Catalytic decomposition of CFC‐12 on solid acids SO42‐/MxOy (M?Zr,Ti, Sn,Fe, Al)

The catalytic decomposition of dichlorodifluoromethane (CFC‐12) in the presence of water vapor on a series of SO₄^2?‐promoted solid adds was investigated. CFC‐12 was decomposed completely on SO₄^2?/ZrO₂, SO₄^2?/TiO₂, SO₄^2?/SnO₂, SO₄^2?/ Fe₂O₃ and SO₄^2–/Al₂O₃ at 265°C, 270°C, 325°C, 350°C and 325°C, respectively, and the selectivity to by‐products was neglectable. Obvious deactivation was found on SO₄^2?/ZrO₂ and SO₄^2?/Al₂O₃, during several hours on stream, while the catalytic activity was maintained on SO₄^2?/TiO₂, SO₄^2?/SnO₂ and SO₄^2?/Fe₂O₃ for 240 h on stream.     

Adsorption of N719 Dye on Anatase TiO2 Nanoparticles and Nanosheets with Exposed (001) Facets: Equilibrium,Kinetic, and Thermodynamic Studies

Anatase TiO₂ nanosheets (TiO₂ NS) with dominant (001) facets and TiO₂ nanoparticles (TiO₂ NP) with dominant (101) facets are fabricated by hydrothermal hydrolysis of Ti(OC₄H₉)₄ in the presence and absence of hydrogen fluoride (HF), respectively. Adsorption of N719 onto the as‐prepared samples from ethanol solutions is investigated and discussed. The adsorption kinetic data are modeled using the pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion kinetics equations, and indicate that the pseudo‐second‐order kinetic equation and intraparticle diffusion model can better describe the adsorption kinetics. Furthermore, adsorption equilibrium data of N719 on the as‐prepared samples are analyzed by Langmuir and Freundlich models; this suggests that the Langmuir model provides a better correlation of the experimental data. The adsorption capacities (q_max) of N719 on TiO₂ NS at various temperatures, determined using the Langmuir equation, are 65.2 (30 °C), 68.2 (40 °C), and 76.6 (50 °C) mg g⁻¹, which are smaller than those on TiO₂ NP, 92.4 (30 °C), 100.0 (40 °C), and 108.2 (50 °C) mg g⁻¹, respectively. The larger adsorption capacities of N719 for TiO₂ NP versus NS are attributed to its higher specific surface areas. However, the specific adsorption capacities (q_max/S_BET) at various temperatures are 1.5 (30 °C), 1.6 (40 °C), and 1.7 (50 °C) mg m⁻² for TiO₂ NS, which are otherwise higher than those for NP, 0.9 (30 °C), 1.0 (40 °C), and 1.1 (50 °C) mg m⁻², respectively. The larger specific adsorption capacities of N719 for TiO₂ NS versus NP are because the (001) surface is more reactive for dissociative adsorption of reactant molecules compared with (101) facets. Notably, the q_max and q_max/S_BET for both TiO₂ samples increase with increasing temperature, suggesting that adsorption of N719 on the TiO₂ surface is an endothermic process, which is further confirmed by the calculated thermodynamic parameters including free energy, enthalpy, and entropy of adsorption process. The present work will provide a new understanding on the adsorption process and mechanism of N719 molecules onto TiO₂ NS and NP, and this should be of great importance for enhancing the performance of dye‐sensitized solar cells.     

Solvent‐free synthesis of new 2,4,6‐triarylpyridines catalyzed by a Brønsted acidic ionic liquid as a green and reusable catalyst

Some new 4‐(aryl)‐2,6‐di‐2‐naphthylpyridines and 4‐(aryl)‐2,6‐di‐2‐thienylpyridines have been prepared through three‐component condensation of 2‐acetylnaphthalene or 2‐acetylthiophene, aromatic aldehydes, and ammonium acetate in presence of 1‐(4‐sulfonylbutyl) pyridinium hydrogensulfate [(CH₂)₄SO₃HPy][HSO₄], a Brønsted acidic ionic liquid as a green and reusable catalyst in solvent‐free conditions. Also some new 4,4'‐(1,4‐phenylene)‐bis‐(2,6‐di‐aryl pyridine) was prepared. J. Heterocyclic Chem., (2011).     

