Partial hydrogenation of benzene catalyzed by Pt/N‐n‐propyl chitosan hybrid membrane

The partial hydrogenation of benzene by a Pt nano‐cluster/N‐n‐propyl chitosan hybrid membrane was investigated in this article. Monodispersed Pt nano‐clusters were prepared by the reduction of H₂PtCl₆ with ethylene glycol under microwave conditions. TEM, FTIR, XRD, ¹H‐NMR, and XPS were used to characterize the structure of Pt nano‐particles, N‐n‐propyl chitosan and Pt/N‐n‐propyl chitosan hybrid membrane, respectively. Experimental results showed that Pt/N‐n‐propyl chitosan hybrid membrane catalyst gave a high selectivity for cyclohexene of 85.2% in the liquid phase hydrogenation of benzene, while the selectivity of cyclohexene was only 58.2% over the Pt/chitosan hybrid membrane catalyst. It was worth noting that there was no cyclohexene in the product when the catalyst was only Pt nano‐particles without chitosan hybrid membrane. So the chitosan or modified‐chitosan membranes played an important role in the controlling to the hydrogenation of benzene, and the relationship of the swelling degree and the catalytic activity was discussed in detail. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ring‐opening copolymerization of maleic anhydride with propylene oxide by double‐metal cyanide

Ring‐opening copolymerization of maleic anhydride (MA) with propylene oxide (PO) was successfully carried out by using double‐metal cyanide (DMC) based on Zn₃[Co(CN)₆]₂. The characteristics of the copolymerization are presented and discussed in this article. The structure of the copolymer was characterized with IR and ¹H‐NMR. Number‐average molecular weight (M_n) and molecular weight distribution (MWD) of the copolymer were measured by GPC. The results showed that DMC was a highly active catalyst for copolymerization of MA and PO, giving high yield at a low catalyst level of 80 mg/kg. The catalytic efficiency reached 10 kg polymer/g catalyst. Almost alternating copolymer was obtained when monomer charge molar ratio reached MA/PO ≥ 1. The copolymerization can be also carried out in many organic solvents; it was more favorable to be carried in polar solvents such as THF and acetone than in low‐polarity solvents such as diethyl ether and cyclohexane. The proper reaction temperature carried in the solvents was between 90 and 100 °C. The M_n was in the range of 2000–3000, and it was linear with the molar ratio of conversion monomer and DMC catalyst. The reactivity ratio of MA and PO in this reaction system was given by the extended Kelen–Tudos equation: η=[r₁+(r₂/α)]ξ?(r₂/α) at some high monomer conversion. The value of reactivity ratio r₁(MA) = 0 for MA cannot be polymerized itself by DMC catalyst, and r₂(PO) = 0.286. The kinetics of the copolymerization was studied. The results indicated that the copolymerization rate is first order with respect to monomer concentration. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1788–1792, 2004     

3D‐foam‐structured nitrogen‐doped graphene‐Ni catalyst for highly efficient nitrobenzene reduction

We report the preparation of a porous 3D‐foam‐structured nitrogen‐doped graphene‐Ni (NG/NF) catalyst and the evaluation of its performance in the reduction of nitrobenzene (NB) through detailed studies of the kinetics. The NG/NF catalyst showed a significantly higher reaction rate than pure Ni foam (NF). Moreover, the separation of the 3D‐foam‐structured catalyst from the products was more convenient than that of NG powdered catalysts. The obtained kinetics data fit well to the Langmuir‐Hinshelwood model, with an error ratio below 10%. Density functional theory (DFT) calculations indicated that the adsorption of sodium borohydride (NaBH₄) on the NG/NF surface was stronger than that of NB, which strongly agreed with the kinetic parameters determined from the Langmuir‐Hinshelwood model. The excellent catalytic efficiency of the 3D‐foam‐structured catalyst combined with the knowledge of the kinetics data make this catalyst promising for application in larger scale nitrobenzene reduction. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1330–1338, 2018     

Poly(propylene‐co‐ethylene) produced with a conventional and a self‐supported ziegler–natta catalyst: Effect of ethylene and hydrogen concentration on activity and polymer structure

