Abstract:

Dibenzo-18-crown-6 (DBC) was immobilized on cross-linked polyvinyl alcohol (CPVA) microspheres to prepare the triphase-transfer catalyst DBC-CPVA. The phase transfer catalytic behavior of DBC-CPVA was mainly studied using the esterification reaction of 1-bromobutane in the organic phase and potassium benzoate in the water phase as a model system. We examined the effects of the main factors on the phase transfer catalytic esterification reaction. The experimental results show that after the benzoic acid in the water phase reacts with KOH to form potassium benzoate, complex cations form between the immobilized DBC and K+ ions. The complex cations will effectively carry negative benzoate ions from the water phase into the organic phase and this enables the esterification reaction between benzoate ion and 1-bromobutane to be favorably carried out. Solvent polarity is advantageous to the esterification reaction. When the volume ratio of the organic phase to the water phase is 1:4, a maximum conversion of about 70%for 1-bromobutane is obtained. The catalyst DBC-CPVA has excellent recycle and reuse properties and the catalytic activity remains stable after eight cycles.

Key words: Phase transfer catalysis, Dibenzo-18-crown-6, Crosslinked polyvinyl alcohol microsphere, Immobilization