Synthesis of a novel triple-site diphosphinoamine （PNP） ligand and its applications in ethylene tetramerization

A novel triple-site diphosphinoamine （PNP） ligand was synthesized and characterized. In combination with Cr（Ⅲ） and methylaluminoxane （MAO）, it generated active catalytic systems for ethylene tetramerization toward 1-octene with high catalytic activity and long lifetime. The effects of reaction temperature, molar ratio of AI/Cr and molar ratio of ligand/Cr on catalytic activity and selectivity to 1-octene were studied with reaction kinetics of the catalytic system for ethylene tetramerization described. At the AI/Cr molar ratio of 100, the catalytic activity is up to 2.29×10^6 g· mol^-1 （Cr）· h^-1 and the selectivity to 1-octene is 49.65 wt%.     

A series of novel bisphosphinoamine ligands: Synthesis,characterization and application in ethylene tetramerization

A series of novel N-halogen-substituted-aryl bisphosphinoamine ligands were synthesized and characterized by elemental analysis, ¹H NMR and mass spectrometry. The combination of these ligands with Cr(III) and activation by methylaluminoxane leads to highly active catalytic systems for the tetramerization of ethylene to form 1-octene. The catalytic activities and product selectivities depend on the aryl ring substituents and the reaction conditions. We found that the location and size of the substituents are important in determining the catalytic activity and selectivity toward 1-octene. This trend is similar to that observed for their alkyl-substituted analogues.     

Ethylene tetramerization with a highly active and long-lifetime trinuclear diphenylphosphinoamine/Cr（III）/MAO catalyst

The synthesis and characterization of a novel trinuclear diphosphinoamine ligand 2 are reported. The ligand combined with Cr(III), activated with methylaluminoxane, lead to highly active and long-lifetime catalytic systems for the tetramerization of ethylene to form 1-octene. The effects of reaction temperature, reaction pressure, molar ratio of Al/Cr and bis(diphenylphosphino)amine/Cr on the catalytic activity and product selectivity were studied. Compared with its mononuclear analogue 1, ligand 2 showed a higher catalytic activity and longer lifetime for ethylene tetramerization in the presence of methylaluminoxane as cocatalyst. High molecular weight polyethylene was generated as a by-product with extremely broad molecular weight distributions.     

碳钛复合材料负载钴基费-托合成 催化剂的结构和催化性能

采用水热法合成碳钛复合材料,以碳钛复合材料为载体制备了钴基费-托合成催化剂.采用氮气物理吸附-脱附、原位X射线衍射(XRD)、透射电子显微镜(TEM)、氢气程序升温还原(H₂-TPR)、X射线光电子能谱(XPS)等对催化剂进行了表征,在固定床反应器上对催化剂的费-托合成催化性能进行了评价.结果表明：利用碳改性二氧化钛可明显影响催化剂的催化活性,由于碳的引入导致催化剂更易于还原,催化剂的分散较好,具有更高的费-托合成活性和重质烃选择性(C₅⁺).     

Preparation of PE/MMT nanocomposite by monomer intercalation and <Emphasis Type="Italic">in situ</Emphasis> copolymerization

The catalyst [(2-ArN=C(Me))₂C₅H₃N]FeCl₂ (Ar = 2-C₆H₄(i-Pr)) with methylaluminoxane (MAO) as cocatalyst was intercalated between layers of montmorillonite (MMT) for ethylene oligomerization. Metallocene catalyst Me₂Si(Ind)₂ZrCl₂ and MAO was then added to form a dual functional catalytic system. A PE/MMT nanocomposite was prepared by copolymerization of ethylene with α-olefins produced in situ from ethylene over the dual functional catalytic system. The catalytic system was of high polymeric activity. The resultant PE/MMT nanocomposites were stable and got increases in tensile strength and temperature of maximum weight loss (T_onset).     

