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Catalysts, Volume 6, Issue 11 (November 2016)

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Research

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Open AccessArticle Enhancing the Enzymatic Activity of a Heme-Dependent Peroxidase through Genetic Modification
Catalysts 2016, 6(11), 166; doi:10.3390/catal6110166
Received: 28 August 2016 / Revised: 14 October 2016 / Accepted: 18 October 2016 / Published: 27 October 2016
Cited by 1 | PDF Full-text (3971 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A heme-dependent peroxidase (HDP) catalyzes the ortho-hydroxylation of l-tyrosine to l-3,4-dihydroxyphenylalanine (l-DOPA) in the presence of hydrogen peroxide. l-DOPA can be used for the treatment of Parkinson's disease. In this work, to improve the catalytic efficiency, the heme-dependent
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A heme-dependent peroxidase (HDP) catalyzes the ortho-hydroxylation of l-tyrosine to l-3,4-dihydroxyphenylalanine (l-DOPA) in the presence of hydrogen peroxide. l-DOPA can be used for the treatment of Parkinson's disease. In this work, to improve the catalytic efficiency, the heme-dependent peroxidase has been genetically modified with an elastin-like polypeptide (ELP). bicinchoninic acid (BCA) assay demonstrated that HDP-ELP has a higher solubility in aqueous solutions than HDP. Circular dichroism (CD) spectra showed that HDP-ELP has a higher stability than HDP. Enzyme kinetics has been investigated over a range of substrate concentrations. It has been demonstrated that HDP-ELP exhibited a catalytic efficiency 2.4 times that of HDP. Full article
(This article belongs to the Special Issue Immobilized Enzymes: Strategies for Enzyme Stabilization)
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Open AccessArticle TiO2 Nanotubes Supported Cu Nanoparticles for Improving Photocatalytic Degradation of Simazine under UV Illumination
Catalysts 2016, 6(11), 167; doi:10.3390/catal6110167
Received: 15 August 2016 / Revised: 20 October 2016 / Accepted: 21 October 2016 / Published: 29 October 2016
Cited by 2 | PDF Full-text (13858 KB) | HTML Full-text | XML Full-text
Abstract
Nano size Copper (Cu) incorporated TiO2 nanotubes was successfully synthesized via the anodic oxidation technique in ethylene glycol (EG) containing 0.5 wt % NH4F and 1.6 wt % KOH for the photocatalytic degradation of Simazine (2-chloro-4, 6-diethylamino-1,3,5-triazine) under Ultraviolet (UV)
[...] Read more.
Nano size Copper (Cu) incorporated TiO2 nanotubes was successfully synthesized via the anodic oxidation technique in ethylene glycol (EG) containing 0.5 wt % NH4F and 1.6 wt % KOH for the photocatalytic degradation of Simazine (2-chloro-4, 6-diethylamino-1,3,5-triazine) under Ultraviolet (UV) illumination. In the present study, the influence of different loading Cu concentrations on the formation of Cu-TiO2 nanotubes film towards the photocatalytic degradation of Simazine is reported. Based on our study, it was found that the optimum Cu loading concentration was about 0.45 wt % on TiO2 nanotubes film for approximately 64% photocatalytic degradation of Simazine after 4 h under UV illumination. This finding was mainly attributed to the uniform surface covering of the Cu loaded TiO2NTs which acted as electron traps, preventing the recombination of electron hole pairs, eventually leading to higher photocatalytic activity of our photocatalyst in degrading the targeted organic pollutant, Simazine. Moreover, an increased kinetic rate of the degradation to 0.0135 h−1 was observed in the presence of Cu in TiO2NTs. Full article
(This article belongs to the Special Issue Photocatalytic Wastewater Treatment)
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Open AccessArticle Efficient Production of Enantiopure d-Lysine from l-Lysine by a Two-Enzyme Cascade System
Catalysts 2016, 6(11), 168; doi:10.3390/catal6110168
Received: 24 September 2016 / Revised: 23 October 2016 / Accepted: 25 October 2016 / Published: 30 October 2016
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Abstract
The microbial production of d-lysine has been of great interest as a medicinal raw material. Here, a two-step process for d-lysine production from l-lysine by the successive microbial racemization and asymmetric degradation with lysine racemase and decarboxylase was developed. The
