Journal of Applied Electrochemistry

, Volume 16, Issue 6, pp 851–866 | Cite as

Selectivity analysis in electrochemical reactors. II. Engineering models of a batch reactor with a complex reaction sequence

  • L. Weise
  • G. Valentin
  • A. Storck
Article

Abstract

This paper presents a mathematical model of a batch stirred-tank electrochemical reactor where a required cathodic reduction reaction is coupled with a complex reaction sequence between the reactant and the key product. The set of coupled, non-linear differential equations is solved numerically and simple dimensionless quantities characterizing the cell performance and selectivity are derived. The experimental results presented in Part I of this paper are found to be in excellent agreement with the model. In the particular case where the homogeneous chemical reactions may be neglected in the cathodic diffusion boundary layer, a simplified analytical expression of the process selectivity is proposed. This quantifies the effects of the operating conditions by means of a single dimensionless criterion.

Keywords

Boundary Layer Reduction Reaction Electrochemical Reactor Batch Reactor Cell Performance 

Nomenclature

Ae

electrode area

ae

specific electrode area

CA,CB,CC

molar concentrations of species A, B, C

CAS,CBS,CCS

bulk molar concentrations

CAO

initial concentration of species A

CA+,CB+

reduced concentrations (with respect toCAS-section 2)

CAO+,CBO+

reduced concentrations (with respect toCAO)

CBS*

=CBS/CAS

CAS, i+;CBS, i+

bulk concentrations in thei th reactor normalized with respect toCAO

DA,DB

molecular diffusion coefficients

DB+

=DB/DA

E

electrode potential

F

Faraday's constant

Ha0,Ha

Hatta numbers defined with respect toCAO orCAS

i

current density

iL

limiting current density

i*

dimensionless current density (Equation 6)

kci

chemical rate constants involved in scheme I

kc

chemical rate constant of scheme II

kd

mass transfer coefficient

K1,K2

dimensionless parameters defined in Equation 13

K

dimensionless parameter defined in Equation 17

N

impeller rotation speed

Qv

volumetric flowrate

ri

chemical reaction rate

RA

conversion factor of species A

S

product selectivity

T

temperature

t

time

t+

dimensionless time=t(kdae)

V

volume of catholyte

XA,XB,XC

molar fractions, i.e.CAS/CAO;CBS/CAO;CCS/CAO

y

coordinate perpendicular to the electrode

y+

reduced coordinate=y

ve

number of electrons involved in the reduction

τ

space time

Subscripts

f

final

L

limiting

0

initial (time=0)

S

in the bulk of the electrolyte

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References

  1. [1]
    L. Weise, G. Valentin and A. Storck,J. Appl. Electrochem. 16 (1986) 836.Google Scholar
  2. [2]
    R. C. Alkire and J. D. Lisius,J. Electrochem. Soc. 132 (1985) 1879.Google Scholar
  3. [3]
    P. V. Danckwerts, ‘Gas-Liquid Reactions’, Mc-Graw Hill, New York (1970).Google Scholar
  4. [4]
    J. C. Charpentier and G. Wild, ‘Absorption avec réaction chimique’, Technique de l'Ingénieur, J2640-12, Paris (1983).Google Scholar
  5. [5]
    W. H. Ray and J. Szekely, ‘Process Optimization’, John Wiley and Sons, New York (1983).Google Scholar
  6. [6]
    J. Villermaux, ‘Génie de la Réaction Chimique’, Technique et Documentation, Lavoisier, Paris (1982).Google Scholar

Copyright information

© Chapman and Hall Ltd. 1986

Authors and Affiliations

  • L. Weise
    • 1
  • G. Valentin
    • 1
  • A. Storck
    • 1
  1. 1.Laboratoire des Sciences du Génie ChimiqueCNRS-ENSICNancy CedexFrance

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