Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh

Singh, Nirala; Lee, Mal‐Soon; Akhade, Sneha A.; Cheng, Guanhua; Camaioni, Donald M.; Gutiérrez, Oliver Y.; Glezakou, Vassiliki Alexandra; Rousseau, Roger; Lercher, Johannes A.; Campbell, Charles T.

doi:10.1021/acscatal.8b04039

Cited by 59 publications

(44 citation statements)

References 66 publications

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“…Two catalysts, Pd/HNO 3 CF‐12h and Pd/HNO 3 CF‐6h, were investigated at pH 2.5, 5.2, and 10.5 (Figure S17). The ECH rates increased with decreasing pH, paralleling a recent study . Importantly, the differences between both catalysts become more pronounced as the pH increases.…”

Section: Figuresupporting

confidence: 85%

Electrochemically Tunable Proton‐Coupled Electron Transfer in Pd‐Catalyzed Benzaldehyde Hydrogenation

et al. 2019

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Acid functionalization of acarbon support allows to enhance the electrocatalytic activity of Pd to hydrogenate benzaldehyde to benzyl alcohol proportional to the concentration of Brønsted-acid sites.I nc ontrast, the hydrogenation rate is not affected when H 2 is used as ar eduction equivalent. The different responses to the catalyst properties are shown to be caused by differences in the hydrogenation mechanism between the electrochemical and the H 2 -induced hydrogenation pathways.T he enhancement of electrocatalytic reduction is realized by the participation of support-generated hydronium ions in the proximity of the metal particles.

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Section: Figuresupporting

confidence: 85%

Electrochemically Tunable Proton‐Coupled Electron Transfer in Pd‐Catalyzed Benzaldehyde Hydrogenation

et al. 2019

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“…They found that the higher reaction rate is attributed to weakening of the hydrogen binding energy on the metal surface with decreasing pH. [34] Comparing the catalytic results with the ones reported in literature (Table 1), commercial Pd/AC 5 % in our operating conditions shows good catalytic performance during both Na-Muc and t,t-MA hydrogenation. Low pressure and temperature allowed to reach full conversion and high AdA yield avoiding the use of pressurized hydrogen, which is a matter of concern for industrial safety reasons.…”

Section: Hydrogenation Of Transtrans Muconic Acidsupporting

confidence: 73%

“…reported the same catalytic behavior during phenol hydrogenation. They found that the higher reaction rate is attributed to weakening of the hydrogen binding energy on the metal surface with decreasing pH …”

Section: Resultsmentioning

confidence: 99%

Bio Adipic Acid Production from Sodium Muconate and Muconic Acid: A Comparison of two Systems

et al. 2019

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sodium muconate and trans,trans‐muconic acid were heterogeneously hydrogenated to adipic acid, a strategic intermediate for the industry of polyamides and high performance polymers. Hydrogen pressure, metal to substrate ratio, substrate concentration and reaction temperature were varied to study the effect of these parameters on the reaction products. Commercial Pd/AC 5 % was used as catalyst and characterized by TEM, BET and XPS analyses. The results revealed that temperature is the parameter which mainly affect the reaction. Moreover, hydrogenation of trans,trans‐muconic acid is faster than sodium muconate reduction. Full conversion and full yield toward adipic acid was obtained using trans,trans‐muconic acid as substrate after 60 min at the following operating conditions: temperature=70 °C, metal/substrate=1/200 (molPd/molsub), trans,trans‐muconic acid concentration=1.42E‐02M and hydrogen pressure=1 bar. In all reactions (2E)hexenedioic acid was detected as main intermediate.

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“…For example, during the hydrogenation of maleic acid at a wired Pt–water interface, changes in rate with H 2 pressure were attributed to spontaneous electrical polarization, without accounting for changes in chemical driving force (i.e., the H 2 reaction order). 46 Likewise, pH-dependent CO oxidation 47 , 48 and phenol hydrogenation 49 rates were indirectly attributed to spontaneous polarization on the basis of shifts in the CO infrared spectrum and molecular dynamics simulations, respectively, but could not rule out contributions from chemical pH effects. Thus, it remains unclear whether spontaneous electrical polarization indeed plays a role in liquid-phase thermochemical heterogeneous catalysis.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous Electric Fields Play a Key Role in Thermochemical Catalysis at Metal−Liquid Interfaces

2021

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Large oriented electric fields spontaneously arise at all solid–liquid interfaces via the exchange of ions and/or electrons with the solution. Although intrinsic electric fields are known to play an important role in molecular and biological catalysis, the role of spontaneous polarization in heterogeneous thermocatalysis remains unclear because the catalysts employed are typically disconnected from an external circuit, which makes it difficult to monitor or control the degree of electrical polarization of the surface. Here, we address this knowledge gap by developing general methods for wirelessly monitoring and controlling spontaneous electrical polarization at conductive catalysts dispersed in liquid media. By combining electrochemical and spectroscopic measurements, we demonstrate that proton and electron transfer from solution controllably, spontaneously, and wirelessly polarize Pt surfaces during thermochemical catalysis. We employ liquid-phase ethylene hydrogenation on a Pt/C catalyst as a thermochemical probe reaction and observe that the rate of this nonpolar hydrogenation reaction is significantly influenced by spontaneous electric fields generated by both interfacial proton transfer in water and interfacial electron transfer from organometallic redox buffers in a polar aprotic ortho -difluorobenzene solvent. Across these vastly disparate reaction media, we observe quantitatively similar scaling of ethylene hydrogenation rates with the Pt open-circuit electrochemical potential ( E OCP ). These results isolate the role of interfacial electrostatic effects from medium-specific chemical interactions and establish that spontaneous interfacial electric fields play a critical role in liquid-phase heterogeneous catalysis. Consequently, E OCP —a generally overlooked parameter in heterogeneous catalysis—warrants consideration in mechanistic studies of thermochemical reactions at solid–liquid interfaces, alongside chemical factors such as temperature, reactant activities, and catalyst structure. Indeed, this work establishes the experimental and conceptual foundation for harnessing electric fields to both elucidate surface chemistry and manipulate preparative thermochemical catalysis.

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Impact of pH on Aqueous-Phase Phenol Hydrogenation Catalyzed by Carbon-Supported Pt and Rh

Cited by 59 publications

References 66 publications

Electrochemically Tunable Proton‐Coupled Electron Transfer in Pd‐Catalyzed Benzaldehyde Hydrogenation

Electrochemically Tunable Proton‐Coupled Electron Transfer in Pd‐Catalyzed Benzaldehyde Hydrogenation

Bio Adipic Acid Production from Sodium Muconate and Muconic Acid: A Comparison of two Systems

Spontaneous Electric Fields Play a Key Role in Thermochemical Catalysis at Metal−Liquid Interfaces

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