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The microbial production of d-lysine has been of great interest as a medicinal raw material. Here, a two-step process for d-lysine production from l-lysine by the successive microbial racemization and asymmetric degradation with lysine racemase and decarboxylase was developed. The whole-cell activities of engineered Escherichia coli expressing racemases from the strains Proteus mirabilis (LYR) and Lactobacillus paracasei (AAR) were first investigated comparatively. When the strain BL21-LYR with higher racemization activity was employed, l-lysine was rapidly racemized to give dl-lysine, and the d-lysine yield was approximately 48% after 0.5 h. Next, l-lysine was selectively catabolized to generate cadaverine by lysine decarboxylase. The comparative analysis of the decarboxylation activities of resting whole cells, permeabilized cells, and crude enzyme revealed that the crude enzyme was the best biocatalyst for enantiopure d-lysine production. The reaction temperature, pH, metal ion additive, and pyridoxal 5′-phosphate content of this two-step production process were subsequently optimized. Under optimal conditions, 750.7 mmol/L d-lysine was finally obtained from 1710 mmol/L l-lysine after 1 h of racemization reaction and 0.5 h of decarboxylation reaction. d-lysine yield could reach 48.8% with enantiomeric excess (ee) ≥ 99%. Full article
(This article belongs to the Special Issue Asymmetric and Selective Biocatalysis)
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Open AccessArticle Practical Pd(TFA)2-Catalyzed Aerobic [4+1] Annulation for the Synthesis of Pyrroles via “One-Pot” Cascade Reactions
Catalysts 2016, 6(11), 169; doi:10.3390/catal6110169
Received: 21 September 2016 / Revised: 18 October 2016 / Accepted: 21 October 2016 / Published: 31 October 2016
Cited by 1 | PDF Full-text (2067 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The Pd(TFA)2-catalyzed [4+1] annulation of chained or cyclic α-alkenyl-dicarbonyl compounds and unprotected primary amines for “one-pot” synthesis of pyrroles is reported here. Enamination and amino-alkene were involved in this practical and efficient tandem reaction. The annulation products were isolated in moderate
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The Pd(TFA)2-catalyzed [4+1] annulation of chained or cyclic α-alkenyl-dicarbonyl compounds and unprotected primary amines for “one-pot” synthesis of pyrroles is reported here. Enamination and amino-alkene were involved in this practical and efficient tandem reaction. The annulation products were isolated in moderate to excellent yields with O2 as the terminal oxidant under mild conditions. In addition, this method was applied to synthesize highly regioselective aminomethylated and di(1H-pyrrol-3-yl)methane products. Full article
(This article belongs to the Special Issue Organometallic Catalysis for Organic Synthesis)
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Open AccessFeature PaperArticle An Alumina-Supported Ni-La-Based Catalyst for Producing Synthetic Natural Gas
Catalysts 2016, 6(11), 170; doi:10.3390/catal6110170
Received: 21 September 2016 / Revised: 25 October 2016 / Accepted: 25 October 2016 / Published: 31 October 2016
Cited by 5 | PDF Full-text (3492 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
LaNi5, known for its hydrogen storage capability, was adapted to the form of a metal oxide-supported (γ-Al2O3) catalyst and its performance for the Sabatier reaction assessed. The 20 wt % La-Ni/γ-Al2O3 particles were prepared
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LaNi5, known for its hydrogen storage capability, was adapted to the form of a metal oxide-supported (γ-Al2O3) catalyst and its performance for the Sabatier reaction assessed. The 20 wt % La-Ni/γ-Al2O3 particles were prepared via solution combustion synthesis (SCS) and exhibited good catalytic activity, achieving a CO2 conversion of 75% with a high CH4 selectivity (98%) at 1 atm and 300 °C. Characteristics of the La-Ni/γ-Al2O3 catalyst were identified at various stages of the catalytic process (as-prepared, activated, and post-reaction) and in-situ DRIFTS was used to probe the reaction mechanism. The as-prepared catalyst contained amorphous surface La–Ni spinels with particle sizes <6 nm. The reduction process altered the catalyst make-up where, despite the reducing conditions, Ni2+-based particles with diameters between 4 and 20 nm decorated with LaOx moieties were produced. However, the post-reaction catalyst had particle sizes of 4–9 nm and comprised metallic Ni, with the LaOx decoration reverting to a form akin to the as-prepared catalyst. DRIFTS analysis indicated that formates and adsorbed CO species were present on the catalyst surface during the reaction, implying the reaction proceeded via a H2-assisted and sequential CO2 dissociation to C and O. These were then rapidly hydrogenated into CH4 and H2O. Full article
