Regioselective Gas-Phase n-Butane Transfer Dehydrogenation via Silica-Supported Pincer-Iridium Complexes

2020 ◽  
Author(s):  
Boris Sheludko ◽  
Cristina Castro ◽  
Chaitanya Khalap ◽  
Thomas Emge ◽  
Alan Goldman ◽  
...  
Keyword(s):  
Gas Phase ◽  
Active Site ◽  
Lower Cost ◽  
Open Systems ◽  
Iridium Complexes ◽  
Terminal Olefin ◽  
Molecular Precursors ◽  
Sterically Demanding ◽  
Olefin Production ◽  
Steam Cracking

<b>Abstract:</b> The production of olefins via on-purpose dehydrogenation of alkanes allows for a more efficient, selective and lower cost alternative to processes such as steam cracking. Silica-supported pincer-iridium complexes of the form [(≡SiO-<sup>R4</sup>POCOP)Ir(CO)] (<sup>R4</sup>POCOP = κ<sup>3</sup>-C<sub>6</sub>H<sub>3</sub>-2,6-(OPR<sub>2</sub>)<sub>2</sub>) are effective for acceptorless alkane dehydrogenation, and have been shown stable up to 300 °C. However, while solution-phase analogues of such species have demonstrated high regioselectivity for terminal olefin production under transfer dehydrogenation conditions at or below 240 °C, in open systems at 300 °C, regioselectivity under acceptorless dehydrogenation conditions is consistently low. In this work, complexes <a>[(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)Ir(CO)] </a>(<b>1</b>) and [(≡SiO-<i><sup>i</sup></i><sup>Pr4</sup>PCP)Ir(CO)] (<b>2</b>) were synthesized via immobilization of molecular precursors. These complexes were used for gas-phase butane transfer dehydrogenation using increasingly sterically demanding olefins, resulting in observed selectivities of up to 77%. The results indicate that the active site is conserved upon immobilization.

Regioselective Gas-Phase n-Butane Transfer Dehydrogenation via Silica-Supported Pincer-Iridium Complexes

2020 ◽  
Author(s):  
Boris Sheludko ◽  
Cristina Castro ◽  
Chaitanya Khalap ◽  
Thomas Emge ◽  
Alan Goldman ◽  
...  
Keyword(s):  
Gas Phase ◽  
Active Site ◽  
Lower Cost ◽  
Open Systems ◽  
Iridium Complexes ◽  
Terminal Olefin ◽  
Molecular Precursors ◽  
Sterically Demanding ◽  
Olefin Production ◽  
Steam Cracking

<b>Abstract:</b> The production of olefins via on-purpose dehydrogenation of alkanes allows for a more efficient, selective and lower cost alternative to processes such as steam cracking. Silica-supported pincer-iridium complexes of the form [(≡SiO-<sup>R4</sup>POCOP)Ir(CO)] (<sup>R4</sup>POCOP = κ<sup>3</sup>-C<sub>6</sub>H<sub>3</sub>-2,6-(OPR<sub>2</sub>)<sub>2</sub>) are effective for acceptorless alkane dehydrogenation, and have been shown stable up to 300 °C. However, while solution-phase analogues of such species have demonstrated high regioselectivity for terminal olefin production under transfer dehydrogenation conditions at or below 240 °C, in open systems at 300 °C, regioselectivity under acceptorless dehydrogenation conditions is consistently low. In this work, complexes <a>[(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)Ir(CO)] </a>(<b>1</b>) and [(≡SiO-<i><sup>i</sup></i><sup>Pr4</sup>PCP)Ir(CO)] (<b>2</b>) were synthesized via immobilization of molecular precursors. These complexes were used for gas-phase butane transfer dehydrogenation using increasingly sterically demanding olefins, resulting in observed selectivities of up to 77%. The results indicate that the active site is conserved upon immobilization.

