Silica‐supported bis(imino)pyridyl iron(II) catalyst: nature of the support–catalyst interactions

Ethylene polymerizations were performed using silica‐supported 2,6‐bis[1‐(2,6‐diisopropylphenylimino) ethyl] pyridine iron(II) dichloride with methylaluminoxane (MAO) as co‐catalyst. Silica was calcined at 600, 400 and 200 °C under vacuum for 8 h. The effect of calcination temperature of silica on the polymerization activity and the properties of the polymers obtained were examined. Catalyst–support interactions were examined by both a chemical method and XPS. It was observed that upon supporting the catalyst on the surface of silica, there is an increase in the binding energy of the metal center. However, no change in the metal binding energy was observed on supporting the catalyst to silica calcined at different temperatures. Ethylene polymerizations were performed using MAO as co‐catalyst. Catalysts were also prepared by first pretreating silica with MAO, followed by addition of the Fe(II) catalyst and contacting a complex of Fe(II) catalyst–MAO with silica previously calcined at 400 °C for 8 h. The results indicate that there is no chemical bonding between the support and the catalyst. Copyright © 2006 Society of Chemical Industry     

Synthesis of branched polyethylene by ethylene homopolymerization with a novel (α‐diimine)nickel complex in the presence of methylaluminoxane

Branched polyethylene (PE) was prepared with a novel (α‐diimine)nickel(II) complex of 2,3‐bis(2,6‐dimethylphenyl)‐butanediimine nickel dichloride {[2,6‐(CH₃)₂C₆H₃? N?C(CH₃)C(CH₃)?N? 2,6‐(CH₃)₂C₆H₃]NiCl₂} activated by methylaluminoxane in the presence of a single ethylene monomer. The influences of various polymerization conditions, including the temperature, Al/Ni molar ratio, Ni catalyst concentration, and time, on the catalytic activity, molecular weight, degree of branching, and branch length of PE were investigated. According to gel permeation chromatography, the weight‐average molecular weights of the polymers obtained ranged from 1.7 × 10⁵ to 6.0 × 10⁵, with narrow molecular weight distributions of 2.0–3.5. The degree of branching in the polymers rapidly increased with the polymerization temperature increasing; this led to highly crystalline to totally amorphous polymers, but it was independent of the Al/Ni molar ratio and catalyst concentration. At polymerization temperatures greater than 20°C, the resultant PE was confirmed by ¹³C‐NMR to contain significant amounts of not only methyl but also ethyl, propyl, butyl, amyl, and long branches (longer than six carbons). The formation of the branches could be illustrated by the chain walking mechanism, which controlled their specific spacing and conformational arrangements with one another. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1123–1132, 2002; DOI 10.1002/app.10398     

Rheology and enhancement of extrusion of linear and branched polyethylenes using low amount of organoclay

Interaction between 0.05 wt % organoclay and polyethylenes of different short chain branching (SCB) was studied. Linear rheology (van Gurp‐Palmen plot) was used to study the effect of organoclay on the rheology of polyethylenes. Organoclay had effect only on the van Gurp‐Palmen plot of linear polyethylene. Fourier transform (FT) rheology, extrusion at high‐shear rates in a slit rheometer, transient stress growth analysis, and extensional rheology were conducted to examine the potential of organoclay as a processing aid. Organoclay reduced the transient stress overshoot, normal stress difference, ηo, onset of shear thinning, and extrusion pressure of polyethylene. The reduction was more pronounced in linear polyethylene without branching. Such effects gradually decreased as the branch content increased. The trend was independent of the type of flow (shear or extensional). It was interesting to note that FT rheology was not effective in explaining the impact of organoclay on polyethylene. The work concluded with the proposition that organoclay (as low as 0.05 wt %) was a good processing aid for linear polyethylene and polyethylenes with low content of SCB. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

亚乙基苊镍催化剂催化乙烯溶液聚合制备超支化聚乙烯

以一种亚乙基苊(α-二亚胺)镍配合物为主催化剂,研究了温度、压力、助催化剂及其用量等对乙烯溶液聚合制备超支化聚乙烯(HBPE)的影响,并对HBPE的结构与性能进行分析.结果表明:随着温度或压力的升高,催化剂活性均呈现先升高后下降的趋势;HBPE的相对分子质量随温度的升高而下降,而支化度与温度呈正比,与压力呈反比;二氯乙...     

