Transesterification of Dimethylcarbonate and Phenol Over Silica Supported TiO2 and Ti-MCM 41 Catalysts: Structure Insensitivity

摘要

Silica-supported titanium dioxide (TiO2/SiO2) and Ti-MCM 41 catalysts have been used for transesterification of dimethylcarbonate (DMC) and phenol to methylphenylcarbonate (MPC). The structure and the chemical state of titanium species in TiO2/SiO2 and Ti-MCM 41 have been investigated by means of X-ray diffraction (XRD), X-ray absorption near edge structure (XANES) for Ti K-edge and X-ray photoelectron spectroscopy (XPS). To understand the role of pore size on the activity of catalysts, different pore size silica supports (Q-series) were utilized in TiO2/SiO2 catalysts. Similarly, to understand the effect of Ti symmetry on the activity of catalysts, Ti-MCM 41 was used with different Ti-loadings. It was observed that the Ti surface area was an only important factor to achieve highest activity. In case of Ti-MCM 41 catalysts, as the Ti-loading increased octahedral symmetry increased and tetrahedral symmetry decreased. But, turnover rates based on the surface Ti atoms were independent of the Ti symmetry. They are also similar to those obtained for TiO2/SiO2 catalysts. Showing that transesterification of DMC and phenol over Ti-based catalysts is a structure insensitive reaction.