Synthesis of a novel titanium complex catalyst and its catalytic performance for olefin polymerization

Russian Journal of Applied Chemistry - A phenoxy-ester Ti based complex of bis[5-methyl-3-trimethylsilyl phenyl salicylate]titanium(IV) dichloride was prepared for olefin polymerization. The...     

苯环上氯取代位对四苯基金属卟啉催化烯烃环氧化性能的影响

以苯乙烯、环己烯和反式二苯乙烯为烯烃底物,以双氧水、叔丁基过氧化氢和异丙苯过氧化氢为氧化剂,以苯环上对位和邻位氯取代的四苯基金属卟啉为仿生催化剂,对烯烃的催化环氧化反应进行了对比研究.讨论了不同氯取代位的四苯基金属卟啉对烯烃环氧化性能的影响.实验结果表明,在没有助催化剂存在下,邻位氯代的四(2,6-二氯苯基)铁(锰)卟啉对烯烃的环氧化具有优异的催化性能,烯烃底物的转化率和环氧选择性都比对位氯代的四苯基铁(锰)卟啉高,且反应条件温和.其中FeⅢ(TDCPP)Cl的催化性能最好,环氧化选择性最高,催化氧化苯乙烯时,环氧苯乙烷的选择性达到了90.4%.相同金属离子不同配体的金属卟啉传递氧原子的能力为TDCPP>T(p-Cl)PP>TPP.氧化剂的结构对环氧化物的选择性有较大影响.过氧键连有吸电子基团的异丙苯过氧化氢对环氧化物的选择性最高.根据实验结果,对金属卟啉催化环氧化机理进行了分析.     

预处理Fe基催化剂CO加氢合成低碳烯烃选择性影响研究

研究了Fe₂O₃在CO和H₂气氛下预处理对催化剂物相、表面组成和性质的影响及CO加氢合成低碳烯烃反应行为。结果表明,300℃ H₂预处理后催化剂主要物相结构为Fe₃O₄和α-Fe,250℃ CO预处理后主要物相为Fe₃O₄,随着CO预处理温度的升高,有碳化铁生成。表面碳化物含量随着CO预处理温度的升高而增加。CO较H₂预处理表面碱性增强,CO₂和CO吸附显著增加,随着预处理时间的延长,表面积炭降低了CO₂和CO吸附。经CO预处理的催化剂具有较高的烯烃选择性,H₂预处理的催化剂烯烃选择性相对较低。     

碳化对超细Fe-Mn催化剂CO加氢反应行为的影响

以超细Fe-Mn催化剂为前驱体,对其进行了CH₄/H₂气氛下的高温碳化及反应行为研究。结果表明,高温碳化后,催化剂比表面积明显降低,主要物相结构为FeO-MnO尖晶石和α-Fe相,并有大量碳化铁微晶生成。在CO加氢反应中,碳化过程明显提高了烯烃选择性,降低了CH₄选择性,促进了链增长。结果认为,碳化过程改变了催化剂表面化学性质,增强了表面碱性,抑制了二次加氢反应,提高了烯烃选择性。     

微波水热制备Fe-Zr催化剂及其CO加氢制烯烃性能研究

以ZrO（NO₃）₂·2H₂O和Fe（NO₃）₃·9H₂O为原料,采用微波水热法制备了不同Fe₂O₃/ZrO₂物质的量比的Fe-Zr催化剂,并经K改性,研究了其催化CO加氢一步法合成低碳烯烃性能。采用XRD、SEM、TEM和N₂吸附-脱附等手段对其物相、形貌和比表面积等进行了表征。结果表明,与共沉淀法相比,微波水热制备的Fe-Zr催化剂颗粒粒径均一,具有相对较小的比表面积和较大的孔径;在CO加氢反应中,Zr助剂的添加显著改善了产物分布,Fe、Zr间适宜的相互作用和相对较大的孔径,有利于抑制CH₄的生成,提高烯烃选择性。随着Fe₂O₃/ZrO₂物质的量比的降低,Fe、Zr间相互作用逐渐增强,烯烃选择性和收率先增加后降低。当Fe₂O₃/ZrO₂物质的量比为75：25时,在340 ℃、1.5 MPa、1 000 h^-1和H₂/CO物质的量比为2的条件下,烯烷比（O/P）达4.86,总烯烃收率达62.57 g/m³。     

