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摘要
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A H3PW12O40/ZrO2 catalyst for effective dimethyl carbonate (DMC) formation via methanol carbonation was prepared using the sol–gel method. X-ray photoelectron spectra showed that reactive and dominant (63%) W(VI) species, in WO3 or H2WO4, enhanced the catalytic performances of the supported ZrO2. The mesoporous structure of H3PW12O40/ZrO2 was identified by nitrogen adsorption–desorption isotherms. In particular, partial sintering of catalyst particles in the duration of methanol carbonation caused a decrease in the Brunauer–Emmett–Teller surface area of the catalyst from 39 to 19 m2/g. The strong acidity of H3PW12O40/ZrO2 was confirmed by the desorption peak observed at 415 °C in NH3 temperature-programmed desorption curve. At various reaction temperatures (T = 110, 170, and 220 °C) and CO2/N2 volumetric flow rate ratios (CO2/N2 = 1/4, 1/7, and 1/9), the calculated catalytic performances showed that the optimal methanol conversion, DMC selectivity, and DMC yield were 4.45, 89.93, and 4.00%, respectively, when T = 170 °C and CO2/N2 = 1/7. Furthermore, linear regression of the pseudo-first-order model and Arrhenius equation deduced the optimal rate constant (4.24 × 10−3 min−1) and activation energy (Ea = 15.54 kJ/mol) at 170 °C with CO2/N2 = 1/7 which were favorable for DMC formation. |
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