Ring-Opening Metathesis Polymerization of 5,6-Bis(Chloromethyl)-Norbornene by Tungsten(II) and Molybdenum(II) Complexes

The reaction of endo,endo-5,6-bis(chloromethyl)bicyclo[2.2.1]hept-2-ene in the presence of seven-coordinate tungsten(II) and molybdenum(II) complexes of the type [MCl(M'Cl₃)(CO)₃(NCMe)₂] (M'=W, Mo; M=Sn, Ge) leads to ring-opening metathesis polymerization and to the formation of high-molecular-weight soluble polymers with dispersity index in the range 1.4-2.0 and number average molecular weights in the range 300 000-790 000 g mol^-1. The geometric structure of these polymers was determined by means of ¹H- and ¹³C-NMR spectroscopy. Molybdenum catalysts gave polymers with lower cis vinylene content (20-50%), whereas tungsten catalysts gave polymers with higher cis vinylene content (84-95%).     

Study of the properties of nickel oxide and nickel as precursors for the tartaric acid-NaBr-modified nickel catalyst

Nickel oxide was prepared by the decomposition of nickel hydroxide and then the nickel oxide was reduced to form the nickel catalyst. The properties of the nickel oxide and the reduced nickel were studied in relation to the enantio-differentiating ability (e.d.a.) of a tartaric acid-NaBr-modified reduced nickel catalyst. The modified nickel catalyst prepared from nickel oxide with less non-stoichiometric oxygen produced a high e.d.a. for the hydrogenation of methyl acetoacetate. The high crystallinity of the nickel oxide and the resultant nickel would be required to attain a high e.d.a.     

Synthesis of branched poly(lactide) using polyglycidol and thermal, mechanical properties of its solution-cast film

Branched poly(lactide)(PLA)s with various lengths of graft chain were synthesized by ring-opening polymerization of l- or d-lactide (l- or d-LA) in bulk using polyglycidol as a macroinitiator. The properties of polymer films of branched PLLA or PDLA obtained and their stereocomplex were investigated through thermal analysis and tensile testing. The branched PLLA or PDLA film exhibited a lower glass transition temperature (T_g), melting temperature (T_m), crystallinity, Young's modulus and a higher strain at break than the corresponding linear PLLA or PDLA film. The branched PLLA/branched PDLA stereocomplex film showed a high maximum stress and a high Young's modulus keeping its high strain at break. Moreover, the usefulness of branched PLLA or PDLA as a plasticizer of linear PLLA was investigated with 1:9 blend or stereocomplex film prepared from the branched PLLA or branched PDLA and linear PLLA. The blend or linear PLLA/branched PDLA stereocomplex film showed a higher strain at break compared with linear PLLA film. The mechanical properties of the blend or linear PLLA/branched PDLA stereocomplex film could easily be controlled by changing the molecular weight of branched PLA.     

Modelling of adsorption of nickel (II) by blend hydrogels (cellulose nanocrystals and corn starch) from aqueous solution using adaptive neuro-fuzzy inference systems (ANFIS) and artificial neural networks (ANN)