(This article belongs to the Special Issue Small Molecule Activation and Catalysis)
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Open AccessArticle Dehydrogenation of Isobutane with Carbon Dioxide over SBA-15-Supported Vanadium Oxide Catalysts
Catalysts 2016, 6(11), 171; doi:10.3390/catal6110171
Received: 31 August 2016 / Revised: 25 October 2016 / Accepted: 25 October 2016 / Published: 31 October 2016
Cited by 2 | PDF Full-text (4911 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A series of vanadia catalysts supported on SBA-15 (V/SBA) with a vanadia (V) content ranging from 1% to 11% were prepared by an incipient wetness method. Their catalytic behavior in the dehydrogenation of isobutane to isobutene with CO2 was examined. The catalysts
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A series of vanadia catalysts supported on SBA-15 (V/SBA) with a vanadia (V) content ranging from 1% to 11% were prepared by an incipient wetness method. Their catalytic behavior in the dehydrogenation of isobutane to isobutene with CO2 was examined. The catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and temperature-programmed reduction (TPR). It was found that these catalysts were effective for the dehydrogenation reaction, and the catalytic activity is correlated with the amount of dispersed vanadium species on the SBA-15 support. The 7% V/SBA catalyst shows the highest activity, which gives 40.8% isobutane conversion and 84.8% isobutene selectivity. The SBA-15-supported vanadia exhibits higher isobutane conversion and isobutene selectivity than the MCM-41-supported one. Full article
(This article belongs to the Special Issue Organometallic Catalysis for Organic Synthesis)
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Open AccessArticle Hydrogen Generation from Catalytic Steam Reforming of Acetic Acid by Ni/Attapulgite Catalysts
Catalysts 2016, 6(11), 172; doi:10.3390/catal6110172
Received: 26 September 2016 / Revised: 24 October 2016 / Accepted: 31 October 2016 / Published: 4 November 2016
Cited by 4 | PDF Full-text (3363 KB) | HTML Full-text | XML Full-text
Abstract
In this research, catalytic steam reforming of acetic acid derived from the aqueous portion of bio-oil for hydrogen production was investigated using different Ni/ATC (Attapulgite Clay) catalysts prepared by precipitation, impregnation and mechanical blending methods. The fresh and reduced catalysts were characterized by
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In this research, catalytic steam reforming of acetic acid derived from the aqueous portion of bio-oil for hydrogen production was investigated using different Ni/ATC (Attapulgite Clay) catalysts prepared by precipitation, impregnation and mechanical blending methods. The fresh and reduced catalysts were characterized by XRD, N2 adsorption–desorption, TEM and temperature program reduction (H2-TPR). The comprehensive results demonstrated that the interaction between active metallic Ni and ATC carrier was significantly improved in Ni/ATC catalyst prepared by precipitation method, from which the mean of Ni particle size was the smallest (~13 nm), resulting in the highest metal dispersion (7.5%). The catalytic performance of the catalysts was evaluated by the process of steam reforming of acetic acid in a fixed-bed reactor under atmospheric pressure at two different temperatures: 550 °C and 650 °C. The test results showed the Ni/ATC prepared by way of precipitation method (PM-Ni/ATC) achieved the highest H2 yield of ~82% and a little lower acetic acid conversion efficiency of ~85% than that of Ni/ATC prepared by way of impregnation method (IM-Ni/ATC) (~95%). In addition, the deactivation catalysts after reaction for 4 h were analyzed by XRD, TGA-DTG and TEM, which demonstrated the catalyst deactivation was not caused by the amount of carbon deposition, but owed to the significant agglomeration and sintering of Ni particles in the carrier. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Open AccessArticle Effect of Ru Species on N2O Decomposition over Ru/Al2O3 Catalysts
Catalysts 2016, 6(11), 173; doi:10.3390/catal6110173
Received: 30 August 2016 / Revised: 16 October 2016 / Accepted: 1 November 2016 / Published: 5 November 2016
Cited by 2 | PDF Full-text (4189 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Ru is considered as an effective active species for N2O decomposition; however, there is disagreement about which ruthenium species is key for catalytic activity. In order to understand the role of Ru species in N2O decomposition, Ru/Al2O
