Zinc‐containing ionic liquid as a dual solvent‐catalyst in base‐free condensations under ultrasonic irradiation

In this study, natural‐based ionic liquid (IL) using caffeine (Caff), trietahnolamine (TEA) and ZnBr₂, [Caff‐TEA]⁺[ZnBr₃]^?, which features high catalytic activity and environmentally‐friendly nature was synthesized with melting point of 76 °C by a facile method. The synthesized [Caff‐TEA]⁺[ZnBr₃]^? has high catalytic activity as both of catalyst and solvent in condensation reactions for the synthesis of benzylidenes, bis‐hydroxyenones and xanthenes. Synthesized IL was characterized by proton nuclear magnetic resonance (¹HNMR), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD) and Energy‐dispersive X‐ray spectroscopy (EDX) analysis. Also synthesized heterocycles were characterized by FT‐IR, proton nuclear magnetic resonance (¹HNMR) and carbon nuclear magnetic resonance (¹³CNMR).     

Polymerization of isoprene with η5‐C5H4(tert‐Bu)TiCl3/MAO catalyst

cis‐Selective polymerizations of isoprene with the catalysts composed of η⁵‐C₅H₄(R)TiCl₃ (1; R?H, 2 ; tert‐Bu) and methylaluminoxane were investigated. Both catalysts showed remarkable catalytic activities for the polymerization of isoprene. The polymerization activities were strongly affected by the substituent introduced on cyclopentadienyl ring. Introduction of bulky tert‐butyl group was found to be effective for enhancement of polymerization activity, but the cis‐content of polyisoprene prepared by the 2 /MAO catalyst was lower than that by 1 /MAO catalyst. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1841–1844, 2004     

Ni‐W Catalysts Supported on HZSM‐5/HMS for the Hydrogenation Reaction of Aromatic Compounds: Effect of Ni/W Ratio on Activity,Stability, and Kinetics

Ni‐W/HZSM5‐HMS catalysts were evaluated for the benzene hydrogenation reaction at 130–190°C. To study the catalyst characterization, X‐ray diffraction, X‐ray fluorescence, Fourier transform infrared, UV–vis, diffuse reflectance spectra, temperature‐programmed desorption of NH₃, FT‐IR of adsorbed pyridine measurements (Py‐IR), H₂ chemisorption, nitrogen adsorption–desorption, and TGA techniques were used. Kinetics of benzene hydrogenation was investigated under various hydrogen and benzene pressures, and the effect of reaction conditions on catalytic performance was studied. The results showed that bimetallic catalysts have better ability than a monometallic catalyst (Ni/HZSM5‐HMS) for this reaction, such as maximum benzene conversion (100%), minimum toluene conversion (1.76–40%), very low converted xylene, benzene selectivity (100%), good catalytic stability against coke deposition, and appropriate kinetic parameters.     

Enhanced epoxidation of soybean oil by novel Al2O3–ZrO2–TiO2 solid acid catalyst

This study aims to develop highly efficient, recyclable solid catalysts for the epoxidation of vegetable oils. An Al₂O₃–ZrO₂–TiO₂ solid acid catalyst was prepared by a co‐precipitation/impregnation method and characterised through scanning electron microscopy, energy‐dispersive spectroscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, Fourier‐transform infrared and nitrogen adsorption–desorption analyses. The solid acid catalyst with a high surface area and typical slit pore adsorption was successfully synthesised. Al₂O₃–ZrO₂–TiO₂ also exhibits high stability and improved catalytic efficiency in the epoxidation of soybean oil. An oil conversion rate of 86.6%, which is higher than that of conventional catalysts, was obtained with a catalyst loading of 0.8 wt% and was maintained at 76.6% even after recycling the catalyst three times. The performance of the solid catalyst was slightly superior to that of H₂SO₄. Therefore, this novel catalyst may potentially be applicable in catalysing soybean oil epoxidation.     

