活性中心

Through computer simulation, on the random distributed active sites surface, the relation between the fraction of available sites and adsorbate amount can be calculated.

通过计算机模拟，在随机分布一定数量活性中心的吸附剂表面上，求得了可接近活性中心分率与吸附量之间的关系，并用带两个参数的新修正的Langmuir式表示。

The relative content of inactive PSII centerof Ailanthus altissima andGinkgo biloba under salt stress.

盐胁迫下，银杏和臭椿PSII无活性的反应中心相对比例增加，银杏无活性中心上升幅度低于臭椿。

It is included that 4-5 types of active sites exist in the catalytic system and the active site produced polymer with low molecular weight is easy to be activiated while TEA is used as the cocatalyst. While TIBA, the active site produced polymer with high molecular weight and seldom active site produced polymer with low one is prone to be activiated. MAO tends to activiate the active site produced polymer with middle-level molecular weight. In TEA-TIBA catalytic system, TEA and TIBA activiate the corresponding active site and the weight of every active site gradationally varied with the change of the ratio of the two cocatalysts. And the activity of the active site produced polymer with high molecular weight is proportion to the concentration of TIBA.

发现：TEA作为助催化剂时产生低分子量产物的活性中心易于活化，且体系中具有活性的活性中心有4～5种；TIBA易于活化产生高分子量的活性中心，基本上不能活化产生低分子量产物的活性中心；MAO对产生中等分子量产物的活性中心活化能力较强；在TEA-TIBA混合物体系中，TEA和TIBA各自对活性中心的作用表现为明显的互补现象，各活性中心的相对强度随着两种助催化剂之间的比例改变呈现渐次变化，其中产生高分子量产物的活性中心的相对活性(来源：c5AB3fC论文网www.abclunwen.com)与TIBA的浓度有明显的正相关性。

Catalyst activity was determined by not only specific surface area of catalyst but also the distributions of active center and utilization ratio of internal surface.

实验结果表明：催化剂活性比为不同催化剂单位质量表面上活性中心的总数目N总值的比值；催化剂活性不仅与比表面有关，还与其活性中心分布情况、内表面利用率有关。

And the mechanism of ATRP is discussed from the view of complex-catalytic reaction. It is deduced that the active center in ATRP is not pure radical but complex active center, which maybe a complex with radical and complex ion. The structure of active center may have a "bridge"structure formed through propaganating radical and transition metal ion, and the active center exists in a"cage"generated by ligand-transition metal ion-organic halide and monomer or solvent.

论文运用基团贡献理论对一些实验现象和结果进行了讨论和分析，并结合研究结果对络合催化引发原子转移自由基聚合反应的机理进行了初步的探讨，认为：过渡金属化合物与有机配体参与的络合催化引发原子转移自由基聚合反应中，聚合反应的活性中心不是纯粹的自由基活性中心，而是与过渡金属相结合的、有着某种"笼"结构存在的复合式活性中心，同时该活性中心以自由基特性为主，同时兼具某种程度的其它活性中心特征（如阳离子和络合聚合活性中心）。

The results of catalytic activity show that both Ni-B and Ni-P sample have the same kinetic equation for hydrogenation of 1, 3-cyclopentadiene to cyclopentene and the same TOF. Therefore, it can be suggested that they have the similar active site. The catalytic activity of Ni-B sample is higher than that of Ni-P sample, and it is due to the more active sites of Ni-B sample having.

催化活性测试表明，Ni-B与Ni-P催化环戊二烯加氢反应对环戊二烯具有相同的动力学方程，而且两者具有相似的氢转换频率，表明两者的活性中心本质上是相似的，类金属不同导致的电子转移方向的不同仅仅影响反应的初活性，宏观活性的差别在于两者活性中心数量的不同。