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Ru is considered as an effective active species for N2O decomposition; however, there is disagreement about which ruthenium species is key for catalytic activity. In order to understand the role of Ru species in N2O decomposition, Ru/Al2O3 (Ru/Al2O3-H2, Ru/Al2O3-NaBH4, Ru/Al2O3-air) catalysts with different ratios of metallic Ru were prepared and evaluated for their catalytic activities. Various characterizations, especially in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), were applied to investigate the relationship between activity and different Ru species. The results indicate that the N2O conversion displayed a linear relationship with the amount of metallic Ru. The DRIFTS results of adsorption for N2O show that metallic Ru was the active site. The catalytic processes are put forward based on metallic Ru species. The deactivation with increasing times used is due to the decrease in the amount of metallic Ru and agglomerates of Ru particles on the surface of catalysts. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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Open AccessArticle Adsorption and Activity of Lipase on Polyphosphazene-Modified Polypropylene Membrane Surface
Catalysts 2016, 6(11), 174; doi:10.3390/catal6110174
Received: 22 September 2016 / Revised: 26 October 2016 / Accepted: 27 October 2016 / Published: 8 November 2016
Cited by 2 | PDF Full-text (2587 KB) | HTML Full-text | XML Full-text
Abstract
In this work, poly(n-butylamino)(allylamino)phosphazene (PBAP) was synthesized and tethered on polypropylene microporous membrane (PPMM) with the aim of offering a biocompatible and, at the same time, moderately hydrophobic microenvironment to lipase for the first time. Lipase from Candida rugosa was used
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In this work, poly(n-butylamino)(allylamino)phosphazene (PBAP) was synthesized and tethered on polypropylene microporous membrane (PPMM) with the aim of offering a biocompatible and, at the same time, moderately hydrophobic microenvironment to lipase for the first time. Lipase from Candida rugosa was used and the influence of membrane surface conditions on the activities of immobilized lipases was evaluated. Water contact angle measurement as well as field emission scanning electron microscopy were used to characterize the morphology of the modified membranes. The results showed an improvement in the adsorption capacity (26.0 mg/m2) and activity retention (68.2%) of the immobilized lipases on the PBAP-modified PPMM. Moreover, the lipases immobilized on the modified PPMM showed better thermal and pH stability. Full article
(This article belongs to the Special Issue Immobilized Enzymes: Strategies for Enzyme Stabilization)
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Open AccessArticle Understanding the Performance and Stability of Supported Ni-Co-Based Catalysts in Phenol HDO
Catalysts 2016, 6(11), 176; doi:10.3390/catal6110176
Received: 11 October 2016 / Revised: 3 November 2016 / Accepted: 8 November 2016 / Published: 11 November 2016
Cited by 2 | PDF Full-text (3779 KB) | HTML Full-text | XML Full-text
Abstract
Performances of bimetallic catalysts (Ni-Co) supported on different acidic carriers (HZSM-5, HBeta, HY, ZrO2) and corresponding monometallic Ni catalysts in aqueous phase hydrodeoxygenation of phenol were compared in batch and continuous flow modes. The results revealed that the support acidity plays
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Performances of bimetallic catalysts (Ni-Co) supported on different acidic carriers (HZSM-5, HBeta, HY, ZrO2) and corresponding monometallic Ni catalysts in aqueous phase hydrodeoxygenation of phenol were compared in batch and continuous flow modes. The results revealed that the support acidity plays an important role in deoxygenation as it mainly controls the oxygen-removing steps in the reaction network. At the same time, sufficient hydrothermal stability of a solid catalyst is essential. Batch experiments revealed 10Ni10Co/HZSM-5 to be the best-performing catalyst in terms of conversion and cyclohexane yield. Complementary continuous runs provided more insights into the relationship between catalyst structure, efficiency and stability. After 24 h on-stream, the catalyst still reveals 100% conversion and a slight loss (from 100% to 90%) in liquid hydrocarbon selectivity. The observed alloy of Co with Ni increased dispersion and stability of Ni-active sites, and combination with HZSM-5 resulted in a well-balanced ratio of metal and acid sites which promoted all necessary steps in preferred pathways. This was proved by studies of fresh and spent catalysts using various characterization techniques (N2 physisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and infrared spectroscopy of adsorbed pyridine (pyr-IR)). Full article