Effects of promoters on catalytic performance of Fe-Co/SiO2 catalyst for Fischer-Tropsch synthesis

2%Fe-10%Co/SiO₂ catalysts with different potassium or zirconium loadings were prepared by aqueous incipient wetness impregnation and tested for Fischer-Tropsch synthesis in a flow reactor, using H₂/CO = 1.6 (molar ratio) in the feed, under the condition of an overall pressure of 1 MPa, GHSV of 600 h⁻¹ and temperature of 503 K. The zirconium and potassium promoters remarkably influenced hydrocarbon distribution of the products. CO conversion increased on the catalysts with the increase of zirconium loadings, which indicated that zirconium enhanced the activity of iron-cobalt catalysts. Low potassium loadings also enhanced the activity of the catalysts. However, high potassium loading made CO conversion on the catalysts decrease and weakened the secondary hydrogenations. The catalyst was characterized by BET, XRD and TPR. The catalyst characterization revealed that the Co₃O₄ phase was presented on the fresh catalyst, whereas the spinel phase of Fe-Co alloy and CoO existed on the used catalyst.     

Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.     

双金属Ce-Mn/ZSM-5催化剂的制备及NH3-SCR脱硝性能研究

采用浸渍法制备了铈锰复合氧化物分子筛催化剂(Ce-Mn/ZSM-5),在固定床反应器上考察不同Ce/Mn质量比对分子筛催化剂选择催化还原NO的影响,利用XRD、TEM、NH_3-TPD、H_2-TPR、in-situ DRIFTS等手段对催化剂进行了表征分析。结果表明,双金属改性的Ce-Mn/ZSM-5催化剂在NH_3-SCR反应中表现出较为优异的催化活性,具有较宽的活性温度窗口。当Ce/Mn质量比为0.4时,催化剂具有最佳的脱硝效率,在265-465℃脱硝率均可达到80%以上,在370℃时,NO的转化率最高可达97.28%。锰和铈物种高度分散于催化剂表面,未改变ZSM-5的晶体结构,且构成协同作用。0.4Ce-Mn/ZSM-5具备丰富的酸性位、良好的氧化还原性能,该配比有助于催化剂的催化活性和稳定性的提高,在NH_3-SCR反应过程同时遵循E-R机理和L-H机理。     

Study on iron-manganese catalysts for Fischer-Tropsch synthesis

Iron-manganese catalysts were prepared by co-precipitation method.Characterization of catalysts was carried out by using X-ray diffraction(XRD),scanning electron microscopy(SEM),temperature program reduction(TPR),N2 adsorption-desorption measurements.The results from catalytic performance tests in Fischer-Tropsch synthesis showed that the iron-manganese catalysts are supersensitive to catalyst composition and materials source.It was found that C2~4 light olefins increased while CH4 and CO2 decreased by using iron-manganese catalyst prepared from iron(II) sulfate(A catalyst).The activity and selectivity of A catalyst was studied in different operational conditions.The results showed that the best operational conditions for C2~4 light olefins production were H2/CO=1/1(GHSV=2400h-1) at 260℃ under 0.3MPa total pressure.     

Optimizing the preparation of an alumina-supported rhenium catalyst for olefin metathesis

The processes involved in the formation of the alumina-supported rhenium catalyst for olefin metathesis, from the impregnation of the support (thermally activated alumina) with ammonium perrhenate to thermal activation, are studied. The monolayer coverage of the Al₂O₃ surface is observed at a rhenium content of 10 wt % (on Re₂O₇ basis), and the surplus rhenium is sublimed as heptoxide from the support upon thermal activation. In the metathesis of both linear α-olefins and methylenecyclobutanes, the optimum supported rhenium content of the catalyst is 10 wt % on Re₂O₇ basis.     

Influence of support recrystallization techniques on catalyst performance in olefin polymerization

This paper is a comparative study of the performance of TiCl₄ catalysts supported on recrystallized MgCl₂ through different techniques for the polymerization of ethylene, propylene and ethylene-propylene copolymers. MgCl₂ was dissolved in 1-hexanol and recrystallized through solvent evaporation, quick cooling and precipitation with SiCl₄. The effect of the recrystallization conditions during the catalyst preparation on the chemical composition of catalysts was discussed with the help of IR spectroscopy. The variations of dealcoholation levels due to the different recrystallization techniques highly influenced the catalytic activity. The catalyst obtained through SiCl₄ recrystallization was not only the most active, but it also showed the highest isotacticity indexes for propylene polymerization.     