An Efficient One-pot Synthesis of β-Amino/β-Acetamido Carbonyl Compounds via ZrCl4-catalyzed Mannich-type Reaction

Zirconium(IV) chloride catalyzed efficient one-pot synthesis of β-amino/β-acetamido carbonyl compounds at room temperature is described. In the presence of ZrCl4, the three-component Mannich-type reaction via a variety of in situ generated aldimines, with various ketones, aromatic aldehydes and aromatic amines in ethanol, led to the formation of β-amino carbonyl compounds and the four-component Mannich-type reaction of aromatic aldehydes with various ketones, acetonitrile and acetyl chloride resulted in the corresponding β-acetamido carbonyl compounds in high to excellent yields. This methodology has also been applied towards the synthesis of dimeric β-amino/β-acetamido carbonyl compounds.     

Copoly(arylene ether nitrile) and copoly(arylene ether sulfone) ionomers with pendant sulfobenzoyl groups for proton conducting fuel cell membranes

Three series of fully aromatic ionomers with naphthalene moieties and pendant sulfobenzoyl side chains were prepared via K₂CO₃ mediated nucleophilic aromatic substitution reactions. The first series consisted of poly(arylene ether)s prepared by polycondensations of 2,6‐difluoro‐2′‐sulfobenzophenone (DFSBP) and 2,6‐dihydroxynaphthalene or 2,7‐dihydroxynaphthalene (2,7‐DHN). In the second series, copoly(arylene ether nitrile)s with different ion‐exchange capacities (IECs) were prepared by polycondensations of DFSBP, 2,6‐difluorobenzonitrile (DFBN), and 2,7‐DHN. In the third series, bis(4‐fluorophenyl)sulfone was used instead of DFBN to prepare copoly(arylene ether sulfone)s. Thus, all the ionomers had sulfonic acid units placed in stable positions close to the electron withdrawing ketone link of the side chains. Mechanically strong proton‐exchange membranes with IECs between 1.1 and 2.3 meq g⁻¹ were cast from dimethylsulfoxide solutions. High thermal stability was indicted by high degradation temperatures between 266 and 287 °C (1 °C min⁻¹ under air) and high glass transition temperatures between 245 and 306 °C, depending on the IEC. The copolymer membranes reached proton conductivities of 0.3 S cm⁻¹ under fully humidified conditions. At IECs above ∼1.6 meq g⁻¹, the copolymer membranes reached higher proton conductivities than Nafion^® in the range between −20 and 120 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Preparation of disk‐like Pt/CeO2‐p‐TiO2 catalyst derived from MIL‐125(Ti) for excellent catalytic performance

A feasible strategy is reported for the synthesis of a disk‐like Pt/CeO₂‐p‐TiO₂ catalyst derived from the titanium‐based metal–organic framework (MOF) MIL‐125(Ti) through a few valid steps. To verify the successful synthesis and structural features of the Pt/CeO₂‐p‐TiO₂ catalyst, as‐prepared samples were characterized using several techniques. The characterizations demonstrated that MOF‐derived porous TiO₂ was appropriate for application as a support owing to its moderate surface area (101 m² g^?1) and suitable pore size (6 nm). Moreover, to study the effect of calcination temperature on the catalytic performance, the obtained catalyst was calcined at various temperatures. It was found that Pt/CeO₂‐p‐TiO₂ calcined at 550 °C exhibited the highest catalytic performance, evaluated by means of the reduction of 4‐nitrophenol monitored by UV–visible spectra. Furthermore, this catalyst showed good reusability with a conversion of 94% even after six cycles. Finally, a possible reaction mechanism was proposed to explain the reduction of 4‐nitrophenol to 4‐aminophenol over the Pt/CeO₂‐p‐TiO₂ catalyst.     

