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Ilaria Braschi - One of the best experts on this subject based on the ideXlab platform.

  • physicochemical regeneration of high silica Zeolite y used to clean up water polluted with sulfonamide antibiotics
    Journal of Environmental Sciences-china, 2016
    Co-Authors: Ilaria Braschi, Sonia Blasioli, Enrico Buscaroli, Daniela Montecchio, Annalisa Martucci
    Abstract:

    High silica Zeolite Y has been positively evaluated to clean-up water polluted with sulfonamides, an antibiotic family which is known to be involved in the antibiotic resistance evolution. To define possible strategies for the exhausted Zeolite regeneration, the efficacy of some chemico-physical treatments on the Zeolite loaded with four different sulfonamides was evaluated. The evolution of photolysis, Fenton-like reaction, thermal treatments, and solvent extractions and the occurrence in the Zeolite pores of organic residues eventually entrapped was elucidated by a combined thermogravimetric (TGA-DTA), diffractometric (XRPD), and spectroscopic (FT-IR) approach. The chemical processes were not able to remove the organic guest from Zeolite pores and a limited transformation on embedded molecules was observed. On the contrary, both thermal treatment and solvent extraction succeeded in the regeneration of the Zeolite loaded from deionized and natural fresh water. The recyclability of regenerated Zeolite was evaluated over several adsorption/regeneration cycles, due to the treatment efficacy and its stability as well as the ability to regain the structural features of the unloaded material.

  • Effect of humic monomers on the adsorption of sulfamethoxazole sulfonamide antibiotic into a high silica Zeolite Y: An interdisciplinary study.
    Chemosphere, 2016
    Co-Authors: Ilaria Braschi, Sonia Blasioli, Annalisa Martucci, L. L. Mzini, Claudio Ciavatta, Maurizio Cossi
    Abstract:

    Abstract The adsorption efficiency of a high silica Zeolite Y towards sulfamethoxazole, a sulfonamide antibiotic, was evaluated in the presence of two humic monomers, vanillin and caffeic acid, representative of phenolic compounds usually occurring in water bodies, owing their dimension comparable to those of the Zeolite microporosity. In the entire range of investigated pH (5–8), adsorption of vanillin, as a single component, was reversible whereas it was irreversible for sulfamethoxazole. In equimolar ternary mixtures, vanillin coadsorbed with sulfamethoxazole, conversely to what observed for caffeic acid, accordingly to their adsorption kinetics and pK a values. Lower and higher adsorptions were observed for sulfamethoxazole and vanillin, respectively, than what it was observed as single components, clearly revealing guest-guest interactions. An adduct formed through H-bonding between the carbonyl oxygen of vanillin and the heterocycle NH of sulfamethoxazole in amide form was observed in the Zeolite pore by combined FTIR and Rietveld analysis, in agreement with Density Functional Theory calculations of the adduct stabilization energies. The formation of similar adducts, able to stabilize other naturally occurring phenolic compounds in the microporosities of hydrophobic sorbents, was proposed.

  • embedding monomers and dimers of sulfonamide antibiotics into high silica Zeolite y an experimental and computational study of the tautomeric forms involved
    RSC Advances, 2013
    Co-Authors: Ilaria Braschi, Giorgio Gatti, Geo Paul, Maurizio Cossi, Leonardo Marchese
    Abstract:

    This work is a second step towards the systematic study of the embedding of sulfonamide antibiotics into a synthetic high silica Zeolite Y (HSZ-Y) with hydrophobic properties. In the previous paper [Braschi et al., Langmuir 2010, 31, 9524], the irreversible adsorption from water into HSZ-Y of three sulfonamides was studied by enlightening the host–guest interactions and, in the case of the smallest sized sulfadiazine, the guest–guest interactions of dimeric species inside the Zeolite cage. Here the HSZ-Y was loaded with six sulfonamides, namely: sulfanilamide, sulfapyridine, sulfathiazole, sulfadimethoxine, sulfadoxine and sulfamerazine. With the exception of sulfanilamide, which showed scarce affinity for HSZ-Y (maximum loading 3% Zeolite dry weight), the other sulfa drugs adsorbed at ca. 28% Zeolite dry weight on average, and this is relevant for both water depollution and drug delivery issues. The low affinity of sulfanilamide for HSZ-Y was ascribed to its high hydrophilicity (water solubility 15–40 times higher than other drugs). The most stable tautomeric (amide or imide) form of each antibiotic adsorbed in Zeolite Y was proposed by means of IR and solid state NMR spectroscopy augmented by computational modelling. The small dimensions and favourable stabilization energy allow the embedding of imidic and amidic dimers of sulfathiazole and sulfapyridine, respectively, inside the Zeolite cage whereas the remaining sulfa drugs adsorbed in monomeric amidic forms.

