Thermochemical Aerobic Oxidation Catalysis in Water Proceeds via Coupled Electrochemical Half-Reactions

<div> <p><b>Heterogeneous aqueous-phase aerobic oxidations are an important emerging class of catalytic transformations, particularly for upgrading next generation bio-derived substrates. The mechanism of these reactions and the precise role of O<sub>2</sub> in particular remains unclear. Herein, we test the hypothesis that thermochemical aerobic oxidation proceeds via two coupled electrochemical half-reactions for oxygen reduction and substrate oxidation. We collect</b><b> electrochemical and thermochemical data on common noble metal catalysts under identical reaction/transport environments, and find that the electrochemical polarization curves of the O<sub>2</sub> reduction and the substrate oxidation half-reaction closely predict the mixed potential of the catalyst measured <i>in operando</i> during thermochemical catalysis across 13 diverse variables spanning </b><b>reaction conditions, catalyst composition, reactant identity, and pH</b><b>. Additionally, we find that driving the oxidation half-reaction reaction electrochemically in the absence of O<sub>2</sub> at the mixed potential leads to very similar rates and selectivities as for the thermochemical reaction in all cases examined. These findings strongly indicate that the role of O<sub>2</sub> in thermochemical aerobic oxidation is solely as an electron scavenger that provides an incipient electrochemical driving force for substrate oxidation. These studies provide a </b><b>quantitative and predictive link between thermochemical and electrochemical catalysis, thereby enabling the rational design of new thermochemical liquid-phase aerobic oxidation schemes by applying the principles of electrochemistry.</b></p> </div> <br>

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Thermochemical Aerobic Oxidation Catalysis in Water Proceeds via Coupled Electrochemical Half-Reactions

10.26434/chemrxiv.13830920 ◽

2021 ◽

Author(s):

Jaeyune Ryu ◽

Daniel Bregante ◽

William C. Howland ◽

Ryan P. Bisbey ◽

Corey J. Kaminsky ◽

...

Keyword(s):

Rational Design ◽

Aerobic Oxidation ◽

Substrate Oxidation ◽

Oxidation Catalysis ◽

Mixed Potential ◽

Noble Metal Catalysts ◽

Catalyst Composition ◽

Electron Scavenger ◽

Reaction Transport

<div> <p><b>Heterogeneous aqueous-phase aerobic oxidations are an important emerging class of catalytic transformations, particularly for upgrading next generation bio-derived substrates. The mechanism of these reactions and the precise role of O<sub>2</sub> in particular remains unclear. Herein, we test the hypothesis that thermochemical aerobic oxidation proceeds via two coupled electrochemical half-reactions for oxygen reduction and substrate oxidation. We collect</b><b> electrochemical and thermochemical data on common noble metal catalysts under identical reaction/transport environments, and find that the electrochemical polarization curves of the O<sub>2</sub> reduction and the substrate oxidation half-reaction closely predict the mixed potential of the catalyst measured <i>in operando</i> during thermochemical catalysis across 13 diverse variables spanning </b><b>reaction conditions, catalyst composition, reactant identity, and pH</b><b>. Additionally, we find that driving the oxidation half-reaction reaction electrochemically in the absence of O<sub>2</sub> at the mixed potential leads to very similar rates and selectivities as for the thermochemical reaction in all cases examined. These findings strongly indicate that the role of O<sub>2</sub> in thermochemical aerobic oxidation is solely as an electron scavenger that provides an incipient electrochemical driving force for substrate oxidation. These studies provide a </b><b>quantitative and predictive link between thermochemical and electrochemical catalysis, thereby enabling the rational design of new thermochemical liquid-phase aerobic oxidation schemes by applying the principles of electrochemistry.</b></p> </div> <br>

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Oxidase Catalysis via an Aerobically Generated Dess-Martin Periodinane Analogue

10.26434/chemrxiv.6149276.v1 ◽

2018 ◽

Author(s):

Asim Maity ◽

Sung-Min Hyun ◽

Alan Wortman ◽

David Powers

Keyword(s):

Chemical Synthesis ◽

Aerobic Oxidation ◽

Substrate Oxidation ◽

Oxidation Catalysis ◽

Hypervalent Iodine ◽

Oxidation Reactions ◽

Broad Array ◽

Oxidation Chemistry ◽

Reactive Oxidants

<p>Hypervalent iodine(V) reagents, such as Dess-Martin periodinane (DMP) and 2-iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to access these reagents from O2 would immediately enable use of O2 as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. Here, we couple aerobic oxidation of iodobenzenes with disproportionation of the initially generated I(III) compounds to generate I(V) reagents. The aerobically generated I(V) reagents exhibit substrate oxidation chemistry analogous to that of DMP. Further, the developed aerobic generation of I(V) has enabled the first application of I(V) intermediates in aerobic oxidation catalysis.</p>

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A Novel Pd-P Nano-Alloy Supported on Functionalized Silica for Catalytic Aerobic Oxidation of Benzyl Alcohol

Catalysts ◽

10.3390/catal12010020 ◽

2021 ◽

Vol 12 (1) ◽

pp. 20

Author(s):

Seyed Sepehr Moeini ◽

Umberto Pasqual Laverdura ◽

Eleonora Marconi ◽

Nicola Lisi ◽

Emanuele Serra ◽

...

