The Study Of Friendly Environmental Al-Based Catalyst For Polyester

There are three general catalysts （antimony-base, titanium-base and germanium-base） which were used in PET polycondensation. They have respective merits, but they have some disadvantages which affect the quality of PET.The contents of Sb in drink of PET packing from market were examined by ICP. Based on the theory of catalysts of polycondensation, Al₂O₃ was selected as the main composition, and added with TiO₂, B₂O₃, and MgO as the second composition separately. The catalysts were synthesized by machine mix, sol-gel and impregnation. Then they were calcinated at 500℃in 3 hours. The mixed oxides were characterized by TG-DTG, XRD, FT-IR and NMR MAS. Catalysts were coordinated with dibenzoylmethane （DBM） to study catalytic activity by FT-IR and UV-Vis. Then, PTA was used to synthesize PET by the catalysts preparated. The characteristic of [η] and DSC of PET showed the activities of catalysts. The results were as follows:1. The ICP indicated that the content of Sb in carbonic acid drink of PET packing reached 0.07μg/ml, which was 12 to 14 times over the GB standard 0.005μg/ml.2.The calcining temperature 500℃was comfirmed by TG-DTG.3.The XRD indicated that the crystal kind of main composition wasγ-Al₂O₃, and crystal kind of TiO₂ was anatase.4.FT-IR showed strong waves between 3300 cm^-1 to 3550 cm^-1, it meaned Al₂O₃ attracted -OH strongly. After added B₂O₃, the broad band at 721 cm^-1 of Al-0 was changed because of the new band Al-O-B.5.¹¹B NMR MAS showed the tetrahedral BO₄ and the trigonal BO₃ were detected as the basic units in B₂O₃/Al₂O₃ catalysts, and the content of BO3 was more than BO4. The water adsorbed on the catalyst surface greatly influenced the BO₄/ BO₃ ratio, BO₄ units could be partly transformed into BO₃ units through removing water from the catalyst, which could reduce the content of-OH in the surface of Al₂O₃.6.²⁷Al NMR MAS showed that octahedral AlO₆ （δ=8.845ppm ） and tetrahedral AlO₄ （δ=64.588ppm） were detected as the basic units in MgO/Al₂O₃. The proportion of contents of AlO₆ and AlO₄ was about 3:1. The sizes of Mg was closed to Al, octahedral AlO₆ was more propitious for Mg to inset. 7. The coordinations of catalysts and DBM were measured by FT-IR and UV-Vis. In FT-IR, the C=O at 1544 cm^-1 moved to the lower areas, and divided into two apices at 1555 cm^-1 and 1529 cm^-1 In UV-Vis, theλof DBM were 362nm and 274nm, and theλof coordinations were moved.8.According to the datas of [η] and DSC of PET, the activities of Al-based catalysts were approached to Sb₂O₃.