球形MgCl2载体催化剂催化乙烯聚合

考察了球形MgCl2载体催化剂在乙烯聚合过程中的催化性能和动力学行为,分析了聚合过程的传热、传质和温度、聚合压力对催化剂行为的影响。聚合温度在30～80℃和乙烯压力在0．12～0．72MPa时,随着温度和压力的提高,聚合活性增加,聚合物堆密度由0．27g/cm^3降低至0．22g/cm^3。     

Polymerization of 1,3-butadiene with MgCl2-supported cobalt catalysts activated by ordinary alkylaluminums

MgCl₂-supported CoBr₂ catalysts were prepared from mixture of MgCl₂ and CoBr₂L₂ (L = triphenylphosphine or pyridine) in toluene. Polymerization of 1,3-butadiene was conducted over the catalysts combined with ordinary alkylaluminums as cocatalyst. The CoBr₂(PPh₃)₂/MgCl₂ catalyst gave polybutadiene with approximately 80% of 1,2 units, whereas cis-1,4-poly-butadiene was obtained with the CoBr₂(C₅H₅N)₂/MgCl₂ catalyst. Addition of triphenylphospine to the latter catalyst caused a marked increase in the content of 1,2 units. The content of 1,2 units could be thus controlled in the range from 0 to 80% by changing the amount of triphenylphosphine. On the other hand, the CoBr₂(PPh₃)₂/MgCl₂ catalyst with very low content of CoBr₂(PPh₃)₂ hardly displayed any activity. Addition of dimethoxydiphenylsilane to the catalyst gave polybutadiene containing 90 % of 1,2 units with a fairly high activity.     

TiCl4/SiO2负载型催化剂用于丁二烯聚合Ⅱ.聚合条件及聚合动力学

使用以球磨法制备的 SiO2负载 TiCl4催化剂进行丁二烯溶液聚合,考察了聚合条件对催化效率的影响以及在 20～ 60℃下的聚合动力学。确定了适宜的聚合条件：以加氢汽油为溶剂, Al/Ti摩尔比为 20, Ti/Bd摩尔比为 2× 10－ 4, 50℃聚合 10 h以上。溶液聚合动力学研究结果表明,本体系在低转化率下为稳态聚合,其稳态聚合速率方程为 Rp=kpf[Ti]0[Bd],聚合的表观活化能为 11.4 kJ/mol。     

外给电子体对MgCl2负载TiCl4催化剂催化乙烯/丙烯共聚合的影响

采用邻苯二甲酸二异丁酯(DIBP)为内给电子体的Mg Cl2负载Ti Cl4催化剂,考察了在无外给电子体及以环己基甲基二甲氧基硅烷(简称C-donor)、二环戊基二甲氧基硅烷(简称D-donor)、苯基三乙氧基硅烷(简称PTES)为外给电子体的条件下,催化剂对乙烯/丙烯共聚合活性、单体竞聚率、共聚物序列分布和热性能的影响。结果表明,在不同外给电子体作用下,随着乙烯进料比的增加,聚合活性先增加后逐渐减小,并呈现出明显的"共单体效应";DIBP与D-donor有很好的协同效应,二者配合可提高催化剂活性,最高可达8.3 kg(以1 g Ti计);当乙烯/丙烯(摩尔比)为40%~65%时,共聚物链段中乙烯和丙烯分布更均匀,无规度更高,具有更短的平均序列长度;当乙烯/丙烯为50%时,所得共聚物的熔融温度最低,可达108℃,玻璃化转变温度为-48.6℃,表明聚合物具有较好的耐低温性能。     

The roles for a Lewis base and MgCl2 in third-generation Ziegler-Natta catalysts

Activity of a titanium catalyst supported on a bimetallic magnesium–aluminium system, involving a Lewis base [MgCl₂(THF)₂/Al(C₂H₅)₂Cl], was studied in ethylene polymerization, and the effect of the catalyst composition on the properties of the final polymer produced was investigated. Analysis and discussion of the findings covering also some part of the kinetic study, resulted in defining the roles for MgCl₂ and a Lewis base in the third-generation Ziegler-Natta catalysts. MgCl₂ forms a bimetallic complex with an organoaluminium compound, which involves also a Lewis base. Its reaction with TiCl₄ yields a very active catalyst wherein the Mg : Ti molar ratio is close to 1. This means that MgCl₂ is involved in creating catalytic active sites. The structure of these catalytic sites were suggested. Hence, the role for MgCl₂ can be twofold: it is a component of a catalytic active site, and it is a support if Mg : Ti > 5. It was found in the study that the catalytic function of MgCl₂ can be maintained while its supporting function can be omitted. Thus, MgCl₂ can be substituted for Al₂O₃ and the catalytic system obtained will have the same activity. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1005–1011, 1998     