A novel self‐supported emulsion‐based catalyst and a conventional MgCl₂‐supported Ziegler–Natta catalyst were used in the copolymerization of propylene and ethylene under industrial conditions using triethyl aluminium as cocatalyst and dicyclopentyl dimethoxy silane as external donor. The effects of the concentration of ethylene and hydrogen on the polymerization behaviors and polymer properties were investigated. The combined effect of both ethylene and hydrogen increased the relative activity of the novel catalyst more than for the conventional catalyst. This trend was consistent with our earlier observed higher degree of dormancy, due to 2,1 insertions, found with the novel catalyst. More importantly, the work has uncovered that the self‐supported catalyst incorporates ethylene in a more random fashion and produces copolymers with relatively narrow molecular weight distribution (MWD). These results in combination with polymer microstructure studies using Fourier transform infrared spectroscopy, ¹³C‐NMR spectroscopy, and differential scanning calorimetry all indicated that the novel catalyst has a narrower distribution of active site types than the conventional reference catalyst. The narrow composition of active site structures, the narrow MWD, and the random incorporation of ethylene into the polymer chain indicated that the emulsion‐based catalyst possesses features that to a certain degree tend to be more indicative for a single‐site‐like catalyst structure and behavior. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Design of Lanthanide Fingers: Compact Lanthanide‐Binding Metalloproteins

Lanthanides have interesting chemical properties; these include luminescent, magnetic, and catalytic functions. Toward the development of proteins incorporating novel functions, we have designed a new lanthanide‐binding motif, lanthanide fingers. These were designed based on the Zif268 zinc finger, which exhibits a ββα structural motif. Lanthanide fingers utilize an Asp₂Glu₂ metal‐coordination environment to bind lanthanides through a tetracarboxylate peptide ligand. The iterative design of a general lanthanide‐binding peptide incorporated the following key elements: 1) residues with high α‐helix and β‐sheet propensities in the respective secondary structures; 2) an optimized big box α‐helix N‐cap; 3) a Schellman α‐helix C‐cap motif; and 4) an optional D ‐Pro‐Ser type II’ β‐turn in the β‐hairpin. The peptides were characterized for lanthanide binding by circular dichroism (CD), NMR, and fluorescence spectroscopy. In all instances, stabilization of the peptide secondary structures resulted in an increase in metal affinity. The optimized protein design was a 25‐residue peptide that was a general lanthanide‐binding motif; this binds all lanthanides examined in a competitive aqueous environment, with a dissociation constant of 9.3 μM for binding Er³⁺. CD spectra of the peptide‐lanthanide complexes are similar to those of zinc fingers and other ββα proteins. Metal binding involves residues from the N‐terminal β‐hairpin and the C terminal α‐helical segments of the peptide. NMR data indicated that metal binding induced a global change in the peptide structure. The D ‐Pro‐Ser type II’ β‐turn motif could be replaced by Thr–Ile to generate genetically encodable lanthanide fingers. Replacement of the central Phe with Trp generated genetically encodable lanthanide fingers that exhibited terbium luminescence greater than that of an EF‐hand peptide.     

Zinc‐based catalyst for the ring‐opening polymerization of cyclic esters

A zinc‐based catalyst zinc bis[bis(trimethylsilyl)amide] was used for the polymerization of cyclic esters including L ‐lactide (L ‐LA) and 2‐methyl‐2‐carboxyl‐propylene carbonate (MBC). The polymerization of L ‐lactide in THF could be carried out successfully under mild conditions in very short time by using the zinc catalyst and alcohols as the initiators. Kinetic study in solution polymerization prooved the polymerization has high monomer conversion degree close to 100% and the molecular weight of the resulting polyester has linear increase with the increase of [M]₀ /[I] (molar ratio of monomer to initiator). Sequential polymerization of L ‐LA and MBC in THF also showed high MBC conversion of 94% with a narrow molecualr weight maintained, indicating a living nature of this polymerization. The zinc catalyst system has also been used for the L ‐LA bulk polymerization with a high monomer conversion. ¹³C NMR indicated the polymer possesses high regioregularity and the minor regioirregular component was owing to the D ‐LA in the monomer inserted into the polymer mainchain during the transesterifcation. Interaction between monomer and zinc catalyst has been found to be a key factor to sustain a homogenous solution during the initiating procedure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polymerization of N‐phenylmaleimide with a rare‐earth coordination catalyst