Keyword(s):

Benzyl Alcohol ◽

Aerobic Oxidation ◽

Critical Role ◽

Chemical Properties ◽

Catalytic Performance ◽

Pure Oxygen ◽

Noble Metal Catalysts ◽

Functionalized Mesoporous Silica ◽

Oxidation Of Benzyl Alcohol

Catalytic aerobic oxidation of benzyl alcohol (BnOH) to benzaldehyde (PhCHO) over supported noble metal catalysts has grabbed the attention of researchers due to the critical role of PhCHO in numerous industrial syntheses. In the present study, a novel catalyst, Pd-P alloy supported on aminopropyl-functionalized mesoporous silica (NH2-SiO2), was prepared through in situ reduction and characterized by BET-BJH analysis, SEM, TEM, XRD, FTIR, TG-DTA, and XPS. Chemical properties and catalytic performance of Pd-P/NH2-SiO2 were compared with those of Pd0 nanoparticles (NPs) deposited on the same support. Over Pd-P/NH2-SiO2, the BnOH conversion to PhCHO was much higher than over Pd0/NH2-SiO2, and significantly influenced by the nature of solvent, reaching 57% in toluene at 111 °C, with 63% selectivity. Using pure oxygen as an oxidant in the same conditions, the BnOH conversion increased up to 78%, with 66% selectivity. The role of phosphorous in improving the activity may consist of the strong interaction with Pd that favours metal dispersion and lowers Pd electron density.

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Oxidase Catalysis via an Aerobically Generated Dess-Martin Periodinane Analogue

10.26434/chemrxiv.6149276 ◽

2018 ◽

Author(s):

Asim Maity ◽

Sung-Min Hyun ◽

Alan Wortman ◽

David Powers

Keyword(s):

Chemical Synthesis ◽

Aerobic Oxidation ◽

Substrate Oxidation ◽

Oxidation Catalysis ◽

Hypervalent Iodine ◽

Oxidation Reactions ◽

Broad Array ◽

Oxidation Chemistry ◽

Reactive Oxidants

<p>Hypervalent iodine(V) reagents, such as Dess-Martin periodinane (DMP) and 2-iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to access these reagents from O2 would immediately enable use of O2 as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. Here, we couple aerobic oxidation of iodobenzenes with disproportionation of the initially generated I(III) compounds to generate I(V) reagents. The aerobically generated I(V) reagents exhibit substrate oxidation chemistry analogous to that of DMP. Further, the developed aerobic generation of I(V) has enabled the first application of I(V) intermediates in aerobic oxidation catalysis.</p>

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Effect of High Salt Concentration on Ion Clustering and Transport in Polymer Solid Electrolytes: a Molecular Dynamics Study of PEO-LiTFSI

10.26434/chemrxiv.6294941.v1 ◽

2018 ◽

Author(s):

Nicola Molinari ◽

Jonathan P. Mailoa ◽

Boris Kozinsky

Keyword(s):

Polymer Electrolyte ◽

Salt Concentration ◽

Rational Design ◽

Material System ◽

Ion Dynamics ◽

High Concentration ◽

Anion Clusters ◽

Poly Ethylene Oxide ◽

Poly Ethylene

<div> <div> <div> <p>The model and analysis methods developed in this work are generally applicable to any polymer electrolyte/cation-anion combination, but we focus on the currently most prominent polymer electrolyte material system: poly(ethylene) oxide/Li- bis(trifluoromethane) sulfonamide (PEO + LiTFSI). The obtained results are surprising and challenge the conventional understanding of ionic transport in polymer electrolytes: the investigation of a technologically relevant salt concentration range (1 - 4 M) revealed the central role of the anion in coordinating and hindering Li ion movement. Our results provide insights into correlated ion dynamics, at the same time enabling rational design of better PEO-based electrolytes. In particular, we report the following novel observations. 1. Strong binding of the Li cation with the polymer competes with significant correlation of the cation with the salt anion. 2. The appearance of cation-anion clusters, especially at high concentration. 3. The asymmetry in the composition (and therefore charge) of such clusters; specifically, we find the tendency for clusters to have a higher number of anions than cations.</p> </div> </div> </div>

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Effect of High Salt Concentration on Ion Clustering and Transport in Polymer Solid Electrolytes: a Molecular Dynamics Study of PEO-LiTFSI