The current study looks at the effectiveness of the removal of nickel (II) from aqueous solution using an adsorption method in a laboratory-size reactor. An artificial neural network (ANN) and an adaptive neuro-fuzzy inference system (ANFIS) were used in this study to predict blend hydrogels adsorption potential in the removal of nickel (II) from aqueous solution. Four operational variables, including initial Ni (II) concentration (mg/L), pH, contact duration (min), and adsorbent dose (mg/L), were used as an input with removal percentage (%) as the only output; they were studied to assess their impact on the adsorption study in the ANFIS model. In contrast, 70% of the data was used for training, while 15% of the data was used in testing and validation to build the ANN model. Feedforward propagation with the Levenberg–Marquardt algorithm was employed to train the network. The use of ANN and ANFIS models for experiments was used to optimize, construct, and develop prediction models for Ni (II) adsorption using blend hydrogels. The adsorption isotherm and kinetic models were also used to describe the process. The results show that ANN and ANFIS models are promising prediction approaches that can be applied to successfully predict metal ions adsorption. According to this finding, the root mean square errors (RMSE), absolute average relative errors (AARE), average relative errors (ARE), mean squared deviation (MSE), and R² for Ni (II) in the training dataset were 0.061, 0.078, 0.017, 0.019, and 0.986, respectively, for ANN. In the ANFIS model, the RMSE, AARE, ARE, MSE, and R² were 0.0129, 0.0119, 0.028, 0.030, and 0.995, respectively. The adsorption process was spontaneous and well explained by the Langmuir model, and chemisorption was the primary control. The morphology, functional groups, thermal characteristics, and crystallinity of blend hydrogels were all assessed.     

Polymerization of styrene using pyrazolylimine nickel (II)/methylaluminoxane catalytic systems

The polymerization of styrene with two pyrazolylimine nickel (II) complexes of (2-(C₃HN₂Me₂-3, 5)(C(Ph) = N(4-R₂C₆H₂(R₁)₂-2, 6)NiBr₂ (Complex 1 , R₁ = ⁱPr, R₂ = H; Complex 2 , R₁ = H, R₂ = NO₂)) activated by methylaluminoxane was studied. The influences of polymerization parameters such as polymerization temperature, Al/Ni molar ratio, and reaction time on catalytic activity and molecular weight of the polystyrene (PS) were investigated in detail. The electron-withdrawing of nitro group in Complex 2 could not enhance the catalytic activity for styrene polymerization; however, the molecular weights of polymers were increased. Both of the two catalytic systems exhibited high activity [up to 8.45 × 10⁵ gPS/(mol Ni h)] for styrene polymerization and provide PS with moderate to low-molecular weights (M_w = 2.21 × 10⁴∼ 5.71 × 10³ g/mol) and narrower molecular weight distributions about 2.0. The obtained PS were characterized by means of IR, ¹H NMR, and ¹³C NMR techniques. The results indicated that the PS was atactic polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

负载型磷化镍催化剂的制备及其催化应用

综述了近年来负载型磷化镍催化剂在制备方法(还原法、热解法和溶剂热法)、活性组分和载体改性及其催化应用方面的研究进展,并对比了各种制备方法的优缺点,其中还原法流程简单,但所用温度较高,时间较长;热解法所需温度较低,制备过程简单,但易于生成副产物水;而溶剂热法具有所需温度低,物相形成过程易控制等优点。负载型磷化镍催化剂由于其良好的加氢氢解及烷烃临氢异构化等反应性能,是一类更加廉价的新型催化剂,具有很好的发展前景。     

Adsorption of chromium(VI) and nickel(II) ions on acid- and heat-activated deoiled spent bleaching clay

