丙烯聚合用高效球形Ziegler-Natta催化剂制备工艺研究进展

综述了丙烯聚合用高效球形Ziegler-Natta催化剂的两种通用制备方法及其研究进展。采用负载法制备球形催化剂主要包括球形载体的制备和用Ti Cl4处理。乙醇含量不同,球形载体的结构不同,从而会影响催化剂的性能;Ti Cl4的处理温度、处理次数和内给电子体的加入情况等直接影响所制催化剂的性能。采用沉淀析出法制备球形催化剂是通过反应析出法直接得到球形催化剂,所制催化剂的性能主要由催化剂制备工艺决定。催化剂的性能可以通过制备路线和工艺进行有效调控,从而满足不同场合的需求。     

微乳液法制备纳米催化剂的应用研究进展

介绍了微乳液法制备纳米催化剂的工艺过程,阐述了微乳液法制备负载型纳米催化剂、无载体型纳米催化剂、分子筛及载体的研究进展,分析了制备过程中影响催化剂粒径大小及分布的因素,评述了微乳液法制备纳米催化剂的特点及发展方向.     

稀释剂对聚丙烯球形齐格勒-纳塔催化剂性能的影响

采用液相本体聚合法考察了异构脱蜡基础油与进口白油对氯化镁载体型高效球形齐格勒-纳塔催化剂催化丙烯聚合性能的影响,并用蒸馏法、密度计法和黏度指数计算法等分析了两种油的组成和基本物性,同时利用SEM和GPC表征了催化剂和聚合物。结果表明,与进口白油相比,异构脱蜡基础油的基本组成与进口白油接近;采用异构脱蜡基础油配制催化剂在技术路线上可行,经济上优于进口白油;异构脱蜡基础油对催化剂活性,以及聚丙烯的堆积密度、熔体流动速率和等规指数影响较小。     

球形氧化铝的制备及其在丙烷脱氢催化剂中的应用

以中和法、水热法、醇铝法和铝粉盐酸回流法合成的氧化铝前驱体为原料分别制备球形氧化铝载体（记为ZH、SR、ST和SOL）,通过强度仪、X射线荧光光谱仪（XRF）、低温氮气吸附-脱附、扫描电镜（SEM）、氨程序升温脱附（NH₃-TPD）等手段对氧化铝载体进行表征,以丙烷脱氢为探针反应研究了氧化铝的制备方法对催化剂（Pt-Sn-K/Al₂O₃）脱氢性能的影响。实验结果表明：不同方法合成的氧化铝前驱体均制备出高强度的球形氧化铝载体,其中水热法和醇铝法制备的载体还具有较大的孔容和适中的比表面积;前驱体的制备方法对催化剂的酸性影响较大,中和法制备的氧化铝载体制备的催化剂主要是弱-中强酸中心,其他方法制备的氧化铝载体制备的催化剂为弱酸中心,催化剂酸量由大到小的顺序为ZH-CAT、SOL-CAT、ST-CAT、SR-CAT;评价结果表明,醇铝法和水热法制备的载体应用于丙烷脱氢催化剂表现出良好的性能,相当于甚至优于工业剂水平。     

稀释剂配制的催化剂对丙烯聚合性能的影响

采用液相本体聚合法,在2 L反应釜中考察了分别用异构脱蜡基础油与进口白油作稀释剂配制的氯化镁为载体的高效球形催化剂催化丙烯聚合性能的影响,并用薄层色谱法、密度计法和运动黏度测定法等分析了这两种油的组成和基本物性。结果表明:异构脱蜡基础油的基本组成与进口白油接近;采用异构脱蜡基础油配制催化剂在技术路线上可行,经济上优于用进口白油配制催化剂;异构脱蜡基础油对催化剂活性,以及聚丙烯的堆密度、熔体流动速率和等规指数影响较小。     

轻油重整催化剂氧化铝载体新工艺的研究

重整催化剂载体是目前工业用量较大的载体之一，现在多采用金属铝和盐酸或三氯化铝为原料制备。由于制备过程流程长、设备腐蚀严重、产品收率低等因素，严重影响该产品的生产。以硫酸铝和铝酸钠为原料，采用沉淀一溶胶一凝胶技术制备重整催化剂载体，并用XRD、BET和压汞法等表征技术，研究了制备工艺过程条件对氧化铝载体性能的影响规律。     

