Effect Of Micro-Mixing On The Yield Of Intermediates In Triplet Consecu Tive/Competi Tive Reactions
Publication Type
Original research
  • Amer M. El-Hamouz
  • Reginald Mann

Micro-mixing calculations based upon a simplified non-deforming one-dimensional diffusion-reaction formulation are presented for the sequence of three reactions denoted by A + B - R + B - S + B + T. This triplet reaction under micro-mixing is posed as five simultaneous parabolic partial differential equations which have been solved using a general purpose NAG library algorithm. The primary product R has an improved yield under perfect mixing conditions. The ultimate product T is shown to be always favoured by the perfect segregation of micro-mixing. By contrast, the central intermediate S gives high yields under micro-mixing at low conversions, but perfect mixing is preferable at higher conversions. In addition, predictions show that yield improvements for S might be possible by an engineered stretching of fluid lamellae and by the combination of micro-mixing followed by perfect mixing, especially at intermediate levels of conversion. The calculations are relevant to multi-step halogenations and they help to explain how the anomolous appearance of a tri-halogenated species ahead of mono- and di-halogenated ones in a stirred vessel can be attributed to micro-mixing. Des calculs de micromClange s’appuyant sur une formulation de diffusion-reaction unidimensionnelle non dCformante simplifike sont present& pour une sCquence de trois reactions notees par A + B - R + B + S + B - T. En micromClange, ce triplet s’exprime sous la forme de cinq Cquations diffkrentielles partielles paraboliques simultanCes qui ont CtC rCsolues au moyen d’un algorithme gCnCral de la bibliothkque NAG. Le produit primaire R a un rendement amCliorC dans des conditions de mClange parfaites. On montre que le produit final T est toujours favoris6 par la sCgrCgation parfaite du micromClange. A I’opposC, le rendement en produit intermediaire S est trbs ClevC pour un micromt5lanage B faible conversion, mais un melange parfait est preferable B une conversion ClevCe. De plus, les prCdictions montrent que des arnCliorations du rendement en S pourraient &tre possibles par un Ctirement des lamelles de fluide et par la combinaison d’un micromClange suivi d’un mClange parfait, particulikrement aux niveaux intermkdiaires de conversion. Ces calculs sont pertinents pour les halogdnations multiCtagCes et aident i expliquer comment l’apparence anormale d’une espkce trihalogCnCe devant des espkces mono et dihalogCnCes dans un rkservoir agitC peut &tre attribuie au micromelange.

The Canadian Journal of Chemical Engineering, Volume 76, Issue 3, pages 650–656, June 1998
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