(730g) Modeling of Mandelic Acid From Benzaldehyde by Phase Transfer Catalysis

Process Modeling of Mandelic Acid from Benzaldehyde by Phase Transfer Catalysis

            Mandelic acid is an important ingredient in urinary antiseptic medicines. Further, its cosmeceutical and antibacterial activities make it a product of considerable commercial significance. 

An attractive process for the production of Mandelic Acid is through reaction between Benzaldehyde and Sodium Hydroxide and Chloroform in the presence of Polyethylene Glycol 4000, a phase transfer catalyst. The reaction is represented by

                                 +                                                 

                                  (NaOH)                (Benzaldehyde)                                      (Mandelic Acid)            

                                         +                                  

                                                                             (Benzoic Acid)

We address the modeling of a well-stirred reactor for the foregoing process in which drops of organic (hexane) droplets (containing benzaldehyde) with catalyst coating on their surfaces are suspended in aqueous phase containing sodium hydroxide. The organic droplets are assumed to coalesce and redisperse, maintaining an exponential equilibrium distribution as found by Bajpai et al. (1977). Further, the drops are assumed to be rigid with diffusion of benzaldehyde from the droplet interior to the catalyst at the periphery for reaction to mandelic acid and a small amount to benzoic acid. A population balance model is formulated and solved by Monte Carlo simulation to assess the role of transport and drop-mixing on conversion and selectivity to mandelic acid. Intrinsic reaction kinetics is extracted from experiments in diffusion-reaction cells (see figure alongside) with the aqueous and organic phases in stagnant layers or with mild stirring of the organic layer.

Our presentation will display conversion and selectivity of the reactor under various conditions obtained from model simulations as well as experiments.