Synthesis of large-pore zeolites from chiral structure-directing agents with two l-prolinol units

In this work, we perform an in-depth experimental and computational study about the structure-directing effect of two new chiral organic quaternary ammonium dications bearing two N-methyl-prolinol units linked by a xylene spacer in para or meta relative orientation, displaying four enantiopure stereogenic centers in (S) configuration. Synthesis results show that the para-xylene derivative is an efficient structure-directing agent, promoting the crystallization of ZSM-12 (in pure-silica composition), beta zeolite (as pure-silica, or in the presence of Al or Ge), and a mixture of polymorphs C, A and B of zeolite beta (in the presence of Ge). In contrast, the meta-xylene derivative showed a much poorer structure-directing activity, yielding only amorphous materials unless Ge is present in the gel, where beta and polymorph C (together with A and B) zeolites crystallized. Molecular simulations showed that the para-xylene dication displays a cylindrical shape suitable for confining in zeolite pores, while the meta-xylene derivative has an angular shape that shifts from the typical dimensions required for 12MR zeolite channels. Despite enantio-purity of the para-xylene dication with (S, S, S, S) configuration, no enrichment in polymorph A of the zeolite beta samples obtained was observed by Transmission Electron Microscopy. With the aid of molecular simulations, the failure in transferring chirality to the zeolite is explained by the loose fit of this SDA in the large-pores of zeolite beta, and a lack of close geometrical fit with the chiral element of polymorph A, as evidenced by the very similar interaction of the cation with the two enantiomorphic space groups of polymorph A. Nevertheless, the molecular-level knowledge gained in this work can provide insights for the future design of more efficient SDAs towards the synthesis of chiral zeolites

Intervención nutricional en el paciente oncohematológico

Background: Oncohematological diseases such as lymphoma or leukaemia affect an increasing number of newly diagnosed patients in Spain and other countries. Both disease and treatment may have a negatively impact in the nutritional status of the patient. Malnutrition is not uncommon among oncohematological patients. This situation can compromised the course of the disease, the clinical response of the treatment and the patient’s quality of life. Method: The implementation of a multidisciplinary approach and a systematic and protocolled nutritional assessment would be useful when dealing with haematological malignancies. Results: We present a proposal of protocol for nutritional intervention in oncohematological patients. This proposal is been developed from the analysis of the published literature as well as clinical practice of a multidisciplinary team specialized in the management of patients with haematological malignanciesObjetivos: Las enfermedades oncohematológicas como el Linfoma o la Leucemia afectan a un número importante y creciente de personas en España. Tanto la enfermedad como las distintas modalidades de tratamiento que puede llegar a precisar el paciente a lo largo del curso de la misma impactan negativamente en el estado nutricional del paciente, no siendo infrecuente el desarrollo de desnutrición, situación que compromete la evolución, la respuesta al tratamiento y la calidad de vida del paciente. Método: La implementación de una estrategia multidisciplinar, sistematizada y protocolizada de valoración nutricional puede resultar de utilidad a la hora de abordar a los pacientes con enfermedades oncohematológicas. Resultados: Se presenta una propuesta de protocolo de evaluación y soporte nutricional en el paciente oncohematológico elaborada a partir del análisis de la literatura publicada al respecto, así como de la práctica clínica habitual de un equipo sanitario multidisciplinar especialmente implicado en el manejo de los pacientes con enfermedades oncohematológica

GTM-3, an extra-large pore enantioselective chiral zeolitic catalyst

The development of chiral zeolitic catalysts possessing extra-large pores and endowed with the capability of enantioselectively processing bulky products represents one of the greatest challenges in chemistry. Here, we report the discovery of GTM-3, an enantio-enriched extra-large pore chiral zeolite material with -ITV framework structure, obtained using a simple enantiopure organic cation derived from the chiral pool, N,N-ethyl-methyl-pseudoephedrinium, as the chiral-inductor agent. We demonstrate the enantio-enrichment of GTM-3 in one of the two enantiomorphic polymorphs using the two enantiomers of the organic cation. Interestingly, we prove the ability of this zeolitic material to perform enantioselective catalytic operations with very large substrates, here exemplified by the catalytic epoxide aperture of the bulky trans-stilbene oxide with alcohols, yielding unprecedented product enantiomeric excesses up to 30%. Our discovery opens the way for the use of accessible chiral zeolitic materials for the catalytic asymmetric synthesis of chiral pharmaceutical compounds

Impact of Controlling the Site Distribution of Al Atoms on Catalytic Properties in Ferrierite-Type Zeolites

Zeolites with the ferrierite (FER) topology are synthesized using a combination of tetramethylammonium (TMA) cations with differently sized cyclic amines (pyrrolidine (Pyr), hexamethyleneimine (HMI), and 1,4- diazabicyclo[2.2.2]octane (DAB)). Using these organic structure-directing agents (SDAs), low Si/Al ratios and concentrated synthesis mixtures favor the crystallization of FER materials. Increasing the size of the cyclic amine or decreasing the aluminum content leads to the crystallization of other phases or the creation of excessive amounts of connectivity defects. TMA cations play a decisive role in the synthesis of the FER materials, and their presence allows the use of HMI to synthesize FER. Proton MAS NMR is used to quantify the accessibility of pyridine to acid sites in these FER samples, where it is found that the FER + HMI + TMA sample contains only 27% acid sites in the 8-MR channels, whereas FER + Pyr and FER + Pyr + TMA contain 89% and 84%, respectively. The constraint index (CI) test and the carbonylation of dimethyl ether (DME) with carbon monoxide are used as probe reactions to evaluate how changes in the aluminum distribution in these FER samples affect their catalytic behavior. Results show that the use of Pyr as an SDA results in the selective population of acid sites in the 8-MR channels, whereas the use of HMI generates FER zeolites with an increased concentration of acid sites in the 10-MR channels

Mordenaite from Spain and its application as pozzolana

Trabajo presentado en el 9th International Conference on the Occurrence, Properties, and Utilization of Natural Zeolites, celebrado en Belgrado (Serbia) del 08 al 13 de junio de 2014.In Spain, natural zeolites have been only found in the volcanic areas of Canary Is lands (San Gil, M.M., 1959). However, several years ago the study of the South Eastern region of continental Spain (Cabo de Gata) revealed the presence of a deposit of mordenite being industrially commercialized as bentonite. The deposit San José-Los Escullos is located in the concession registered as Los Murcianos, managed by Bentonitas Especiales, S.A. (BENESA) who was extracting bentonite while ignoring the presence of the zeolite. The name San José-Los Escullos refers to the discovery of mordenite in this deposit (Calvo Perez et al., 2005). The deposit is located in a volcanic area, constituted by pyroxenic andesites, breccias, tuffs, pyroclasts with andesitic and dacitic composition, largely altered by the hydrothermal solutions. The recent discovery of this zeolite with mordenite content up to 97%, has changed the initial vision about that deposit, end new possible uses of this mineral in the pozzolanic cement industry are foreseen. This work intends to give preliminary data on the characterization of th is zeolite according to X-ray diffraction (XRD), ICP analyses, and scann ing electron microscopy (SEM), as well as to emphasize the pozzolanic properties of this material , using both chemical and mechanical tests.LGH, JPP and ID gratefully acknowledge the financia! support from the Spanish Government through the MINECO, MAT2012-3 1 127 project. Dr. Pedro Bosch is also acknowledged for valuable comments and discussion.Peer Reviewe