Process intensification of heterogeneous dehydrochlorination of β-chlorohydrin using phase transfer catalysts

Abstract

Terminal epoxides are important monomers and modifiers that are widely used in the polymer and coating industries. Apart from direct oxidation of alkenes to produce ethylene oxide or propylene oxide, many terminal epoxides are still synthesized through the chlorohydrin method. Due to the limited mass transfer performance and complex thermodynamics and kinetics in this heterogeneous reaction system, the dehydrochlorination reaction still suffers from low reaction efficiency, large amounts of solid precipitation waste, and highly excessive use of alkali. Herein, the dehydrochlorination process of 3-chloro-2-hydroxypropyl neodecanoate (CHPDA), selected as a typical β-chlorohydrin with extremely poor solubility in water, was intensified using phase transfer catalysts (PTCs). The structure–function relationship of PTCs was elucidated and it was demonstrated that tetrabutylammonium chloride (TBACl) is one of the most effective catalysts for heterogeneous dehydrochlorination. Due to the significant promotion of mass transfer by applying a catalytic amount of TBACl, the reaction time was shortened from several hours to just 3 min, and the usage of the reactant sodium hydroxide can be reduced from multiple equivalents to nearly stoichiometric with β-chlorohydrin, while the selectivities of the side products, neodecanoic acid (NDA) and diester, were only 0.4 and 1 mol%, respectively. Compared to existing works, this study could be very helpful for the development of continuous and green synthesis technology for epoxides.