Effects of the ratio of Fe to Co over Fe-CO/SiO2 bimetallic catalysts on their catalytic performance for Fischer-Tropsch synthesis

The Fe-Co/SiO2 bimetallic catalysts with different ratios of Fe to Co were prepared by aqueous incipient wetness impregnation. The catalysts of 10%Fe:0%Co/SiO2, 10%Fe:6%Co/SiO2, 10%Fe:2%Co/SiO2, 10%Fe:10%Co/SiO2, 6%Fe:10%Co/SiO2, 2%Fe:10%Co/SiO2 and 0%Fe: 10%Co/SiO2 by mass were tested in a fixed reactor by the Fischer-Tropsch synthesis. Activity and hydrocarbon distribution were found to be determined by the ratio of iron to cobalt of the catalysts. Higher iron content inhibited the activity, whereas higher cobalt content enhanced the activity of the Fe:Co/SiO2 catalysts. On the other hand, for the catalysts of 10%Fe:6%Co/SiO2, 10%Fe:10%Co/SiO2, 6%Fe:10%Co/SiO2, and 2%Fe:10%Co/SiO2, the total C2–C4 fraction increased (from 10.65% to 26.78%) and C5+ fraction decreased (from 75.75% to 57.63%) at 523 K. Temperature programmed reduction revealed that the addition of cobalt enhanced the reducibility of the Fe:Co/SiO2 catalyst. Metal oxides were present in those catalysts as shown by XRD. The Fe-Co alloy phase was found in the 2%Fe:10%Co/SiO2, 6%Fe:10%Co/SiO2, 10%Fe:10%Co/SiO2, 10%Fe:6%Co/SiO2 catalysts and their crystals were perfect.     

Doping effects of manganese on the catalytic performance and structure of NiMgO catalysts for controllabe synthesis of multi-walled carbon nanotubes

Doping effects of manganese （Mn） on catalytic performance and structure evolution of NiMgO catalysts for synthesis of multi-walled carbon nanotubes （MWCNTs） from methane were investigated for the first time. Addition of Mn in NiMgO catalyst can greatly improve the MWCNTs yield. Mno.2NiMgO catalyst among the tested ones gives the highest MWCNTs yield as 2244%, which is two times higher than that of the catalyst without Mn. The structure evolution, reduction behaviors and surface chemical properties of MnNiMgO catalysts with various Mn contents were studied in detail. It was found that the stable solid solution of NiMgO2 formed in NiMgO catalyst was disturbed by the addition of Mn. Instead, another solid solution of MnMg608 is formed. More amount of Ni can be reduced and dispersed on the catalyst surface to be acted as active sites. Importantly, the changes of Ni content on the surface are correlated with the Ni particle size and the outer diameter of MWCNTs, suggesting the controllable synthesis of MWCNTs over MnNiMgO catalysts.     

Effects of the ratio of Fe to Co over Fe-Co/SiO2 bimetallic catalysts on their catalytic performance for Fischer-Tropsch synthesis

The Fe-Co/SiO2 bimetallic catalysts with different ratios of Fe to Co were prepared by aqueous incipient wetness impregnation. The catalysts of 10%Fe:0%Co/SiO2, 10%Fe:6%Co/SiO2, 10%Fe:2%Co/SiO2, 10%Fe: 10%Co/SiO2, 6%Fe: 10%Co/SiO2, 2%Fe: 10%Co/SiO2 and 0%Fe: 10%Co/SiO2 by mass were tested in a fixed reactor by the Fischer-Tropsch synthesis. Activity and hydrocarbon distribution were found to be determined by the ratio of iron to cobalt of the catalysts. Higher iron content inhibited the activity, whereas higher cobalt content enhanced the activity of the Fe-Co/SiO2 catalysts. On the other hand, for the catalysts of 10%Fe:6%Co/SiO2, 10%Fe: 10%Co/SiO2, 6%Fe: 10%Co/SiO2, and 2%Fe: 10%Co/SiO2, the total C2-C4 fraction increased (from 10.65% to 26.78%) and C5+ fraction decreased (from 75.75% to 57.63%) at 523 K. Temperature programmed reduction revealed that the addition of cobalt enhanced the reducibility of the Fe-Co/SiO2 catalyst. Metal oxides were present in those catalysts as shown by XRD. The Fe-Co alloy phase was found in the 2%Fe: 10%Co/SiO2, 6%Fe: 10%Co/SiO2, 10%Fe:10%Co/SiO2, 10%Fe:6%Co/SiO2 catalysts and their crystals were perfect.     