Water Soluble Antioxidant Dextran–Quercetin Conjugate with Potential Anticancer Properties

Quercetin, a naturally occurring potent antioxidant, is limited in therapeutic use, owing to its poor water solubility and stability. Herein, a method of conjugating quercetin to an aldehyde functionalized dextran via an HCl catalyzed condensation reaction to yield a water soluble quercetin functionalized polymer is reported. The prepared conjugate is characterized by ¹H and ¹H‐¹³C heteronuclear single quantum correlation (HSQC) NMR, which demonstrate that conjugation occurs via both the A‐ and B‐rings of quercetin. The degree of quercetin functionalization can be tuned by varying the reaction temperature and/or the concentration of the HCl catalyst. However, as temperatures and HCl concentrations are increased above 40 °C and 2 m , respectively, the increase in functionalization is accompanied by an increase in the oxidation of the conjugated quercetin and a decrease in polymer yield. The prepared conjugate is shown to have improved stability compared with native quercetin while maintaining substantial free‐radical scavenging activity. Anticancer activity is evaluated in vitro in a neuroblastoma cell line. The dextran–aldehyde–quercetin conjugate prepared at 40 °C and 2 m HCl is shown to be cytotoxic to neuroblastoma cells (SH‐SY5Y–IC₅₀ = 123 µg mL⁻¹ and BE(2)‐C–IC₅₀ = 380 µg mL⁻¹) but shows no activity against nonmalignant MRC‐5 cells at concentrations up to 400 µg mL⁻¹.     

A new acidic Ti sol impregnated kaolin photocatalyst: synthesis, characterization and visible light photocatalytic performance

In this study, a photocatalyst with visible light photocatalytic activity was obtained using raw materials, including commercial TiO₂, sulfuric acid, and calcined kaolin (CK). The photocatalyst was prepared via a dissolving/impregnating process, in which acidic Ti sol was obtained by initially dissolving TiO₂ particles in sulfuric acid, and then using the sol as impregnant for the CK. The prepared photocatalyst had wide spectral region and narrow band gap. In addition, the impregnation can create acid sites on the obtained composite surface and consequently improve the activity. A series of tests was performed to characterize the properties of the prepared samples. The visible light photocatalytic degradation of methyl orange (MO) in an aqueous solution was used as a probe reaction to evaluate the photocatalytic activities of the obtained samples. Under visible light irradiation, approximately 80 % of MO (with initial concentration of 20 mg/m³) was degraded in 3 h on the photocatalyst prepared by impregnating CK in acidic Ti sol, which was obtained using approximately 60 % H₂SO₄ solution followed by calcination at 400 °C. The acidity of the photocatalyst is the main factor that affects the catalytic activity of the photocatalytic degradation of MO.     

Influence of Support Type and Metal Loading in Methane Decomposition over Iron Catalyst for Hydrogen Production

Natural gas resources, stimulate the method of catalytic methane decomposition. Hydrogen is a superb energy carrier and integral component of the present energy systems, while carbon nanotubes exhibit remarkable chemical and physical properties. The reaction was run at 700 °C in a fixed bed reactor. Catalyst calcination and reduction were done at 500 °C. MgO, TiO₂ and Al₂O₃ supported catalysts were prepared using a co‐precipitation method. Catalysts of different iron loadings were characterized with BET, TGA, XRD, H₂‐TPR and TEM. The catalyst characterization revealed the formation of multi‐walled nanotubes. Alternatively, time on stream tests of supported catalyst at 700 °C revealed the relative profiles of methane conversions increased as the %Fe loading was increased. Higher %Fe loadings decreased surface area of the catalyst. Iron catalyst supported with Al₂O₃ exhibited somewhat higher catalytic activity compared with MgO and TiO₂ supported catalysts when above 35% Fe loading was used. CH₄ conversion of 69% was obtained utilizing 60% Fe/Al₂O₃ catalyst. Alternatively, Fe/MgO catalysts gave the highest initial conversions when iron loading below 30% was employed. Indeed, catalysts with 15% Fe/MgO gave 63% conversion and good stability for 1 h time on stream. Inappropriateness of Fe/TiO₂ catalysts in the catalytic methane decomposition was observed.     

