scholarly journals QM/MM study of the reactivity of zeolite bound methoxy and carbene groups

2021 ◽  
Author(s):  
Stefan Adrian F Nastase ◽  
Andrew J Logsdail ◽  
C. Richard A. Catlow
Keyword(s):  
Pivotal Role ◽  
Methanol To Hydrocarbons ◽  
Autocatalytic Process

The conversion of methanol-to-hydrocarbons (MTH) is known to occur via an autocatalytic process in zeolites, where framework-bound methoxy species play a pivotal role, especially during catalyst induction. Recent NMR and...

scholarly journals QM/MM Study of the Reactivity of Zeolite Bound Methoxy and Carbene Groups

2021 ◽  
Author(s):  
Andrew Logsdail ◽  
Richard Catlow ◽  
Stefan A. F. Nastase
Keyword(s):  
Acid Site ◽  
Alternative Pathway ◽  
Experimental Studies ◽  
Acid Sites ◽  
Site Formation ◽  
Methanol To Hydrocarbons ◽  
Hydrocarbon Formation ◽  
Autocatalytic Process ◽  
Ft Ir

<div>The conversion of methanol-to-hydrocarbons (MTH) is known to occur via an autocatalytic process in zeolites, where framework-bound methoxy species play a pivotal role, especially during catalyst induction. Recent NMR and FT-IR experimental studies suggest that methoxylated zeolites are able to produce hydrocarbons by a mechanism involving carbene migration and association. In order to understand these observations, we have performed QM/MM computational investigations on a range of reaction mechanisms for the reaction of zeolite bound methoxy and carbene groups, which are proposed to initiate hydrocarbon formation in the MTH process. Our simulations demonstrate that it is kinetically unfavourable for methyl species to form on the framework away from the zeolite acid site, and both kinetically and thermodynamically unfavourable for methyl groups to migrate through the framework and aggregate around an acid site. Formation of carbene moieties was considered as an alternative pathway to the formation of C-C bonds; however, the reaction energy for conversion of a methyl to a carbene is unfavourable. Metadynamics simulations help confirm further that methyl species at the framework acid sites would be more reactive towards formed C<sub>2+</sub> species, rather than inter-framework migration and that the role of carbenes in the formation of the first –C bond will be via a concerted type of mechanism rather than stepwise. </div>

scholarly journals QM/MM Study of the Reactivity of Zeolite Bound Methoxy and Carbene Groups

2021 ◽  
Author(s):  
Andrew Logsdail ◽  
Richard Catlow ◽  
Stefan A. F. Nastase
Keyword(s):  
Acid Site ◽  
Alternative Pathway ◽  
Experimental Studies ◽  
Acid Sites ◽  
Site Formation ◽  
Methanol To Hydrocarbons ◽  
Hydrocarbon Formation ◽  
Autocatalytic Process ◽  
Ft Ir

<div>The conversion of methanol-to-hydrocarbons (MTH) is known to occur via an autocatalytic process in zeolites, where framework-bound methoxy species play a pivotal role, especially during catalyst induction. Recent NMR and FT-IR experimental studies suggest that methoxylated zeolites are able to produce hydrocarbons by a mechanism involving carbene migration and association. In order to understand these observations, we have performed QM/MM computational investigations on a range of reaction mechanisms for the reaction of zeolite bound methoxy and carbene groups, which are proposed to initiate hydrocarbon formation in the MTH process. Our simulations demonstrate that it is kinetically unfavourable for methyl species to form on the framework away from the zeolite acid site, and both kinetically and thermodynamically unfavourable for methyl groups to migrate through the framework and aggregate around an acid site. Formation of carbene moieties was considered as an alternative pathway to the formation of C-C bonds; however, the reaction energy for conversion of a methyl to a carbene is unfavourable. Metadynamics simulations help confirm further that methyl species at the framework acid sites would be more reactive towards formed C<sub>2+</sub> species, rather than inter-framework migration and that the role of carbenes in the formation of the first –C bond will be via a concerted type of mechanism rather than stepwise. </div>

Bacon's "Envy": An Evaluation of Punctuation

2018 ◽  
Keyword(s):  
Pivotal Role ◽  
Complex Sentence ◽  
The Individual ◽  
Individual Style

Punctuation plays a pivotal role in enhancing the comprehensibility of a text. It not only abolishes ambiguity from the text but also adorns the individual style of the author. This paper analyses Bacon’s essay “Envy” evaluating the aberrant use of punctuation to understand its impact on the holistic comprehension of the essay. Bacon has deviated in some punctuation marks in different situations. Most deviations occur in the use of the comma and the semicolon. The least deviations occur in the use of the period. Two explanations may be inferred from the analysis: First, what seems to be deviant in this regard was normal in his time; second, he deviates on purpose to make the long, complex sentence clear and easy for the reader.

1853-P: Neutrophils Play a Pivotal Role in Obesogenic Diet-Induced Nonalcoholic Steatohepatitis

Diabetes ◽  
2020 ◽  
Vol 69 (Supplement 1) ◽  
pp. 1853-P
Author(s):  
QIONG L. ZHOU ◽  
SHOAIB KHAN ◽  
MICHAEL RIGOR ◽  
INDEEVAR BEERAM ◽  
ZHEN Y. JIANG
Keyword(s):  
Nonalcoholic Steatohepatitis ◽  
Pivotal Role ◽  
Obesogenic Diet

The impact of exchange rate on price and export of agricultural production

2018 ◽  
Vol 1 (4) ◽  
pp. 9-18
Author(s):  
Rasulov Tulkin Sattarovich ◽  
Khushvaktov Kuvonchbek Ravshanovich
Keyword(s):  
International Trade ◽  
Exchange Rate ◽  
Agricultural Production ◽  
Global Economy ◽  
Agricultural Economics ◽  
Agricultural Products ◽  
Pivotal Role ◽  
Price Formation ◽  
International Trade Laws ◽  
The Impact

In today’s world of swiftly increasing global economy and continuously changing international trade laws and technology exchange rate plays a pivotal role in the production, price formation, export and import of agricultural products. For many years exchange rate as an integral part of agricultural economics has been ignored. The present study was intended to investigate exchange rate as an impacting factor on the agricultural production. It also considers the researches that have been carried about the impact of the exchange rate on prices and export of agricultural products, theirs analyses and how much impact it has in the situation of Uzbekistan.

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