SO_4^(2-)/ZrO_2-CeO_2催化剂溶剂回流法合成聚乳酸

Synthesis of PLA catalyzed by SO_4^(2-)/ZrO_2-CeO_2 through solvent refluxing method

采用负载-浸渍法制备了一系列SO42-/ZrO2-CeO2固体超强酸,用于催化合成聚乳酸,考察了催化剂用量、聚合时间、聚合方法等因素对聚乳酸合成的影响。结果表明,当CeO2与ZrO2的摩尔比为1∶20,0.8 mol/L硫酸浸渍,650℃焙烧时,得到的固体超强酸酸强度最大,掺杂的CeO2处于高度分散,增强了固体超强酸的酸强度,合成的聚乳酸的分子量与固体超强酸的酸强度具有很好的相关性,当催化剂用量为乳酸质量的1%,反应时间为30 h时,得到了粘均分子量为11.6×103的聚乳酸。

SO4^2-/ZrO2-CeO2 Samples were prepared by impregnation of hydrous zirconium oxides and CeO2 with different concentration of H2SO4 solutions. The above catalysts were used in synthesis of poly （ lactic acid） （PLA） by solution refluxing polycondensation of lactic acid and the effects of reaction time, catalyst amount and polycondensation methods on polycondensation of lactic acid were studied. The results indicated that the SO4^2-/ZrO2-CeO2 sample,which with n（CeO2） ： n（ZrO2） = 1 ：20 was impregnated in 0.8 mol/L H2SO4 solution and calcined at 650 ℃ ,was the strongest acid strength （ H0 ≤ - 14.52）. The CeO2 was high dispersed on catalysts and promoted the acidity of solid superacids. The viscosity average molecular weight of PLA correlated well with the acid strength of those superacid sites. The viscosity-average molecular weight of PLA reached 11.6×10^3 when the amount of catalyst was 1% of the mass of lactic acid and reaction time was 30 h.