scholarly journals Application Limits of the Ferrioxalate Actinometer

2021 ◽  
Author(s):  
Benjamin Wriedt ◽  
Dirk Ziegenbalg
Keyword(s):  
Quantum Yield ◽  
Operation Mode ◽  
Continuous Operation ◽  
Data Consistency ◽  
Incident Photon ◽  
Photochemical Processes ◽  
Suitable Tool ◽  
Systematic Development ◽  
Application Limit

<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>

scholarly journals Application Limits of the Ferrioxalate Actinometer

2021 ◽  
Author(s):  
Benjamin Wriedt ◽  
Dirk Ziegenbalg
Keyword(s):  
Quantum Yield ◽  
Operation Mode ◽  
Continuous Operation ◽  
Data Consistency ◽  
Incident Photon ◽  
Photochemical Processes ◽  
Suitable Tool ◽  
Systematic Development ◽  
Application Limit

<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>

scholarly journals Industrial Production of Poly-β-hydroxybutyrate from CO2: Can Cyanobacteria Meet this Challenge?

Processes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 323 ◽  
Author(s):  
Roberta Carpine ◽  
Giuseppe Olivieri ◽  
Klaas J. Hellingwerf ◽  
Antonino Pollio ◽  
Antonio Marzocchella
Keyword(s):  
Low Cost ◽  
Operation Mode ◽  
Commercial Production ◽  
Continuous Operation ◽  
Attractive Alternative ◽  
Bacterial Fermentation ◽  
Plastic Materials ◽  
Phb Production ◽  
Global Concern ◽  
Environmentally Friendly Process

The increasing impact of plastic materials on the environment is a growing global concern. In regards to this circumstance, it is a major challenge to find new sources for the production of bioplastics. Poly-β-hydroxybutyrate (PHB) is characterized by interesting features that draw attention for research and commercial ventures. Indeed, PHB is eco-friendly, biodegradable, and biocompatible. Bacterial fermentation processes are a known route to produce PHB. However, the production of PHB through the chemoheterotrophic bacterial system is very expensive due to the high costs of the carbon source for the growth of the organism. On the contrary, the production of PHB through the photoautotrophic cyanobacterium system is considered an attractive alternative for a low-cost PHB production because of the inexpensive feedstock (CO2 and light). This paper regards the evaluation of four independent strategies to improve the PHB production by cyanobacteria: (i) the design of the medium; (ii) the genetic engineering to improve the PHB accumulation; (iii) the development of robust models as a tool to identify the bottleneck(s) of the PHB production to maximize the production; and (iv) the continuous operation mode in a photobioreactor for PHB production. The synergic effect of these strategies could address the design of the optimal PHB production process by cyanobacteria. A further limitation for the commercial production of PHB via the biotechnological route are the high costs related to the recovery of PHB granules. Therefore, a further challenge is to select a low-cost and environmentally friendly process to recover PHB from cyanobacteria.

scholarly journals The Steps from Batchwise to Continuous Crystallization for a Fine Chemical: A Case Study

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 542 ◽  
Author(s):  
Christian Melches ◽  
Hermann Plate ◽  
Jürgen Schürhoff ◽  
Robert Buchfink
Keyword(s):  
Crystal Size ◽  
Operation Mode ◽  
Continuous Operation ◽  
Industrial Plant ◽  
Fine Chemical ◽  
Industrial Implementation ◽  
Stepwise Development ◽  
Initial Idea ◽  
Definition Of

Many processes to produce fine chemicals and precursors of pharmaceuticals are still operated in batchwise mode. However, recently, more producers have taken a change to continuous operation mode into consideration, performing studies and trials on such a change, while some have even already exchanged their production mode from batchwise to continuous operation. In this paper, the stepwise development from an initial idea to industrial implementation via laboratory testing and confirmation is revealed through the example of an organic fine chemical from the perspective of a crystallization plant manufacturer. We begin with the definition of the objectives of the project and a brief explanation of the advantages of continuous operation and the associated product properties. The results of the laboratory tests, confirming the assumptions made upfront, are reported and discussed. Finally, the implementation of an industrial plant using a draft tube baffled (DTB) crystallizer and the final product properties are shown. Product properties such as crystal size distribution, crystal shape, related storage stability and flowability have successfully been improved.

