Methanol conversion on ZSM-22, ZSM-35 and ZSM-5 zeolites: effects of 10-membered ring zeolite structures on methylcyclopentenyl cations and dual cycle mechanism

RSC Advances ◽  
2016 ◽  
Vol 6 (98) ◽  
pp. 95855-95864 ◽  
Author(s):  
Mozhi Zhang ◽  
Shutao Xu ◽  
Yingxu Wei ◽  
Jinzhe Li ◽  
Jingrun Chen ◽  
...  
Keyword(s):  
Methanol Conversion ◽  
Membered Ring ◽  
Organic Species ◽  
Dual Cycle ◽  
Reaction Routes

The different behaviors of retained organic species and their reaction routes in three 10-membered ring zeolites are presented.

A mechanism for methanol conversion over HZSM-5 catalyst

1982 ◽  
Vol 35 (12) ◽  
pp. 2483 ◽  
Author(s):  
MB Sayed ◽  
RP Cooney
Keyword(s):  
Gas Phase ◽  
Internal Surface ◽  
Side Reaction ◽  
Methanol Conversion ◽  
Product Formation ◽  
Zeolitic Catalyst ◽  
Side Reactions ◽  
Organic Species ◽  
The Reformation ◽  
Aromatic Product

Mechanistic stages in the conversion of methanol into hydrocarbons, over the zeolitic catalyst HZSM-5, have been studied by means of infrared spectroscopy. Data are reported for both internal surface and gas-phase species. Evidence is presented on the following aspects: the involvement of Lewis sites in the initial dehydration of methanol; the existence of carboxylate side reactions generating CO and CO2; a role for intermediate isobutene; and the reformation of methanol. The extent of the CO2 side reaction appears to correlate with the extent of aromatic product formation. This is interpreted in terms of the involvement of the co-product, hydrogen, in the disproportionation of aromatic products. These observations are embodied in a mechanism invoking both organic species and surface sites for the overall process.

White fluorescence of polyaromatics derived from methanol conversion in Ca2+-exchanged small-pore zeolites

2021 ◽  
Author(s):  
Hongjun Park ◽  
Jae Hwan An ◽  
Jisuk Bang ◽  
Doo-Sik Ahn ◽  
Seung Hyeon Ko ◽  
...  
Keyword(s):  
Methanol Conversion ◽  
Membered Ring ◽  
Polyaromatic Hydrocarbon ◽  
Small Pore ◽  
Hydrocarbon Product

Coronene and its derivatives were synthesized using methanol inside Ca2+ ion-exchanged small-pore zeolites with an 8-membered ring window, such as LTA and RHO zeolites. The polyaromatic hydrocarbon product exhibited white...

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

Catalytic Synthesis of Cyclic Guanidines via Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Shunya Ohuchi ◽  
Hiroki Koyama ◽  
Hiroki Shigehisa
Keyword(s):  
Hydrogen Atom ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Catalytic Synthesis ◽  
Membered Ring ◽  
Biologically Active ◽  
Atom Transfer ◽  
Powerful Method ◽  
Protective Groups ◽  
The Common

A catalytic synthesis of cyclic guanidines, which are found in many biologically active compounds and natu-ral products, was developed, wherein transition-metal hydrogen atom transfer and radical-polar crossover were employed. This mild and functional-group tolerant process enabled the cyclization of alkenyl guanidines bearing common protective groups, such as Cbz and Boc. This powerful method not only provided the common 5- and 6-membered rings but also an unusual 7-membered ring. The derivatization of the products afforded various heterocycles. We also investigated the se-lective cyclization of mono-protected or hetero-protected (TFA and Boc) alkenyl guanidines and their further derivatiza-tions.

