Synergistic catalysis over hollow CeO2-CaO-ZrO2 nanostructure for polycarbonate methanolysis with methanol
Herein, CeO 2 -CaO nanoparticle coated on hollow ZrO 2 nanostructure (denoted as CeO 2 -CaO-ZrO 2 ) was prepared via a template impregnation method, which showed excellent catalytic performance for polycarbonate (PC) transesterification with methanol (named as methanolysis). The lattice oxygen (O 2− ) generated from the incorporation of CeO 2 and CaO to ZrO 2 , adsorbed atomic oxygen (O − ), or adsorbed molecular oxygen (O 2− ) generated from predominately via CeO 2 serve as the active species to promote PC methanolysis. In order to explore the detailed synergistic effect of different components and the influence of structure tailor, the mesoporous CaO-Al 2 O 3 was also investigated and compared with hollow CeO 2 -CaO-ZrO 2 . CeO 2 plays an important role in the storage and release of oxygen and forms stronger O 2− /O − /O 2 − basic sites. Notably, interfacial active species (electron-enriched O 2− /O − /O 2 − sites) participate in stripping protons from CH 3 OH which is the rate determination step for PC methanolysis. Such interfacial sites of CeO 2 -CaO-ZrO 2 catalyst serve as the optimal active site with the substantially declined activation energy barrier (∼0.31 eV) for stripping protons from CH 3 OH in contrast to that of 0.83 eV of CaO-Al 2 O 3 . The activation energy is considerably declined due to the interfacial synergistic component catalysis and abundant activation sites over hollow structure. The PC conversion over such hollow CeO 2 -CaO-ZrO 2 achieved almost 100% under the conditions of temperature 100 °C, m(cat):m(PC) = 0.05:1, n(methanol):n(PC) = 8:1 and time 2 h, while the conversion was only 13.4% over CaO-Al 2 O 3 under the same conditions. The hollow CeO 2 -CaO-ZrO 2 catalyst could be reused for 5 times without obvious decrease in PC conversion and BPA yield. This work supplies an extended understanding on interfacial synergistic catalysis toward PC methanolysis, which is important for efficient design and building of heterogeneous catalysts with higher activity.
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