用四氯化钛催化体系合成聚异丁烯

Synthesis of polyisobutylene initiated with titanic chloride catalyst systems

比较了单一的四氯化钛催化体系与3种不同质子酸/四氯化钛催化体系(四氯化钛/水、四氯化钛/乙醇和四氯化钛/乙酸催化体系)在合成聚异丁烯时的催化性能,其中四氯化钛/水体系的催化活性最高,初步推断该体系形成活性中心～～C^+(CH_3)_2TiCl_4OH^-的活性比四氯化钛体系形成的活性中心～～C^+(CH_3)_2TiCl_5^-要高。以二氯甲烷和正己烷为溶剂,在用四氯化钛/水作为催化体系的条件下,考察了溶剂极性、聚合温度以及催化剂和异丁烯浓度对异丁烯聚合时的催化活性和聚合物性能的影响。结果表明,当正己烷与二氯甲烷的体积比为40/60、聚合温度为-60℃、异丁烯浓度为9 mol/L时,催化体系的活性相对较高,可得到α双键含量也较高的聚异丁烯;催化体系的活性均随着水和四氯化钛浓度的增加而先增大后减小;α双键含量随水浓度的增加呈阶段性下降趋势,但四氯化钛浓度对其几乎没有影响。

The performance of TiC14 catalyst system and three different protonic acids/TiC14 systems, including TIC14/ H20, TiC14/CH3CI-I2OH and TiC14/CH3GOOH, were com- pared in the isobutylene polymerization. Among all these cat- alysts, the catalytic activity of TiC14/H20 was the highest, indicating that the active center -- C ＋ （ CI-I3 ） 2TiC14OH - in TiC14/H20 was more reactive than ＋C ＋ （CH3 ）2TIC15 - in TiC14 catalyst. Meanwhile, the effects of solvent ratio, reac- tion temperature, catalyst concentration and isobutylene con- centration on the catalytic activity and polymerization were studied with CH2C12 and n-hexane as mixed solvent and TiC14/H20 as catalyst system. The results showed that whenthe hexane/CH2C12 was 40/60 （volume ratio） and the isobu- tylene concentration was 9 mol/L at -60 ℃, the mole fraction of α double bond in polyisobutylene was the highest and the catalytic activity was relatively high. In addition, increasing the concentration of H2O and TiC14 caused the catalytic activity to increase first and then decrease. The mole fraction of α double end group decreased periodically with the in- crease of H20 concentration, while TiCl4 concentration almost had no effect on the mole fraction of a double bond.