The polymerization of N‐phenylmaleimide was carried out with the binary rare‐earth coordination catalyst lanthanum phosphonate [La(P₅₀₇)]–trisobutyl aluminum [Al(i‐Bu)₃] in toluene at 60°C. The dependence of the polymerization on the polymerization time, the molar ratio of Al(i‐Bu)₃ to La(P₅₀₇), and the concentration of the catalyst were studied. The structures of the resultant polymer were characterized with ¹H‐NMR, ¹³C‐NMR, and Fourier transform infrared spectrophotometry, and the thermal properties of the polymer were measured with thermogravimetric analysis. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 979–982, 2005     

Tailor‐Made Designer Helical Peptides that Induce Mitochondrion‐Mediated Cell Death without Necrosis

Managing protein–protein interactions is essential for resolving unknown biological events at the molecular level and developing drugs. We have designed and synthesized a side‐chain‐crosslinked helical peptides based on the binding domain of a pro‐apoptotic protein (Bad) that induces programed cell death. The peptide showed high helical content and bound to its target, Bcl‐X_L, more strongly than its non‐crosslinked counterparts. When HeLa cells were incubated with the crosslinked peptide, the peptide entered the cytosol across the plasma membrane. The peptide formed a stable complex with Bcl‐X_L localized at the outer mitochondrial membrane, and this binding event caused the release of cytochrome c from the intermembrane space of mitochondria into the cytosol. This activated the caspase cascade: 70 % of HeLa cells died by the apoptosis pathway (without evidence of necrosis).     

Production of bio‐crude from forestry waste by hydro‐liquefaction in sub‐/super‐critical methanol

Hydro‐liquefaction of a woody biomass (birch powder) in sub‐/super‐critical methanol without and with catalysts was investigated with an autoclave reactor at temperatures of 473–673 K and an initial pressure of hydrogen varying from 2.0 to 10.0 MPa. The liquid products were separated into water soluble oil and heavy oil (as bio‐crude) by extraction with water and acetone. Without catalyst, the yields of heavy oil and water soluble oil were in the ranges of 2.4–25.5 wt % and 1.2–17.0 wt %, respectively, depending strongly on reaction temperature, reaction time, and initial pressure of hydrogen. The optimum temperature for the production of heavy oil and water soluble oil was found to be at around 623 K, whereas a longer residence time and a lower initial H₂ pressure were found to be favorite conditions for the oil production. Addition of a basic catalyst, such as NaOH, K₂CO₃, and Rb₂CO₃, could significantly promote biomass conversion and increase yields of oily products in the treatments at temperatures less than 573 K. The yield of heavy oil attained about 30 wt % for the liquefaction operation in the presence of 5 wt % Rb₂CO₃ at 573 K and 2 MPa of H₂ for 60 min. The obtained heavy oil products consisted of a high concentration of phenol derivatives, esters, and benzene derivatives, and they also contained a higher concentration of carbon, a much lower concentration of oxygen, and a significantly increased heating value (>30 MJ/kg) when compared with the raw woody biomass. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

A facile one‐step method for spherical support preparation of Ziegler‐Natta catalyst

This study reports a novel one‐step method to synthesize a new spherical support for Ziegler‐Natta catalyst under moderate condition. The support is obtained from a dispersion system where the particle stabilizer polyvinylpyrrolidone plays a main role to stabilize the spherical particles. The new chemical of the support is CH₃CH₂OMgOCH(CH₂Cl)₂, which is first reported here, has been approved by newly filed patents and also confirmed by solution NMR, solid state NMR, pyrolysis‐gas chromatography‐mass spectrometry (Py‐GC‐MS), and ICP‐MS. The support and catalyst particles have uniform distributions. The catalyst prepared from this support has been evaluated with high activity. The polypropylene obtained has high isotacticity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41014.     