10.26434/chemrxiv.6294941 ◽

2018 ◽

Author(s):

Nicola Molinari ◽

Jonathan P. Mailoa ◽

Boris Kozinsky

Keyword(s):

Polymer Electrolyte ◽

Salt Concentration ◽

Rational Design ◽

Material System ◽

Ion Dynamics ◽

High Concentration ◽

Anion Clusters ◽

Poly Ethylene Oxide ◽

Poly Ethylene

<div> <div> <div> <p>The model and analysis methods developed in this work are generally applicable to any polymer electrolyte/cation-anion combination, but we focus on the currently most prominent polymer electrolyte material system: poly(ethylene) oxide/Li- bis(trifluoromethane) sulfonamide (PEO + LiTFSI). The obtained results are surprising and challenge the conventional understanding of ionic transport in polymer electrolytes: the investigation of a technologically relevant salt concentration range (1 - 4 M) revealed the central role of the anion in coordinating and hindering Li ion movement. Our results provide insights into correlated ion dynamics, at the same time enabling rational design of better PEO-based electrolytes. In particular, we report the following novel observations. 1. Strong binding of the Li cation with the polymer competes with significant correlation of the cation with the salt anion. 2. The appearance of cation-anion clusters, especially at high concentration. 3. The asymmetry in the composition (and therefore charge) of such clusters; specifically, we find the tendency for clusters to have a higher number of anions than cations.</p> </div> </div> </div>

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Role of the Structure and Electronic Properties of Fe2O3-MoO3 Catalyst on the Dehydration of Isopropyl Alcohol

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19931591 ◽

1993 ◽

Vol 58 (7) ◽

pp. 1591-1599 ◽

Cited By ~ 3

Author(s):

Abd El-Aziz A. Said

Keyword(s):

Active Sites ◽

Isopropyl Alcohol ◽

Oxide Catalyst ◽

Flow System ◽

Charge Carriers ◽

X Ray Diffraction ◽

X Ray ◽

Catalyst Composition ◽

Surface Active

Molybdenum oxide catalyst doped or mixed with (1 - 50) mole % Fe3+ ions were prepared. The structure of the original samples and the samples calcined at 400 °C were characterized using DTA, X-ray diffraction and IR spectra. Measurements of the electrical conductivity of calcined samples with and without isopropyl alcohol revealed that the conductance increases on increasing the content of Fe3+ ions up to 50 mole %. The activation energies of charge carriers were determined in presence and absence of the alcohol. The catalytic dehydration of isopropyl alcohol was carried out at 250 °C using a flow system. The results obtained showed that the doped or mixed catalysts are active and selective towards propene formation. However, the catalyst containing 40 mole % Fe3+ ions exhibited the highest activity and selectivity. Correlations were attempted to the catalyst composition with their electronic and catalytic properties. Probable mechanism for the dehydration process is proposed in terms of surface active sites.

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Oxidation of Terpenoids to Achieve High-Value Flavor and Fragrances—Questioning Microalgae Oxidative Capabilities in the Biotransformation of the Sesquiterpene Valencene and of Selected Natural Apocarotenoids

Chemistry ◽

10.3390/chemistry3030059 ◽

2021 ◽

Vol 3 (3) ◽

pp. 821-830

Author(s):

Davide De Simeis ◽

Stefano Serra ◽

Alessandro Di Fonzo ◽

Francesco Secundo

Keyword(s):

Experimental Data ◽

Natural Products ◽

Aqueous Medium ◽

Photochemical Reaction ◽

Substrate Oxidation ◽

Market Size ◽

Chlorella Sp ◽

General Opinion ◽

Natural Way

Natural flavor and fragrance market size is expected to grow steadily due to the rising consumer demand of natural ingredients. This market request is guided by the general opinion that the production of natural compounds leads to a reduction of pollution, with inherent advantages for the environment and people’s health. The biotransformation reactions have gained high relevance in the production of natural products. In this context, few pieces of research have described the role of microalgae in the oxidation of terpenoids. In this present study, we questioned the role of microalgal based oxidation in the synthesis of high-value flavors and fragrances. This study investigated the role of three different microalgae strains, Chlorella sp. (211.8b and 211.8p) and Chlorococcum sp. (JB3), in the oxidation of different terpenoid substrates: α-ionone, β-ionone, theaspirane and valencene. Unfortunately, the experimental data showed that the microalgal strains used are not responsible for the substrate oxidation. In fact, our experiments demonstrate that the transformation of the four starting compounds is a photochemical reaction that involves the oxygen as oxidant. Even though these findings cast a shadow on the use of these microorganisms for an industrial purpose, they open a new possible strategy to easily obtain nootkatone in a natural way by just using an aqueous medium, oxygen and light.

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