Transesterification of Dimethylcarbonate and Phenol Over Silica Supported TiO 2 and Ti-MCM 41 Catalysts: Structure Insen
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Transesterification of Dimethylcarbonate and Phenol Over Silica Supported TiO2 and Ti-MCM 41 Catalysts: Structure Insensitivity Upendra A. Joshi Æ Sun Hee Choi Æ Jum Suk Jang Æ Jae Sung Lee
Received: 26 November 2007 / Accepted: 9 January 2008 / Published online: 31 January 2008 Ó Springer Science+Business Media, LLC 2008
Abstract 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.
U. A. Joshi J. S. Jang J. S. Lee (&) Eco-friendly Catalysis and Energy Laboratory (NRL), Department of Chemical Engineering and School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyojadong, Namgu, Pohang 790-784, Korea e-mail: [email protected] S. H. Choi Beamline Research Division, Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH), San 31, Hyojadong, Namgu, Pohang 790-784, Korea
Keywords Transesterification of dimethylcarbonate Phenol TiO2/SiO2 Ti-MCM 41 Linear combination of XANES Structure insensitivity
1 Introduction Polycarbonate is a widely used engineering plastic because of its excellent mechanical, optical, electrical and heat resistance properties. Conventionally it is produced by the interfacial polycondensation of bisphenol-A (BPA) and phosgene [1]. The major drawback of this conventional phosgene process is an environmental and safety problem involved in using copious amounts of methlyene chloride as the solvent and highly toxic phosgene as the reagent [2]. With increasing demands for safer and cleaner processes, the hazardous phosgene process has to be replaced by more environmentally friendly processes. The current phosgenefree process employs transesterification of diphenylcarbonate (DPC) with BPA. In 2002, about 12% of polycarbonate was produced by the phosgene-free technology. By 2007, this portion is expected to be greater than 20% [3]. Several alternative non-phosgene methods for
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