Amidinato Germylene‐Zinc Complexes: Synthesis,Bonding, and Reactivity

Despite the explosive growth of germylene compounds as ligands in transition metal complexes, there is a modicum of precedence for the germylene zinc complexes. In this work, the synthesis and characterization of new germylene zinc complexes [PhC(NtBu)₂Ge{N(SiMe₃)₂}→ZnX₂]₂ (X= Br ( 2 ) and I ( 3 )) supported by (benz)‐amidinato germylene ligands are reported. The solid‐state structures of 2 and 3 have been validated by single‐crystal X‐ray diffraction studies, which revealed the dimeric nature of the complexes, with distorted tetrahedral geometries around the Ge and Zn center. DFT calculations reveal that the Ge–Zn bonds in 2 and 3 are dative in nature. The reaction of 2 with elemental sulfur resulted in the first structurally characterized germathione stabilized ZnBr₂ complexes PhC(NtBu)₂Ge(=S){N(SiMe₃)₂}→ZnBr₂ ( 5 ). Therefore, the Ge=S in 5 is in‐between Ge–S single and Ge=S double bond length, owing to the coordination of a sulfur lone pair of electrons to ZnBr₂.     

Differential scanning calorimetry,small‐angle X‐ray scattering,and wide‐angle X‐ray scattering on homogeneous and heterogeneous ethylene‐α‐copolymers

The objective of this work was to use both X‐ray and differential scanning calorimetry techniques in a comparative study of the lamellar and crystalline structures of heterogeneous and homogeneous ethylene‐α‐copolymers. The samples differed in the comonomer type (1‐butene, 1‐hexene, 1‐octene, and hexadecene), comonomer content, and catalyst used in the polymerizations. Step crystallizations were performed with differential scanning calorimetry, and the crystallinity and lamellar thicknesses of the different crystal populations were determined. Wide‐angle X‐ray scattering was used to determine crystallinities, average sizes of the crystallites, and dimensions of the orthorhombic unit cell. The average thickness, separation of the lamellae, and volume fractions of the crystalline phase were determined by small‐angle X‐ray scattering (SAXS). The results revealed that at densities below 900 kg/m³, polymers were organized as poorly organized crystal bundles. The lamellar distances were smaller and the lamellar thickness distributions were narrower for the homogeneous ethylene copolymers than for the heterogeneous ones. Step‐crystallization experiments by SAXS demonstrated that the long period increased after annealing. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1860–1875, 2001     

Synthesis,characterization and catalytic application of a new organometallic oligomer based on polyhedral oligomeric silsesquioxane

Although homogeneous catalysts provide high performance and selectivity, the difficulty of separation and recycling of these catalysts has bothered the scientific community worldwide. Therefore, the demand for heterogeneous catalysts that possess the advantages of homogeneous ones, with ease of separation and recyclability remains a topic of major impact. The oligomeric catalyst synthesized in this work was characterized using elemental analysis, Fourier transform infrared, ¹³C NMR, ²⁹Si NMR and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy and Brunauer–Emmett–Teller analysis and compared to its homogeneous counterpart [W(CO)₃Br₂(ATC)] in the epoxidation of 1‐octene, cyclooctene, (S )‐limonene, cis ‐3‐hexen‐1‐ol, trans ‐3‐hexen‐1‐ol and styrene. The results showed that the percentage conversion for the homogeneous species [W(CO)₃Br₂(ATC)] was slightly higher than for the oligomeric catalyst (POSS‐ATC‐[W(CO)₃Br₂]). Furthermore, the selectivity for epoxide of the oligomeric catalyst was greater than that of the homogeneous catalyst by about 25% when (S )‐limonene was used. Great conversions (yields) of products were obtained with a wide range of substrates and the catalyst was recycled many times without any substantial loss of its catalytic activity.     

Olefin polymerization with Me4Cp–Amido complexes with electron‐withdrawing groups

A series of Me₄Cp–amido complexes {[η⁵:η¹‐(Me₄C₅)SiMe₂NR]TiCl₂; R = t‐Bu, 1 ; C₆H₅, 2 ; C₆F₅, 3 ; SO₂Ph, 4 ; or SO₂Me, 5 } were prepared and investigated for olefin polymerization in the presence of methylaluminoxane (MAO). X‐ray crystallography of complexes 3 and 4 revealed very long Ti N bonds relative to the bonds of 1 . These complexes were employed for ethylene–styrene copolymerizations, styrene homopolymerizations, and propylene homopolymerizations in the presence of MAO. The productivities of the catalysts derived from 3 – 5 were much lower than the productivity of the catalyst derived from 1 for the propylene polymerizations and ethylene–styrene copolymerizations, whereas the styrene polymerization activities were much higher for the catalysts derived from 3 – 5 than for the catalyst derived from 1 . The polymerization behavior of the catalysts derived from the metallocenes 3 – 5 were more reminiscent of monocyclopentadienyl titanocene Cp′TiX₃/MAO catalysts than of CpATiX₂/MAO catalysts such as 1 containing alkylamido ligands. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4649–4660, 2000     

