A kaolinite-tetrabutylphosphonium bromide intercalation compound as an effective intermediate for intercalation of bulky organophosphonium salts

Abstract A kaolinite-tetrabutylphosphonium bromide (TBPBr) intercalation compound (Kaol-TBPBr) underwent intercalation of dodecyltributylphosphonium bromide (C12TriBPBr), while a kaolinite-dimethyl sulfoxide (DMSO) intercalation compound (Kaol-DMSO) and methoxy-modified kaolinite (MeO-Kaol) showed no such capability. As for the reaction of Kaol-TBPBr and C12TriBPBr, the X-ray diffraction (XRD) patterns revealed expansion of the basal spacing from 1.53 nm of Kaol-TBPBr to 2.10 nm. Fourier transform infrared, solid-state 13C nuclear magnetic resonance (NMR) with cross polarization and magic angle spinning (13C CP/MAS NMR) spectroscopies and the C/P and the Br/P molar ratios indicated intercalation of C12TriBPBr between the layers of kaolinite upon removal of the pre-intercalated TBPBr. As concerns the reactions of Kaol-DMSO and C12TriBPBr, the XRD patterns exhibited no difference as compared to that of Kaol-DMSO or the decrease in basal spacing from the 1.12 nm of Kaol-DMSO to the 0.72 nm of pristine kaolinite. With respect to the reactions of MeO-Kaol with C12TriBPBr, the XRD patterns displayed no expansion of the basal spacing from 0.86 nm of MeO-Kaol. Kaol-TBPBr was also used as an intermediate for successful intercalation of relatively bulk organophosphonium salts, hexadecyltributylphosphonium bromide, tetradecyltrihexylphosphonium chloride and tetraoctylphosphonium bromide. These results clearly reveal the versatility of Kaol-TBPBr as an effective intermediate for use in kaolinite intercalation chemistry.