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Open AccessFeature PaperArticle Enantiopure C1-symmetric N-Heterocyclic Carbene Ligands from Desymmetrized meso-1,2-Diphenylethylenediamine: Application in Ruthenium-Catalyzed Olefin Metathesis
Catalysts 2016, 6(11), 177; doi:10.3390/catal6110177
Received: 14 October 2016 / Revised: 8 November 2016 / Accepted: 9 November 2016 / Published: 14 November 2016
Cited by 1 | PDF Full-text (4486 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In order to design improved chiral ruthenium catalysts for asymmetric olefin metathesis, enantiomeric catalysts incorporating C1-symmetric N-Heterocyclic carbenes (NHC) ligands with syn-related substituents on the backbone were synthesized starting from meso-1,2-diphenylethylenediamine. The absolute configuration of the enantiomers of
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In order to design improved chiral ruthenium catalysts for asymmetric olefin metathesis, enantiomeric catalysts incorporating C1-symmetric N-Heterocyclic carbenes (NHC) ligands with syn-related substituents on the backbone were synthesized starting from meso-1,2-diphenylethylenediamine. The absolute configuration of the enantiomers of the desymmetrized meso diamine was assigned by optical rotation analysis and in silico calculations, and was found to be maintained in their respective ruthenium catalysts by comparison of the relative electronic circular dichroism (ECD) spectra. The catalytic behaviour of the enantiomeric ruthenium complexes was investigated in model asymmetric metathesis transformations and compared to that of analogous complexes bearing C1-symmetric NHC ligands with an anti backbone. Modest enantioselectivities were registered and different catalyst properties depending on the nature of stereochemical relationship of substituents on the backbone were observed. Full article
(This article belongs to the Special Issue Tailor-Made NHC Ligands)
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Open AccessArticle Au Capping Agent Removal Using Plasma at Mild Temperature
Catalysts 2016, 6(11), 179; doi:10.3390/catal6110179
Received: 15 September 2016 / Revised: 20 October 2016 / Accepted: 1 November 2016 / Published: 17 November 2016
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Abstract
To prevent sintering, ozone treatment at mild temperature is used to remove the capping agent from supported Au nanoparticles. The Au nanoparticles are first synthesized as a colloidal solution and then supported on alumina. Fourier Transform Infra Red (FTIR) shows the capping agent
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To prevent sintering, ozone treatment at mild temperature is used to remove the capping agent from supported Au nanoparticles. The Au nanoparticles are first synthesized as a colloidal solution and then supported on alumina. Fourier Transform Infra Red (FTIR) shows the capping agent is removed completely. Transmission Electron Microscopy (TEM) and catalytic test reactions show the Au does not sinter significantly upon low temperature ozone treatment. Full article
(This article belongs to the collection Gold Catalysts)
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Open AccessArticle Pulsed Laser Deposition of Platinum Nanoparticles as a Catalyst for High-Performance PEM Fuel Cells
Catalysts 2016, 6(11), 180; doi:10.3390/catal6110180
Received: 29 September 2016 / Revised: 7 November 2016 / Accepted: 17 November 2016 / Published: 22 November 2016
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Abstract
The catalyst layers for polymer-electrolyte-membrane (PEM) fuel cells were fabricated by deposition of platinum directly onto the gas diffusion layer using pulsed laser deposition (PLD). This technique reduced the number of steps required to synthesize the catalyst layers and the amount of Pt
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The catalyst layers for polymer-electrolyte-membrane (PEM) fuel cells were fabricated by deposition of platinum directly onto the gas diffusion layer using pulsed laser deposition (PLD). This technique reduced the number of steps required to synthesize the catalyst layers and the amount of Pt loading required. PEM fuel cells with various Pt loadings for the cathode were investigated. With a cathode Pt loading of 100 μ g·cm 2 , the current density of a single cell reached 1205 mA·cm 2 at 0.6 V, which was close to that of a single cell using an E-TEK (trademark) Pt/C electrode with a cathode Pt loading of 400 μ g·cm 2 . Furthermore, for a PEM fuel cell with both electrodes prepared by PLD and a total anode and cathode Pt loading of 117 μ g·cm 2 , the overall Pt mass-specific power density at 0.6 V reached 7.43 kW·g 1 , which was five times that of a fuel cell with E-TEK Pt/C electrodes. The high mass-specific power density was due to that a very thin nanoporous Pt layer was deposited directly onto the gas diffusion layer, which made good contact with the Nafion membrane and thus resulted in a low-resistance membrane electrode assembly. Full article
