Aldol condensation of acetone with reactive distillation using water as a selectivity enhancer

Aldol condensation of acetone in the presence of acid catalyst gives diacetone alcohol (DAA) as an intermediate product, which further dehydrates to give mesityl oxide (MO). By using reactive distillation (RD), one can improve selectivity toward DAA, by continuously removing it from the reactive zone and thereby suppressing the dehydration reaction. The presence of water in the reaction mixture has a predominant effect on the intrinsic reaction rates of the individual reactions. This rate-inhibiting effect of water can be advantageously used to improve the selectivity toward the desired intermediate products. The present study, through experiments and simulation, shows that introduction of water in RD can further increase the selectivity toward DAA. Batch kinetics of the reaction in the presence of water is studied, and a suitable kinetic expression is proposed. Further, the batch and continuous reactive distillation experiments are performed to assess the feasibility. The experimental results are explained with the help of an equilibrium-stage model, and the operating parameters for the desired performance are suggested based on the validated model

Simultaneous Hydrogenation and Isomerization of Diisobutylenes over Pd-Doped Ion-Exchange Resin Catalyst

The present work evaluates the applicability of a bifunctional ion-exchange-resin catalyst for the effective hydrogenation of diisobutylene, which is generally available as an equilibrium mixture of its isomers, mainly 2,4,4-trimethylpent-1-ene and 2,4,4-trimethylpent-2-ene. The terminal double bond in 2,4,4-trimethylpent-1-ene gets hydrogenated Substantially more quickly than the relatively stable internal double bond in 2,4,4-trimethylpent-2-ene under relatively mild reaction conditions, Therefore, there is a need for a catalyst that is active for hydrogenation as well as simultaneous isomerization of 2,4,4-trimethylpent-2-ene to 2,4,4-trimethylpent-1-ene under mild reaction conditions. The present catalyst was found to be capable of performing simultaneous hydrogenation and isomerization, thereby increasing the reaction rate. The effects of various operating parameters were studied, and a kinetic model is proposed to explain the observed reaction rates