Dealcoholization temperature markedly influences the surface area and porosity of the resultant MAO-supports. When the support was pretreated at lower or higher temperature, the corresponding MAO-support shows very low surface area;2.XRD and IR analyses indicate that MAO has reacted with the residual ethanol in the supports, which is an important manner to get MAO fixed on the carrier. Morever, XPS analyse indicates that MAO can also be coordinated with MgCl_2, which is another way to get MAO fixed on the support;3.ICP and EDX analyses indicate that dealcoholization temperature not only determined the element content on the solid catalyst, but also influences the element distribution on the carrier;4.The activities of the supported phenoxy-imine catalysts and the properties of resultant polymers are strongly dependent on the dealcoholization temperature. The support (MSP-5) obtained by treating MgCl_2·2.56C_2H_5OH at 160℃for 4 h, then modified by MAO is very effective for immobilizing complex 3, the resultant solid catalyst (MSPC-5) shows very high activity in ethylene polymerization, and its kinetics of polymerization is stable during the reaction process. Finally, PEs with spherical morphology and high bulk density (over 0.35g/ml) were obtained, without reactor fouling;5.In this work, polymerization conditions such as alkylaluminums, Al/Zr ratio, temperature and H_2 had a pronounced effect on the activity of MSPC-5 and properties of PE;(3). New MgCl_2-Supported Single-Site Catalysts for Ethylene PolymerizationIn this work, a kind of new MgCl_2 support was obtained by anhydrous MgCl_2 co-milled with solid MAO, and it is a creative contribution. Then some single-site catalysts were supported on the new MgCl_2 support, and the resulted solid catalysts were tested in ethylene polymerization, the results indicated that:1.XRD and IR analyses indicate that MAO does be coordinated with MgCl_2, which is in good agreement with the results obtained by XPS;2.co-mlling time had no obvious effect on the texture of support after 12 hours;3.In this work, MgCl_2 was co-milled with solid MAO for different hours, and then complex 3 was supported on these co-milled supports. It was found that co-milling time markedly influences the activity of solid catalysts, but it had negligible effect on the kinetic profile and the properties of resultant PE.

XPS研究结果表明，MAO不仅仅只和乙醇作用，MAO还与MgCl_2本身有一定的作用，这是一个极为重要的发现；3、通过ICP和EDX表征，发现载体的脱醇温度直接影响着元素在固体催化剂中的含量及分布；4、脱醇温度极大地影响着负载苯氧基亚胺类催化剂的活性和聚合物的性能，特别是原始载体经160℃活化4小时制备得到的固体催化剂MSPC-5的活性明显高于其他脱醇温度条件下制得的固体催化，并且催化剂寿命长，表现出稳定的动力学行为，最终获得了高堆密度(大于0.35g／ml)的球形聚乙烯颗粒；5、本文选择MSPC-5为研究对象，考察了聚合反应参数对催化剂的活性及其聚合物的影响，研究发现：不同的烷基铝对催化剂具有非常重要的影响，特别足TIBA对MSPC-5的助催化活性最高，烷基铝的加入量有一个较佳值，聚合温度为80度时活性最高，H_2的加入使催化剂的活性明显降低且聚合物的分子量也减小；、新型氯化镁载体负载单活性中心催化剂催化乙烯聚合本文创造性采用固体MAO与无水氯化镁直接进行共研磨，制备出了一种的新型的氯化镁载体，并将该载体用于多种单活性中心催化剂的负载化研究，研究表明：1、通过BET、XRD的表征，再次证实了MAO与MgCl_2之间具有直接作用，与XPS的研究结果相一致；2、当研磨时间高于12小时时，延长研磨时间对载体的结构没有显著的影响；3、将配合物3负载于共研磨时间不同的一系列载体上，乙烯聚合结果表明，尽管共研磨时间对负载催化剂的活性具有明显的影响，但是它对聚合物的性能以及催化剂的影响不明显。