De-oiled spent bleaching clay was activated either by acid treatment followed by heat activation or by heat activation alone at temperatures between 200 and 800°C. The surface area of the heat-activated clay attained a maximal value of ≈120 m² g⁻¹ at temperatures between 400 and 500°C while the acid-heat-treated clay attained maximal surface area of ≈140 m² g⁻¹. The adsorption capacities of chromium [Cr(VI)] for both series studied increased as the activation temperature increased until 300°C and decreased again at higher temperatures. At lower pH, more than 95% of the Cr(VI) was absorbed in a solution with initial concentration of 1 mg L⁻¹ per gram of adsorbent activated at 300°C. The adsorption patterns followed Freudlich's isotherms. Two maximal values of adsorption capacities of nickel [Ni(II)] were observed at activation temperatures of 200 and 500°C for acid-treated samples, whereas these were at 200 and 700°C for the nonacid-treated samples. The amount of Ni(II) adsorbed increased with the pH of the solution for all samples studied. The maximal adsorption capacities of the adsorbents in solution containing initial Ni(II) concentration of 5 mg L⁻¹ per 0.5 g of adsorbent and at pH 6 were found to be 44 and 42%, respectively, for the acid-treated sample activated at 500°C and for the nonacid-treated sample activated at 700°C. They all obeyed both the Langmuir's and Freundlich's isotherms.     

海泡石和稀土对镍催化剂性能的影响

本文研究了海泡石和稀土Sm镍催化剂的苯加氢活性及CO_２甲烷化活性的影响，并用XPS、活性比表面积及CS_２中毒等方法表征了催化剂的表面性质。结果表明，海泡石和稀土Sm能提高镍催化剂的加氢活性和抗毒性，并能增大活性镍的比表面及镍上的电子云密度，降低CO_２甲烷化反应的活化能。     

Preparation of highly branched polyethylene using (α‐diimine) nickel complex covalently supported on modified SiO2

Bis(4‐(4‐amine‐3,5‐diisopropylbenzyl)‐2,6‐diisopropylphenylimino) acenaphthene NiBr₂ (Catalyst I) was synthesized. The complex covalently supported on Et₃Al‐treated silica (SC) and used for ethylene polymerization was produced with cocatalyst of common inexpensive alkylaluminum compounds. Polyethylenes (PEs) with branching numbers of 12.94 (1000C) to 116.02 (1000C) were prepared in heptane. The polymerization conditions, such as the cocatalyst, Al/Ni ratio, and temperature, had significant effects on catalytic activity and properties of polyethylenes. Confirmed by high‐temperature ¹³C NMR, the polyethylenes synthesized contain significant amounts of not only methyl but also ethyl, propyl, butyl, pentyl, and other long branches (longer than six carbons). The branching degree of polyethylenes increased with temperature, while their molecular weight and melting point decreased correspondingly, resulting in linear semicrystalline to totally amorphous polymers. The formation of the branches could be illustrated by the chain walking mechanism, which controlled their specific spacing and conformational arrangements with one another. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 103: 1483–1489, 2007     

合成N263(SCN型)萃淋树脂用于研制高纯镍

选择利用合成的Ｎ２６３（ＳＣＮ型）萃淋树脂用于Ｃｏ＾２＋,Ｎｉ＾２＋的分离,研究了使用该树脂的料液酸度、料液浓度及洗脱液浓度等因素对钴、镍分离的影响,实验结果表明,该树脂在高纯镍制备上效果良好,料液中的镍浓度为８５％￣９５％时,一次过柱,镍的浓度可提高至９９．９５％￣１００％。本文还对萃钴机理进行了初步探讨。     

硫氰酸锰及其相关衍生物的合成及化学表征

合成了金属有机配合物非线性光学晶体硫氰酸汞锰，及其相关衍生物，二二甲亚砜合硫氰酸汞锰，乙二醇一甲醚合硫氰酸汞锰，二水合二N，N－二甲基乙酰胺合硫氰酸汞锰，二水合二N－甲基－α－吡咯烷酮合硫氰酸汞锰。采用元素分析，红外光谱以及紫外－可见－近红外透央求我谱分析对其进行了化学表征。     

Investigation of the operation time dependence of the yield of ammonia conversion to nitrogen(II) oxide by platinum catalyst sets

The origins of changes in the catalytic activity of platinum catalysts in the ammonia oxidation process are studied. A general mathematical model for the dependence of the catalyst activity on the operation time of a single platinum gauze is proposed. Simplified expressions for the catalytic activity of two basic types of catalyst sets are obtained. Optimization of the catalyst operation mode is investigated and an optimal mode is selected based on the industrial data. © 2001 Society of Chemical Industry     

