Copolymerization of propylene oxide and carbon dioxide to form poly(propylene carbonate) was carried out under in-situ -Al2O3 supported rare earth ternary catalyst.Two in situ supporting routes were employed

one was dropping ZnEt2into -Al2O3pre-supported Y(CCl3OO)3-Glycerin system (Y(CCl3OO)3-Glycerin/-Al2O3/ZnEt2)

the other was reacting -Al2O3pre-supported ZnEt2with Y(CCl3OO)3-Glycerin system (ZnEt2/-Al2O3/Y(CCl3OO)3-Glycerin).However

the two supported catalysts showed unexpected 24%~36% lower catalytic activity than their unsupported analog.By monitoring the ethane evolution during catalyst preparation

it was observed that the diffusion of three components of rare earth ternary catalyst into pores of -Al2O3 leading to molar ratio disparity of the components and decrease in number of active species

and subsequently loss of the catalytic activity.Moreover

the surface hydroxyl groups react with ZnEt2 forming low active species

also leading to catalytic activity loss.Therefore

two main factors were proposed for improving the catalytic activity of supported catalysts

one was the activity of the active species

the other was the number of active species.By adjusting the molar ratio of three components

the time for grinding-stirring during supporting process

the active species of the in situ supported catalyst

the surface chemistry of the support

the catalytic activity of the supported catalyst may be improved significantly

a state-of-the-art optimal catalytic activity for the in situ supported catalyst showed 3.5% increase over the unsupported analog.