Dealcoholization temperature markedly influences the surface area and porosity of the resultant MAO-supports. When the support was pretreated at lower or higher temperature, the corresponding MAO-support shows very low surface area; 2.XRD and IR analyses indicate that MAO has reacted with the residual ethanol in the supports, which is an important manner to get MAO fixed on the carrier. Morever, XPS analyse indicates that MAO can also be coordinated with MgCl_2, which is another way to get MAO fixed on the support; 3.ICP and EDX analyses indicate that dealcoholization temperature not only determined the element content on the solid catalyst, but also influences the element distribution on the carrier; 4.The activities of the supported phenoxy-imine catalysts and the properties of resultant polymers are strongly dependent on the dealcoholization temperature. The support (MSP-5) obtained by treating MgCl_2·2.56C_2H_5OH at 160℃for 4 h, then modified by MAO is very effective for immobilizing complex 3, the resultant solid catalyst (MSPC-5) shows very high activity in ethylene polymerization, and its kinetics of polymerization is stable during the reaction process. Finally, PEs with spherical morphology and high bulk density (over 0.35g/ml) were obtained, without reactor fouling; 5.In this work, polymerization conditions such as alkylaluminums, Al/Zr ratio, temperature and H_2 had a pronounced effect on the activity of MSPC-5 and properties of PE;(3). New MgCl_2-Supported Single-Site Catalysts for Ethylene Polymerization In this work, a kind of new MgCl_2 support was obtained by anhydrous MgCl_2 co-milled with solid MAO, and it is a creative contribution. Then some single-site catalysts were supported on the new MgCl_2 support, and the resulted solid catalysts were tested in ethylene polymerization, the results indicated that: 1.XRD and IR analyses indicate that MAO does be coordinated with MgCl_2, which is in good agreement with the results obtained by XPS; 2.co-mlling time had no obvious effect on the texture of support after 12 hours; 3.In this work, MgCl_2 was co-milled with solid MAO for different hours, and then complex 3 was supported on these co-milled supports. It was found that co-milling time markedly influences the activity of solid catalysts, but it had negligible effect on the kinetic profile and the properties of resultant PE.

XPS研究结果表明，MAO不仅仅只和乙醇作用，MAO还与MgCl_2本身有一定的作用，这是一个极为重要的发现； 3、通过ICP和EDX表征，发现载体的脱醇温度直接影响着元素在固体催化剂中的含量及分布； 4、脱醇温度极大地影响着负载苯氧基亚胺类催化剂的活性和聚合物的性能，特别是原始载体经160℃活化4小时制备得到的固体催化剂MSPC-5的活性明显高于其他脱醇温度条件下制得的固体催化，并且催化剂寿命长，表现出稳定的动力学行为，最终获得了高堆密度(大于0.35g／ml)的球形聚乙烯颗粒； 5、本文选择MSPC-5为研究对象，考察了聚合反应参数对催化剂的活性及其聚合物的影响，研究发现：不同的烷基铝对催化剂具有非常重要的影响，特别足TIBA对MSPC-5的助催化活性最高，烷基铝的加入量有一个较佳值，聚合温度为80度时活性最高，H_2的加入使催化剂的活性明显降低且聚合物的分子量也减小；、新型氯化镁载体负载单活性中心催化剂催化乙烯聚合本文创造性采用固体MAO与无水氯化镁直接进行共研磨，制备出了一种的新型的氯化镁载体，并将该载体用于多种单活性中心催化剂的负载化研究，研究表明： 1、通过BET、XRD的表征，再次证实了MAO与MgCl_2之间具有直接作用，与XPS的研究结果相一致； 2、当研磨时间高于12小时时，延长研磨时间对载体的结构没有显著的影响； 3、将配合物3负载于共研磨时间不同的一系列载体上，乙烯聚合结果表明，尽管共研磨时间对负载催化剂的活性具有明显的影响，但是它对聚合物的性能以及催化剂的影响不明显。

As to MNa-ZSM-5, the order is CuNa-ZSM-5〓AgNa-ZSM-5＞CeNa-ZSM-5＞ CoNa-ZSM-5〓FeNa-ZSM-5＞Na-ZSM-5. Among the samples tested, CoHZSM-5 shows the highest activity, the conversion of NO is about 60%, and the activity is higher than that of CoNa-ZSM-5 with the same exchanged level. Suggests that the exist of some Bronsted acidity is benefited for this reaction. For Fe-ZSM-5, the activity are changed obviously with the various of preparation condition. It was also found that mordenite zeolite is a good support for this reaction.

其中，Co-HZSM-5表现出最佳的反应活性，NO的最高转化率达60％以上，并且活性明显高于具有相同交换度的CoNa-ZSM-5，表明适量的酸中心存在有利于该反应的进行；对于Fe-ZSM-5，制备条件不同Fe-ZSM-5的反应活性影响很大，反应的活性中心应是处在交换位上的铁离子；另外，通过考察不同载体对铁离子交换分子筛催化剂反应性能的影响，发现丝光分子筛也是较好的催化剂载体。

In chain-growth polymerisation, the highly-reactive spot on the growing polymer chain where new monomer is added.

活性中心活性中心是指连锁聚合中具有高活性的反应活性点，即新单体加入到增长的聚合物链的位置。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。