Synergistic Effects between Atomically Dispersed Fe−N−C and C−S−C for the Oxygen Reduction Reaction in Acidic Media

Various advanced catalysts based on sulfur‐doped Fe/N/C materials have recently been designed for the oxygen reduction reaction (ORR); however, the enhanced activity is still controversial and usually attributed to differences in the surface area, improved conductivity, or uncertain synergistic effects. Herein, a sulfur‐doped Fe/N/C catalyst (denoted as Fe/SNC) was obtained by a template‐sacrificing method. The incorporated sulfur gives a thiophene‐like structure (C−S−C), reduces the electron localization around the Fe centers, improves the interaction with oxygenated species, and therefore facilitates the complete 4 e⁻ ORR in acidic solution. Owing to these synergistic effects, the Fe/SNC catalyst exhibits much better ORR activity than the sulfur‐free variant (Fe/NC) in 0.5 m H₂SO₄.     

Aromatic poly(benzoxazole)s from multiring diacids containing (phenylenedioxy)diphenylene or (naphthalenedioxy)diphenylene groups: Synthesis and thermal properties

Poly(arylether benzoxazole)s (PAEBOs) were prepared from a series of fully aromatic dicarboxylic acids containing (phenylenedioxy)diphenylene or (naphthalenedioxy) diphenylene groups and 3,3′‐dihydroxy‐4,4′‐diaminobiphenyl (I) or 4‐4′‐(hexafluoroisopropylidene)bis(2‐aminophenol) (II) through high‐temperature direct polycondensation. A phosphorous pentoxide/methanesulfonic acid mixture or trimethylsilylpolyphosphate was used as a condensing agent. All the PAEBOs were amorphous and soluble in strong acids, and those derived from II were also readily soluble in polar organic solvents. Flexible films were cast from their chloroform solutions. The PAEBOs showed inherent viscosity values of 0.68–2.06 dL/g (CH₃SO₃H, T = 30 °C, c = 0.15 g · dL⁻¹). Thermal analysis indicated glass‐transition temperatures ranging from 236 to 270 °C and thermal stability (5% weight loss) in nitrogen up to 526 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1172–1178, 2000     

Kinetic study of some reactions related to the Mn(II)-catalyzed bromate-saccharide oscillating reactions

In the stirred batch experiment, the Mn(II)-catalyzed bromate-saccharide reaction in aqueous H₂SO₄ or HClO₄ solution exhibits damped oscillations in the concentrations of bromide and Mn(II) ions. Peculiar multiple oscillations are observed in the system with arabinose or ribose. The apparent second-order rate constants of the Mn(III)-saccharide reactions at 25°C are (0.659, 1.03, 1.76, 2.32, and 6.95) M⁻¹ s⁻¹ in 1.00 M H₂SO₄ and (4.69, 7.51, 10.2, 13.5, and 36.2) M⁻¹ s⁻¹ in (2.00–4.00) M HClO₄ for (glucose, galactose, xylose, arabinose, and ribose), respectively. At 25°C, the observed pseudo-first-order rate constant of the Mn(III)-Br⁻ reaction is k_obs = (0.2 ± 0.1) [Br⁻] + (130 ± 5)[Br⁻]² + (2.6 ± 0.1) × 10³[Br⁻]³ + (1.2 ± 0.2) × 10⁴[Br⁻]⁴ s⁻¹ and the rate constant of the Br₂ Mn(II) reaction is less than 1 × 10⁻⁴ M⁻¹ s⁻¹. The second-order rate constants of the Br₂-saccharide reactions are (3.65 ± 0.15, 11.0 ± 0.5, 4.05, 12.5 ± 0.7, and 2.62) × 10⁻⁴ M⁻¹ s⁻¹ at 25°C for glucose, galactose, xylose, arabinose, and ribose, respectively.     

