Clay-Supported Quaternary Ammonium and Phosphonium Cations in Triphase Catalysis and the Effect of Cosolvent in Catalytic Activity

In this research, a naturally occurring clay mineral, hectorite, was used as the support for several quaternary ammonium and phosphonium cations to measure and compare their catalytic activity in a triphase catalytic system. The intercalation of the catalysts in the clay has the advantage of easy catalyst recovery; the catalyst can be removed by a simple separation technique, such as filtration or centrifugation, upon completion of the reaction. The rate of conversion of n-butyl bromide to n-butyl chloride was measured in the presence of two classes of phase transfer catalyst: Quaternary ammonium and quaternary phosphonium cations. The rate of the reaction was measured for the biphase reactions (no supporting clay) and for the triphase catalytic system (with supporting clay). The results have shown that quaternary phosphonium catalysts are somewhat more reactive than the corresponding quaternary ammonium catalysts. It was also found that the intercalated catalysts could be used several times before losing their catalytic activity. Also, a remarkable increase in catalytic activity has been observed using a co-solvent. However, it appears that there is a limit for the co-solvent concentration to be effective.