《Table 2Thermal properties of the copolymer produced over rare‐earth‐metal ternary catalyst with var

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《稀土三元催化体系ZnO/SiO_2负载化及季铵盐催化CO_2与环氧丙烷合成高分子量聚碳酸酯（英文）》

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a Onset of degradation with respect to 5 wt%loss.b The maximum weight loss rate temperature for the PPC.

Anchoring the organometallic species on the solid support has been achieved by a variety of routes involving the function‐al group of the support.Due to the air sensitivity of Zn Et2，the immobilization of the active center on the inorganic support was performed in propylene oxide reactant during the progress of the mixture of the reaction system under an inert atmos‐phere.Zn Et2 can react with hydroxyl groups on the silica sur‐face，which has been confirmed to be easily anchored[20]，and a–Zn‐O‐Zn‐Et structure might be formed as theγ‐Al2O3‐sup‐ported analog[21].Table 1 shows the results of CO2/PO co‐polymerization over the Zn O/Si O2‐supported rare‐earth‐metal ternary catalyst.The activities for the Zn O/Si O2‐supported catalysts（Table 1，entries 3–5）increased compared to the sili‐ca‐supported one（Table 1，entry 2）.The yield was at the level of 4009.2 g/mol Zn（based on the amount of Zn Et2 involved）with 3.0 g of 3 wt%Zn O/Si O2 support.As a typical amphoteric oxide，the Zn O‐modified silica catalyst showed higher activity than that of the acidic Al2O3‐modified one[12].Better disper‐sion of the active sites on Zn O/Si O2 might be obtained.Theadsorption of CO2 on Zn O[22]would also benefit the ring‐opening of PO and promote increased activity，though the Gibbs free energy of the adsorption and the insertion of CO2 into the Zn Et2 active site are relatively low，according to our calculation[12].