Acid Zeolites as Electron Acceptors. Use of Thianthrene Radical Cation as a Probe

Corma, Avelino; Fornés, Vicente; Garcı́a, Hermenegildo; Martí, Vicenç; Miranda, Miguel A.

doi:10.1021/cm00059a022

Cited by 39 publications

(43 citation statements)

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“…74 Pyridine as a probe can distinguish between Brønsted or Lewis acid sites leading to the formation of pyridinium ions or Lewis acid adducts that can be differentiated and quantified by monitoring in IR the intensity of the vibration bands at about 1550 and 1450 cm À1 characteristic of each of these species. 75 Similarly, CO exhibits distinctive vibration bands in the region between 2200 and 1900 cm À1 that also reports on the interaction with the Brønsted/ Lewis acid sites. 76 These studies provide information about the nature of the active sites and serve to design more active and selective materials for these condensation reactions.…”

Section: Quinoline Based Heterocyclesmentioning

confidence: 77%

Metal–organic frameworks as solid catalysts for the synthesis of nitrogen-containing heterocycles

2014

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Metal-organic frameworks (MOFs) are finding increasing application as solid catalysts for liquid phase reactions leading to the synthesis of fine chemicals. In the present review we have focused on those reports describing the use of MOFs as catalysts for the synthesis of N-containing heterocycles that is a class of organic compounds with high added value due to their therapeutic use as drugs and their remarkable biological activities. After an introduction describing relevant structural features of MOFs and the nature of their active sites, this manuscript is organized according to the type of N-containing heterocycle synthesized employing MOFs as catalysts including pyrimidines, N-substituted piperidines, quinolines, indoles, N-substituted imidazoles, triazoles and heterocyclic amides. Special attention has been paid to the structural stability of MOFs under the reaction conditions, to the occurrence of metal leaching and reusability. The final section of this review provides some concluding remarks and future prospects for the field, with emphasis on showing the superiority of MOFs with respect to other solid catalysts for this type of liquid phase organic reactions and pointing out that the final goal in this research would be the use of these materials as catalysts in real industrial synthesis.

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Section: Quinoline Based Heterocyclesmentioning

confidence: 77%

Metal–organic frameworks as solid catalysts for the synthesis of nitrogen-containing heterocycles

2014

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“…This model does not require the presence of any extra-framework species for acidity enhancement and points towards a direct link between Brùnsted and Lewis acidity in zeolites. [10,12,83,84] The Al hydroperoxide defect could easily be responsible for the formation of either radical ions or chargetransfer complexes in carbonium-ion type catalysis or in radical-type cracking. Similar defects play a crucial role in metalsubstituted zeolites such as TS-1, defining unique oxidation chemistry for these materials.…”

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confidence: 99%

Computational Investigation into the Origins of Lewis Acidity in Zeolites

et al. 2000

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The catalytic abilities of zeolites are attributed largely to their acidic properties, in both the Brønsted (proton donating) and Lewis (electron accepting) senses, although the origin and mechanism of the Lewis acidity remain unclear. Here is presented a computational approach to identifying Lewis acid sites in zeolite frameworks by analyzing the major candidate structures, such as the Al hydroperoxide shown in the Figure.

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“…The very microporous structure of the activated carbon itself is also likely to play a role in the catalytic activity observed in the formation of the described pyrolysis products, with micropores themselves showing an ability to stabilise free radicals, and promote bimolecular reactions in the pore space (such as the radical mediated formation of aromatic species described previously) [249][250][251].…”

Section: Microporous Structurementioning

confidence: 99%

Microwave-assisted pyrolysis of HDPE using an activated carbon bed

et al. 2012

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Plastics play an enormous role in modern manufacturing, but the extraction and refining of raw materials, followed by the synthesis of plastics themselves, represents an enormous energy investment into a product that is all too often simply "thrown away" into a landfill after a single use. Microwave-assisted pyrolysis is a recycling technique that allows the recovery of chemical value from plastic waste by breaking down polymers into useful smaller hydrocarbons using microwave heat in the absence of oxygen. This dissertation examines the use of a catalytic activated carbon bed in this procedure, using high density polyethylene (HDPE) as a model plastic. Initial tests with the batch input of HDPE produced a condensed pyrolysis oil comprising 35.5-45.3% aromatics, with the remainder primarily short-chain aliphatics. This oil was approximately three times lighter than that produced in the absence of catalyst, with a narrower range of molecular masses that matched those of the liquid transport fuels petrol and diesel (C 5-C 21). The non-condensable gases that resulted were short-chain aliphatics that could be used as feedstock for the creation of new chemicals (such as virgin HDPE), or fuels such as natural gas and LPG. The development of apparatus capable of adding sample in a continuous fashion enabled the processing of larger quantities of HDPE, and resulted in condensed products with a significantly higher aromatic content (>80% at 450°C), and which I owe a debt of thanks to many people for the support and kindness they have shown me throughout my time in Cambridge. I would like to thank my supervisor, Professor Howard Chase, for his generous provision of tutelage, expertise, and support throughout the production of this work. A further thank you to my colleagues and the department support staff for their extremely skilled time and advice. I would also like to acknowledge the generous financial support that I have received from the Cambridge Commonwealth Trust, The Higher Education Funding Council for

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Acid Zeolites as Electron Acceptors. Use of Thianthrene Radical Cation as a Probe

Cited by 39 publications

References 0 publications

Metal–organic frameworks as solid catalysts for the synthesis of nitrogen-containing heterocycles

Metal–organic frameworks as solid catalysts for the synthesis of nitrogen-containing heterocycles

Computational Investigation into the Origins of Lewis Acidity in Zeolites

Microwave-assisted pyrolysis of HDPE using an activated carbon bed

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