Active site separation of photocatalytic steam reforming of methane using Gas‐Phase Photoelectrochemical system

2021 ◽  
Author(s):  
Tomoki Kujirai ◽  
Akira Yamaguchi ◽  
Takeshi Fujita ◽  
Hideki Abe ◽  
Masahiro Miyauchi
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
High Temperatures ◽  
Steam Reforming ◽  
Active Site ◽  
Side Reaction ◽  
System P ◽  
Steam Reforming Of Methane

Steam reforming of methane (SRM) requires high temperatures to be promoted, and the production of carbon dioxide from the side reaction has also become a problem. In this study, we...

Selective Hydrogenation of Crotonaldehyde Over Cobalt Based Self-Supported Catalysts

1994 ◽  
Vol 368 ◽  
Author(s):  
A. N. Patil ◽  
M. A. Bañares ◽  
X. Lei ◽  
T. P. Fehlner ◽  
E. E. Wolf
Keyword(s):  
Gas Phase ◽  
Supported Catalysts ◽  
Catalyst Activity ◽  
Maximum Yield ◽  
Metal Core ◽  
Molecular Precursors ◽  
Crotyl Alcohol ◽  
Carboxylate Groups ◽  
Heterogenous Catalyst ◽  
Metal Layers

ABSTRACTComplex cobalt-carbonyl ligand based clusters of clusters are used as molecular precursors for self-supported model catalysts. These precursors consist of two metal layers: an outer of the complex Co-carbonyl ligands, and a core of metal (e.g. Co or Zn) carboxylate groups. Partial thermolysis at low temperature (LT) of these materials under hydrogen results in almost completely decarbonylated material with a mainly unchanged carboxylate metal core. Complete pyrolysis at higher temperatures (HT) in hydrogen leads to mixed metal environment. These materials were used as a heterogenous catalyst in the gas phase hydrogenation of crotonaldehyde. The maximum yield of 27 % of desired product crotyl alcohol was observed when HT-CoCo was used as the catalyst at 423 K. The catalyst activity and the crotyl alcohol selectivity remained unchanged over 2 days of operation. The bimetallic ZnCo catalysts showed lower selectivity to crotyl alcohol than the CoCo catalysts.

scholarly journals Experimental Identification of the Active Site in the Heteronuclear Redox Couples [AlVO x ]+. /CO/N2 O (x= 3, 4) by Gas-Phase IR Spectroscopy

2018 ◽  
Vol 57 (25) ◽  
pp. 7448-7452 ◽  
Author(s):  
Sreekanta Debnath ◽  
Harald Knorke ◽  
Wieland Schöllkopf ◽  
Shaodong Zhou ◽  
Knut R. Asmis ◽  
...  
Keyword(s):  
Ir Spectroscopy ◽  
Gas Phase ◽  
Active Site ◽  
Experimental Identification ◽  
Redox Couples

scholarly journals Conformational Flexibility and the Interaction of Huperzine A in the Active Site of Acetylcholinesterase: A Quantum Chemical and Charge Density Study

2016 ◽  
Author(s):  
Renuga Parameswari Azhagesan ◽  
Saravanan Kandasamy ◽  
Kumaradhas Poomani
Keyword(s):  
Molecular Docking ◽  
Density Distribution ◽  
Charge Density ◽  
Gas Phase ◽  
Active Site ◽  
Quantum Chemical ◽  
Conformational Flexibility ◽  
Huperzine A ◽  
Charge Density Distribution ◽  
Density Analysis

Huperzine A is an herbal reversible inhibitor of Acetylcholinesterase (AChE). A molecular docking analysis on Huperzine A molecule has been carried out to understand its structure, conformational flexibility, intermolecular interaction and the binding affinity in the active site of AChE enzyme. Further, the charge density distribution of huperzine A molecule (lifted from the active site of AChE) was determined from the high level quantum chemical calculations coupled with charge density analysis. The binding affinity of Huperzine A towards AChE was calculated from the molecular docking; the lowest docked energy is -8.46 kcal/mol. In the active site, huperzine A molecule interacts with acyl binding pocket-Phe330 of AChE, that is, the bicyclo ring group of huperzine A forms an intermolecular interaction with the oxygen atom of main chain of the amino acid residue Phe330 at the distances 3.02 and 3.25 &Aring; respectively. On the other hand, a gas phase study on huperzine A molecule also performed using HF and DFT (B3LYP) methods with the basis set 6-311G**. The molecular structure, conformation, and the charge density distribution of huperzine A molecule in the gas phase have determined using quantum chemical calculations and the charge density analysis. The comparative studies between the gas phase and the active site forms of huperzine A molecule, explicitly reveals the degree of conformational modification and the charge density redistribution of huperzine A when present in the active site. The dipole moment of the molecule in the active site is 6.85 D, which is slightly higher than its gas phase value (5.91 D). The electrostatic potential (ESP) surface of active site molecule clearly shows the strong electronegative and positive ESP regions of the molecule, which are the expected strong reactive locations of the molecule.

