摘要
研究了多种不同烷基(R)结构的烷氧基钕化合物Nd(OR)_3对异戊二烯(Ip)聚合的催化活性及影响因素。结果表明,只有Nd(OR)_3-Al(i-Bu)_3-AlEt_2Cl(Nd-Al-Cl)同时存在,体系才显示催化活性。当R为直链烷基,Al/Nd≥30(mol比),Cl/Nd=3(mol比),加料顺序为Al+Nd+Cl,有少量Ip存在。于60℃左右陈化0.5h,Nd/Ip=2.5×10^(-4)(mol比)时,Ip转化率可达到80％以上。
Various alkoxyl neodymium compounds [Nd (OR)3] of different alkyl structure were synthesized and the catalytic activity of these compounds for isoprene (Ip) polymerization and the factors that influence the catalyticactivity were investigated .The experimental results showed that there was no any catalytic activity in the cases of Nd (OR)3 + Al (i- Bu)3 without halogen , or Nd (OR)3 + AlEt2Cl(orAl2Et3Cl3) without Al (i-Bu)3.The catalytic activity was only shown when there existed three components ofNd(OR)3 + Al (i- Bu)3 + AlEt2Cl (or halogenated compounds). The effects of various halogenated compounds (X)on catalytic activity were given in Figure . For all the systems with different X the highest activities appeared when X/Nd= 3 (molar ratio).The AlEt2Cl , AL2Et3Cl3 and AlEt2Br are more preferable among them .The activity sequence responding to the alkyl structures in the Nd (OR)3 is : n-octyl≈n--bexyl>n- butyl > isopropyl >isobutyl . It can be seen that the activity is higher when the alkyl chain structure is linear than that when it is branched .The feeding order had a remarkable influence on the catalyst morphology ,and therefore ,on the catalytic activity , because the catalyst systems used were heterogeneous . It turned out to be that the highest activity was obtained with such a sequence of Al + Nd+Cl .The results also showed that the catalytic activity increased remarkably when the components of catalyst were aged together under high concentration in the presence of a small amount of Ip at 50 -60°C for 0.5 - 1 h .Under above conditions , and with Nd/Ip=2.5× 10-4 (molar ratio), a conversion of 80% could be reached .This activity could match that of the rare-earth naphthenate systems .The results from the analysis of chloride content in the catalyst precipitate were shown in Table . It was found that the higher the aging concentration of the catalyst ,the higher the chloride content in the precipitate ,and eventually , the higher the catalytic activity . From the facts that the chloride content of the high active catalyst in precipitated form could reach the level of Cl/Nd=2.5,the highest activity was always shown when Cl/Nd = 3,and the catalytic activity of Nd (OR), or Nd (naph)3 was extremely similar to that of NdCl3 solubilized with alkyl phosphate , it was estimated that the active center has such a structure as R 'NdCl2 probably without RO group . The RO or naph group in Nd(OR)3 or Nd(naph)3 only serves for increasing the solubility , not surely taking part in the constitution of the active center .
出处
《合成橡胶工业》
CAS
CSCD
北大核心
1992年第1期23-27,共5页
China Synthetic Rubber Industry
基金
国家自然科学基金
关键词
稀土催化剂
异戊二烯
配位
聚合
rare earth catalyst
isoprene
coordination polymerization
catalytic activity