Blending ultrahigh‐molecular‐weight polyethylene and poly(ethylene/10‐undecen‐1‐ol) in one nascent particle

Ultrahigh‐molecular‐weight polyethylene (UHMWPE)/polar polyethylene (PE) composites were blended in one nascent particle by in situ polymerization with a hybrid catalyst. Polystyrene‐coated SiO₂ particles were used to support the hybrid catalyst. Fe(acac)₃/2,6‐bis[1‐(2‐isopropylanilinoethyl)] was supported on SiO₂ for the synthesis of UHMWPE, whereas [PhN?C(CH₃)CH?C(Ph)O]VCl₂ was immobilized on a polystyrene layer to prepare a copolymer of ethylene and 10‐undecen‐1‐ol (polar PE). Importantly, the core part of the supports (the polystyrene layer) exhibited pronounced transfer resistance to 10‐undecen‐1‐ol; this provided an opportunity to keep the inside iron active sites away from the poisoning of 10‐undecen‐1‐ol. Therefore, UHMWPE was simultaneously synthesized with polar PE by in situ polymerization. Interestingly, the morphological results show that UHMWPE and the polar PE were successfully blended in one nascent polymer. This improved the miscibility of the composites, where most of the chains were difficult to crystallize because of the strong interactions between the PE chains and polar chains. The blends showed an extremely low crystallinity, that is, 9.9%. Finally, the hydrophilic properties of the polymer composites were examined. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46652.     

Optimization of Process Variables for Biodiesel Production Using the Nanomagnetic Catalyst CaO/NaY‐Fe3O4

Due to decreasing oil resources, alternative fuels such as biodiesel are required. The nanomagnetic catalyst CaO/NaY‐Fe₃O₄ was synthesized and used for biodiesel production from canola oil. The structure of the catalysts was characterized by X‐ray diffraction, field emission scanning electron microscopy, Brunauer‐Emmett‐Teller method, Fourier transform infrared spectroscopy, and vibrating sample magnetometer method. To optimize the influence of the operating variables, such as the methanol/canola oil molar ratio, the amount of catalyst, and the reaction time, on the yield of transesterification reaction, an experimental design was applied based on the Box‐Behnken method. The optimum values of these variables were predicted by the cubic model and were in excellent agreement with the experimental results.     

Ethylene/α‐olefin copolymerization using diphenylcyclopentadienyl‐phenoxytitanium dichloride/Al(iBu)3/[Ph3C][B(C6F5)4] catalyst systems

Copolymerization of ethylene with 1‐octene and 1‐octadecene using constrained geometry catalysts 2‐(3,4‐diphenylcyclopentadienyl)‐4,6‐di‐tert‐butylphenoxytitanium dichloride (1), 2‐(3,4‐diphenylcyclopentadienyl)‐6‐tert‐butylphenoxytitanium dichloride (2), 2‐(3,4‐diphenylcyclopentadienyl)‐6‐methylphenoxytitanium dichloride (3), and 2‐(3,4‐diphenylcyclopentadienyl)‐6‐phenylphenoxytitanium dichloride (4) was studied in the presence of Al(ⁱBu)₃ and [Ph₃C][B(C₆F₅)₄](TIBA/B). The effect of the catalyst structure, comonomer, and reaction conditions on the catalytic activity, comonomer incorporation, and molecular weight of the produced copolymers was also examined. The 1 /TIBA/B catalyst system exhibits high catalytic activity and produces high molecular weight copolymers. The melting temperature and the degree of crystallinity of the copolymers show a decrease with the increase in the comonomer incorporation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Copper(I) bromide coordinated by the ionic liquid 1‐[(diethyl amine)amine]ethyl‐3‐methyl imidazolium chloride to catalyze the atom transfer radical polymerization of methyl methacrylate in 1‐allyl‐3‐methyl imidazolium chloride