SO_4~(2-)/M_xO_y型固体超强酸催化剂改性及应用研究进展

SO2-4/M x O y型固体超强酸型催化剂具有活性高、污染小、不腐蚀设备和可重复使用等优点,是一种典型的环境友好催化剂。分析微乳液法、水热法、回流老化法和模板法等制备方法对催化剂催化性能的影响,介绍催化剂载体改性、引入金属或分子筛、促进剂等改性方面的研究进展,综述SO2-4/M x O y型固体超强酸催化剂在有机反应包括异构化反应、酯化反应、烷基化反应、酰化反应、脱水反应和齐聚反应中的应用。今后研究重点是如何利用新技术改进催化剂的制备过程和提高固体酸比表面积。     

硅胶载体镁-钛催化剂乙烯聚合性能研究

研究了硅胶载体镁-钛催化剂的制备方法以及制备过程中影响聚合性能的关键因素,研究表明采用新生态氯化镁-硅胶复合载体,用醇类化合物和氯化烷基铝进行改性的工艺路线制得的催化剂具有高的催化效率和优良的氢调能力,确定了n(醇)∶n(镁)=2.0~2.3和n(铝)∶n(镁)=1.50~1.83时催化剂具有最好的聚合性能,以及采用升温程序2煅烧活化的硅胶载体制得的催化剂颗粒形态最好。研究还表明在不改变催化剂关键配方的情况下,可以通过调整硅胶载体的煅烧活化温度和镁-钛催化剂中的钛/镁质量分数比来实现对催化剂聚合动力学行为的调控。     

球形MgCl_2载体催化剂催化乙烯聚合

制备和分析了不同粒径催化剂及其催化聚合物,研究了球形MgCl_2载体催化剂在乙烯聚合过程中的催化性能和动力学行为。结果表明:大颗粒催化剂的聚合过程中明显存在传热和传质阻力;一定的预聚合可以改善聚合物的形态和堆密度。     

负载型钌炭加氢催化剂的工艺研究

通过对负载型钌炭催化剂的制备工艺的研究,分析讨论了载体种类、制备工艺中的负载和还原操作对钌炭催化剂性能的影响。研究结果表明:在催化剂的制备过程中,活性炭载体、负载方式和还原操作对表面活性金属的分散度有影响,从而造成催化剂的性能差异。选择椰壳炭为载体、沉淀法进行活性金属的负载,经过液相法硼氢化钠还原得到的催化剂表面活性金属的分散度高,催化剂在苯部分加氢反应中具有高活性和高选择性,环己烯的收率达到55%。     

蒙脱土/碳纳米管多维增强的聚乙烯复合材料的制备

引言聚烯烃是国民生活和现代国防不可或缺的基础原材料,但与ABS、PC等工程塑料相比,其刚性不足,低温脆性也较明显,因此很难作为结构材料使用。纳米技术的出现为聚烯烃材料性能的提高提供了广阔的空间[1],其中,纳米复合材料中存在纳米尺寸效应、超大的比表面积以及很强的界面相互作用,具有比强度高、可设计性强、抗疲劳性好等优点,因此,纳米复合聚乙烯中含少量纳米材料便能极大增强材料本身的性能,同时聚合物中纳米材料的低含量也大大减少了无机载体在聚合物中的灰分,有利于聚合物材料高性能的保持,这引起了研究工作者的广泛关注。     

POSS改性负载型Ziegler-Natta催化剂及其乙烯/1-己烯共聚反应

采用具有开放型骨架结构的大孔SiO₂（Macro-SiO₂）与MgCl₂形成复合载体,同时引入聚倍半硅氧烷（POSS）形成具有空间分隔作用的POSS/MgCl₂纳米团聚体,负载TiCl₄后制备得到改性Ziegler-Natta催化剂。采用红外分析、热重分析、CO低温吸附红外、扫描电镜、粒径分析等手段对POSS改性前后催化剂的结构进行表征,发现POSS的引入能诱导MgCl₂形成更多Mg_4c²⁺缺陷位点,并促进了Lewis酸性位点的形成,有利于TiCl₄有效活性中心的负载。乙烯/1-己烯共聚结果表明,POSS改性催化剂活性较高,最高可达1.03×10⁶ g?（mol?h）^-1,同时具有更高的共聚能力,共聚产物中共聚单体摩尔分数可达3.79%,且聚合产物具有较窄的分子量分布（MWD=3~6）。     

Carbon formation and its influence on ethanol steam reforming over Ni/Al2O3 catalysts

