis of Ge-containing IWR zeolites with outstanding hydrothermal stability. A simple quaternary ammonium cation, diethyldimethylammonium, was used as the structure-directing agent for the first time. The structure and chemical composition of the framework wa...

To investigate template effect on physicochemical properties of zeolite and enhance the molecular sieving properties, adsorption of methionine amino acid was studied by spectroscopic methods. Four zeolites such as methionine templated analcime, methionine templated zeolite P, N, N-dibenzyl N,N,N,N-tetramethylethylenediamine (DBTMED) templated analcime and free template analcime were synthesized...

AECL’s CHEMIC process has effectively treated in excess of 4 million gallons of radiostrontiumcontaminated water since 1993. One aspect of the ongoing effort to expand the application of the process involves the use of powdered sorbents such as biomass in addition to natural zeolites in conjunction with precipitation for the removal of different contaminants including radiostrontium from waste ...

Two-dimensional triple-quantum (2D-3Q) 23Na MAS NMR spectroscopy has been applied for the investigation of sodium cations in dehydrated zeolites NaY, NaEMT, NaZSM-5 and NaMOR. The experiments have shown that the new 2D-3Q technique allows the determination of the isotropic chemical shifts and quadrupolar couplings of sodium cations with SOQE (second-order quadrupolar effect) parameters of up to...

The direct catalytic conversion of methane to liquid oxygenated compounds, such as methanol or dimethyl ether, at low temperature using molecular oxygen is a grand challenge in C-H activation that has never been met with synthetic, heterogeneous catalysts. We report the first demonstration of direct, catalytic oxidation of methane into methanol with molecular oxygen over copper-exchanged zeolit...

The concept of a porous solid might sound like a term of contradiction as solids are typically regarded as a dense and compact state of matter. Of course this is obviously not so, and zeolites are probably the most prominent representatives of such solids, known for already more than 250 years, and have been used in technical applications for more than 50 years in industry. 200 different struct...

Despite the sustained use of forcefield methodologies to study SiO(2) polymorphs few reviews on the subject are available in the literature. The present study is an attempt to help fill this gap, focusing on classical forcefields used to reproduce and predict properties of pure silica zeolites (or zeosils) such as cell parameters, SiO distance and especially pore size. Instead of an exhaustive ...

Two strategies, namely chiral inductor and chiral auxiliary approaches, have been examined within zeolites with the aim of achieving asymmetric induction during the photocyclization of cyclohexadienone, naphthalenone and pyridone derivatives. Within zeolites, enantioselectivity as high as 55% and diastereoselectivity as high as 88% have been obtained. The observed stereoselectivities are signif...