Void-column liquid chromatographic reactor studies to determine reaction rates in mobile and stationary phases

Abstract

A liquid chromatographic reactor system was modified to incorporate a void column, connected between two packed octadecylsilane columns. By varying the voil-column volume and the eluent flow-rate, reactant retention times in both the mobile and stationary phases can be decoupled, facilitating the simultaneous measurement of rate constants in both phases. The knowledge of mobile phase rates is of special significance, since this makes it possible to evaluate reaction rates in the stationary phase for a variety of columns. From these phase rates it is possible to obtain information about phase compositions and possibly retention mechanisms. The pseudo-first order base-catalyzed esterification reactions of tetrachloroterephthaloyl chloride were studied in the voil-column liquid chromatographic reactor for comparison with earlier studies. Kinetic measurements in the methanol eluent in both the void and packed sections were comparable with those obtained from a batch reactor, indicating no significant external or internal mass transfer effects under moderate operating conditions. The stationary phase kinetic data obtained here support the previous generalized model in which solute molecules interact with both the associated methanol pseudo-layer and the octadecylsilane moieties.