Control de la arquitectura microporosa y de las propiedades de materiales zeolíticos mediante su síntesis en presencia de combinaciones de compuestos orgánicos como agentes directores de estructura

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química-Física Aplicada. Fecha de lectura: 29-06-201

Template-controlled acidity and catalytic activity of ferrierite crystals

A synthesis strategy to tailor the acid sites location in ferrierite crystals has been developed. The zeolite catalysts were synthesised in fluoride medium using different combinations of organic structure directing agents (SDAs) in the absence of inorganic cations. Therefore, the negative charge associated to the incorporation of aluminium to the framework was compensated exclusively by the positive charge of the organic SDAs. In this way, Al sitting in the zeolite framework was driven by the specific location of the different SDA molecules within the zeolite void volume. Following this synthesis strategy, it has been found that the distribution of strongly acidic hydroxyl groups in the proton form of the zeolites obtained after removal of the organic templates was dependent on the combination of organic molecules used as SDAs. Moreover, the catalytic activity of the zeolites in m-xylene and 1-butene isomerisation increased as the relative population of strong Brönsted acid groups in sterically constrained sites inside the ferrierite cavity decreased.This work has been financially supported by the MICINN (project CTQ2006-06282).Peer reviewe

Influence of Al distribution and defects concentration of ferrierite catalysts synthesized from Na-free gels in the skeletal isomerization of n-butene

The skeletal isomerization of n-butenes to isobutene has been carried out over ferrierite catalysts (Si/Al ~ 15) containing different acid sites distribution and different amount of defects. The zeolite crystals were synthesized under hydrothermal conditions in fluoride medium in the absence of alkaline cations by using suitable combinations of structure directing agents. Template-driven low density of acid sites in 10-membered-ring channels enhances the isobutene selectivity and decreases catalyst deactivation. The presence of high amount of silanol groups and Lewis acid sites increases the yields of by-products and catalysts decay.MICINN (CTQ2006-06282) CSIC (JAE-doc contract)Peer reviewe

Instantaneous Wave-Free Ratio for the Assessment of Intermediate Left Main Coronary Artery Stenosis: Correlations With Fractional Flow Reserve/Intravascular Ultrasound and Prognostic Implications: The iLITRO-EPIC07 Study

Background: There is little information available on agreement between fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) in left main coronary artery (LMCA) intermediate stenosis. Besides, several meta-analyses support the use of FFR to guide LMCA revascularization, but limited information is available on iFR in this setting. Our aims were to establish the concordance between FFR and iFR in intermediate LMCA lesions, to evaluate with intravascular ultrasound (IVUS) in cases of FFR/iFR discordance, and to prospectively validate the safety of deferring revascularization based on a hybrid decision-making strategy combining iFR and IVUS. Methods: Prospective, observational, multicenter registry with 300 consecutive patients with intermediate LMCA stenosis who underwent FFR and iFR and, in case of discordance, IVUS and minimal lumen area measurements. Primary clinical end point was a composite of cardiovascular death, LMCA lesion-related nonfatal myocardial infarction, or unplanned LMCA revascularization. Results: FFR and iFR had an agreement of 80% (both positive in 67 and both negative in 167 patients); in case of disagreement (31 FFR+/iFR- and 29 FFR-/iFR+) minimal lumen area was & GE;6 mm(2) in 8.7% of patients with FFR+ and 14.6% with iFR+. Among the 300 patients, 105 (35%) underwent revascularization and 181 (60%) were deferred according to iFR and IVUS. At a median follow-up of 20 months, major adverse cardiac events incidence was 8.3% in the defer group and 13.3% in the revascularization group (hazard ratio, 0.71 [95% CI 0.30-1.72]; P=0.45). Conclusions: In patients with intermediate LMCA stenosis, a physiology-guided treatment decision is feasible either with FFR or iFR with moderate concordance between both indices. In case of disagreement, the use of IVUS may be useful to indicate revascularization. Deferral of revascularization based on iFR appears to be safe in terms of major adverse cardiac events

Synthesis of ferrierite from gels containing a mixture of two templates

Ferrierite synthesis from gels containing a mixture of two template molecules, in the absence of inorganic cations and in fluoride media, is described. One of them is a bulky structure-directing agent (SDA), 1-benzyl-1-methylpyrrolidinium cation (bmp), and the other one is a small organic cation acting as a co-template. We present here the results obtained with tetramethylammonium (TMA) and quinuclidinium (Qui) compounds as co-templates in a gel containing bmp cation as SDA. It has been observed that in both cases co-templates exert a marked effect on the nature of the synthesis productsThis work has been financially supported by the CICYT (project CTQ2006-06282).Peer reviewe

Template-controlled acidity and catalytic activity of ferrierite crystals

A synthesis strategy to tailor the acid sites location in ferrierite crystals has been developed. The zeolite catalysts were synthesised in fluoride medium using different combinations of organic structure directing agents (SDAs) in the absence of inorganic cations. Therefore, the negative charge associated to the incorporation of aluminium to the framework was compensated exclusively by the positive charge of the organic SDAs. In this way, Al sitting in the zeolite framework was driven by the specific location of the different SDA molecules within the zeolite void volume. Following this synthesis strategy, it has been found that the distribution of strongly acidic hydroxyl groups in the proton form of the zeolites obtained after removal of the organic templates was dependent on the combination of organic molecules used as SDAs. Moreover, the catalytic activity of the zeolites in m-xylene and 1-butene isomerisation increased as the relative population of strong Brönsted acid groups in sterically constrained sites inside the ferrierite cavity decreased.This work has been financially supported by the MICINN (project CTQ2006-06282).Peer reviewe