Ethanol steam reforming was studied over Ni/Al₂O₃ catalysts. The effect of support (- and γ-Al₂O₃), metal loading and a comparison between conventional H₂ reduction with an activation method employing a CH₄/O₂ mixture was investigated. The properties of catalysts were studied by N₂ physisorption, X-ray diffraction (XRD) and temperature programmed reduction (TPR). After activity tests, the catalysts were analyzed by scanning electron microscopy (SEM) and thermogravimetric analysis (TG/DTA). Ni supported on γ-Al₂O₃ was more active for H₂ production than the catalyst supported on -Al₂O₃. Metal loading did not affect the catalytic performance. The alternative activation method with CH₄/O₂ mixture affected differently the activity and stability of the Ni/γ-Al₂O₃ and the Ni/-Al₂O₃ catalyst. This activation method increased significantly the stability of Ni/-Al₂O₃ compared to H₂ reduction. SEM and TG/DTA analysis indicate the formation of filamentous carbon during the CH₄/O₂ activation step, which is associated with the increasing catalyst activity and stability. The effect of temperature on the type of carbon formed was investigated; indicating that filamentous coke increased activity while encapsulating coke promoted deactivation. A discussion about carbon formation and the influence on the activity is presented.     

Support effects in the hydrotreatment of model molecules

The support effect on the activity of hydrotreating catalysts using model molecules was analyzed for catalysts supported on TiO₂, SiO₂ and MgO. The results reported in the literature indicate that adequate design of the characteristics of the catalytic support is of great importance in the development of better hydrotreating catalysts. It was shown that by means of an adequate support design it is possible to increase significantly the HDS, HYD and HDN functionalities of hydrotreating catalysts. Semiconducting supports like TiO₂ can improve the HDS and HYD activities by exerting electronic effects on the active phase, helping in this way the formation of sulfur vacancies. Alumina supports modified by SiO₂ can facilitate the sulfidation of the active species, leading to better-promoted type II active sites with increased HDS and HYD catalyst functionalities. The nature of the support affects the sulfidation and dispersion of the catalysts even when chelating agents are used during catalyst preparation.     

Effects of identities of supports on Fe-based catalyst and their consequences on activities of CO2 hydrogenation to olefins

The direct synthesis of olefins by CO₂ hydrogenation with iron-based catalysts is one of the best ways to achieve CO₂ emission reduction and CO₂ conversion and utilization. At present, the CO₂ hydrogenation activity and structural strength of the iron-based catalysts are still relatively low during CO₂ hydrogenation process, which has become an important challenge for the industrialization of CO₂ hydrogenation to olefins. In this work, a series of the supported iron-based catalyst was prepared by the impregnation method to study the influence of the properties of support materials on the structure of iron-based catalysts and the reactivities of the direct synthesis of olefins from CO₂ hydrogenation. This work found that the support induced the iron species formed during the process of CO₂ hydrogenation, simultaneously affected the order degree of carbon species on the surface of iron-based catalyst, and tuned the capability of CO₂ adsorption and the activities of CO₂ activation. The results shown that the Fe-based catalyst supported on ZrO₂ exhibited the best catalytic performance for CO₂ hydrogenation to olefins at 320℃ and 2.0 MPa. The CO₂ conversion (>30%) and the selectivity of olefins in C₂—C₇ hydrocarbon products were as high as over 85%, the ratio of olefins to paraffins was 8.2, and the CO selectivity was 17.1%.     

载体对铁基催化剂结构及CO2加氢制烯烃反应性能的影响特性

铁基催化剂CO₂加氢直接合成烯烃是实现CO₂减排及CO₂转化与利用的最佳途径之一。目前铁基催化剂的CO₂加氢活性及反应过程中铁基催化剂结构强度仍然较低,成为CO₂加氢制烯烃产业化生产的重要挑战。通过浸渍法制备一系列负载型铁基催化剂,研究载体材料性质对铁基催化剂结构及CO₂加氢直接合成烯烃的影响特性。研究发现,载体可诱导铁基催化剂在CO₂加氢反应过程中形成的铁物种,同时影响铁基催化剂表面碳物种的有序度,调变对CO₂吸附及活化能力;研究结果表明ZrO₂负载的Fe催化剂展现出最佳的CO₂加氢合成烯烃催化性能,在温度320℃和反应压力2.0 MPa时,CO₂转化率>30%,C₂~C₇烃类产物中烯烃选择性高达85%以上,烯烷比为8.2,且CO选择性较低为17.1%。     