Measurement of ethylene and methane production in a temperate forest soil using inhibition of acetylene and carbon monoxide

We studied in the laboratory the effects of acetylene （C2H2） concentrations on the accumulation and consumption of ethylene and methane in a temperate pine forest soil, and in situ ethylene and methane production and flush effects of nitrogen sources on both productions in the pine forest stand （Pinus sylvestris L.）. The addition of C2H2 at concentrations more than 50 Pa C2H2 in the headspace caused a more than 95% reduction in rates of ethylene and methane consumption in forest soil compared to those with no C2H2. Furthermore, addition of acetylene within a range of 50 to 10, 000 Pa C2H2 induced a similar rate of methane accumulation in forest soil. Hence, it can be concluded that presence of more than 50 Pa C2H2 in the headspace is an effective method to measure methane production in forest soil. The addition of C2H2 at concentrations more than 50 Pa C2H2 induced an increasing concentration of ethylene in the headspace （P≤0.05）, indicating the reduction of acetylene to ethylene in forest soil. Using inhibition of 0.5 kPa C2H2 in combination with 5 kPa carbon monoxide that inhibits the reduction of acetylene in a short term, it was observed that there was a larger in situ methane production rate （218±26 μg C m^-2 h^-1（μg C per square meter per hour, the same below）） than in situ ethylene production rate （92±6 μg C m^-2 h^-1） in the pine forest soil. The addition of nitrogen sources such as urea, urea plus a nitrification inhibitor dicyandiamide, and potassium nitrate, could induce a 5-fold greater increase in rates of in situ ethylene and methane production compared to those in the control, particularly in the latter （P≤0.05）. The results can promote in situ measurement of ethylene and methane production in forest soils at different sites.     

LLDPE/TiO2 nanocomposites produced from different crystallite sizes of TiO2 via in situ polymerization

Nano-TiO2 particles with a range of crystallite sizes were synthesized by a conventional sol-gel method,and then used as nanoparticle substrates in the synthesis of LLDPE/TiO2 nanocomposites via in situ polymerization of ethylene/1-hexene with zirconocene/MMAO catalyst.It was found that the size of the nano-TiO2 crystallite nanoparticles can influence the catalytic activity in the polymerization system.The larger nano-TiO2 crystallites provided better catalytic activity in the polymerization system due to more space for monomer attack.In addition,by thermo-gravimetric analysis,it can be seen that the larger nano-TiO2 crystallites also exhibited lower interaction with available MMAO.Consequently,the MMAO reacted more efficiently with the zirconocene catalyst during the activation process,and enhanced polymerization catalysis.All the polymer nanocomposites products did not have well defined melting temperature indicating non-crystalline polymers.This is due to the high amount of hexene incorporation(based on 13C NMR).The difference in crystallite sizes of the nano-TiO2 also affected how 1-hexene became incorporated into the polymer nanocomposites.The smaller crystallite size of nano-TiO2 allowed greater 1-hexene incorporation due to depression of the reactivity of the ethylene.The contribution of this work helps develop a better understanding of the role of nano-TiO2 in the catalytic activity of the polymerization system and in the microstructure of the polymer composite product.However,this study only considers work on the laboratory scale,so for commercial application of these results,it is necessary to scale up the polymerization process.It is only at this stage,that other physical properties,such as the mechanical properties of these materials can be sensibly determined.     

Styrene polymerization catalyzed by nickel complexes bearing hydroxyindanone-iminate ligands

Activated by methylaluminoxane, mononuclear bis（hydroxyindanone-iminate）nickel complexes Ni[ArN=CC2H3（CH3）C6H2（R）O]2 （Ar = 2,6-i-Pr2C6H3, R=Me（1）, R=CI（2）, and R=H（3）） showed good activity for the styrene polymerization. The effect of many reaction parameters including the AI/Ni ratio, temperature, and reaction time on catalytic activities of catalytic systems and the molecular weights of the obrained polystyrene was ascertained. The highest activity of 1.34×10^5g（PS）·mol^-1（Ni）·h^-1 was obtained under the optimum reaction condition. The ^13C NMR spectra of the polymers revealed that the polymer was isotactic-rich atactic polystyrene. And the coordination mechanism was confirmed by the analyses of the polymer chain end-groups.     