High Catalytic Performance of Mesoporous Dual Brønsted Acidic Ternary Poly (Ionic Liquids) for Friedel‐Crafts Alkylation

A newfangled cross‐linked dual Brønsted acidic ternary mesoporous poly (ionic liquids)(MPILs) with mesoporous structure was successfully synthesized with divinylbenzene as cross linker, 1‐vinyl‐3‐butyl imidazole bromide and sodium p‐styrene sulfonate as functional group through an ordinary post‐modification method and anion exchange process. A sponge‐like mesoporous tunnel structure was observed and the obtained P (BVS‐SO₃H)‐SO₃CF₃ sample appeared a relatively high thermal stability, a large surface area (up to 286.8 m²/g) and great pore volume (0.73 cm³/g). The abundant dual acidic group of sulfonic acid and trifluoromethanesulfonic acid of the composite in the polymer framework impart Brønsted acidity. For the sake of demonstrating our claims, the sample has been used as a novel solid acid catalyst for the reaction of alkylation of o‐xylene with styrene to 1‐diphenylethane (PXE). Under optimal reaction conditions (reaction under 120 °C for 3 hr, catalyst amount was 0.5 wt% of the reaction system, and the mass ratio of o‐xylene/styrene was 7.5:1, a 100% conversion of styrene and 93.7% PXE yield was acquired. After four times recycle, the yield remains 53.3%. Comparing with the commercial liquid acid catalyst, it processing a higher catalytic property and recyclability. Moreover, this fresh dual acidic heterogeneous catalyst owning a promising future applied in other acidic catalytic reactions and provide a new method to modify catalyst.     

Novel materials from bis(arene)metal‐containing polyacrylonitrile

Novel bis(arene)metal‐containing polyacrylonitrile materials have been prepared by the polycyanoethylation reaction between acrylonitrile and (arene)₂M (M = Cr or V; arene = PhH, C₆H₄Et₂ or mesitylene) in the absence of solvent. The resulting star‐shaped molecules consist of a central (arene)₂M species with up to four polyacrylonitrile arms covalently bonded to the arene ligands. The materials are readily soluble and films can be cast from solutions in acetonitrile. The IR and solid state ¹³C NMR spectra (or EPR spectrum for the oxidized chromium‐containing polymer) are consistent with the presence of a metal–arene bond and confirm the persistence of the sandwich structure. The properties of the thermolysed materials are consistent with the formation of conjugated naphthyridine‐type structures. The value of |n₂| determined by the degenerate four‐wave mixing technique at 1064 nm with a 6 ns pulse duration for a solution in conc. H₂SO₄ (1 g l⁻¹) of the chromium‐containing polymer pyrolysed at 350 °C was found to be 0.8 × 10⁻¹³ cm² W⁻¹ corresponding to |lRe _χ⁽³⁾| = 0.4 × 10⁻¹¹ esu.     

Fe3O4@SiO2@sulfated boric acid as superparamagnetic and recyclable nanocatalyst‐assisted,one‐pot,pseudo four‐component synthesis of 5‐amino‐2‐aryl‐3H‐chromeno[4,3,2‐de][1,6]naphthyridine‐4‐carbonitrile derivatives

The catalytic performance of the superparamagnetic nanocatalyst Fe₃O₄@SiO₂@Sulfated boric acid as a green, recyclable, and acidic solid catalyst in the synthesis of chromeno[4,3,2‐de][1,6]naphthyridine derivatives has been studied. Chromeno[4,3,2‐de][1,6]naphthyridine derivatives via a pseudo four‐component reaction from aromatic aldehydes (1 mmol), malononitrile (2 mmol), and 2′‐hydroxyacetophenone in the presence of Fe₃O₄@SiO₂@Sulfated boric acid (0.004 g) as a nanocatalyst in 3 mL of water as a green solvent at 80°C has been synthesized. The advantages of this method are higher product yields in shorter reaction times, easy recyclability and reusability of the catalyst, and easy work‐up procedures. The nanocatalyst was reused at least six times. The nanocatalyst retained its stability in the reaction, and after reusability, it was separated easily from the reaction by an external magnet.     