负载茂金属催化剂催化乙烯气相聚合

研究了负载茂金属催化剂(n-BuNeCp)_2ZrCl_2/SiO_2的乙烯气相聚合行为及其催化聚合产品的性能。三乙基铝加入聚合体系后可降低负载茂金属催化剂的初始活性,有利于聚合过程中的温度控制。气相聚合产品聚乙烯的重均分子量为(1 42～2.28)×10~5,相对分子质量分布为2.6～3.1,熔点在135℃以上,结晶度约为60%,聚乙烯产物颗粒形态以球形为主.堆密度大于0.35 g/cm~3。     

球形MgCl2载体催化剂催化1-丁烯聚合

在以三乙基铝(AlEt3)为助催化剂、n(Al)/n(Ti)为300、聚合压力为0.10 MPa、聚合温度为30℃、通入氢气3 mL、环己基甲基二甲氧基硅烷(CHMMS)与Al的摩尔比为0.033、聚合2h的条件下,球形MgCl2载体催化刺的活性为607g/g,聚1-丁烯的等规指数为82.3%.依催化剂活性大小,外给电...     

TiCl4—C60Cln催化体系引发异丁烯正离子聚合

研究了碳笼烯非质子酸经体系引发异丁烯正离子聚合的反应规律,并与ＴｉＣｌ４正离子催体系进行了比较。ＧＰＣ的测试结果表明,ＴｉＣｌ４－Ｃ６０Ｃｌｎ催化体系中可能存在２种活性中心：（１）体系中的微量水与ＴｉＣｌ４配位形成的质子引发体系;（２）（ＴｉＣｌ５）－（Ｃ６０Ｃｌｎ－１）＾＋离子引对引发活性中心。     

逆水煤气变换耦合乙烷脱氢反应中助剂对Cr/SiO2催化剂性能的影响

分别制备了以Mn、Ce、Cu、Zn、K等为助剂的Cr/SiO2催化剂,考察了助剂在逆水煤气变换耦合乙烷脱氢制乙烯反应中对Cr/SiO2催化剂反应性能的影响。结果表明,高温下Mn的加入有利于催化活性的提高,Cr-Mn/SiO2催化剂显示了较好的催化活性。在740℃、n(CO2)/n(C2H6)=7的条件下,乙烷转化率为47%,乙烯选择性为99%。XRD、XPS、UV-DRS和TPR技术的表征表明催化剂表面存在Cr3+、Cr6+、Mn4+物种,Mn的加入使得催化剂还原性能增强,有助于反应过程中氧化还原循环的进行,提高了反应活性。     

硅胶负载硫酸铈催化合成苯乙醛缩乙二醇

以苯乙醛和乙二醇为原料,以硅胶负载硫酸铈(Ce2(SO4)3/S iO2)为催化剂,合成了苯乙醛缩乙二醇,考察了醛醇摩尔比、反应时间、催化剂用量及其稳定性等因素对收率的影响。实验结果表明,较优反应条件为:苯乙醛0.1 mol,n(苯乙醛)∶n(乙二醇)=1.0∶1.5,催化剂用量0.2 g,带水剂环己烷12 mL,回流反应2.0 h,苯乙醛缩乙二醇的产率可达96.0%以上。     

MgCl2-BuOH/TiCl4催化剂催化乙烯聚合动力学

研究了MgCl2-正丁醇/TiCl4催化剂常压下催化乙烯聚合的性能和动力学行为.考察了n(Al)/n(Ti)、聚合温度、共聚单体浓度、氢气分压对催化剂性能的影响.研究表明:三乙基铝为助催化剂,n(Al)/n(Ti)为200,聚合压力为0.1 MPa,温度为50℃,聚合时间为2 h时,该催化剂具有较高的活性:聚合动力学行为平稳,活性衰减较慢,活性可达1 550.2 g/g;该催化剂具有良好的乙烯均聚合和共聚合性能以及氢调性能.     

硅胶负载四氯化锡合成丙酸正丁酯

以SnCl4/SiO2为催化剂,由丙酸与正丁醇合成丙酸正丁酯.讨论了醇酸比,催化剂用量,反应时间对酯化转化率的影响,得出最佳反应条件为:丙酸为0.1 moL,醇酸比为1.4∶1,催化剂用量为1.5 g,反应时间为2 h,最终丙酸转化率为94.1%.     