催化剂形貌对沸腾床渣油加氢Ni-Mo/Al2O3催化剂活性位的影响机制

随着原油供应趋于劣质化和严格的环保法规出台,沸腾床渣油加氢技术引起了广泛关注。采用挤压成型法和STRONG沸腾床的特殊成型法分别制备了圆柱形和球形Ni-Mo/Al₂O₃催化剂,系统地研究了催化剂的颗粒形貌对活性相和渣油加氢性能的影响。采用XRD、N₂物理吸脱附、H₂-TPR、HRTEM、XPS和电子微探针分析等手段对催化剂进行了表征。结果表明,球形催化剂具有活性更强的Type Ⅱ类型活性位点、更优异的孔道结构性质和更好的流化性能,这使得其具有更高的渣油加氢活性。球形催化剂中的金属和载体之间相互作用较弱,这有利于形成更高硫化程度和堆垛层数的Ni-Mo-S Ⅱ型活性相,这种活性相在渣油加氢中具有更高的活性。此外,球形催化剂具有比圆柱形催化剂更大的孔径和孔体积,这有利于大分子杂质在孔道中的扩散和活性位点上的吸附,并且使得金属沉积物均匀分布在球形催化剂中,而不是集中分布在孔口。而且球形催化剂尺寸更小,可能更易于流化,这增强了催化剂的传质性能。     

Ni-P/TiO2非晶态催化剂对α-蒎烯加氢的性能

采用化学还原法制备Ni-P/TiO₂非晶态催化剂,以α-蒎烯加氢反应为探针反应,考察了催化剂制备条件对其催化性能的影响,得到适宜的制备条件为载体与NiCl₂?6H₂O质量比为3∶1,P/Ni摩尔比为2.5∶1,反应温度为25℃,pH为11。结果表明：该条件下制备的催化剂对α-蒎烯加氢具有较高的催化活性,α-蒎烯转化率为99.89%,顺式蒎烷选择性为98.48%,收率为98.37%,且可重复使用8次。以XRD、BET、DSC、XPS、TEM为表征手段,对催化剂失活前后的结构及形貌进行了分析,结果表明：新鲜催化剂为粒径均一的球形颗粒,粒径约为100nm,分散性较好,引入TiO₂有效提高了Ni-P粒子的热稳定性,将其晶化温度分别提高了78℃、190℃和115.1℃,而失活催化剂的分散度、Ni⁰含量均有下降,出现了活性组分流失、氧化及团聚等现象,这可能是导致催化剂失活的主要原因。     

Activation of monolithic catalysts based on diatomaceous earth for sulfur dioxide oxidation

The formation of the active phases during the activation process of monolithic catalysts based on V₂O₅–K₂SO₄ supported on diatomaceous earth for SO₂ to SO₃ oxidation in flue gases, has been shown to be a crucial factor to achieve satisfactory catalytic performance. As the temperature is increased from room temperature to 470°C, SO₂ and SO₃ are taken up by the green catalyst and the precursors are transformed into the active species. The role of each component of the catalyst during the activation was analyzed by studying the behavior towards SO₂ adsorption of four materials, which contained: diatomaceous earth, diatomaceous earth + V, diatomaceous earth + K, and diatomaceous earth + V + K. The influence of the potassium sulfate accessibility in the green catalyst was studied by using two different preparation methods, which gave rise to differences in the catalysts SO₂ adsorption properties and catalytic performance. Furthermore, the influence of the activation atmosphere was studied using nitrogen, oxygen or a flue gas composition. It was shown that pyrosulfate species should be formed at temperatures below 400°C, to keep the vanadium in the active 5+ oxidation state.     

Effects of small MoO3 additions on the properties of nickel catalysts for the steam reforming of hydrocarbons III. Reduction of Ni-Mo/Al2O3 catalysts

Ni/Al₂O₃ catalyst modified by small amounts of Mo show unusual properties in the steam reforming of hydrocarbons. There are no data about the effect of small amounts of molybdenum on reduction of the Ni-Mo supported catalysts. The properties of these very complex systems depend on the conditions of successive preparation stages (calcination, reduction) or the process conditions.

A series of Ni/Al₂O₃ catalysts modified by Mo were prepared in order to investigate the influence of promoter amounts and preparation sequence on their properties. Temperature programmed reduction (TPR) has been employed to study the reducibility of Ni-Mo/Al₂O₃ catalysts. Catalysts were further characterized by BET area, H₂ chemisorption and X-ray diffraction measurements.

The TPR curves of Ni-Mo/Al₂O₃ catalysts are very complex. Mo addition leads to the decrease of catalysts reducibility. However, complete reduction of NiO and MoO₃ can be achieved at 800 °C. The reduction course depends on the sequence of nickel and molybdenum addition into the support. Precise measurements of Ni peaks positions in the XRD pattern of Ni/Al₂O₃ and Ni-Mo/Al₂O₃ samples show the possibility of Ni-Mo solid solution formation.