Influence of preparation parameters on characteristics of zirconia-pillared clay using ultrasonic technique and its catalytic performance in phenol hydroxylation reaction

Ultrasonication method was employed for preparation of zirconia-pillared mo ntmorillonite (Zr-PILC) by using polyhydroxy zirconium cation. The influenc es of various preparation parameters such as pH, concentration of pillaring agent, aging period on physico-chemical properties of Zr-PILCs are reporte d. The characterization was done by using different characterizing tools su ch as powder X-ray diffraction (XRD), thermal analysis (TG/DTA), Fourier tr ansform infrared spectroscopy (FTIR), X-ray photo-electron spectroscopy (XP S), X-ray fluorescence spectroscopy (XRF) and surface area measurements. Ef fective pillaring was obtained in the pH range 2.0-2.8 at reduced preparati on time by using ultrasonication. Ultrasonication, especially at higher pH and concentration of pillaring agent with no aging after ultrasonic agitati on of the clay slurry was found to increase zirconium content and specific BET surface area leaving no scope for remarkable increase in d001 spacing. The presence of-OH groups attached to Zr has been revealed by pyridine-adso rbed FTIR, TG/DTA and XPS techniques. The acidic character, ease of accessi bility and good dispersion of active sites in Zr-PILC were found to be cont rolling factors for the challenging activity in hydroxylation reaction of p henol. Probably, this first report on the use of Zr-PILC in hydroxylation o f phenol and its preparation by employing ultrasonication technique may att ract great attention in the catalysis area of academic and industrial impor tance.