(This article belongs to the Special Issue Catalysis for Low Temperature Fuel Cells)
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Review

Jump to: Research

Open AccessReview Design of Efficient Molecular Catalysts for Synthesis of Cyclic Olefin Copolymers (COC) by Copolymerization of Ethylene and α-Olefins with Norbornene or Tetracyclododecene
Catalysts 2016, 6(11), 175; doi:10.3390/catal6110175
Received: 15 October 2016 / Revised: 24 October 2016 / Accepted: 28 October 2016 / Published: 9 November 2016
Cited by 2 | PDF Full-text (1593 KB) | HTML Full-text | XML Full-text
Abstract
Selected results for the synthesis of cyclic olefin copolymers (COCs)—especially copolymerizations of norbornene (NBE) or tetracyclododecene (TCD) with ethylene and α-olefins (1-hexene, 1-octene, 1-dodecene)—using group 4 transition metal (titanium and zirconium) complex catalysts have been reviewed. Half-titanocenes containing an anionic ancillary donor ligand,
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Selected results for the synthesis of cyclic olefin copolymers (COCs)—especially copolymerizations of norbornene (NBE) or tetracyclododecene (TCD) with ethylene and α-olefins (1-hexene, 1-octene, 1-dodecene)—using group 4 transition metal (titanium and zirconium) complex catalysts have been reviewed. Half-titanocenes containing an anionic ancillary donor ligand, Cp’TiX2(Y) (Cp’ = cyclopentadienyl; X = halogen, alkyl; Y = anionic donor ligand such as aryloxo, ketimide, imidazolin-2-iminato, etc.), are effective catalysts for efficient synthesis of new COCs; ligand modifications play an important role for the desired copolymerization. These new COCs possess promising properties (high transparency, thermal resistance (high glass transition temperature), low water absorption, etc.), thus it is demonstrated that the design of an efficient catalyst plays an essential role for the synthesis of new fine polyolefins with specified properties. Full article
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Open AccessFeature PaperReview Advances in the Knowledge of N-Heterocyclic Carbenes Properties. The Backing of the Electrochemical Investigation
Catalysts 2016, 6(11), 178; doi:10.3390/catal6110178
Received: 25 October 2016 / Revised: 9 November 2016 / Accepted: 10 November 2016 / Published: 16 November 2016
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Abstract
In the last twenty years, N-heterocyclic carbenes (NHCs) have acquired considerable popularity as ligands for transition metals, organocatalysts and in metal-free polymer synthesis. NHCs are generally derived from azolium based salts NHCH+X by deprotonation or reduction (chemical or electrochemical)
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In the last twenty years, N-heterocyclic carbenes (NHCs) have acquired considerable popularity as ligands for transition metals, organocatalysts and in metal-free polymer synthesis. NHCs are generally derived from azolium based salts NHCH+X by deprotonation or reduction (chemical or electrochemical) of NHCH+. The extensive knowledge of the physicochemical properties of NHCH+/NHC system could help to select the conditions (scaffold of NHC, nature of the counter-ion X, solvent, etc.) to enhance the catalytic power of NHC in a synthesis. The electrochemical behavior of NHCH+/NHC system, in the absence and in the presence of solvent, was extensively discussed. The cathodic reduction of NHCH+ to NHC and the anodic oxidation of NHC, and the related effect of the scaffold, solvent, and electrodic material were emphasized. The electrochemical investigations allow acquiring further knowledge as regards the stability of NHC, the acidic and nucleophilic properties of NHCH+/NHC system, the reactivity of NHC versus carbon dioxide and the effect of the hydrogen bond on the catalytic efficiency of NHC. The question of the spontaneous or induced formation of NHC from particular ionic liquids was reconsidered via voltammetric analysis. The results suggested by the classical and the electrochemical methodologies were compared and discussed. Full article
(This article belongs to the Special Issue Tailor-Made NHC Ligands)
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