Characterization of a nitrogenase CrFe protein from a mutant UW3 of Azotobacter vinelandii grown on a Cr-containing medium

Biological nitrogen fixation is one of the most im-portant biochemical reactions in nature. It is catalyzed by an anaerobic metalloenzyme complex-nitrogenase. Three genetically distinct nitrogenase systems exist in Azotobacter vinelandii (A. vinelandii): Mo-containing nitrogenase, V-containing one and “Fe only” nitro-genase[1―4]. They are composed of two separable com-ponent proteins. For example, conventional Mo-con- taining nitrogenase is composed of component I (MoFe protein) and com…     

Ethylene oligomerization by novel iron(Ⅱ) diimine complexes/MAO

Two novel Fe(Ⅱ) diimine complexes have been synthesized. In combination with MAO, they generate active catalytic systems that oligomerize ethylene with both high catalytic activity and high selectivity for α-olefins. The effects of substituents on the aryl ring, reaction temperatures and molar ratios of Al/Fe on catalytic activity and product distribution are studied.     

Effect of aging temperature on the microstructures and mechanical properties of ZG12Cr9Mo1Co1NiVNbNB ferritic heat-resistant steel

The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9Mo1Co1NiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant. The results show that the main precipitates during aging are Fe(Cr, Mo)₂₃C₆, V(Nb)C, and (Fe₂Mo) Laves in the steel. The amounts of the precipitated phases increase during aging, and correspondingly, the morphologies of phases are similar to be round. Fe(Cr, Mo)₂₃C₆ appears along boundaries and grows with increasing temperature. In addition, it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization. The hardness and strength decrease gradually, whereas the plasticity of the steel increases. What’s more, the hardness of this steel after creep is similar to that of other 9%–12%Cr ferritic steels. Thus, ZG12Cr9Mo1Co1NiVNbNB can be used in the project.     

Selective catalytic oxidation of ammonia to nitrogen over orderly mesoporous CuFe2O4 with high specific surface area

Orderly mesoporous CuFe2O4 spinel-type mixed oxide with high specific surface area was prepared successfully by a hard-template method in which KIT-6 mesoporous silica was selected as the hard template. The KIT-6 hard template and CuFe2O4 samples were charac- terized by X-ray diffraction, X-ray photoelectron spec- troscopy, X-ray fluorescence, transmission electron microscopy, scanning electron microscopy, nitrogen physisorption, and hydrogen-temperature programmed reduction. The KIT-6 hard template had perfect crystalli- zation and ordered mesoporous structure with a probable pore distribution of about 9.1 nm, large enough to be filled by the spinel precursor. The mesoporous CuFe2O4 spinel oxide synthesized inside the KIT-6 mesopores had a rela- tively small pore size （4.3 nm）, orderly arrangement, and high specific area （194 m2/g）. The catalytic activity of the mesoporous CuFe2O4 was tested for the selective oxidation of ammonia to nitrogen. The conversion of ammonia reached nearly 100 % at 300 ℃with a nitrogen selectivity as high as 96 %. The nitrogen selectivity remained high with increasing temperature and even maintained a value of 80 % at 600 ℃.     