Synthesis of TiO2 on different substrates by chemical vapor deposition for photocatalytic reduction of Cr(VI) in water

TiO₂ loaded on several substrates such as carbon fiber, aluminum plate, silica plate, and glass plate was prepared using the chemical vapor deposition (CVD) method for the photocatalytic reduction of Cr(VI) in water with the presence of ethanol under Ultraviolet (UV) illumination. As‐prepared samples were characterized by X‐Ray Diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), and scanning electron microscopy (SEM). The catalyst with TiO₂ loaded on carbon fiber possessed an extremely large surface area (1,463,91 m²/g), while the other catalysts possessed small surface areas (0.05–0.21 m²/g). The photocatalytic activity of TiO₂ loaded on carbon fiber, which was determined by the conversion of Cr(VI) and the degradation of chemical oxygen demand (COD), was much higher than that of other catalysts. The reusability of TiO₂ loaded on carbon fiber catalyst exhibited almost the same activity as the fresh catalyst. The results indicated that TiO₂ loaded on carbon fiber is feasible for practical application.     

Redox initiated cationic polymerization of oxetanes

3,3‐Disubstituted oxetane monomers were found to undergo rapid, exothermic redox initiated cationic ring‐opening polymerization in the presence of a diaryliodonium or triarylsulfonium salt oxidizing agent and a hydrosilane reducing agent. The redox reaction requires a noble metal complex as a catalyst and several potential catalysts were evaluated. The palladium complex, Cl₂(COD)Pd^II, was observed to provide good shelf life stability while, at the same time, affording high reactivity in the presence of a variety of hydrosilane reducing agents. A range of structurally diverse oxetane monomers undergo polymerization under redox cationic conditions. When a small amount of an alkylated epoxide was added as a “kick‐start” accelerator to these same oxetanes, the redox initiated cationic polymerizations were extraordinarily rapid owing to the marked reduction in the induction period. A mechanistic interpretation of these results is offered. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1854–1861     

Visualization of Heterogeneous Oxygen Storage Behavior in Platinum‐Supported Cerium‐Zirconium Oxide Three‐Way Catalyst Particles by Hard X‐ray Spectro‐Ptychography

The cerium density and valence in micrometer‐size platinum‐supported cerium–zirconium oxide Pt/Ce₂Zr₂O_x (x=7–8) three‐way catalyst particles were successfully mapped by hard X‐ray spectro‐ptychography (ptychographic‐X‐ray absorption fine structure, XAFS). The analysis of correlation between the Ce density and valence in ptychographic‐XAFS images suggested the existence of several oxidation behaviors in the oxygen storage process in the Ce₂Zr₂O_x particles. Ptychographic‐XAFS will open up the nanoscale chemical imaging and structural analysis of heterogeneous catalysts.     

Synthesis of micronized CaO assisted by NH4HCO3 with Ca(OH)2 and its application in heterogeneously catalyzing transesterification reaction for producing biodiesel

Micronized CaO with pores was synthesized by calcining the reaction product CaCO₃ from NH₄HCO₃ and Ca(OH)₂. Scanning electron microscopy, X‐ray diffraction, energy dispersive X‐ray spectroscopy, X‐ray fluorescence, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller analysis were used to characterize CaO, which confirmed that after calcining at 800°C for 2 hr, CaCO₃ was completely converted into porous micronized CaO with a surface area of about 7.295 m²/g and a particle size of 0.5–1.5 μm. The porous CaO microparticles were used as heterogeneous catalysts for producing biodiesel from transesterification of soybean oil and methanol. The influences of reaction time, calcined temperature, and reusability of CaO were explored. The experiments showed that CaO has high catalytic activity for transesterification reaction, and the yield of biodiesel reaches more than 98% under the conditions of methanol/oil mole ratio of 9, and the catalyst amount (catalyst/oil) of 3% after reaction for 2.5 hr. The CaO catalyst can be recycled easily and it also has the advantage of low pollution. Simple synthetic route, low cost, high catalytic activity, good reusability, and great potential for industrialization are the advantages of the porous micronized CaO catalyst that was proposed in this work.     

