Real-Time Raman Monitoring during Photocatalytic Epoxidation of Cyclohexene over V-Ti/MCM-41 Catalysts

Chan, Hsiang Yu; Wu, Jeffrey C.S.; Casilda, Vanesa Calvino; Bañares, Miguel Á.; Bai, Hsun-Ling

doi:10.3390/catal5020518

Cited by 14 publications

(9 citation statements)

References 35 publications

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“…When excess epoxide was present it was possible to isolate essentially pure cyclohexene oxide by simple decantation (see the Supporting Information). Unreacted acetophenone and the ester group were indicated by the carbonyl stretches 1683 and 1690 cm –1 of ketone and ester groups, respectively (Figure c,d). ,− It is evident from these data that aqueous DMAB can be used as a selective reducing agent for saturated aliphatic carbonyl compounds in the presence of conjugated carbonyl compounds, aryl alkyl ketones, and epoxides.…”

Section: Results and Discussionmentioning

confidence: 99%

Real-Time Monitoring of Aqueous Organic Reduction Reactions Using Ex Situ Fiber Optic Raman Spectroscopy

Amberchan

Allen

Golden

et al. 2021

ACS Sustainable Chem. Eng.

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Here, we demonstrate the use of Raman spectroscopy for real-time monitoring and analysis of the reduction of nitroarenes and ketones in an aqueous medium using an external fiber optic probe. In one case, the catalytic reduction of nitroarenes using hydrazine hydrate and a nickel boron composite catalyst was studied by monitoring the disappearance of the distinct nitro stretching frequency at 1350 cm–1. Quantitative Raman spectroscopic techniques showed that the aqueous reduction reaction proceeds with pseudo-first-order kinetics. The biphasic reduction of cyclic ketones by aqueous dimethylamine borane (DMAB) was also examined. A nonpolar carbonyl compound and aqueous DMAB were mixed and an external Raman probe monitored the loss of the starting material via the carbonyl stretch at 1713 cm–1 in the top organic phase. We also found that saturated aliphatic carbonyl compounds were reduced much faster than α,β-unsaturated and aromatic carbonyl compounds. Additionally, DMAB was found to be unreactive toward epoxides and esters, allowing for selective reduction of aliphatic ketones. Density functional theory analysis suggests that carbonyl reduction occurred through a dissociation mechanism followed by a concerted hydride transfer pathway.

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Section: Results and Discussionmentioning

confidence: 99%

Real-Time Monitoring of Aqueous Organic Reduction Reactions Using Ex Situ Fiber Optic Raman Spectroscopy

Amberchan

Allen

Golden

et al. 2021

ACS Sustainable Chem. Eng.

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“…For example, M. A. Bañares et al [90] studied the photocatalytic epoxidation of cyclohexane in the presence of ter-butyl hydroperoxide (t-BuOOH) over VxTiy/MCM-41 catalyst under UV-light using the real-time NIR-Raman spectroscopy. In the experimental set-up (Fig.…”

Section: Operando Raman For Investigating Photocatalysis In Liquid-phasementioning

confidence: 99%

In situ and Operando Spectroscopies in Photocatalysis: Powerful Techniques for a Better Understanding of the Performance and the Reaction Mechanism

et al. 2022

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In photocatalysis, a set of elemental steps are involved together at different time scales to govern the overall efficiency of the process. These steps are divided as follow: 1) photon absorption and excitation (in femtoseconds), 2) charge separation (femto-to picoseconds), 3) charge carrier diffusion/transport (nano-to microseconds), 4 & 5) reactant activation/conversion and mass transfer (micro-to milliseconds). The identification and quantification of these steps, using the appropriate tool/technique, can provide the guidelines to emphasize the most influential key parameter that improve the overall efficiency and to develop the "photocatalyst by design" concept. In this review, the identification/quantification of reactant activation/conversion and mass transfer (steps 4&5) is discussed in details using the in-situ/operando techniques, especially the infrared (IR), Raman and XAS spectroscopy. The use of these techniques in photocatalysis was highlighted by the most recent and conclusive case studies which allow a better characterization of the active site and revealing the reaction pathways in order to establish a structureperformance relationship. In each case study, the reaction conditions and the reactor design for photocatalysis (pressure, temperature, concentration, etc.) were thoroughly discussed. In the last part, some examples in the use of time-resolved techniques (time-resolved FTIR, photoluminescence and transient absorption) are also presented as an author's guideline to study the elemental steps in photocatalysis at shorter time scale (ps, ns and µs).

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“…In accordance with the SciFinder data, for instance, operando Raman spectroscopy has triggered researchers high attention (by Oct. 2015, 187 papers included) because of the following factor: (1) it is sensitive to a tiny modification of the structure; (2) the Raman signal is less affected by the presence of H2O and other gases; (3) it could be operated in a broad temperature range 25~1000 ºC and pressure range 0.1~10.0 MPa. Using operando NIR-Raman, Banares and co-workers have studied the photocatalytic epoxidation of cyclohexene over V-based catalysts and revealed that the cyclohexene was directly photo-epoxidized to 1,2-epoxycyclohexane by t-BuOOH during the reaction [34]. Li's group has monitored the synthesis process of various catalytic materials, such as Fe-, V-, Mo-based and zeolite catalysts and so on, using operando UV-Raman [35].…”

Section: Monitoring Catalytic Reactions Using Operando Spectroscopymentioning

confidence: 99%

Application of operando spectroscopy on catalytic reactions

Zhang

et al. 2016

Current Opinion in Chemical Engineering

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This mini-review summarizes the use of operando spectroscopy to investigate the dynamic structure of heterogeneous catalysts under working conditions. Following the background to the development of operando spectroscopy, we briefly reviewed the latest highlight on this subject. Then, two challenging but attention-grabbing techniques, i.e. operando techniques under the harsh conditions and the integration of operando techniques in a unit cell, were introduced. Likely, Operando techniques open up new vistas to explore reaction mechanisms and help us design the next generation industrial catalysts

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Real-Time Raman Monitoring during Photocatalytic Epoxidation of Cyclohexene over V-Ti/MCM-41 Catalysts

Cited by 14 publications

References 35 publications

Real-Time Monitoring of Aqueous Organic Reduction Reactions Using Ex Situ Fiber Optic Raman Spectroscopy

Real-Time Monitoring of Aqueous Organic Reduction Reactions Using Ex Situ Fiber Optic Raman Spectroscopy

In situ and Operando Spectroscopies in Photocatalysis: Powerful Techniques for a Better Understanding of the Performance and the Reaction Mechanism

Application of operando spectroscopy on catalytic reactions

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