Common pitfalls in chemical actinometry

Wriedt, Benjamin; Ziegenbalg, Dirk

doi:10.1007/s41981-019-00072-7

Cited by 41 publications

(55 citation statements)

References 33 publications

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“…It is important to mention that when the total liquid volume in the reactor, V liquid , was estimated using the gas fraction, β G , the volume was underestimated for all flow conditions [Eq. (10)…”

Section: Prediction Of the Photon Flux Per Liquid Volumementioning

confidence: 99%

Photon Transport and Hydrodynamics in Gas‐Liquid Flows Part 1: Characterization of Taylor Flow in a Photo Microreactor

2020

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Gas-liquid photoreactions are increasingly implemented in microreactors. Taylor flows containing an inert dispersed phase were previously used to increase the conversion of photochemical reactions in comparison to using a single liquid phase. However, identifying the optimal flow conditions requires an extensive experimental effort. This work aims to understand the photon transport and hydrodynamics in a Taylor flow photo microreactor so that the reactor behavior can be understood and predicted. Chemical actinometry, flow imaging and residence time distribution experiments were used to develop a multi-region photochemical reaction model. This model shows that the conversion is significantly affected by the liquid distribution, and not by the light scattering or liquid mixing. Moreover, an empirical relation was proposed to predict the optical pathlength in gas-liquid flows. The knowledge gained in this study helps to optimize the performance of Taylor flow photo microreactors, but also to design improved multiphase flow photochemical systems.

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Section: Prediction Of the Photon Flux Per Liquid Volumementioning

confidence: 99%

Photon Transport and Hydrodynamics in Gas‐Liquid Flows Part 1: Characterization of Taylor Flow in a Photo Microreactor

2020

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“…[8,9,35] Furthermore, a potential influence of the pH value at the applied experimental conditions could be ruled out according to a former investigation. [32] Consequently, this parameter is unlikely to cause the observed inconsistencies.…”

Section: Resultsmentioning

confidence: 98%

“…To overcome pitfalls leading to systematic errors during the measurements, a revised general working procedure was recently published. [32] The procedure is split in three main parts. The preliminary considerations consist of a verification of the physical and chemical properties, data acquisition of the reactor setup, adjustments of the absorption fraction within the experimental limits and the actinometer preparation.…”

Section: Systematic Inaccuraciesmentioning

confidence: 99%

Application Limits of the Ferrioxalate Actinometer

Wriedt¹,

Ziegenbalg²

2021

Preprint

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<div>Evaluating the efficiency of newly designed photoreactors is crucial for systematic development and optimization of photochemical processes. A suitable tool is actinometry, prominently represented by the most widely studied and applied ferrioxalate system. However, such measurements show reproducible problems in the data consistency. This study scrutinizes these issues and approaches an experimental elucidation. An application limit for the ferrioxalate actinometer under intense irradiation was identified and experimentally validated. A drop of the quantum yield at high incident photon fluxes, generating high local concentrations of carboxyl radicals, leads to systematically wrong measurements. For reliable measurements with the ferrioxalate actinometry, a continuous operation mode or extensive mixing should be ensured.</div>

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“…Actinometric measurements were conducted with the ferrioxalate actinometer according to literature. [54,55] Firstly a 0.04mol L −1 ferrioxalate solution was prepared by dissolving iron(III)chloride and potassium oxalate monohydrate in a 0.05mol L −1 aqueous solution of sulfuric acid. 160 mL of the actinometer solution were transferred to the reservoir of the reactor and pumped through the system.…”

Section: Methodsmentioning

confidence: 99%

Imposed dynamic irradiation to intensify photocatalytic reactions

2021

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Dynamic irradiation is a potent option to influence the interaction between photochemical reactions and mass transport to design high performant and efficient photochemical processes. To systematically investigate the impact of this parameter, the photocatalytic reduction of nitrobenzene was conducted as a test reaction. Dynamic irradiation was realized through provoked secondary flow patterns, multiple spatially distributed light emitting diodes (LEDs) and electrical pulsation of LEDs. A combined experimental and theoretical approach revealed significant potential to enhance photochemical processes. The reaction rate was accelerated by more than 70% and even more important the photonic efficiency was increased by more than a factor of 4. This renders imposed dynamic irradiation an innovative and powerful tool to intensify photoreactions on the avenue to large scale sustainable photochemical processes.

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Common pitfalls in chemical actinometry

Cited by 41 publications

References 33 publications

Photon Transport and Hydrodynamics in Gas‐Liquid Flows Part 1: Characterization of Taylor Flow in a Photo Microreactor

Photon Transport and Hydrodynamics in Gas‐Liquid Flows Part 1: Characterization of Taylor Flow in a Photo Microreactor

Application Limits of the Ferrioxalate Actinometer

Imposed dynamic irradiation to intensify photocatalytic reactions

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