  • sulfonamide antibiotics embedded in high silica Zeolite y a combined experimental and theoretical study of host guest and guest guest interactions
    Langmuir, 2010
    Co-Authors: Ilaria Braschi, Giorgio Gatti, Geo Paul, C Gessa, Maurizio Cossi, Leonardo Marchese
    Abstract:

    A combined experimental and computational study of the interactions of three sulfonamides—sulfadiazine, sulfamethazine, and sulfachloropyridazine—embedded into the cages of high silica Zeolite Y is here proposed. For all host−guest systems, the close vicinity of aromatic rings with Zeolite framework was evidenced by multidimensional and multinuclear (1H, 13C, 29Si) SS-NMR measurements. Host−guest and guest−guest interactions were also elucidated by in situ FTIR spectroscopy and confirmed by ab initio computational modeling. Single molecules of sulfamethazine and sulfachloropyridazine were stabilized inside the Zeolite cage by the vicinity of methyl and amino groups, respectively. Sulfadiazine is present in both monomeric and dimeric forms. Multiple weak H-bonds and van der Waals type interactions between organic molecules and Zeolite are responsible for the irreversible extraction from water of all the examined sulfa drugs.

Gavin D. Mclellan - One of the best experts on this subject based on the ideXlab platform.

  • Coke formation in High-Silica Zeolites
    Applied Catalysis A General, 1992
    Co-Authors: David M Bibby, Russell F. Howe, Gavin D. Mclellan
    Abstract:

    The formation of coke during hydrocarbon transformations over acid Zeolite catalysts has important practical consequences for a growing number of industrial processes. This review presents available material on the formation, nature and properties of coke in high silica Zeolite catalysts, and on the resulting deactivation and regeneration of the catalysts. Techniques for analyzing and characterizing coke, the role of acid sites in coke formation and the chemistry of coke formation are discussed, with particular emphasis on the methanol to gasoline process. © 1992.

T. V. Harris - One of the best experts on this subject based on the ideXlab platform.

Stacey I. Zones - One of the best experts on this subject based on the ideXlab platform.

  • well defined silanols in the structure of the calcined high silica Zeolite ssz 70 new understanding of a successful catalytic material
    Journal of the American Chemical Society, 2017
    Co-Authors: Stef Smeets, Dan Xie, Lynne B. Mccusker, Wei Wan, Xiaodong Zou, Stacey I. Zones, Zachariah J Berkson, Mingfeng Hsieh, Bradley F Chmelka, Christian Baerlocher
    Abstract:

    The structure of the calcined form of the High-Silica Zeolite SSZ-70 has been elucidated by combining synchrotron X-ray powder diffraction (XRPD), high resolution transmission electron microscopy (HRTEM), and two-dimensional (2D) dynamic nuclear polarization (DNP)-enhanced NMR techniques. The framework structure of SSZ-70 is a polytype of MWW and can be viewed as a disordered ABC-type stacking of MWW-layers. HRTEM and XRPD simulations show that the stacking sequence is almost random, with each layer being shifted by ±1/3 along the direction with respect to the previous one. However, a small preponderance of ABAB stacking could be discerned. DNP-enhanced 2D 29Si{29Si} J-mediated NMR analyses of calcined Si-SSZ-70 at natural 29Si isotopic abundance (4.7%) establish the through-covalent-bond 29Si-O-29Si connectivities of distinct Si sites in the framework. The DNP-NMR results corroborate the presence of MWW-layers and, more importantly, identify two distinct types of Q3 silanol species at the surfaces ...

