【作者】 姚培洪；

【导师】 王兴亚；

【作者基本信息】 西北师范大学 ， 高分子化学与物理， 2009， 博士

【摘要】 研究了聚烯烃催化剂用载体硅胶及含钛硅胶的制备工艺,制备出符合技术要求的聚烯烃催化剂载体硅胶及含钛硅胶;考察了硅胶基茂金属催化剂负载化影响因素,形成了茂金属催化剂负载化技术,所得催化剂聚合性能及聚合物性能达到工业生产技术要求。采用溶胶—凝胶法制得载体硅胶,其物化性能达到了聚乙烯催化剂用载体的技术指标要求,对制备过程涉及的各种工艺条件进行了全面筛选与优化。结果表明,母液成核温度为70～80℃,pH值为9.0～9.5,时间为40～50min,母液中SiO₂质量分数为3%～5%;在溶胶粒子增长过程中,控制后加入的SiO₂与母液中SiO₂的摩尔比为7～10,pH值为9.0～9.5,水玻璃加入速度为150～250ml/h（水玻璃密度为1.11g/cm³）,反应温度为80～90℃;水溶胶凝胶化控制pH值为6.0～8.0,温度为60～70℃;水凝胶稳定化的老化时间为5～6h,pH值约为9.0;采用喷雾干燥方式对硅胶进行干燥,干燥前SiO₂含水滤饼的匀化条件为:搅拌转速600r/min,匀化时间40～50min,浆料固含量14%～16%;喷雾干燥机转盘转速12000r/min,干燥机入口温度300～320℃,出口温度90～130℃。采用溶胶—凝胶法制得钛质量分数为0.1%～0.3%的含钛硅胶。对钛源与硅源的水解速率等关键工艺条件进行调控。结果表明,采用无机钛源Ti（SO₄）₂及有机钛源Ti（OC₄H₉）₄均可制得合格含钛硅胶,在反应体系中加入一定量的H₂O₂,使钛源水解时产生的大量Ti（OH）₄迅速与其络合并形成动态平衡,以保证钛源和硅源的水解速度相匹配,从而使原料钛得以全部反应进入硅胶骨架;H₂O₂的用量控制在H₂O₂/钛摩尔比大于5,原料中钛的质量分数以小于0.3%为宜。这是因为原料中加入钛越少,进入硅胶骨架的效果越好的缘故,反应温度为30～40℃。采用实验制得的载体硅胶和含钛硅胶,对茂金属催化剂进行负载研究。结果显示,在催化剂负载过程中,MAO二段加入的效果优于一次性加入,催化剂干燥前须过滤与洗涤;催化剂负载的最佳参数为:MAO/硅胶（ml/g）10:1,Al质量分数15%～17%,锆质量分数0.3%～0.45%;制得的茂金属负载型催化剂的活性大于6200gPE/g.cat;所得聚乙烯产品的粒径分布、分子量及其分布、熔点均达到现有工业生产技术要求;自制硅胶用于Unipol气相聚乙烯工艺催化剂的负载化及聚合研究,各项性能达到现有工业装置的生产技术要求;含钛硅胶用作茂金属催化剂的载体时,发现有部分碎裂,催化剂活性较低,聚合产物形态也较自制不含钛硅胶的差,含钛硅胶应用于聚烯烃的负载化有待进一步研究。更多还原

【Abstract】 Process for preparing silica and titanium-containing silica was studied and the support silicas suitable for olefin polymerization catalyst were obtained. The metallocene catalyst was supported on as-prepared silicas and the influencing factor was investigated. Both properties of resultant supported catalyst and polymers could meet the need of industrial technologies.Silicas with desired physico-chemical properties for ethylene polymerization catalysts were prepared via sol-gel process, all the operating conditions in the process were selected and optimized. The results showed that temperature for nucleation of mother liquor was 70～80℃,pH value was 9.0～9.5, time was 40～50min, SiO₂ mass concentration in mother liquor was 3%～5%;In the process of sol particlegrowth, the mole ratio of SiO₂ added subsequently to SiO₂ remained in mother liquor was controlled at 7～10, pH at 9.0～9.5, feed flow of water glass at 150～250ml/h（d water glass was 1.11g/cm³）, temperature at 80～90℃; hydrosol gelfication was controlled at pH 6.0～8.0,temperature 60～70℃; aging time for hydrogel stabilization was 5～6h, pH value was 9.0; the silica was dried by spray drying, the homogenization conditions for aqueous silica filter cake before drying were: the stirring speed 600r/min, time 40～50 min, solid mass fraction in slurry 14%～16%; the rotating speed of spray dryer was kept at 12000r/min, the temperature at inlet and outlet at 300～320℃and 90～130℃, respectively.Titanium-containing silica with Ti mass fraction of 0.1%～0.3% was prepared via sol-gel process and the hydrolysis rates of Ti and Si sources were controlled .The results indicated that either inorganic Ti（SO₄）₂ or organic Ti（OC₄H₉）₄ was suitable for producing qualified titanium-containing silica. In the reaction system, predetermined amount of H₂O₂ was added to complex quickly with a great deal of Ti（OH）₄ formed during Ti source hydrolysis to establish a dynamic equilibrium with H₂O₂ ,thus ensuring the match between hydrolysis rates of Ti and Si sources and perfect incorporation of Ti from raw material into framework. A mole ratio of H₂O₂/Ti above 5 was sufficient to realize this object. Low Ti contents in raw material （should below mass ratio of 3%） and reaction temperature between 30～40℃were better for incorporation of Ti into the framework.The metallocene catalyst was supported on as-prepared silicas. The results indicated that in the supporting process, the addition of methylaluminoxane （MAO） in two-step was better than in one-step. The catalyst should be filtered and washed before drying. Optimized parameters were MAO/silica（ml/g） of 10:1, Al loading mass fraction of 15%～17%, Zr loading mass fraction of 0.13%～0.45%. For ethylene polymerization with the as-supported metallocene catalyst, the polymerization activities were greater than 6200gPE/g.cat, polyethylene （PE） particle size distribution , molecular weight and its distribution ,and melting temperature all met the requirements from existing industrial technology. The as-prepared silica was successfully applied to Unipol gas PE process as well. In addition, titanium-containing silica used as support for metallocene catalysts led to partial breaking and exhibited lower ethylene polymerization activities and more inferior PE morphology compared with that supported by self-made titanium-free silica. The problems remaining need to be solved.更多还原