Improvement in thermal stability and catalytic activity of titanium containing mordenite by cerium using hydrothermal methods for hydroxylation of benzene into phenol

Abstract

Cerium–titanium–mordenite (Ce–Ti/Mor) were synthesized using ortho-phenylenediamine (OPDA) as a templating agent, and varying amounts of cerium (0.5–4.0 mol%) have been successfully prepared by direct hydrothermal synthesis. These micropore materials were compared with pure mordenite synthesized at the same conditions. The influence of Ce/Ti–Mor composite on the phase, crystal structure and morphology has been investigated by X-ray diffraction (XRD), scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The probable assignments of the thermal degradation products of OPDA in Ce–Ti/Mor samples were studied by complementary thermogravimetric analysis and differential scanning calorimetry. XRD appeared of α-quartz (Si3O6) phase in Ti–Mor disappeared by the addition of Ce and reformation of pure mordenite structure. The increase in unit cell parameters observed with replacement Al by Ti is indicative of incorporation of Ti into the framework structure of microporous material mordenite, while a decrease in unit cell by replacement of Ti by Ce attributed to the presence of Ce–O–Ti bond on the surface of mordenite. The hydroxylation of benzene to phenol has been extensively investigated using hydrogen peroxide as an oxidant. All the Ce-supported catalysts exhibited high catalytic activity in the oxidation of benzene.