Polypropylene reactor mixture obtained with homogeneous and supported catalysts

Propylene polymerizations were performed with homogeneous ?₂C(Flu)(Cp)ZrCl₂ and SiMe₂(Ind)₂ZrCl₂ catalyst mixtures and with mixtures supported on the zeolite acid mordenite. The polymerizations were performed in toluene and hexane/triisobutylaluminum at different temperatures and Al(MAO)/Zr concentration ratios. The effects of these variables on the catalyst activity were investigated with statistical experimental planning. The average molecular weights, molecular weight distributions, melting temperatures, and crystallinities of the obtained polymers were examined. The results showed lower activities for the homogeneous catalyst mixture than for the isolated systems. On the other hand, high activities were obtained for the syndiospecific heterogeneous system, but very low values were obtained for the supported isospecific metallocene, although both catalysts were prepared under the same conditions. The supported binary system showed intermediary catalyst activity in comparison with the syndiospecific and isospecific supported catalysts. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 263–272, 2005     

Poly(ester urethane)s derived from lactide,isosorbide, terephthalic acid,and various diisocyanates

Isosorbide‐initiated oligomerizations of l ‐lactide were preformed in bulk using SnCl₂ as catalyst. The resulting telechelic OH‐terminated oligoesters were in situ subjected to simultaneous polycondensation and polyaddition with mixtures of terephthaloyl chloride and diisocyanates. Most polymerizations were conducted with 4,4′‐diisocyanatodiphenyl methane and 2,4‐diisocyanato toluene. The consequences of excess diisocyanate and four different catalysts were studied. The isosorbide/lactide ratio and the terephthalic acid/diisocyanate ratio were varied. Number average molecular weights up to 15 kDa with polydispersities around 3–5 were obtained. Depending on the chemical structure of the copolyester and on the feed ratio, incorporation of urethane groups may reduce or enhance the glass‐transition temperature, but the thermal stability decreases dramatically regardless of composition. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 867–875     

A one‐pot method for synthesis of reduced graphene oxide‐supported Cu–Cu2O and catalytic application in tandem reaction of halides and sodium azide with terminal alkynes

Reduced graphene oxide (RGO)‐supported Cu–Cu₂O nanocomposite material (Cu‐Cu₂O@RGO) was prepared through a one‐pot reflux synthesis method. The morphology, crystal structure and composition of the prepared Cu‐Cu₂O@RGO were characterized using transmission electron microscopy, X‐ray diffraction, and X‐ray photoelectron, infrared and Raman spectroscopies. Cu‐Cu₂O@RGO as a heterogeneous catalyst was applied to tandem reactions of halides and sodium azide with terminal alkynes to synthesize effectively 1,4‐disubstituted 1,2,3‐triazoles. Moreover, the catalyst showed excellent recyclability performance with very little leaching of the metal. Compared with homogeneous catalysts, Cu‐Cu₂O@RGO as a green and efficient catalyst was recoverable, easy to separate and highly stable in the tandem method for the synthesis of 1,2,3‐triazole compounds.     

Manganese‐based transition metal complexes as new catalysts for olefin polymerizations

Three manganese complexes, Mn(acac)₃ (acac = acetylacetonate), Cp₂Mn (Cp = cyclopentadienyl), and Mn(salen)Cl [salen = 1,2‐cyclohexanediamino‐N,N′‐bis(3,5‐dit‐butyl‐salicylidene)], were used for ethylene and propylene polymerizations. These complexes, in combination with an alkylaluminum cocatalyst such as methylaluminoxane (MAO) or diethyl aluminum chloride (AlEt₂Cl), could promote ethylene polymerizations that yielded extremely high molecular weight linear polymers, but were inactive for propylene polymerizations. The counterparts supported on MgCl₂ showed activities even for propylene polymerizations and had remarkably enhanced activities for ethylene polymerizations. In the presence of an electron donor such as ethylbenzoate, the MgCl₂‐supported manganese‐based catalysts yielded a highly isotactic polypropylene with a high molecular weight. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3733–3738, 2001     

New asymmetric vanadium catalyst for highly selective oxidative coupling polymerization