Changes of photosynthetic capacity of some plant species under very high CO2 concentrations in Biosphere 2

Conclusions The initial slope of A/ light curve became steep under high CO₂ (700 μmol · mol^-1) compared with that under low CO₂ (350 μmol · mol^-1) for the C₃ species growing in very high CO₂(>2 200 μmol · mol^-1) for a long period. The light compensation points remained unchanged, but the light saturation points were found increased. The ϕ_m,_app and A_max of the C₃ species increased respectively by 79 % and 80 %, while those of C₄ species decreased by 10% and 14%, respectively. The shape of A/light curve of C₄ species did not change. Such results indicated that C₃ species increased the capacity of photosynthesis, while C₄ did not change, otherwise it decreased a little. This work only compared the changes of capacity in photosynthesis of some species under different CO₂ levels in Biosphere 2. We need further investigation on the effects of high CO₂ on the same species outside Biosphere 2, in order to fully undertand the effects and mechanism of response of plants to the elevated CO₂.     

A novel bimetallic RuFe nanocluster to enable highly efficient oxygen reduction in zinc-air batteries

Zinc-air batteries (ZABs) have the advantages of high energy density and safety but their large-scale application is hindered by sluggish kinetics of four-electron aqueous O₂ redox reactions. Widely used Ruthenium (Ru)-based catalysts possess intrinsic oxygen evolution catalytic activity but suffer from insufficient oxygen reduction reaction (ORR) performance. Herein, to optimize the ORR activity of Ru-based catalyst, an iron (Fe)-coordinated, bimetallic RuFe cluster is constructed and homogeneously dispersed within nitrogen (N)-doped carbon layers (denoted as RuFe@NC). Benefitting from the optimized ORR activity and more active site exposure, the RuFe@NC exhibits superior ORR activity with a half wave potential (E_1/2) of 0.88 ?V higher than that of Pt/C (0.82 ?V). Accordingly, the RuFe@NC-based ZAB outperforms the Pt/C ?+ ?IrO₂-based device, presenting a reduced polarization of 0.7 ?V and an enhanced cycling lifetime of 50 ?h at 10 ?mA ?cm^?2. Moreover, the optimized structural design ultralow Ru loading (0.013 mg_Ru cm^?2) overcomes the cost barriers and demonstrates its high practicality. This bimetallic RuFe nanocluster opens a new way for future design of more efficient and stable catalytic systems.     

Development of Fe(III)-containing ether-functionalized imidazolium ionic liquids for aryl Grignard cross-coupling of alkyl halides

A series of Fe(Ⅲ)-containing imidazolium-based ionic liquids containing ether substituents,including[C3OMim][FeCl4](1,[C3OMim]=1-(2-methoxyethyl)-3-methylimidazolium),[C3OiPim][FeCl4](2,[C3OiPim]=1-isopropyl-3-(2-methoxyethyl)imidazolium),[C3OBim][FeCl4](3,[C3OBim]=1-butyl-3-(2-methoxyethyl)imidazolium),[(C3O)2im][FeCl4](4,[(C3O)2im]=1,3-bis(2-methoxyethyl)imidazolium),[C3OMim][FeBr4](5)and[(C3O)2im][FeBr4](6),were prepared and characterized by elemental analysis,Raman spectroscopy and electrospray ionization mass spectrometry.The catalytic performances of 1–6 and related Fe(III)-based catalysts in the cross-coupling of aryl Grignard reagents with alkyl halides bearing-hydrogens were studied,revealing that mono(ether)functionality improves the catalytic activity and that bis(ether)functionality improves the reusability.After simply decanting the product contained in the ethereal layer,complex 4,which containing bis(ether)-functionalized imidazolium cation,could be successfully recycled seven times.     

Synthesis of mesoporous polymeric carbon nitride exhibiting enhanced and durable visible light photocatalytic performance

A thiourea precursor was employed to synthesize mesoporous carbon nitride(C3 N4) by a thermal polycondensation process with high surface area SiO2 and nanosphere SiO2 as two types of hard templates. The resultant mesoporous C3 N4 samples have high surface areas(105–112 m2/g) and mesopores with narrow sizes distribution(9.3 nm). Photocatalytic performance was evaluated by removal of NO in air under visible light irradiation. The results showed that mesoporous C3 N4 samples exhibited significantly improved photocatalytic activity in comparison with bulk C3 N4, which also exceeded that of N-doped TiO2 and C-doped TiO2. The activity enhancement can be ascribed to the synergistic effects of large surface area and pore volume, enhanced light-harvesting ability, increased redox potential, and reduced recombination of charge carriers. In addition to the high activity, the mesoporous C3 N4 samples also showed high photochemical stability. The mesoporous C3 N4 photocatalysts with enhanced and durable activity could provide a new efficient material for environmental pollution control.     