Method for preparation of an aluminosilicate with ferrierite structure from gels containing tetramethyl ammonium and benzylmethylpyrrolidine, and uses thereof

Fecha de solicitud: 28-02-2008.- Titular: Consejo Superior de Investigaciones Científicas (CSIC)The present invention comprises a new methiod for hydrothermal synthesis of ferrierite zeolite, using tetramethyl ammounium and benzylmethylpyrrodlidine as directional structure agents, and does not require a subsequent process in order to obtain the acid form of the material. This aspect is very important as it avoids subject treatments of calcination and successive interchanges which degrade the structure of the zeolite. The synthetic ferrierite obtained by means of the invention process has uses in catalytic processes of transformation of hydrocarbons, such as cracking, isomerization, alkylation and polymerization. Specifically, it can be used in the isomerization of butene to isobutene. To be used in catalytic processes the zeolite ferrierite must be heated in an oxidant atmosphere in conditions such that the organic material occluded in the interior is eliminated.La presente invención comprende un methiod nuevo para la síntesis hidrotérmica de la zeolita de la ferrierita, usando ammounium del tetrametil y benzylmethylpyrrodlidine como agentes direccionales de la estructura, y no requiere un proceso subsiguiente para obtener la forma ácida del material de tipo. Este aspecto es muy importante pues él evita tratamientos del sujeto de la calcinación y los intercambios sucesivos que degradan la estructura de la zeolita. La ferrierita sintética obtuvo por medio del procedimiento de la invención tiene usos en procedimientos catalíticos de la transformación de hidrocarburos, tales como agrietarse, isomerización, alquilación y polimerización. Específicamente, bote sea utilizado en la isomerización del buten al isobuteno. Ser utilizado en procedimientos catalíticos la ferrierita de la zeolita debe ser calentado en una atmósfera del oxidante en condiciones tales que el material orgánico ocluido en el interior está eliminado.Peer reviewe

Influence of Al distribution and defects concentration of ferrierite catalysts synthesized from Na-free gels in the skeletal isomerization of n-butene

The skeletal isomerization of n-butenes to isobutene has been carried out over ferrierite catalysts (Si/Al ~ 15) containing different acid sites distribution and different amount of defects. The zeolite crystals were synthesized under hydrothermal conditions in fluoride medium in the absence of alkaline cations by using suitable combinations of structure directing agents. Template-driven low density of acid sites in 10-membered-ring channels enhances the isobutene selectivity and decreases catalyst deactivation. The presence of high amount of silanol groups and Lewis acid sites increases the yields of by-products and catalysts decay.MICINN (CTQ2006-06282) CSIC (JAE-doc contract)Peer reviewe

Estudio de la ferrierita como catalizador en la reacción de metanol a gasolina

Trabajo presentado en la Reunión de la Sociedad Española de Catálisis, SECAT'15, celebrada en Barcelona (España) del 13 al 15 de julio de 2015.El interés sobre el proceso de transformación de metanol a gasolina (MTG), descubierto por investigadores de la Mobil en la década de los 70 del siglo pasado [1,2], ha vuelto a resurgir en los últimos años como una alternativa viable al refino de petróleo para la obtención de gasolina, tanto por motivos económicos como medioambientales. Si bien el catalizador desarrollado por Mobil, la zeolita ZSM-5, presenta notables prestaciones en cuanto a selectividad y estabilidad, las investigaciones recientes se han centrado en el desarrollo de catalizadores aún más eficientes. La zeolita Ferrierita es un aluminosilicato cristalino que posee una combinación de dos tipos de canales en su estructura, con un tamaño de poro similar al de la ZSM-5 [3]. Recientemente se ha demostrado, en esta zeolita, la posibilidad de controlar, mediante síntesis, la localización preferente de los centros ácidos, activos para la reacción de MTG, en distintas posiciones de la red cristalina de la zeolita [4,5]. En este sentido, la utilización de catalizadores de Ferrierita con una distribución de centros ácidos controlada, podría ser ventajosa en la reacción de MTG como posibles catalizadores más selectivos y más resistentes a la desactivación por coque.Este trabajo ha sido financiado en parte por el MINECO (Proyecto MAT2012-31127).Peer Reviewe

Direct evidence of the effect of synthesis conditions on aluminum siting in zeolite ferrierite: A 27Al MQ MAS NMR study

The tailoring of the aluminum distribution over the various T sites in zeolites remains a major challenge. By using differing combinations of templating molecules, we managed to control the aluminum siting over the T sites as identified by 27Al MQ MAS NMR in samples of the same Si/Al ratio. This is unique evidence of a modified aluminum distribution in samples prepared following a strategy to tailor the location of aluminum in the zeolite ferrierite framework.A.B.P. is thankful for the support of the European Community under a Marie Curie Intra-European Fellowship for Career Development. Funding from the Spanish Ministry of Economy (project MAT2012-31127) is greatly acknowledged.Peer Reviewe