Dimethyl Carbonate Synthesis via Transesterification of Propylene Carbonate Using a Titanium-Praseodymium-Based Catalyst

Dimethyl carbonate (DMC) and propylene glycol (PG) synthesis through a methanol and propylene carbonate (PC) reaction, also referred to as a transesterification reaction, is a new and green alternative to other routes, such as phosgene methanolysis, urea methanolysis, etc. In this paper, the titanium-praseodymium-based catalyst prepared via the co-precipitation method has been used to improve the yield and selectivity of DMC production. Different combinations of catalysts were synthesized, referred to as Ti0.99Pr0.01, Ti0.97Pr0.03, Ti0.96Pr0.04, and Ti0.95Pr0.05, according to the molar ratio of Ti with respect to Pr. The catalysts have been studied and analyzed through various characterization techniques, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier trans -form infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The Brunauer-Emmett-Teller (BET) surface area and pore volume diameter have been studied through N2 adsorption-desorption using BET and Barrett-Joyner-Halenda (BJH) models, respectively. The basicity was determined through the carbon dioxide temperature-programmed desorption (CO2- TPD) for understanding the reaction mechanism. The reaction was carried out in the batch reactor, keeping the temperature range of 160-180 degrees C and the molar ratio of methanol/PC in the range of 3-10. The study has also been made on oxygen vacancy concentrations in the mixed oxide catalysts as a result of the mixing of Pr with Ti, thereby affecting the yield and selectivity of DMC. The maximum yield of DMC was obtained with the Ti0.96Pr0.04 catalyst at a temperature of 170 degrees C which resulted in the PC conversion of 81.7%, turnover frequency (TOF) of 0.120 h-1, and selectivity of 71.6% for DMC.