A coordinating ionic liquid (IL), 1‐[(diethyl amine)amine]ethyl‐3‐methyl imidazolium chloride ([N₃MIM]Cl), was prepared as an alternative to a simple organic ligand to coordinate to copper(I) bromide (CuBr). We, thereby, obtained a novel catalyst for atom transfer radical polymerization (ATRP) reactions. This catalyst was applied to the ATRP of methyl methacrylate in the IL 1‐allyl‐3‐methyl imidazolium chloride ([AMIM]Cl). The chemical structures of the ILs obtained were confirmed by Fourier transform infrared spectroscopy, mass spectrometry, and ¹H‐NMR analyses. The coordination ability of [N₃MIM]Cl was assessed by cyclic voltammetry, and the redox potential of [N₃MIM]Cl–CuBr was ?0.507 V. The [N₃MIM]Cl–CuBr complex was expected to be a markedly more active catalyst than the amine DETA–CuBr complex. The coordination mode toward CuBr was also examined. The [N₃MIM]Cl–CuBr catalyst system showed good controllability in the aforementioned ATRP reaction in [AMIM]Cl. The Cu catalyst was easily separated from the obtained polymer with the coordinating IL as a ligand. Consequently, the coordinating IL overcame the shortcomings of traditional organic ligands, such as poor compatibility with IL media and poor separation of the catalyst from the polymer; this makes it highly promising for applications in the ATRP field. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45484.     

Copper (I) ion stabilized on fe3o4‐core ethylated branched polyethyleneimine‐shell as magnetically recyclable catalyst for ATRP reaction

Branched polyethyleneimine (bPEI) was used to modify the surface of Fe₃O₄ nanoparticles coated with silica layer, and then, it was treated with ethyl iodide to prepare Fe₃O₄@SiO₂@Ethylated‐bPEI. In the next step, the yolk–shell structure was gained by selectively etching the SiO₂ middle layer. Finally, copper(I) was introduced to the yolk–shell Fe₃O₄@Ethylated‐bPEI and the activity of the catalyst was evaluated for atom transfer radical polymerization (ATRP) of styrene, led to obtain the well‐defined polymer with relatively low polydispersity. The toxicity of the residual copper in the polymer product was a limiting issue for applicability of ATRP reactions especially for biological purposes. In this report, the copper content in the polymer was reduced to the excellent value of 1.1 ppm. Moreover, the magnetic isolation, recyclability, and remove the need for an external ligand were other advantages of the synthesized catalyst which makes it suitable for employing in ATRP reactions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42337.     

High catalytic efficiency in liquid‐phase oxidation of 1,4‐dioxane using a Pt/CeO2‐ZrO2‐SnO2/SBA‐16 catalyst

A Pt/CeO₂–ZrO₂–SnO₂/SBA‐16 (SBA‐16: Santa Barbara Amorphous No. 16) catalyst was developed for the efficient removal of 1,4‐dioxane. Because the catalyst showed synergistic action between the high catalytic activity of Pt and the high oxygen release and storage abilities of CeO₂–ZrO₂–SnO₂, high catalytic efficiency in the liquid phase was obtained in an air atmosphere without the supply of any strongly oxidizing additives or photoirradiation. After reaction at 80°C for 4 h, the residual percentage of 1,4‐dioxane reached 31%. Furthermore, the Pt/CeO₂–ZrO₂–SnO₂/SBA‐16 catalyst exhibited high reusability and durability and the rate of net decrease in 1,4‐dioxane reached 44% at 80°C.     

Diffusion‐enhanced hierarchically macro‐mesoporous catalyst for selective hydrogenation of pyrolysis gasoline