The Charge Transfer Photochemistry of the Hexaaquoiron(III) Ion, the Chloropentaaquoiron(III) Ion, and the µ-Dihydroxo Dimer Explored with tert-Butyl Alcohol Scavenging

1975 ◽  
Vol 53 (16) ◽  
pp. 2430-2435 ◽  
Author(s):  
Cooper H. Langford ◽  
John H. Carey
Keyword(s):  
Charge Transfer ◽  
Quantum Yield ◽  
Butyl Alcohol ◽  
Extinction Coefficients ◽  
Photochemical Processes ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Radical Yield

There have been several studies of the charge transfer photochemistry of aqueous Fe3+ but the complexity of hydrolytic equilibria and the requirement for scavengers to render the primary photochemical processes observable has left several issues moot as recent reports show. Using tert-butyl alcohol as a scavenger, it is shown that (at 35 °C), charge transfer irradiation at 254 nm of Fe(OH2)63+ gives free •OH with a quantum yield of 0.065, charge transfer irradiation of Fe(OH2)5Cl2+ at 350 nm gives free Cl• with a quantum yield of 0.093, and that as a result of the combined patterns of extinction coefficients and hydrolytic equilibria it is difficult to make Fe(OH2)5OH + the main absorbing species at either wavelength. The dihydroxo-bridged dimer gives only a small radical yield. The scavenger, tert-butyl alcohol, appears to react with •OH or Cl• to give •CH2—C(CH3)2OH which, on reaction with a second Fe(OH2)63+ gives HOCH2C(CH3)2OH.

Spectral Dependencies of the Quantum Yield of Photochemical Processes on the Surface of Wide Band Gap Solids. 3. Gas/Solid Systems†

2000 ◽  
Vol 104 (14) ◽  
pp. 2989-2999 ◽  
Author(s):  
A. V. Emeline ◽  
G. N. Kuzmin ◽  
D. Purevdorj ◽  
V. K. Ryabchuk ◽  
N. Serpone
Keyword(s):  
Quantum Yield ◽  
Band Gap ◽  
Wide Band ◽  
Wide Band Gap ◽  
Photochemical Processes

The UV Photolysis (λ = 185 nm) of Liquid Methyl n-Propyl Ether

1975 ◽  
Vol 30 (5-6) ◽  
pp. 399-403 ◽  
Author(s):  
Heinz-Peter Schuchmann ◽  
Clemens von Sonntag
Keyword(s):  
Quantum Yield ◽  
Methyl Ether ◽  
Quantum Yields ◽  
Uv Photolysis ◽  
Photochemical Processes ◽  
Butyl Methyl Ether ◽  
Bond Splitting

The main products of the 185 nm photolysis of liquid methyl n-propyl ether (quantum yields in parentheses) are n-propanol (0.70), methane (0.29), sec-butyl methyl ether (0.20), methanol (0.16), propionaldehyde (0.13), 3,4-dimethoxyhexane (0.09), ethane (0.08), and ethyl n-propyl ether (0.08). The quantum yields of further 24 minor products have been measured. The quantum yield of the sum of primary photochemical processes, the main ones of which are the homolytic scissions of the C–O bonds (reactions i and ii), is close to unity.Reaction (i) is favoured over reaction (ii) by nearly a factor of five. The elimination of molecular methane (iii) is the only other process of importance. C–H and C–C bond splitting is marginal.

scholarly journals CFD Analysis of a Buffer Tank Redesigned with a Thermosyphon Concentrator Tube

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2162
Author(s):  
Miguel A. Gómez ◽  
Sergio Chapela ◽  
Joaquín Collazo ◽  
José L. Míguez
Keyword(s):  
Thermal Stratification ◽  
Operation Mode ◽  
Heating Time ◽  
Continuous Operation ◽  
Hot Water ◽  
Cfd Analysis ◽  
Domestic Hot Water ◽  
Buffer Tank ◽  
Opening And Closing ◽  
Heating Mode

This study analyzes a buffer tank simulated in both continuous operation mode and heating mode using CFD techniques. The analysis is focused in the thermal behavior of the tank, especially in parameters such as heat exchanged, heating time, and temperature distributions into the tank, in order to propose a better design. The results of the different simulations show that the tank heats water extremely slowly and extremely evenly when producing domestic hot water (DHW), which negatively affects the thermal stratification that is critical for rapidly reaching the DHW temperature. Therefore, the main problem of the tank is an inefficient heat exchange and a poor distribution of temperature. In order to overcome these operational limitations, a new design is proposed by installing a tube inside the tank that encloses the heating coil and sends hot water directly to the tank top region such that high-temperature DHW is rapidly provided, and thermal stratification is improved. Several simulations are performed with different open and closed configurations for the outlets of the inner tube. The different results show that the heating times significantly improve, and the time needed to reach the 45 °C set point temperature is reduced from 44 to 15 min. In addition, the simulations in which the opening and closing of the water outlets are regulated, the outlet DHW temperature is kept within 45–60 °C, which prevents overheating to unsafe use temperatures. Furthermore, the results of the simulation in continuous operation mode show a clear improvement of thermal stratification and an increase in the heat transmitted to the inside of the tank.

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