Convergent Total Synthesis of Principinol D, a Rearranged Kaurane Diterpenoid

2019 ◽  
Author(s):  
Timothy Newhouse ◽  
Aneta Turlik ◽  
Yifeng Chen ◽  
Anthony Scruse
Keyword(s):  
Total Synthesis ◽  
Natural Product ◽  
Late Stage ◽  
Membered Ring ◽  
Entry Point ◽  
Ketone Reduction ◽  
Coupling Approach

<div> <p>The total synthesis of principinol D, a rearranged kaurane diterpenoid, is reported. This grayanane natural product is constructed via a convergent fragment coupling approach, wherein the central 7-membered ring is synthesized at a late stage. The bicyclo[3.2.1]octane fragment is accessed by a Ni-catalyzed α-vinylation reaction. Strategic reductions include a diastereoselective SmI<sub>2</sub>-mediated ketone reduction with PhSH and a new protocol for selective ester reduction in the presence of ketones. The convergent strategy reported herein may be an entry point to the larger class of kaurane diterpenoids.</p> </div>

Isomerization of the Isoprene Hydroxy Nitrates and Formation of Orthonitrite Compounds

2019 ◽  
Author(s):  
Gabriel da Silva
Keyword(s):  
Hydroxy Group ◽  
Peroxyl Radical ◽  
Branching Fractions ◽  
Membered Ring ◽  
Low Energy ◽  
Peroxyl Radicals ◽  
Aerosol Formation ◽  
Subsequent Removal ◽  
Ring Compounds ◽  
Group Migration

Atmospheric oxidation of isoprene produces significant yields of eight unique nitrate 11 compounds, each with a β- or δ-hydroxy group. These isoprene hydroxy nitrates (ISOPNs) 12 significantly impact upon global NOx budgets, O3 levels, and aerosol formation. 13 Uncertainties exist, however, in our understanding of ISOPN chemistry, particularly in their 14 yields from the reaction of isoprene peroxyl radicals with NO. This study describes novel 15 isomerization reactions of the ISOPNs, identified through the application of computational 16 chemistry techniques. These reactions produce saturated polycyclic orthonitrite compounds 17 via attack of the R–NO2 group on the vinyl moiety. For the δ-hydroxy nitrates, low-energy 18 isomerization pathways exist to six-membered ring compounds that are around 5 kcal mol-1 19 exothermic. These reactions proceed with barriers around 15 kcal mol-1 below the 20 respective peroxyl radical + NO reactants and yield orthonitrites that can further isomerize 21 to β-hydroxy ISOPNs. Moreover, the δ-hydroxy nitrates can directly interconvert with their β 22 substituted counterparts via NO3 group migration, with barriers that are lower yet. It follows 23 that β-hydroxy nitrates may be stabilized in the δ-hydroxy form, and vice versa. Moreover, 24 the lowest-energy pathway for dissociation of the δ-hydroxy ISOPNs is for the formation of 25 β-hydroxy alkoxyl radicals, and because of this established branching fractions between the 26 various isoprene peroxyl radicals may require re-evaluation. The results presented here also 27 suggest that ISOPNs may be stabilized to some extent in their saturated orthonitrite forms, 28 which has implications for both the total nitrate yield and for their subsequent removal by 29 OH, O3, and photolysis.<br><br>

Tropolone-Based Treatments for Visualising Latent Fingermarks on Porous Surfaces

2019 ◽  
Author(s):  
Clara M. Agapie ◽  
Melissa Sampson ◽  
William Gee
Keyword(s):  
Amino Acids ◽  
Uv Radiation ◽  
Membered Ring ◽  
Diazonium Salts ◽  
Chemical Detection ◽  
Latent Fingerprints ◽  
Porous Surfaces

The work describes a new chemical means of visualising latent fingerprints (fingermarks) using tropolone. Tropolone reacts with amino acids within the fingermark residue to form adducts that absorb UV radiation. These adducts provide useful contrast on highly-fluorescent prous surfaces will illuminated with UV radiation. The conjugated seven-membered ring of the tropolone adduct can be reacted further diazonium salts, which is demonstrated here with formation of two dyes. The methodology is extremely rapid, occurring in minutes with mild heating, and can be applied before ninhydrin in a chemical detection sequence. <br>

Temperature-Programmed Methanol Conversion and Coke Deposition on Fluidized-Bed Catalyst of SAPO-34

2013 ◽  
Vol 33 (2) ◽  
pp. 367-374 ◽  
Author(s):  
Cuiyu YUAN ◽  
Yingxu WEI ◽  
Jinzhe LI ◽  
Shutao XU ◽  
Jingrun CHEN ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Methanol Conversion ◽  
Coke Deposition ◽  
Temperature Programmed
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