Study of Thermodynamics and Experiment on Direct Synthesis of Dimethyl Carbonate from Carbon Dioxide and Methanol over Yttrium Oxide

The thermodynamics on the direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH was calculated and analyzed. Using Y(NO 3 ) 3 ·6H 2 O as the precursor, a series of Y 2 O 3 were prepared through the one-pot calcination method, which were employed to catalyze DMC synthesis. The decomposition temperature of Y(NO 3 ) 3 ·6H 2 O was measured by thermogravimetric analysis, and Y 2 O 3 was obtained after the precursor calcination at desired temperatures, denoted as Y 2 O 3 - T (°C). The catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller method, transmission electron microscopy, NH 3 /CO 2 temperature-programmed desorption, and X-ray photoelectron spectroscopy to detect the crystal phase, surface property, particle size, acidity–basicity amounts, and oxidation state, respectively. The characterization results indicated that Y 2 O 3 -750 can favor the formation of moderate acidic and basic sites and facilitate the activation of CO 2 and CH 3 OH. The catalytic performance evaluation was experimentally investigated, and Y 2 O 3 -750 owned the highest DMC yield of 1.02 mmol/g·cat under 90 °C, 8 MPa, and 6 h, which also exhibited reliable recycle ability.