Mixing and product distribution for a liquid‐phase, second‐order, competitive‐consecutive reaction

Abstract Mixing effects for the homogeneous, liquid‐phase, second‐order, competitive‐consecutive reaction of iodine ( B ) with L‐tyrosine ( A ) to form 3‐iodo‐L‐tyrosine ( R ) and 3,5‐diiodo‐L‐tyrosine ( S ) were determined for the following conditions: vessel volume, 5 and 36 liters (baffled and unbaffled); turbine diameter (2 to 6 in.) and speed (95 to 1,600 r.p.m.); feed inlet locations (3), addition rate (0.25 to 18 min.), and distribution; temperature (11° to 43°C.); initial A concentration (0.1 to 0.4 g.‐mole/liter); and kinematic viscosity (0.765 to 6.35 centistokes). A was initially charged to the reactor and an equimolar quantity of feed B was added over a time period. Yields of R are less than that expected for perfect mixing owing to local regions of excess B concentration that exist for time periods during which R over‐reacts to S . Agitation power for a given yield is less in unbaffled vessels without an air‐liquid interface than for baffled vessels. The local fluctuating velocity u ′ where feed is introduced correlates the mixing variables and predicts mixing requirements for maintaining yields of R on scale‐up. Regions of excess B concentration are related to a concept of partial segregation. The extent of reaction occurring under this condition is correlated by the dimensionless group ( k 1 b τ) ( a 0 / b ), where τ is a microtime scale of mixing related to u ′ and the characteristic length of a microscale eddy. The magnitude of this group provides a criterion for predicting the importance of mixing effects on other reaction systems.