scholarly journals Direct Identification of Acetaldehyde Formation and Characterization of the Active Site in the [VPO 4 ] .+ /C 2 H 4 Couple by Gas‐Phase Vibrational Spectroscopy

2019 ◽  
Vol 131 (52) ◽  
pp. 19044-19048 ◽  
Author(s):  
Ya‐Ke Li ◽  
Sreekanta Debnath ◽  
Maria Schlangen ◽  
Wieland Schöllkopf ◽  
Knut R. Asmis ◽  
...  
Keyword(s):  
Gas Phase ◽  
Vibrational Spectroscopy ◽  
Active Site ◽  
Direct Identification

scholarly journals Understanding the role of active site residues in CotB2 catalysis using a cluster model

2020 ◽  
Vol 16 ◽  
pp. 50-59 ◽  
Author(s):  
Keren Raz ◽  
Ronja Driller ◽  
Thomas Brück ◽  
Bernhard Loll ◽  
Dan T Major
Keyword(s):  
Gas Phase ◽  
Active Site ◽  
Cluster Model ◽  
Electronic Energy ◽  
Active Site Residues ◽  
Multistep Synthesis ◽  
Site Cluster ◽  
Phase Data ◽  
Streptomyces Melanosporofaciens

Terpene cyclases are responsible for the initial cyclization cascade in the multistep synthesis of a large number of terpenes. CotB2 is a diterpene cyclase from Streptomyces melanosporofaciens, which catalyzes the formation of cycloocta-9-en-7-ol, a precursor to the next-generation anti-inflammatory drug cyclooctatin. In this work, we present evidence for the significant role of the active site's residues in CotB2 on the reaction energetics using quantum mechanical calculations in an active site cluster model. The results revealed the significant effect of the active site residues on the relative electronic energy of the intermediates and transition state structures with respect to gas phase data. A detailed understanding of the role of the enzyme environment on the CotB2 reaction cascade can provide important information towards a biosynthetic strategy for cyclooctatin and the biomanufacturing of related terpene structures.

The effect of steam on maximizing light olefin production by cracking of ethanol and oleic acid over mesoporous ZSM-5 catalysts

2020 ◽  
Vol 10 (19) ◽  
pp. 6618-6627
Author(s):  
Zhixia Li ◽  
Fuwei Li ◽  
Tingting Zhao ◽  
Hongchang Yu ◽  
Shilei Ding ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Light Olefin ◽  
Olefin Production ◽  
Steam Cracking ◽  
Olefin Selectivity

Steam cracking significantly improved light olefin selectivity: mainly ethylene was obtained from ethanol and propylene from oleic acid.

Sustainable innovations in steam cracking: CO2 neutral olefin production

2020 ◽  
Vol 5 (2) ◽  
pp. 239-257 ◽  
Author(s):  
Ismaël Amghizar ◽  
Jens N. Dedeyne ◽  
David J. Brown ◽  
Guy B. Marin ◽  
Kevin M. Van Geem
Keyword(s):  
Heat Transfer ◽  
Green Energy ◽  
Light Olefins ◽  
Main Process ◽  
Olefin Production ◽  
Steam Cracking ◽  
Enhancing Heat Transfer

Steam cracking of hydrocarbons is and will be the main process to produce light olefins but emits large quantities of CO2. Enhancing heat transfer in the radiation section, using green energy and novel furnace designs will be key to substantially reducing CO2 emissions.

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