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滴定沉淀法制备了SO42-/TiO2-Ce4+稀土固体超强酸催化剂,得到了可作为直接法合成聚乳酸催化剂的制备工艺:硫酸浸渍浓度1.0 mol/L,Ce4+浓度0.08 mol/L,浸渍时间10 h,焙烧温度500℃,焙烧时间3 h,并将该固体超强酸催化剂用于直接催化合成聚乳酸。考察了聚合温度、聚合时间、催化剂用量及聚合压力对聚乳酸合成的影响,得到了最佳工艺条件为:催化剂用量为乳酸质量的0.174%,先在120℃,2 000 Pa下预聚5 h,然后在180℃,1 000 Pa下聚合15 h,最后在120℃,500 Pa下聚合20 h,得到的聚乳酸分子量为1.39×104。
Titration precipitation method was prepared SO42- / TiO2-Ce4 + rare earth solid superacid catalyst, obtained as a direct synthesis of polylactic acid catalyst preparation: sulfuric acid concentration of 1.0 mol / L, Ce4 concentration of 0.08 mol / L, immersion time of 10 h , Calcination temperature 500 ℃, calcination time 3 h, and the solid superacid catalyst for direct catalytic synthesis of polylactic acid. The effects of polymerization temperature, polymerization time, amount of catalyst and polymerization pressure on the synthesis of polylactic acid were investigated. The optimum conditions were obtained as follows: the amount of catalyst was 0.174% of the mass of lactic acid, first prepolymerized at 120 ℃ and 2000 Pa for 5 h , Then polymerized at 180 ℃ and 1000 Pa for 15 h and finally polymerized at 120 ℃ and 500 Pa for 20 h. The molecular weight of polylactic acid was 1.39 × 104.