Hydrotalcite-supported Pd-Cu catalyst for nitrate adsorption and reduction from water

With the rapid development of industry and agricul- ture, the nitrate contamination in groundwater becomes increasingly serious in many countries [1]. Therefore, the remediation of nitrate-contaminated groundwater is one of the targets urgently confronted…     

Theoretical study of partial oxidation of ethylene by vanadium trioxide cluster cation

Density functional theory （DFT） study of reaction between vanadium trioxide cluster cation （VO3^＋） and ethylene （C2H4） to yield VO2^＋ ＋ CH3CHO （acetaldehyde） and VO2CH2^＋ ＋ HCHO （formaldehyde） is carried out. Structures of all reactants, products, intermediates, and transition state in the reaction have been optimized and characterized. The results show unexpected barriers in the reaction due to the existence of a η^2-O2 moiety in the ground state structure of VO3^＋. The initial reaction steps combining ethylene adsorption, C=C activation and O-O cleavage are proposed as rate limiting processes. Comparison of reactions of VO3^＋ ＋ C2H4 with VO3 ＋ C2H4 and VO2^＋ ＋ C2H4 in the previous studies is made in detail. The results of this work may shed light on the understanding of C=C bond cleavage in related heterogeneous catalysis.     

γ-Al2O3催化剂上乙醇脱水制乙烯的实验研究

考察了低浓度乙醇在固定床管式反应器中活性氧化铝上催化脱水生成乙烯的反应行为。研究了反应温度、进料流率、乙醇浓度等因素对反应行为的影响规律。结果表明，在410～440℃范围内催化剂对主反应的选择性随着温度的升高而升高，在达到一定的温度后趋于稳定。乙醇转化率对温度并不敏感，而随空速的增大而降低。催化剂选择性随着进料流率增大而增大，之后稳定在99.5%以上。在进料流率小于1mL/min时乙醇转化率高于85%，乙烯收率均在80%以上。当利用低浓度乙醇作原料时，乙醇转化率随乙醇浓度增大而增大，催化剂选择性维持稳定。最终选定的适宜工艺条件：温度420℃左右，进料流率1.0mL/min左右。     

ZIF-derived Co–N–C ORR catalyst with high performance in proton exchange membrane fuel cells

Metal and nitrogen-doped carbon (M-N-C) materials have been considered as the most promising non-precious metal oxygen reduction (ORR) catalysts to replace expensive Pt catalysts. Due to high Fenton catalytic activity of Fe element and the resulting instability, Co-based N–C (Co–N–C) catalysts without Fenton catalytic activity should be a worthier ORR catalyst being explored. Although the high ORR activity of Co–N–C catalyst has been demonstrated in aqueous half-cell tests, their performance under PEMFC working condition is still far away from that of state-of-the-art Fe–N–C catalysts. In this study, a high-performance Co–N–C catalyst was synthesized by one-step pyrolyzing Co-doped ZIF-8 (zeolitic imidazolate framework-8) particles in-situ grown on the high-surface-area KJ600 carbon black with high electronic conductivity. The resulting Co–N–C catalyst exhibited high intrinsic ORR activity, fast mass transfer rate and high electronic conductivity, and thus yielded a remarkable peak power density of 0.92 W cm^-2 in H₂–O₂ PEMFC, which is comparable to state-of-the-art Fe–N–C catalyst. This strategy is helpful to synthesize highly active M-N-C ORR catalysts with improved mass transfer and electric conductivity.