Chlorination semibatch reactors

Solution From the kinetic expressions given in Example 7.3, it can be concluded that n/ri = k Clca. In order to increase the selectivity of the reactions, the Clcii should be minimized. A semibatch reactor would thus be preferred, in which BA is charged at the beginning of the batch and CL fed continuously during the reaction. In any case, charging all of the chlorine at the beginning of the reaction will be impractical. 

In many organic substitution reactions, the product generated by the reaction is prone to additional substitution. A semibatch reactor was used to produce monochlorobenzene by reacting benzene with chlorine. The reactor was charged with 20 mol of liquid benzene. A stream of gaseous chlorine bubbled through the liquid, and the chlorine not reacted upon was recycled. During the operation, monochlorobenzene reacted with the chlorine to produce dichlorobenzene, and the dichlorobenzene reacted with the chlorine to produce trichlorobenzene ... 

Van de Vusse [16, 17] also performed experiments on the chlorination of n-decane, a reaction system of the type considered here, in a semibatch reactor. In such a reactor the chlorine gas is bubbled continuously through a batch of n-decane. In some experiments the n-decane was pure, in others it was diluted with dichlorobenzene. In some experiments the batch was stirred, in others not. The experimental results could be explained in terms of the above considerations. In all experiments y > 1 (from 150 to 500), hence the rate of the process was limited by diffusion, but the selectivity was only affected when Cgo/C i < y. This condition was only fulfilled for the experiments in which n-decane (B) was diluted. For only these experiments were the selectivities in nonstirred conditions found to differ from those with stirring. 

Van de Vusse [1966 a, b] also performed experiments on the chlorination of. n-decane, with a reaction scheme of the type considered here, in a semibatch reactor. In such a reactor the chlorine gas is bubbled continuously through a batch of /2-decane. In some experiments the /2-decane was pure, in others it was diluted with dichlorobenzene. In some experiments the batch was stirred, in others not. 

Chlorination of butanoic acid to a-monochloro- and a,a-dichlorobutanoic acid was studied on the laboratory scale in a semibatch reactor ... 

The selective a-chlorination of propionic acid was achieved by heating the acid with a mixture of chlorine, chlorosulfonic acid and oxygen in a semibatch reactor at 70-110 °C. The kinetics of the chlorination were autocatalytic, when the concentration of the chlorosulfonic acid catalyst was kept constant. The primary product was sulfopropionic acid and the autocatalytic kinetics were explained by a mechanism involving acid-catalysed enolization of the key intermediate, propanoyl chloride, as the rate-determining step. ° ... 

Example 14.1 Consider again the chlorination reaction in Example 7.3. This was examined as a continuous process. Now assume it is carried out in batch or semibatch mode. The same reactor model will be used as in Example 7.3. The liquid feed of butanoic acid is 13.3 kmol. The butanoic acid and chlorine addition rates and the temperature profile need to be optimized simultaneously through the batch, and the batch time optimized. The reaction takes place isobarically at 10 bar. The upper and lower temperature bounds are 50°C and 150°C respectively. Assume the reactor vessel to be perfectly mixed and assume that the batch operation can be modeled as a series of mixed-flow reactors. The objective is to maximize the fractional yield of a-monochlorobutanoic acid with respect to butanoic acid. Specialized software is required to perform the calculations, in this case using simulated annealing3. 

Conventional mechanically agitated gas-liquid reactors, wherein gas and liquid make contact in batch, semibatch, or continuous mode, are widely used in processes involving chlorination, sulfonation, hydrogenation, selective absorptions in amine solutions, etc. (Doraiswamy and Sharma, 1984). These reactors are popular for laboratory studies because of their simplicity in construction and low cost. As a rule of thumb with noncorrosive liquids, the mechanically agitated reactor is most economical when the overall reaction rate is five times greater than the mass transfer rate in a bubble column. If a... 

Example 2-8 Benzene is chlorinated in the liquid phase in a kettle-type reactor operated on a semibatch basis i.e., the reactor is initially charged with liquid benzene, and then chlorine gas is bubbled into the well-agitated solution. The reactor is equipped with a reflux condenser which will condense the benzene and chlorinated products but will not interfere with the removal of hydrogen,chloride. Assume that the chlorine is added sufiiciently slowly that (1) the chlorine and hydrogen chloride concentrations in the liquid phase are small and (2) all the chlorine reacts. 

Semibatch Operation In semibatch operation the rates of mass flow into and out of the system are unequal (see Fig. 3-1 c). For example, benzene may be chlorinated in a stirred-tank reactor by first adding the charge of liquid benzene and catalyst and then continuously adding chlorine gas until the required ratio of chlorine to benzene has been obtained. Operation of this kind is. batch from the standpoint that the composition of the reaction mixture changes with time. However, from a process standpoint the chlorine is added continuously. The system is still an ideal stirred-tank reactor if the... 

There are many examples of hydrogenations, oxidations, and chlorinations that are carried out in stirred tank reactors, either batch, semibatch, or continuous. 

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