Structural characterization of HPM-7, a more ordered than expected germanosilicate zeolite

HPM-7, a germanosilicate synthesized using long imidazolium-based dications with two different linkers, is shown to possess the POS topology, although disorder may exist but it is very difficult to discern. First, three simple ordered polymorphs (POS-A to POS-C) with very similar energies and structural motifs could give rise to intergrowths that would be very difficult to recognize by powder X-ray diffraction, according to DIFFaX simulations. Another four structures (POS-D to POS-G) can be derived from POS by changing the orientation of two single four rings within the structure, possibly providing an additional source of disorder. While 3D EDT strongly suggests that HPM-7 basically possesses the POS-A (i.e. POS) topology, a detailed HR-STEM study demonstrates the rare existence of some disorder compatible with the polymorph POS-D. The general avoidance of polymorphs with very similar structural motifs and comparable energies points to a rather specific structure-direction by the organic dications used

Tailoring the acid strength of microporous silicoaluminophosphates through the use of mixtures of templates: Control of the silicon incorporation mechanism

SAPO-5 samples have been synthesized with triethylamine (TEA), benzylpyrrolidine (BP) and mixtures of them as structure directing agents (SDAs). It has been observed that in the as-synthesised materials the concentration of SDAs (molecules per unit cell) and the Si content are similar. According to the different molecular size of both SDAs, the samples exhibit higher organic weight and lower water content as the molar fraction of BP in the synthesis gel increases. These differences in selectivity for organic/water incorporation influences the mechanism of Si substitution in the AlPO lattice: the higher organic content obtained at higher BP/TEA ratio leads to the formation of large Si islands, while the higher water content of the sample obtained with TEA enhances the formation of isolated Si(OAl)4 environments. Interestingly, it has been found that these two opposite trends can be tailored to a certain point by using mixtures of both SDAs, TEA and BP, in the required ratio. The catalytic activity of the samples has been tested in the isomerisation of m-xylene. It has been observed a higher activity of samples obtained with BP as the main SDA, thus evidencing the better performance of large Si islands in this reaction.MEC (CTQ2006-06282)Peer reviewe

Mordenite from Spain and its application as pozzolana

In Spain, natural zeolites have been only found in the volcanic areas of Canary Islands (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. 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, and new possible uses of this mineral in the pozzolanic cement industry are foreseen. This work intends to give preliminary data on the characterization of this zeolite according to X-ray diffraction (XRD), ICP analyses, and scanning electron microscopy (SEM), as well as to emphasize the pozzolanic properties of this material, using both chemical and mechanical tests

Simulaciones Moleculares Aplicadas al Estudio de la Dirección de Estructura de Materiales Microporosos

Trabajo presentado en el 2º Ciclo de Palestras sobre Peneiras Moleculares, celebrado en Natal (Brasil) del 13 al 14 de noviembre de 2014.Peer Reviewe

Efecto director de estructura de moléculas fluoradas en la síntesis de aluminofosfatos microporosos cristalinos

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química-Física Aplicada. Instituto de Catálisis y Petroleoquímica (ICP-CSIC).--Fecha de lectura 10-01-2006El objetivo general de esta tesis doctoral consiste en realizar un estudio sobre el efecto de las moléculas orgánicas que actúan como agentes directores de estructura (ADEs) en la síntesis de aluminofosfatos microporosos cristalinos. Puesto que no existe enlace entre ellos, la capacidad de una molécula orgánica para dirigir la síntesis de una determinada estructura zeolítica depende fundamentalmente de las interacciones intermoleculares que se establezcan entre ambas. El llenado de los poros y cavidades de la zeolita por parte de estos agentes orgánicos, así como el estrecho ajuste que se establece entre ellos, implica que las interacciones químicas intermoleculares que se establecen entre estas moléculas orgánicas y las estructuras zeolíticas tienen lugar, fundamentalmente, a través de los átomos de hidrógeno terminales de las moléculas orgánicas. El tipo de moléculas más utilizado como agentes directores de estructuras zeolíticas han sido aminas terciarias y sales de amonio cuaternario. En este tipo de moléculas, todos los átomos de hidrógeno están enlazados a átomos de carbono; de este modo, las interacciones que se establezcan siempre serán a través de esos átomos de hidrógenos enlazados a átomos de carbono. Por tanto, la aparentemente amplia diversidad de agentes directores de estructura que se ha usado hasta hoy en la síntesis de materiales zeolíticos se refiere sólo a la forma y al tamaño de las moléculas. Sin embargo, el carácter químico de esas interacciones ha permanecido inalterado, pues éstas siempre han tenido lugar a través de esos átomos de hidrógeno enlazados a átomos de carbono. Por ello, el objetivo principal de este trabajo consiste en tratar de modificar el carácter químico de esas interacciones intermoleculares, en un intento por obtener nuevos materiales zeolíticos, tanto nuevas estructuras como nuevas composiciones, así como por entender el significado y función de las moléculas orgánicas en la síntesis de estas estructuras.Peer reviewe

accordion-like effect of flexible organic structure-directing agents in the synthesis of ferrierite zeolite

Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.micromeso.2020.110149[EN] Ferrierite zeolite was synthesized by a co-structure-directing route using a highly flexible diquaternary ammo-nium cation (N,N0-bis-triethylpentanediyldiammonium) as a structure directing agent in combination with tet-ramethylammonium as a small co-structure-directing agent. Strong alterations of the 13C NMR bands of the bulky organic dication upon confinement within the ferrierite framework suggest a change of conformation driven by host-guest interactions. A combination of molecular mechanics and DFT calculations of the theoretical 13C NMR chemical shifts allowed to explain the observed differences in the NMR bands of the dication in solution and when hosted in ferrierite: upon confinement, the flexible dication needs to squeeze through the flexible pentyl chain which locates along the 10 MR ferrierite channels in order to host the two bulky triethyl ammonium groups in adjacent intersections with 8 MR channels. Our work suggests that highly flexible cations, usually considered as less convenient organic structure-directing agents because of low specificity, have the advantage of being able to properly fit with different zeolite cell dimensions through an accordion-like effect by squeezing or stretching their flexible chains.This work has been partially financed by the Spanish State Research Agency (Agencia Española de Investigación, AEI) and the European Regional Development Fund (Fondo Europeo de Desarrollo Regional, FEDER) through the Project MAT2016-77496-R (AEI/FEDER, UE), and by Consejo Superior de Investigaciones Científicas (CSIC) through project 201780I043. R.K.S.A. is grateful to Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP (Process nº 2014/10609-5) for the scholarship and financial support during post-doctoral internship at Instituto de Catálisis y Petroleoquímica (CSIC). Secretaría General Adjunta de Informática-CSIC is acknowledged for running the calculations, and BIOVIA for providing the computational software.Peer reviewe

Synthesis of a germanosilicate zeolite HPM-12 using a short imidazolium-based dication: Structure-direction by charge-to-charge distance matching

[EN] A short imidazolium based dication, with only three methylene units in the spacer linker, selectively directs the crystallization of zeolite HPM-12 (?UOE) as long as there is enough germanium present in the synthesis gel. The integrity of the dication is proved by dissolution of the zeolite and H and C NMR spectroscopy, where significant effects of organic dication concentration and the presence and concentration of HF need to be taken into account. For the as-made HPM-12 zeolite, a large shift of 9 ppm of one resonance in the C MAS NMR spectrum is due to the particular conformation of the dication imposed by confinement in the zeolite framework, as found by DFT calculations. The structure-directing ability of this kind of dication with varying length of the linker suggests that matching of the distance between positive charges (imidazolium moieties) and negative charges (double four rings in which fluoride resides) plays a crucial role during crystallization.The authors acknowledge financial support from the Spanish Ministerio de Economía y Competitividad, the Spanish Agencia Estatal de Investigación and the EU's Fondo Europeo de Desarrollo Regional under projects MAT2016-77496-R (AEI/FEDER, UE) and MAT2015-71117-R (MINECO/FEDER, UE). We acknowledge the support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). P.L. is grateful to the China Scholarship Council (CSC) for a fellowship and to the Dalian Institute of Chemical Physics for permission to leave. Centro Técnico Informático-CSIC is acknowledged for running the calculations and Biovia for providing the computational software. We also thank L. A. Villaescusa for helpful comments

Material compuesto de estilbita-nanohidroxiapatita, procedimiento de preparación y utilización para la eliminación de fluoruro del agua

La presente invención se refiere a un material compuesto basado en una zeolita natural rica en Calcio, estilbita, en cuya superficie se hace crecer de manera controlada hidroxiapatita de tamaño nanométrico, al procedimiento mediante el cual se obtiene dicho material compuesto, así como a su aplicación en la eliminación de fluoruro del agua con fines de potabilización. Como consecuencia de las citadas características particulares de los cristales de hidroxiapatita, ésta posee una capacidad intrínseca (en base a peso de hidroxiapatita) de eliminación de fluoruro extremadamente elevada lo cual, unido al bajo coste y fácil accesibilidad de los materiales empleados en su preparación, así como a la facilidad del procedimiento, convierte estos materiales en candidatos idóneos para su empleo en la eliminación de fluoruro de aguas ricas en este contaminante.Peer reviewedConsejo Superior de Investigaciones Científicas, Addis Ababa UniversityB1 Patente sin examen previ

Structural characterization of HPM-7, a more ordered than expected germanosilicate zeolite

[EN] HPM-7, a germanosilicate synthesized using long imidazolium-based dications with two different linkers, is shown to possess the POS topology, although disorder may exist but it is very difficult to discern. First, three simple ordered polymorphs (POS-A to POS-C) with very similar energies and structural motifs could give rise to intergrowths that would be very difficult to recognize by powder X-ray diffraction, according to DIFFaX simulations. Another four structures (POS-D to POS-G) can be derived from POS by changing the orientation of two single four rings within the structure, possibly providing an additional source of disorder. While 3D EDT strongly suggests that HPM-7 basically possesses the POS-A (i.e.POS) topology, a detailed HR-STEM study demonstrates the rare existence of some disorder compatible with the polymorph POS-D. The general avoidance of polymorphs with very similar structural motifs and comparable energies points to a rather specific structure-direction by the organic dications used.The authors acknowledge the financial support by the Spanish Ministerio de Economía y Competitividad, the Spanish Agencia Estatal de Investigación and the EU’s Fondo Europeo de Desarrollo Regional under projects MAT2016-77496-R (AEI/FEDER, UE) and MAT2015-71117-R (MINECO/FEDER, UE). We are indebted to the ERSF (Grenoble) and the BM25 Spline staff, particularly to G. Castro and A. Serrano as well as to L. A. Villaescusa (Valencia) for help in collecting the SPXRD data and for helpful comments and suggestions. P. L. is grateful to the China Scholarship Council (CSC) for a fellowship and to the Dalian Institute of Chemical Physics for permission to leave. AM acknowledges the Natural National Science Foundation of China (NFSC) through the grants NFSC-21850410448 & NSFC-21835002. AM and YZ acknowledge the Centre for Highresolution Electron Microscopy (CħEM), supported by SPST of ShanghaiTech University under contract no. EM02161943. We acknowledge the support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)