Acetic Anhydride as an Oxygen Donor in the Non-Hydrolytic Sol–Gel Synthesis of Mesoporous TiO2 with High Electrochemical Lithium Storage Performances

An original, halide-free non-hydrolytic sol–gel route to mesoporous anatase TiO₂ with hierarchical porosity and high specific surface area is reported. This route is based on the reaction at 200 °C of titanium(IV) isopropoxide with acetic anhydride, in the absence of a catalyst or solvent. NMR spectroscopic studies indicate that this method provides an efficient, truly non-hydrolytic and aprotic route to TiO₂. Formation of the oxide involves successive acetoxylation and condensation reactions, both with ester elimination. The resulting TiO₂ materials were nanocrystalline, even before calcination. Small (about 10 nm) anatase nanocrystals spontaneously aggregated to form mesoporous micron-sized particles with high specific surface area (240 m² g⁻¹ before calcination). Evaluation of the lithium storage performances shows a high reversible specific capacity, particularly for the non-calcined sample with the highest specific surface area favouring pseudo-capacitive storage: 253 mAh g⁻¹ at 0.1 C and 218 mAh g⁻¹ at 1 C (C=336 mA g⁻¹). This sample also shows good cyclability (92 % retention after 200 cycles at 336 mA g⁻¹) with a high coulombic efficiency (99.8 %). Synthesis in the presence of a solvent (toluene or squalane) offers the possibility to tune the morphology and texture of the TiO₂ nanomaterials.     

Kinetics and mechanisms of the oxidation of sulfur dioxide over titanium dioxide and nickel oxide

The reactions between SO₂ and O₂ were carried out in the presence of TiO₂ and NiO under various partial pressures of SO₂ and O₂ at temperatures from 240 to 330°C. TiO₂ and NiO were pretreated by applying an annealing effect from which the catalysts would have the different activity. The rates are the highest for TiO₂ pretreated at high temperature in the region of 400 to 600deg;C in vacuum, 1.21 × 10^?4 mmHg. In contrast, the rates are the lowest for NiO pretreated at high temperaturefrom 350 to 550°C. The data have been correlated with 1.4 and first-order kinetics for TiO₂ and NiO, respectively. A reaction mechanism to explain the data was suggested. The quantities of anionic vacancies in TiO₂ surfaces and of positive holes in NiO appeared to be paramount in determining the type of kinetics.     

Electrochemical Performance of PEO10LiX-Li2TiO3 Composite Polymer Electrolytes

Introduction Recently, polymer electrolytes have attracted much attention for their potential use in replacing flammable organic solvent electrolytes currently used in lith-ium-ion batteries, thus improving the safety of re-chargeable lithium batteries. Moreover, the batteries with PE can be made in any shape, which make fully use of the space of electronic devices. PEO is a linear polymer with helix structure, and its structure makes it have much higher dissolution ability for salt even tho…     

Fe3O4@ZrO2/SO42‐: A recyclable magnetic heterogeneous nanocatalyst for synthesis of β‐amino carbonyl derivatives and synthesis of benzylamino coumarin derivatives through Mannich reaction

In the present work, we developed an effective protocol for the synthesis of β‐amino carbonyl compounds and synthesis of benzylamino coumarin derivatives through Mannich type reaction in high yields. Fe₃O₄@ZrO₂/SO₄^2‐ was employed as an effective heterogeneous nanocatalyst for the Mannich reaction. This research consists of two sections. In first section, β‐amino carbonyl derivatives were synthesized under solvent‐free condition. In the other section, benzylamino coumarin compounds were synthesized at room temperature. The present approach offers several advantages such as short reaction times, low cost, easy work‐up, mild reaction conditions, high yields and ease of recovery and reusability of the catalyst without significant loss of activity.     

Sulfated titania catalyzed water mediated efficient synthesis of dicoumarols—a green approach

An efficient, mild, and environmental friendly method has been developed for the synthesis of dicoumarols in water over Lewis and Bronsted acid catalyst sulfated titania (TiO₂/SO₄²⁻). The method involves the condensation of various aromatic and aliphatic aldehydes with 4-hydroxycoumarin. It affords the corresponding product in high yield with short reaction times employing a very low loading of catalyst. The catalyst was reused several times without significant change in activity.