Synthesis of azo‐functionalized ion‐imprinted polymeric resin for selective extraction of nickel(II) ions

The work presented involved the fabrication and evaluation of an ion‐imprinted azo‐functionalized phenolic resin for selective extraction of Ni²⁺ ions from aqueous media. The azo‐containing ligand was first synthesized by coupling of a p‐aminophenol diazonium salt with resorcinol. The ligand was coordinated with Ni²⁺ ion template before condensation polymerization with formaldehyde and resorcinol was performed. The Ni²⁺ ions were extracted from the crosslinked resin matrix to finally afford the Ni²⁺ ion‐imprinted Ni‐PARF adsorbent. The synthetic steps were extensively investigated using elemental analysis and Fourier transform infrared, NMR and energy‐dispersive X‐ray spectroscopies. Also, the surface morphologies along with the surface areas of the adsorbent resin were evaluated using scanning electron microscopy and Brunauer–Emmett–Teller techniques, respectively. Batch experiments indicated that the pseudo‐second‐order kinetic equation provided the best fit with the experimentally obtained kinetic data and equilibrium was reached after 40 min. The isotherm studies were also in a good fit with the Langmuir model and the maximum adsorption capacities of Ni²⁺ ions with respect to both Ni‐PARF and control non‐imprinted C‐PARF adsorbents were around 260 and 100 mg g^?1, respectively. In the presence of Co²⁺, Cu²⁺, Zn²⁺ and Pb²⁺ as competing coexisting ions, the relative selectivity coefficients of Ni‐PARF for Ni²⁺ were, respectively, 84.91, 44.97, 30.41 and 32.20. Regeneration experiments indicated that after eight adsorption/desorption cycles, the Ni‐PARF adsorbent still maintained around 97% of its initial efficiency. © 2018 Society of Chemical Industry     

镍二亚胺配合物/复合载体催化剂合成支化PE

研究了在不用甲基铝氧烷.只以通用烷基铝为助催化剂的条件下,以SiO2和MgCl2的复合载体负载3种镍二亚胺配合物催化乙烯进行聚合,庚烷为溶剂制备支化聚乙烯(PE)。结果发现,聚合条件(如配体、载体改性方式、助催化剂、铝/镍、聚合温度和金属镍浓度等)对催化活性有很大的影响。没有经三乙基铝改性的复合载体负载空间位阻最小的镍二亚胺配合物在以-氯二乙基铝为助催化剂、聚合温度14℃、金属镍浓度0.12 mmol/L、铝/镍为80的条件下催化活性达290 kg/mol·h),生成的支化PE的支化度随着聚合温度的升高而迅速增加,受铝/镍的影响不大     

Recent studies in adsorption of Pb(II), Zn(II) and Co(II) using conventional and modified materials:a review

ABSTRACT

Heavy metal contamination and its detrimental effects on human health and environment have been a worldwide concern. Over the years, various technologies have been adapted to tackle this problem. Adsorption is still considered to be one of the most feasible and cost-effective methods for treating wastewater contaminated with heavy metals. Adsorbents such as activated carbon, clay, zeolites and silica have been studied extensively in the past. Modification of these conventional adsorbents and the synthesis of nonconventional adsorbents such as nanocomposites and metal organic frameworks (MOF’s) have been the main focus of study in recent times. This review article attempts to present a detailed account of various adsorbents and their removal efficiencies for the treatment of wastewater contaminated with lead(II), zinc(II) and cobalt(II) in the current decade. Influence of various parameters, adsorption isotherms and kinetics best described for their removal have also been reviewed in detail. It is observed that most of the adsorbents followed pseudo second order kinetics suggestive of a chemisorption process. After conducting a thorough review of more than 120 recently published papers, it can be inferred that nanomaterials and nanocomposites have shown excellent adsorption capacity for removal of these heavy metals.