Application of catalytic distillation for the aldol condensation of acetone: the effect of the mass transfer and kinetic rates on the yield and selectivity

Abstract

We have recently developed a catalytic distillation (CD) process for the aldol condensation of acetone to produce diacetone alcohol (DAA) which undergoes subsequent dehydration to produce mesityl oxide (MO). A rate-based model consisting of mass, energy and component balances, rate expressions, equilibrium and summation (MECRES) equations has been proposed to predict the yield and selectivity for this CD process. In this paper, the Onda et al. mass transfer correlations previously used in the MECRES equations were replaced by a new overall vapour–liquid mass transfer correlation determined in our laboratory for the non-reactive section in our CD column. Good agreement between model predictions and experimental data for the yield of DAA, MO and the temperature profile in the CD column was obtained without using any scaling factor. The effect of the mass transfer and kinetic rates on the yield and selectivity of the CD process were also examined. It was concluded that an increase in the external liquid–solid mass transfer rate through the catalyst bags results in a higher production rate of DAA but has little influence on the MO production rate, while increasing the kinetic rate results in a significant increase in the MO production but essentially no effect on the DAA production. This indicates that the DAA productivity is limited by the external liquid–solid mass transfer through the catalyst bags while the MO productivity is controlled by the apparent kinetic rate. Thus, an improvement on the packing geometry for the catalytic reaction zone with less mass transfer resistance will be required in order to achieve a higher selectivity to DAA.