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Journal of Applied Electrochemistry

, Volume 42, Issue 9, pp 667–677 | Cite as

Design and optimization of electrochemical microreactors for continuous electrosynthesis

  • C. Renault
  • J. Roche
  • M. R. Ciumag
  • T. Tzedakis
  • S. Colin
  • K. Serrano
  • O. Reynes
  • C. André-Barrès
  • P. Winterton
Original Paper

Abstract

The study focuses on the design and construction, as well as the theoretical and experimental optimization of electrochemical filter press microreactors for the electrosynthesis of molecules with a high added value. The main characteristics of these devices are firstly a high-specific electrochemical area to increase conversion and selectivity, and secondly the shape and size of the microchannels designed for a uniform residence time distribution of the fluid. A heat exchanger is integrated into the microstructured electrode to rapidly remove (or supply) the heat required in exo- or endothermic reactions. The microreactors designed are used to perform-specific electrosynthesis reactions such as thermodynamically unfavorable reactions (continuous NADH regeneration), or reactions with high enthalpy changes.

Keywords

Electrochemistry Microreactors Electrosynthesis Fluorination NADH regeneration Optimization Simulation POISEUILLE Pressure drop 

List of symbols

C or c

Concentration (mol L−1)

Cp

Heat capacity of the coolant EG (2,400 J·kg−1·K−1)

Cp,j

Specific heat of each reactant or product j

D

Diffusion coefficient (m² s−1)

DG

Deoxy-d-glucose

DME

Dimethoxyethane

E

Potential (V)

Eelect. E exch.

Electrical and exchanged energy, respectively

EG

Ethylene glycol

ebl

Thickness of the metallic fin of the heat exchanger (m)

Et3N·3HF/TEAHF

Triethylamine trihydrofluoride

F

Faraday constant (96,485 C mol−1)

F°

Molar flux at the input and the output of the microreactor

FAD/FADH2

Flavin redox mediator (oxidized and reduced forms)

FDH

Formate dehydrogenase enzyme

FDG

Fluoro-deoxy-d-glucose

g

Acceleration due to gravity 9.80665 m s−2

h

Convective exchange coefficient of the coolant (W m−2 K−1)

i

Current density (A m−2)

k

Mass transfer coefficient (m s−1)

K

Equilibrium constant

kcat

Rate of the enzyme catalyzed reaction (s−1)

Km,j

Michaelis–Menten constants (L−1 mol−1)

L

Length of the considered “reactive” channel or microchannel segment (m)

Lbl

Length of the metallic fin of the heat exchanger (m)

n

Electron number

nμ

Number of microchannels on the plate

NAD+/NADH

Nicotinamide dinucleotide pyridinic cofactor (oxidized and reduced forms)

Nu

Nusselt number (Nu = hL bl/λ)

p

Pressure (Pa)

pexch

Overall perimeter of the fin section (m)

Po

Poiseuille number

Q

Charge (F mol−1)

Qv

Volumetric flow rate (m3 s−1)

R

Universal gas constant (8.31 J mol−1 K−1)

I

Current (A)

rj

Rate of homogeneous reactions (mol m−3 s−1)

rχR

Rate of chemical reaction (mol m−3 s−1)

S

Cross-section area of the flow channel (m2)

Sa

Electrode active surface area (m2)

Sexch

Total surface area of all the fins (m2)

t

Time (s)

T

Absolute temperature (K)

TBAP

Bu4NClO4

uEG

Coolant velocity (0.02 m·s−1)

VEC

Electrolytic compartment volume (m3)

X

Conversion of the limiting reagent

x, y, z

Axis coordinate

Δf\( H_{j}^{ \circ } \)

Standard formation enthalpy of the species j (J mol−1)

ΔRH°

Standard reaction enthalpy (J mol−1)

ΔRG°

Standard reaction-free enthalpy (J mol−1)

ΔP

Pressure drop (Pa)

ΔV

Cell voltage (V)

θ

Opening angle of the distributing and/or collecting channels (°)

λ

Coolant thermal conductivity (W m−1 K−1)

μ

Dynamic viscosity Pa s)

νj

Stoichiometric coefficient

ρ

Specific gravity of the coolant (1,109 kg·m−3)

τ

Residence time in the reactor (s)

\( \overrightarrow {\upsilon } \)

Fluid velocity (m s−1)

ϕ

Heat flux (J s−1)

Notes

Acknowledgments

We would like to thank P. Cognet from the LGC for his helpful discussions.

References

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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • C. Renault
    • 2
  • J. Roche
    • 1
  • M. R. Ciumag
    • 1
  • T. Tzedakis
    • 1
  • S. Colin
    • 3
  • K. Serrano
    • 1
  • O. Reynes
    • 1
  • C. André-Barrès
    • 4
  • P. Winterton
    • 5
  1. 1.Laboratoire de Génie ChimiqueUniversité de Toulouse, UPSToulouseFrance
  2. 2.Laboratoire de Génie ChimiqueUniversité de Toulouse, INP-ENSIACETToulouseFrance
  3. 3.Université de Toulouse; INSA, UPS, Mines Albi, ISAE; ICA (Institut Clément Ader)ToulouseFrance
  4. 4.Laboratoire de Synthèse et Physicochimie des molécules d’intérêt biologiqueUniversité de Toulouse, UPSToulouseFrance
  5. 5.Département Langues & GestionUniversité de Toulouse, UPSToulouseFrance

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