Spectroscopic characterization and photo/thermal resistance of a hybrid palygorskite/methyl red Mayan pigment

Giustetto, Roberto; Seenivasan, Kalaivani; Pellerej, Diego; Ricchiardi, Gabriele; Bordiga, Silvia

doi:10.1016/j.micromeso.2012.01.024

Cited by 48 publications

(57 citation statements)

References 74 publications

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“…The spectra of the dehydrated samples exhibit six peaks in the region of stretching O-H vibrations. In agreement with the literature [20,[35][36][37][38][39], the peaks at 3740 and 3724 cm −1 are assigned to Si-OH groups of the tetrahedral silicate layer and those at 3691 and 3673 cm −1 to Mg(3)-OH groups in the octahedral sheets of the sepiolite structure. The bands at 3597 and 3531 cm −1 have been attributed to water molecules coordinated to Mg cations.…”

Section: Resultssupporting

confidence: 91%

Catalytic performance of microporous materials for the production of renewable fuels

et al. 2018

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ETS-10, zeolite A and sepiolite based nano-structured materials were prepared and modified with potassium containing compounds using ion-exchange or impregnation and evaluated as basic catalysts for transesterification of vegetable oils using microwave heating. The structural features of these catalysts were characterised in detail by the variable temperature in situ X-ray diffraction, N 2 adsorption-desorption, scanning electron microscopy with energy dispersive X-ray analysis and in situ FTIR spectroscopy using adsorption-desorption of acetylene as a basic probe in order to evaluate their structure-catalytic performance relationship in the methanolysis of triglycerides. A wide range of parameters were utilised in order to optimise the reaction conditions. Although a high yield of fatty acid methyl esters with almost 100% selectivity can be achieved in transesterification reactions in the presence of K-containing sepiolite, this system shows significant deactivation due to its structural degradation and loss of the active component during the reaction and regeneration cycles. In contrast, zeolite KA and ETS-10, which are thermally stable crystalline materials, demonstrated no decrease in their activity for up to four reaction runs, and therefore can be used as effective solid basic catalysts in this reaction. Here we explore for the first time how the thermal and structural stability of the supported clay can affect its activity, an essential issue which has not been sufficiently studied in the recent research related to the biofuel production over solid catalysts.

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Section: Resultssupporting

confidence: 91%

Catalytic performance of microporous materials for the production of renewable fuels

et al. 2018

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“…For such a reason, the term "Maya Red" pigment was tentatively proposed as a suitable name for this hybrid material. 33, 34 According to some authors, one of the essential conditions to be accomplished by original "Mayan" materials is the oxidation/ reduction cycle undergone by some of the guest molecules during preparation of the pigment. This particular mechanism (redox tuning) causes different topological isomers to be fixated to the palygorskite framework in genuine Maya Blue (i.e., indigo, dehydroindigo, and isatin), each contributing to this polyfunctional hybrid color.…”

Section: Introductionmentioning

confidence: 99%

Evolution and Reversibility of Host/Guest Interactions with Temperature Changes in a Methyl Red@Palygorskite Polyfunctional Hybrid Nanocomposite

et al. 2014

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Palygorskite is a microporous clay mineral with several important applications, including use as a dye nanoscaffold, due to its ability to incorporate apt guest molecules and form exceptionally stable composites. Such a property covers widespread fields of interest, from pottery pigments to light harvesting. In all these applications, the stability of these composites at progressively increasing temperatures is an important parameter to determine their condition of usage. This work investigates the nature and strength of the stabilizing host/guest interactions at the basis of the exceptional stability of the methyl red@palygorskite composite system, which undergo a dynamic but reversible evolution depending on the level of heating. A multitechnique analytical protocol involving synchrotron X-ray powder diffraction (S-XRPD) and thermogravimetric analysis (TGA) coupled with infrared spectroscopy (FTIR) and gas chromatography (GC-MS) was followed, which allowed us to sharply identify the species evolved during heating. Moderate temperatures (140−300°C) cause stabilization of H-bonds between the structural H 2 O and the carboxyl group of the dye, whereas higher ones (>300°C) trigger formation of direct COOH/octahedral Mg bonds favored by dehydration. Cooling below 300°C implies gradual reversibility of the observed trend due to rehydration from environmental moisture; additional heating (>400°C), conversely, causes methyl red decomposition, fragmentation, and further expulsion from the host tunnels (∼500°C). The encapsulated dye in zwitterionic, trans, and/or protonated form affects the hosting system properties, preventing structural folding and strongly modifying the mechanism of water release for both structural and zeolitic H 2 O. Experimental results were interpreted also with the help of structural models obtained by molecular mechanics simulations, offering atomistic insights on the mechanisms at the basis of the observed phenomena.

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“…[9] Furthermore, dyes other than indigo have been inserted into palygorskites, thereby expanding the color range and thus affording a range of novel hybrid pigments. [10] Morphologically related to palygorskite is the natural clay mineral hectorite; [11] nanoscaled synthetic derivatives of these, namely laponites, are available commercially. [12] Much to our delight, the marriage between indigo and Laponite RD afforded a water-soluble hybrid, which we term Laponite Blue, as its aqueous solutions closely mimic solid Maya Blue and indigo optically.…”

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Laponite Blue: Dissolving the Insoluble

et al. 2012

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The neutral organic dye indigo forms an inorganic-organic hybrid material with nanoclays (see picture; blue circles on disks symbolizing indigo, spheres indicating liberated cations) and can thus be transferred into aqueous solution. Solids recovered from these solutions resemble the ancient Maya Blue pigment. The method can also be applied to other hydrophobic species and may open the gate for novel solution chemistry, including photonic and catalytic applications.

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Spectroscopic characterization and photo/thermal resistance of a hybrid palygorskite/methyl red Mayan pigment

Cited by 48 publications

References 74 publications

Catalytic performance of microporous materials for the production of renewable fuels

Catalytic performance of microporous materials for the production of renewable fuels

Evolution and Reversibility of Host/Guest Interactions with Temperature Changes in a Methyl Red@Palygorskite Polyfunctional Hybrid Nanocomposite

Laponite Blue: Dissolving the Insoluble

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