Chapter 14 - Fast competitive/consecutive (C/C) chemical reactions

Abstract

Acid/base neutralization in the presence of organic substrates is one the most common examples where inadequate feed blending (i.e., poor mixing) can promote undesired side reactions. The neutralization is the desired reaction; however, many organic species are very reactive under high concentrations of acid or base and under high feed concentration. Rapid mixing will promote the very fast neutralization reaction, whereas slow mixing will allow organic species, in the presence of acids or bases, to react by substitution or decomposition thereby producing side products. Fast competitive/consecutive (C/C) reaction systems are particularly prevalent in the pharmaceutical and specialty chemical industries. The technical literature contains myriad examples where inadequate mixing promotes the slow reaction in a C/C situation. The technical literature contains several examples of fast C/C chemical reaction systems encountered in the pharmaceutical industry. Two examples where feed blending was extremely important are mentioned as examples in this chapter (1) when polyacrylamide fouled the coolant tubes in a pigment binder reactor and (2) strong neutralization caustic caused dark color bodies in an alkyl polyglycoside reactor. The research covering the chemistry of parallel/consecutive reactions goes back to 1926; that body of research is covered here; the review of research work covering testing and modeling of C/C chemical reactions is included and the most important scale-up literature has been researched and summarized. The most appropriate design and scale-up protocols and techniques are recommended.