  • Well-Defined Silanols in the Structure of the Calcined High-Silica Zeolite SSZ-70: New Understanding of a Successful Catalytic Material
    2017
    Co-Authors: Stef Smeets, Dan Xie, Lynne B. Mccusker, Wei Wan, Xiaodong Zou, Stacey I. Zones, Zachariah J Berkson, Mingfeng Hsieh, Bradley F Chmelka, Christian Baerlocher
    Abstract:

    The structure of the calcined form of the High-Silica Zeolite SSZ-70 has been elucidated by combining synchrotron X-ray powder diffraction (XRPD), high-resolution transmission electron microscopy (HRTEM), and two-dimensional (2D) dynamic nuclear polarization (DNP)-enhanced NMR techniques. The framework structure of SSZ-70 is a polytype of MWW and can be viewed as a disordered ABC-type stacking of MWW-layers. HRTEM and XRPD simulations show that the stacking sequence is almost random, with each layer being shifted by ±1/3 along the ⟨110⟩ direction with respect to the previous one. However, a small preponderance of ABAB stacking could be discerned. DNP-enhanced 2D 29Si­{29Si} J-mediated NMR analyses of calcined Si-SSZ-70 at natural 29Si isotopic abundance (4.7%) establish the through-covalent-bond 29Si–O-29Si connectivities of distinct Si sites in the framework. The DNP-NMR results corroborate the presence of MWW layers and, more importantly, identify two distinct types of Q3 silanol species at the surfaces of the interlayer regions. In the first, an isolated silanol group protrudes into the interlayer space pointing toward the pocket in the adjacent layer. In the second, the surrounding topology is the same, but the isolated −SiOH group is missing, leaving a nest of three Si–O–H groups in place of the three Si–O–Si linkages. The analyses clarify the structure of this complicated material, including features that do not exhibit long-range order. With these insights, the novel catalytic behavior of SSZ-70 can be better understood and opportunities for enhancement recognized

  • High‐Silica Zeolite SSZ‐61 with Dumbbell‐Shaped Extra‐Large‐Pore Channels
    Angewandte Chemie (International ed. in English), 2014
    Co-Authors: Stef Smeets, Dan Xie, Christian Baerlocher, Lynne B. Mccusker, Wei Wan, Xiaodong Zou, Stacey I. Zones
    Abstract:

    The synthesis of the High-Silica Zeolite SSZ-61 using a particularly bulky polycyclic structure-directing agent and the subsequent elucidation of its unusual framework structure with extra-large dumbbell-shaped pore openings are described. By using information derived from a variety of X-ray powder diffraction and electron microscopy techniques, the complex framework structure, with 20 Si atoms in the asymmetric unit, could be determined and the full structure refined. The Si atoms at the waist of the dumbbell are only three-connected and are bonded to terminal O atoms pointing into the channel. Unlike the six previously reported extra-large-pore Zeolites, SSZ-61 contains no heteroatoms in the framework and can be calcined easily. This, coupled with the possibility of inserting a catalytically active center in the channel between the terminal O atoms in place of H+, afford SSZ-61 intriguing potential for catalytic applications.

  • diquaternary ammonium compounds in Zeolite synthesis cyclic and polycyclic n heterocycles connected by methylene chains
    Journal of the American Chemical Society, 2009
    Co-Authors: Anna Jackowski, Stacey I. Zones, Sonjong Hwang, Allen W Burton
    Abstract:

    An additional dimension has been added to our long-standing studies in high silica Zeolite synthesis via a guest/host synergism. We have created and studied the impact of making symmetric diquaternary ammonium compounds, by varying the chain length between nitrogen charge centers, and the heterocycle size and geometry containing the nitrogen. This allows the introduction of a second spatial parameter in the use of the charged organo-cation guest in the Zeolite synthesis. The series of 15 diquaternary ammonium compounds (5 heterocycles synthesized onto chain lengths of C4−C6) were tested in a total of 135 Zeolite syntheses reactions. Nine screening reactions were employed for each guest molecule, and the conditions built upon past successes in finding novel high silica Zeolites via introduction of boron, aluminum, or germanium as substituting tetrahedral framework atoms for silicon. Eighteen different Zeolite structures emerged from the studies. The use of specific chain lengths for derivatives of the pyrrolidine ring system produced novel Zeolite materials SSZ-74 and 75.

Christian Baerlocher - One of the best experts on this subject based on the ideXlab platform.

