Synergistic catalysis over hollow CeO2-CaO-ZrO2 nanostructure for polycarbonate methanolysis with methanol

Herein, CeO2-CaO nanoparticle coated on hollow ZrO2 nanostructure (denoted as CeO2 -CaO-ZrO2) was prepared via a template impregnation method, which showed excellent catalytic performance for polycarbonate (PC) transes-terification with methanol (named as methanolysis). The lattice oxygen (O2-) generated from the incorporation of CeO2 and CaO to ZrO2, adsorbed atomic oxygen (O-), or adsorbed molecular oxygen (O2-) generated from predominately via CeO2 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-Al2O3 was also investigated and compared with hollow CeO2-CaO-ZrO2. CeO2 plays an important role in the storage and release of oxygen and forms stronger O2-/O-/O2- basic sites. Notably, interfacial active species (electron-enriched O2-/O-/O2- sites) participate in stripping protons from CH3OH which is the rate determination step for PC methanolysis. Such interfacial sites of CeO2-CaO-ZrO2 catalyst serve as the optimal active site with the substantially declined activation energy barrier (similar to 0.31 eV) for stripping protons from CH3OH in contrast to that of 0.83 eV of CaO-Al2O3. 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 CeO2-CaO-ZrO2 achieved almost 100% under the conditions of temperature 100 degrees 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-Al2O3 under the same conditions. The hollow CeO2-CaO-ZrO2 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.