Mesoporous alumina modified calcium catalyst for alcoholysis of polycarbonate

Calcium-fuctionalized mesoporous γ-alumina was synthesized for alcoholysis of Polycarbonate (PC). Compared with the traditional homogeneous depolymerization process, such alcoholysis process presents a higher capacity, more time effective and environmental benign. Benefited from such mild condition, the operation can be continuously performed without any equipment corrosion occurring. Such mesoporous γ-alumina composite can be synthesized in one step sol-gel method by utilizing aluminium isopropoxide, calcium nitrate as basic precursors and Pluronic P123 as a structure directing agent. One-pot method can effectively avoid the loss of active components namely Ca species in comparison to conventional impregnation method. As for the reasons leading to such great degradation efficiency, one is the strengthened basicity supplied by the introduction of Ca species, the other is the typical mesoporous nanostructure which is beneficial for improving the kinetic driving force, in other words, the synergistic effects make the superior work efficiency for PC degradation. The operation conditions were optimized including the molar ratio of Ca/Al, temperature, methanol and tetrahydrofuran (THF) dosage and Ca-Al2O3 dosage. Under such optimum conditions, the conversion of PC was approximately 100 wt.% . The catalyst endures a long recycle without any obvious inactive tendency as well as remained mesoporous structure. The transesterification kinetic behaviors were also investigated with an activation energy of 153 kJ/mol. In addition, a plausible catalysis mechanism for the methanolysis of PC was proposed.