Templated synthesis and catalytic properties of an Rh/ceria-zirconia catalyst

Ceria-zirconia nanophase with structural defects and high thermal stability was synthesized by a surfactant-templated method. The 0.5 wt.% Rh/ceria-zirconia catalyst shows high activity for NO reduction by CO under an oxygen-rich condition, and the selectivity to 100% N₂ below 200°C was achieved.     

Novel polystyrene‐supported zirconocene catalyst for olefin polymerization and its catalytic kinetics

Through the Diels–Alder reaction between cyclopentadiene groups attached to polystyrene in the presence of zirconocene, novel polystyrene‐supported metallocene catalysts were prepared. A novel method for immobilizing metallocene catalysts was investigated, and the resultant polystyrene‐supported metallocene for olefin polymerization was studied. The results of olefin polymerization showed that different crosslinking degrees of support in the catalyst system had significant effects on the catalytic behavior. The influence of the [Al]/[Zr] molar ratio and the temperature on the (co)polymerization activity was studied. When 1‐hexene and 1‐dodecene were used for copolymerization with ethylene, an obvious positive comonomer effect was observed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2650–2656, 2005     

Al2O3助剂对Co/SiC催化剂F-T反应性能的影响

分别采用沉淀法、尿素水解法制备Al₂O₃/SiC复合载体,采用等体积浸渍法制备Co/Al₂O₃-SiC催化剂。结合N₂吸附、XRD、H₂-TPR、XPS等表征手段,研究Al₂O₃助剂对钴基催化剂物相结构、还原行为以及F-T合成性能等的影响。结果表明,氧化铝加入后增强了载体与钴物种之间的相互作用,提高了钴物种的分散度,降低了钴物种的还原度。尿素水解法引入Al₂O₃后,载体与钴物种具有适中的相互作用,表现出较高的反应活性。沉淀法制备的载体负载钴物种后由于较强的金属-载体相互作用,表现出较优的稳定性。     

Role of surface defects of carbon nanotubes on catalytic performance of barium promoted ruthenium catalyst for ammonia synthesis

Carbon nanotubes(CNTs) with abundant surface defects are prepared by a liquid oxidation and thermal annealing method. The defective CNTs-D supported Ba–Ru/CNTs-D catalysts exhibit superior catalytic performance in ammonia synthesis with a TOF be increased up to 0.30 s-1, which is 2.5 times of oxidized CNTs-O supported Ba–Ru/CNTs-O catalysts and 5 times of the Ba–Ru/CNTs. The characterizations by CO chemisorption, transmission electron microscope, Raman, and X-ray photoelectron spectroscopy revealed that the uniformly well dispersed Ru NPs can be stabilized on the defective sites of CNTs-D. The great improvement of the catalytic performance and stability of the Ba–Ru/CNTs-D is contributed to the strong interaction between Ru NPs and surface defect of the CNTs.     

表面活性剂Tween对TS-1合成及催化性能影响的研究

以添加吐温的少量四丙基氢氧化铵（TPAOH）为模板剂,水热下合成了钛硅分子筛（TS-1）。采用FTIR、XRD、SEM、BET、UV-Vis等手段对分子筛进行表征。XRD结果表明,所得样品完全晶化,具有典型的MFI拓扑学结构;FTIR结果表明,样品在960 cm－1处出现了强吸收峰,表明钛已进入骨架;UV-Vis谱图表明,所合成样品在330 nm附近没有电子跃迁信号,表明其中没有锐钛矿型TiO2;SEM结果表明所合成样品的晶粒大小均匀。在添加适量吐温所得的胶团溶液中,模板剂分子与吐温之间的协同作用有助于TPAOH与硅、钛源定向反应,避免非骨架TiO2的生成,减少了TPAOH的用量,丙烯环氧化反应结果表明,吐温20、吐温40、吐温60及吐温80等非离子表面活性剂的添加都有助于降低模板剂（TPAOH）的用量和提高TS-1的催化活性,其中吐温40的影响尤为显著,吐温40/TPAOH摩尔比为0.02时,过氧化氢转化率达98.1%,环氧丙烷选择性和收率分别可达96.1％和94.3％。