A study of a phase transfer catalytic reaction between n-butylbromide and sodium phenolate in an oscillatory baffled reactor

Abstract

The most basic form of a Phase Transfer Catalytic (PTC) reaction consists of two immiscible liquid phases each with a reagent that, until the introduction of a Phase Transfer Catalyst (PT-Cat), cannot react with each other. The PT-Cat manages to transfer one of the reagents from one phase to the other phase whereupon the second reagent can react with the catalyst-reagent transient. This paper presents our current investigation into the use of an Oscillatory Baffled Reactor (OBR) for a PTC reaction between n -butyl bromide (BuBr, with Toluene as the organic solvent) and sodium phenolate (NaOPh, dissolved in water) with tetrabutylammonium bromide (QBr) as the catalyst. The OBR consists of a cylindrical column containing periodically placed orifice baffles together with superimposing fluid oscillation. The OBR is of 25 mm in diameter and 140 mm in length, and is operated vertically. The oscillating fluid motion in the OBR interacts with each baffle to form vortices, which gives efficient and uniform mixing between each baffled cavity. It has been known that PTC process development remains - almost exclusively - a chemistry based field, and has not yet been examined with chemical engineering principles. This work is the first of its kind. Industrial applications of PTC are concentrated upon the manufacture of Fine Chemicals and Organic Intermediates. Recent reviews identify the potential of PTC in these fields as ‘almost unlimited’. The reasons for such an endorsement are the advantages of cost and environmental friendliness that PTC enjoys over existing technologies. In this paper, we examined the effects of oscillation amplitude and frequency on the reaction rate and conversion of the PTC reaction, and compared the results with those carried out in a Continuously Stirred Tank Reactor (STR). Our preliminary results show that the OBR promotes improved reaction rates and conversion at lower power requirements.