The Dehydrocyclization Reaction.

Hansch, Corwin

doi:10.1021/cr60166a001

Cited by 35 publications

(15 citation statements)

References 66 publications

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“…The concentration of paraffinic and olefinic compounds generated was higher for the high SAR catalyst and lower for the low SAR catalyst. The low SAR catalyst generated a higher concentration of aromatic compounds primarily due to the high acid strength sites facilitating the dehydrocyclization of paraffins and olefins to aromatics [14]. In another example, Mukarakate et al upgraded pine pyrolysis vapors using β-zeolite with widely varying SARs.…”

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confidence: 99%

Effect of ZSM-5 acidity on aromatic product selectivity during upgrading of pine pyrolysis vapors

et al. 2016

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The impact of catalyst acidity on the selectivity of upgraded biomass pyrolysis products was studied by passing pine pyrolysis vapors over five ZSM-5 catalysts of varying acidity at 500°C. The SiO 2 -to-Al 2 O 3 ratio (SAR) of the ZSM-5 zeolite was varied from 23 to 280 to control the acidity of the catalyst and the composition of upgraded products. The upgraded product stream was analyzed by GCMS. Additionally, catalysts were characterized using temperature programmed desorption, diffuse-reflectance FTIR spectroscopy, N 2 physisorption, and X-ray diffraction. The results showed that the biomass pyrolysis vapors were highly deoxygenated to form a slate of aromatic hydrocarbons over all of the tested ZSM-5 catalysts. As the overall acidity of the ZSM-5 increased the selectivity towards alkylated (substituted) aromatics (e.g., xylene, dimethylnaphthalene, and methyl-anthracene) decreased while the selectivity towards unsubstituted aromatics (e.g., benzene, naphthalene, and anthracene) increased. Additionally, the selectivity towards polycyclic aromatic compounds (2-ring and 3-ring) increased as catalyst acidity increased, corresponding to a decrease in acid site spacing. The increased selectivity towards less substituted polycyclic aromatic compounds with increasing acidity is related to the relative rates of cyclization and alkylation reactions within the zeolite structure. As the acid site concentration increases and sites become closer to each other, the formation of additional cyclization products occurs at a greater rate than alkylated products. The ability to adjust product selectivity within 1-, 2-, and 3ring aromatic families, as well as the degree of substitution, by varying ZSM-5 acidity could have significant benefits in terms creating a slate of upgraded biomass pyrolysis products to meet specific target market demands.

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confidence: 99%

Effect of ZSM-5 acidity on aromatic product selectivity during upgrading of pine pyrolysis vapors

et al. 2016

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“…Zuvor hatten Jones,Jr. [233] Ein frühes Beispiel ist die Synthese von Carbazol, indem Diphenylamin über einen Pt-Katalystor bei 300 8 8Cgeleitet wurde. 0.1 hPa gegeben worden waren.…”

Section: Angewandte Chemieunclassified

“…[229] [232] Cyclisierung und Aromatisierung von aliphatischen Verbindungen durch Pyrolyse über festen Trägern wie Chromoxiden oder Zeolithen sind in der petrochemischen Industrie gut bekannt. [233] Ein frühes Beispiel ist die Synthese von Carbazol, indem Diphenylamin über einen Pt-Katalystor bei 300 8 8Cgeleitet wurde. [234] Va kuum-Gas-Feststoff-Reaktionen (vacuum gas- [235,236] Analog wurden reines Methanimin, CH 2 = NH, und andere Alkanimine hergestellt, indem die entsprechenden primären Alkylamine erst mit N-Chlorsuccinimid (NCS) bei Raumtemperatur/10 À1 hPa chloriert und danach über tBuOK bei 55 8 8Cdehydrochloriert wurden.…”

Section: Angewandte Chemieunclassified

Flash‐Vakuumpyrolyse – Techniken und Reaktionen

Wentrup

2017

Angewandte Chemie

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Die Anfänge der Flash‐Vakuumpyrolyse (FVP) ergaben sich in den 1940er und 1950er Jahren hauptsächlich aus dem massenspektrometrischen Nachweis pyrolytisch entstandener freier Radikale. In den 1960er Jahren begannen Organiker mit der Durchführung von FVP‐Experimenten zum Zweck der Isolierung neuer und interessanter Verbindungen und zum Verständnis pyrolytischer Prozesse. Seitdem wurden viele unterschiedliche Typen von Apparaten und Techniken entwickelt. Zielsetzung dieses Aufsatzes ist es, die wichtigsten Methoden vorzustellen wie auch eine Übersicht über typische Reaktionen und Beobachtungen zu geben, die mit den verschiedenen Techniken erreicht werden können. Dies umfasst unter anderem präparative FVP, chemische Abfangreaktionen, Matrixisolierung sowie Tieftemperatur‐Spektroskopie reaktiver Intermediate und instabiler Moleküle. Darüber hinaus ist die Kombination von FVP mit Matrixisolierung und Photochemie ein wirkungsvolles Instrument für Untersuchungen von Reaktionsmechanismen.

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“…As such, it is proposed that upon deprotonation by Cs 2 CO 3 base, the resorcinarene phenoxide B forms a radical C in the presence of a DMF radical. The radical C then loses H to form the ortho-quinonoid derivative D, which upon tautomerization gives the vinylphenol E. Although the exact reaction mechanism of the ring closure is not yet known, it has been suggested that the intramolecular dehydrocyclization occurs via the addition of the hydroxyl group across the alkenyl side chain to give the intermediate F, which finally upon loss of H 2 leads to the formation of the benzofuran derivative G. [20,21] To further verify the proposed mechanism for the formation of a benzofuran ring, the standard synthesis procedure was repeated at 60 °C and at 90 °C in the presence of potassium ferricyanide (0.9 eq;entries 4 and 5 in Table 1), which is known to act as "oneelectron abstracter" that transforms the deprotonated hydroxyl groups into radicals. [ 22 ] The reaction with the radical initiator produced only a small amount (yield < 2%) of benzofuran monocrown 1 at 60 °C, but at 90 °C a slight increase in the yield (6.1%) was observed supporting the idea of a possible radical mechanism.…”

Section: Synthesismentioning

confidence: 99%

The Structural Diversity of Benzofuran Resorcinarene Leads to Enhanced Fluorescence

Tero

Salorinne

Lehtivuori

et al. 2014

Chemistry An Asian Journal

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An unexpected and previously unknown resorcinarene mono‐crown with a fused benzofuran moiety in its macrocyclic core was obtained as a byproduct from a bridging reaction of tetramethoxy resorcinarene with tetraethylene glycol ditosylate. The formation of the fused benzofuran moiety in the resorcinarene macrocycle resulted in a unique rigid and puckered boat conformation, as shown by XRD studies in the solid state. Modification of the macrocycle was also observed to affect the photophysical properties in solution by enhancing the fluorescence brightness compared with a conventional resorcinarene macrocycle. The fluorescent properties enabled unique detection of structural features, that is, the rigid boat conformation with the conjugated benzofuran system and the more flexible crown bridge part, in solution.

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The Dehydrocyclization Reaction.

Cited by 35 publications

References 66 publications

Effect of ZSM-5 acidity on aromatic product selectivity during upgrading of pine pyrolysis vapors

Effect of ZSM-5 acidity on aromatic product selectivity during upgrading of pine pyrolysis vapors

Flash‐Vakuumpyrolyse – Techniken und Reaktionen

The Structural Diversity of Benzofuran Resorcinarene Leads to Enhanced Fluorescence

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