A novel Pd/Al₂O₃ catalyst with the hierarchically macro‐mesoporous structure was prepared and applied to the selective hydrogenation of pyrolysis gasoline. The alumina support possessed a unique structure of hierarchical mesopores and macropores. The as‐prepared and calcined alumina were characterized by X‐ray diffraction, N₂ adsorption‐desorption, and scanning electron microscopy. It showed that the hierarchically porous structure of the alumina was well preserved after calcination at 1073 K, indicating high thermal stability. The 1073 K calcined alumina was impregnated with palladium metal and compared with a commercial catalyst without macrochannels. Both the catalytic activity and the hydrogenation selectivity of the novel Pd/Al₂O₃ catalyst were higher than those of the commercial Pd/Al₂O₃ catalyst. In addition, apparent reaction activation energies obtained with the novel catalyst for model pyrolysis gasoline were 46–81% higher than those with the commercial catalyst. The results adequately demonstrated the enhanced mass transfer characteristics of the novel macro‐mesostructured catalyst. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Deactivation Kinetics of Metallocene‐Catalyzed Ethene Polymerization at High Temperature and Elevated Pressure

Summary: The kinetics of ethene polymerization with metallocene/[Me₂PhNH]⁺[B(C₆F₅)₄]^?/AlⁱBu₃ (ternary systems) and metallocene/methylaluminoxan (MAO) systems respectively has been investigated at 100–140 °C and 7 MPa. Overall, eight different unbridged and ansa‐metallocenes were tested. The effect of ligand structure, cocatalyst and catalyst concentration on the thermostability and the activation energy of deactivation were studied. Deactivation with respect to the catalyst concentration followed a first order reaction. The half‐life as well as the activation energy of the ternary systems depended strongly on ligand structure while the ligand structure of MAO‐activated metallocenes merely influenced the half‐life. The half‐life associated with MAO activation is approximately twice as high as that in ternary activation. Based on these results, conclusions about the deactivation reactions have been drawn.

Influence of catalyst concentration on deactivation.     

Investigation of kinetics of 4‐methylpentene‐1 polymerization using Ziegler–Natta‐type catalysts

The kinetics of 4‐methylpentene‐1 (4MP1) polymerization by use of Ziegler–Natta‐type catalyst systems, M(acac)₃‐AlEt₃ (M = Cr, Mn, Fe, and Co), are investigated in benzene medium at 40°C. The effect of various parameters such as Al/M ratio, reaction time, aging time, temperature, catalyst, and monomer concentrations on the rate of polymerization and yield are examined. The rate of polymerization increased linearly with increasing monomer concentration with first‐order dependence, whereas the rate of polymerization with respect to catalyst concentration is found to be 0.5. For all cases, the polymer yield is maximum at an Al/M ratio of 2. The activation energies obtained from linear Arrhenius plots are in the range of 25.27–33.51 kJ mol^?1. It is found that the aging time to give maximum percentage yield of the polymer varies with the catalyst systems. Based on the experimental results, a plausible mechanism is proposed that envisages a free‐radical mechanism. Characterization of the resulting polymer product, for all the cases, through FTIR, ¹H‐NMR, and ¹³C‐NMR studies, showed isomerized polymeric structures with 1,4‐structure as dominant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2468–2477, 2003     

One‐pot synthesis of sheet‐like MFI as high‐performance catalyst for toluene disproportionation

In this study, one‐pot hydrothermal synthesis of sheet‐like ZSM‐5 as a high‐performance catalyst for toluene disproportionation was carried out using binary surfactants. In the dual template, tetraethylammonium hydroxide was used to construct the microporous structure of ZSM‐5, and cationic surfactant (e.g., octadecyltrimethylammonium chloride (C₁₈TMAC), hexadecyltrimethyl ammonium bromide (C₁₆TMAB), and tetradecyltrimethylammonium bromide, (C₁₄TMAB)) can change the growth habits of the ZSM‐5 crystals by hindering the regular stacking of zeolite layers from their longer hydrophobic chain. From the XRD pattern of the as‐synthesized samples which were hydrothermally treated for different time, it was found that a lamellar mesostructured intermediate gradually transformed into the sheet‐like ZSM‐5 during hydrothermal process. With a proper amount of cationic surfactant, the thickness of the sheet‐like ZSM‐5 could be controlled to less than 30 nm. Concerning the catalyst application, the toluene disproportionation performance over the sheet‐like ZSM‐5 is 1.5 times higher than that of the commercial ZSM‐5. The higher conversion is ascribed to the faster diffusion amount due to the sheet‐like ZSM‐5.