Kinetic study for the decay rate of ethylene polymerization catalyzed over silica supported TiCl4/MgCl2 catalysts

The kinetics for decay rate of ethylene polymerization catalyzed with TiCl₄/MgCI₂/Si0₂ has been investigated in the range of temperatures between 40 and 90°C and in the range of ethylene pressures between 4 and 12.4 atm. The decay of polymerization rale was fitted well by the type of first order decay. The decay rale constant caused by monomer could be expressed by k _d ^/′ = C ·[M]^−1/2. Some plausible speculations have been proposed on the deactivation mechanism caused by monomer. The activation energy for the deactivation reaction is 9.8 kcal/mole.     

CeO_2掺杂对Cu/SiO_2催化剂热稳定性的影响

采用蒸氨法制备了CeO2掺杂的Cu/SiO2催化剂,考查了CeO2掺杂对Cu/SiO2催化剂在草酸二甲酯催化加氢制取乙二醇反应中热稳定性的影响。采用H2-程序升温还原(H2-TPR),透射电镜(TEM)对催化剂的物理化学性能进行了表征。在反应温度T=200℃,压力P=3.0 MPa,液时空速LHSV=0.4 h-1,氢气、草酸二甲酯摩尔比H2∶DMO=80∶1,400℃高温处理2.0 h的条件下测定了催化剂的活性变化。结果表明,CeO2掺杂对Cu物种的分散起到了促进作用,提高了催化剂的热稳定性。     

Studies on highly active coordination catalysts for polymerization of α-olefins: 3. Polymerization of propylene with MgCl2/TiCl4/AlEt3 or MgCl2/PhCOOC2H5/TiCl4/AlEt3 systems

Activity and stereospecificity of the $\text{MgCl}{}_2\text{TiCl}{}_4$ catalyst in the polymerization of propylene follow curves showing maxima with grinding time of the MgCl₂ support. Using MgCl₂/PhCOOC₂H₅/TiCl₄ catalysts, no decrease in activity and stereospecificity was observed presumably because of complex formation between MgCl₂ support and ethyl benzoate.     

Effect of hydrogen on the ethylene polymerization process over Ziegler–Natta catalysts supported on MgCl2(THF)2. I. Studies of the chain‐transfer reaction

The effect of hydrogen on the molecular weight of polyethylene obtained over vanadium catalysts (based on VCl₄ and VOCl₃) supported on MgCl₂(THF)₂ was studied and the results were compared to those obtained for similar titanium catalysts. It was confirmed that the dependencies of the transfer reaction on the hydrogen concentration are a half‐order in all investigated systems. However, the transition metal of the catalytic site affects the ratio of the transfer rate with hydrogen to the propagation rate (k_tr,H/k_p) and the results showed that hydrogen is a more effective agent of polyethylene molecular weight control in vanadium‐based systems as compared to the titanium catalyst. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 356–360, 2001     

Observation of bimodal polyethylene derived from TiO2-supported zirconocene/MAO catalyst during polymerization of ethylene and ethylene/1-hexene

The bimodal polyethylene obtained from TiO₂-supported zirconocene/MAO catalyst was observed during polymerization of ethylene and ethylene/1-hexene. By means of XPS, it revealed that TiO₂ consisted of Ti³⁺ (BE = 462.6 eV) and Ti⁴⁺ (BE = 464.9 eV). The dual catalytic sites were attributed to the presence of Ti³⁺ and Ti⁴⁺ in TiO₂.     

Propene polymerization with MgCl2-supported TiCl4/dioctylphthalate catalyst. II. Effects of polymerization conditions on the microstructure of isotactic polymer

Propene was polymerized over the MgCl₂-supported TiCl₄/dioctylphthalate catalyst in heptane. Polymer products obtained under different polymerization conditions were separated into isotactic and atactic polypropenes by the extraction of boiling n-heptane. The effects of polymerization time, cocatalyst type, cocatalyst/catalyst ratio, polymerization temperature, and external base/cocatalyst ratio on the isotactic triad of the isotactic portion of polypropene were investigated 2,2,6,6-Tetramethyl piperidine (TMPIP), dimethoxy diphenyl silane (DMDPS), and t-butylmethyl ether (TBME) were employed as the external Lewis base. High concentrations of the first two bases caused a decrease in isotactic triads in the isotactic polymer, while TBME showed no significant effects. The difference can be attributed to the different roles these external bases play in polymerization. © 1995 John Wiley & Sons, Inc.