  • well defined silanols in the structure of the calcined high silica Zeolite ssz 70 new understanding of a successful catalytic material
    Journal of the American Chemical Society, 2017
    Co-Authors: Stef Smeets, Dan Xie, Lynne B. Mccusker, Wei Wan, Xiaodong Zou, Stacey I. Zones, Zachariah J Berkson, Mingfeng Hsieh, Bradley F Chmelka, Christian Baerlocher
    Abstract:

    The structure of the calcined form of the High-Silica Zeolite SSZ-70 has been elucidated by combining synchrotron X-ray powder diffraction (XRPD), high resolution transmission electron microscopy (HRTEM), and two-dimensional (2D) dynamic nuclear polarization (DNP)-enhanced NMR techniques. The framework structure of SSZ-70 is a polytype of MWW and can be viewed as a disordered ABC-type stacking of MWW-layers. HRTEM and XRPD simulations show that the stacking sequence is almost random, with each layer being shifted by ±1/3 along the direction with respect to the previous one. However, a small preponderance of ABAB stacking could be discerned. DNP-enhanced 2D 29Si{29Si} J-mediated NMR analyses of calcined Si-SSZ-70 at natural 29Si isotopic abundance (4.7%) establish the through-covalent-bond 29Si-O-29Si connectivities of distinct Si sites in the framework. The DNP-NMR results corroborate the presence of MWW-layers and, more importantly, identify two distinct types of Q3 silanol species at the surfaces ...

  • Well-Defined Silanols in the Structure of the Calcined High-Silica Zeolite SSZ-70: New Understanding of a Successful Catalytic Material
    2017
    Co-Authors: Stef Smeets, Dan Xie, Lynne B. Mccusker, Wei Wan, Xiaodong Zou, Stacey I. Zones, Zachariah J Berkson, Mingfeng Hsieh, Bradley F Chmelka, Christian Baerlocher
    Abstract:

    The structure of the calcined form of the High-Silica Zeolite SSZ-70 has been elucidated by combining synchrotron X-ray powder diffraction (XRPD), high-resolution transmission electron microscopy (HRTEM), and two-dimensional (2D) dynamic nuclear polarization (DNP)-enhanced NMR techniques. The framework structure of SSZ-70 is a polytype of MWW and can be viewed as a disordered ABC-type stacking of MWW-layers. HRTEM and XRPD simulations show that the stacking sequence is almost random, with each layer being shifted by ±1/3 along the ⟨110⟩ direction with respect to the previous one. However, a small preponderance of ABAB stacking could be discerned. DNP-enhanced 2D 29Si­{29Si} J-mediated NMR analyses of calcined Si-SSZ-70 at natural 29Si isotopic abundance (4.7%) establish the through-covalent-bond 29Si–O-29Si connectivities of distinct Si sites in the framework. The DNP-NMR results corroborate the presence of MWW layers and, more importantly, identify two distinct types of Q3 silanol species at the surfaces of the interlayer regions. In the first, an isolated silanol group protrudes into the interlayer space pointing toward the pocket in the adjacent layer. In the second, the surrounding topology is the same, but the isolated −SiOH group is missing, leaving a nest of three Si–O–H groups in place of the three Si–O–Si linkages. The analyses clarify the structure of this complicated material, including features that do not exhibit long-range order. With these insights, the novel catalytic behavior of SSZ-70 can be better understood and opportunities for enhancement recognized

  • High‐Silica Zeolite SSZ‐61 with Dumbbell‐Shaped Extra‐Large‐Pore Channels
    Angewandte Chemie (International ed. in English), 2014
    Co-Authors: Stef Smeets, Dan Xie, Christian Baerlocher, Lynne B. Mccusker, Wei Wan, Xiaodong Zou, Stacey I. Zones
    Abstract:

    The synthesis of the High-Silica Zeolite SSZ-61 using a particularly bulky polycyclic structure-directing agent and the subsequent elucidation of its unusual framework structure with extra-large dumbbell-shaped pore openings are described. By using information derived from a variety of X-ray powder diffraction and electron microscopy techniques, the complex framework structure, with 20 Si atoms in the asymmetric unit, could be determined and the full structure refined. The Si atoms at the waist of the dumbbell are only three-connected and are bonded to terminal O atoms pointing into the channel. Unlike the six previously reported extra-large-pore Zeolites, SSZ-61 contains no heteroatoms in the framework and can be calcined easily. This, coupled with the possibility of inserting a catalytically active center in the channel between the terminal O atoms in place of H+, afford SSZ-61 intriguing potential for catalytic applications.