Novel oxovanadium(IV)–bisoxazoline catalysts, such as vanadyl sulfate (VOSO₄)–(R)‐2,2′‐isopropylidenebis(4‐phenyl‐2‐oxazoline) [(R)Phbox], for the asymmetric oxidative coupling polymerization (AOCP) of 2,3‐dihydroxynaphthalene were developed. For example, the AOCP with VOSO₄–(R)Phbox in CH₂Cl₂–MeOH [7/1 (v/v)] at room temperature for 24 h under an O₂ atmosphere, followed by acetylation of the hydroxyl groups, afforded a polymer in a 58% yield with a specific rotation of [α]_D = ?147. The enantioselectivity during the polymerization was estimated to be 80% enantiomeric excess (S), a value much higher than that observed for the polymerizations with the copper(I)‐based catalyst systems and the typical oxovanadium(IV) catalysts reported for the asymmetric oxidative coupling producing the 1,1′‐bi‐2‐naphthol derivatives. © 2005 Wiley Periodicals, Inc., Inc. J Polym Sci Part A: Polym Chem 43: 5872–5878, 2005     

Iron(III)‐mediated AGET ATRP of styrene using tris(3,6‐dioxaheptyl)amine as a ligand

A commercially available tris(3,6‐dioxaheptyl)amine (TDA‐1) was used as a novel ligand for activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) of styrene in bulk or solution mediated by iron(III) catalyst in the presence of a limited amount of air. FeCl₃ · 6H₂O and (1‐bromoethyl)benzene (PEBr) were used as the catalyst and initiator, respectively; and environmentally benign ascorbic acid (VC) was used as the reducing agent. The polymerizations show the features of “living”/controlled free‐radical polymerizations and well‐defined polystyrenes with molecular weight M_n = 2400–36,500 g/mol and narrow polydispersity (M_w/M_n = 1.11–1.29) were obtained. The “living” feature of the obtained polymer was further confirmed by a chain‐extension experiment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2002–2008, 2009     

Polymerization of 3‐ethynylthiophene with homogeneous and heterogeneous Rh catalysts

3‐Ethynylthiophene (3ETh) was polymerized with Rh(I) complexes: [Rh(cod)acac], [Rh(nbd)acac], [Rh(cod)Cl]₂, and [Rh(nbd)Cl]₂ (cod is η²:η²‐cycloocta‐1,5‐diene and nbd η²:η²‐norborna‐2,5‐diene), used as homogeneous catalysts and with the last two complexes anchored on mesoporous polybenzimidazole (PBI) beads: [Rh(cod)Cl]₂/PBI and [Rh(nbd)Cl]₂/PBI used as heterogeneous catalysts. All tested catalyst systems give high‐cis poly(3ETh). In situ NMR study of homogeneous polymerizations induced with [Rh(cod)acac] and [Rh(nbd)acac] complexes has revealed: (i) a transformation of acac ligands into free acetylacetone (Hacac) occurring since the early stage of polymerization, which suggests that this reaction is part of the initiation, (ii) that the initiation is rather slow in both of these polymerization systems, and (iii) a release of cod ligand from [Rh(cod)acac] complex but no release of nbd ligand from [Rh(nbd)acac] complex during the polymerization. The stability of diene ligand binding to Rh‐atom in [Rh(diene)acac] catalysts remarkably affects only the molecular weight but not the yield of poly(3ETh). The heterogeneous catalyst systems also provide high‐cis poly(3ETh), which is of very low contamination with catalyst residues since a leaching of anchored Rh complexes is negligible. The course of heterogeneous polymerizations is somewhat affected by limitations arising from the diffusion of monomer inside catalyst beads. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2776–2787, 2008     

Cobalt Single‐Atom Catalysts with High Stability for Selective Dehydrogenation of Formic Acid

Metal–organic framework (MOF)‐derived Co‐N‐C catalysts with isolated single cobalt atoms have been synthesized and compared with cobalt nanoparticles for formic acid dehydrogenation. The atomically dispersed Co‐N‐C catalyst achieves superior activity, better acid resistance, and improved long‐term stability compared with nanoparticles synthesized by a similar route. High‐angle annular dark‐field–scanning transmission electron microscopy, X‐ray photoelectron spectroscopy, electron paramagnetic resonance, and X‐ray absorption fine structure characterizations reveal the formation of Co^IIN_x centers as active sites. The optimal low‐cost catalyst is a promising candidate for liquid H₂ generation.