H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> anchored on graphene-grafted silica-coated MnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> as magnetic catalyst for Mannich reaction

In this study, a three-component nanocomposite consisted of graphene, manganese ferrite and phosphotungstic acid (PTA) has been prepared. This composite, which is designated as Graphene/MnFe₂O₄@PTA, was synthesized through anchoring of PTA–imidazolium ionic liquid on magnetic graphene sheets. The structural and magnetic properties of the fabricated nanocomposite were studied by employing FT-IR, SEM, EDX, TEM, ICP, VSM, P-XRD and BET techniques. The synthesized magnetic nanocomposite was examined as an efficient and recyclable acidic catalyst for Mannich reaction under solvent-free conditions. The products of this reaction, which are an important class of potentially bioactive compounds, were obtained with good to excellent yields, and the catalyst could be readily recycled without any significant loss of its activity.     

No-Glycerol rapid heterogeneous biodiesel production on K<Subscript>2</Subscript>CO<Subscript>3</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst by coupling process

Biodiesel containing almost no glycerol has been produced by coupling reaction carried out over K₂CO₃ supported by calcium oxide as solid base catalysts. The solid base catalysts synthesized by wet impregnation exhibit an exceedingly high activity in biodiesel production. It was found that the reaction time required for the highest yield of biodiesel, 99.2%, can be shortened to 30 min over K₂CO₃/Al₂O₃ under the optimum reaction conditions: 8: 1: 1 molar ratio of methanol/DMC/oil, 30 wt % K₂CO₃/Al₂O₃ catalyst, and 65°C reaction temperature. Solid basic catalysts examined in the study were characterized by BET surface area, XRD, CO₂-TPD, and SEM techniques. The strong interaction between K₂CO₃ and the support yields a new basic active site, which can be probably responsible for the high activity of K₂CO₃/Al₂O₃.     

Chemoselective synthesis of 1,1-diacetates from aldehydes in the presence of Al(HSO<Subscript>4</Subscript>)<Subscript>3</Subscript> under mild solvent-free conditions

A novel efficient procedure has been developed for the preparation of acylals in high yields by reaction of the corresponding aldehydes with acetic anhydride in the presence of Al(HSO₄)₃ as catalyst under mild (room temperature) solvent-free conditions. Published in Russian in Zhurnal Organicheskoi Khimii, 2007, Vol. 43, No. 6. pp. 855–857. The text was submitted by the authors in English.     

Nitration of Aromatic Compounds Catalyzed by Divanadium-Substituted Molybdophosphoric Acid,H<Subscript>5</Subscript>[PMo<Subscript>10</Subscript>V<Subscript>2</Subscript>O<Subscript>40</Subscript>]

Summary. The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molybdophosphoric acid, H₅PMo₁₀V₂O₄₀, as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid the ortho- and para-nitro compounds were obtained in good to excellent yields under mild reaction conditions.     

A concise synthesis of furo[3,2-c]coumarins catalyzed by nanocrystalline ZnZr<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>6</Subscript> ceramics under microwave irradiation

A simple and concise method catalyzed by nanocrystalline ZnZr₄(PO₄)₆ ceramics has been reported for the synthesis of a series of trans-2-benzoyl-3-(aryl)-2H-furo[3,2-c]chromen-4(3H)-ones using a multicomponent reaction of 2,4′-dibromoacetophenone, benzaldehydes and 4-hydroxycoumarin under microwave irradiation. This method provides several advantages including easy workup, excellent yields, short reaction times, using of microwave as clean method, recoverability of the catalyst and little catalyst loading.     

Na<Subscript>2</Subscript>EDTA: an efficient,green and reusable catalyst for the synthesis of biologically important spirooxindoles,spiroacenaphthylenes and spiro-2-amino-4<Emphasis Type="Italic">H</Emphasis>-pyrans under solvent-free conditions

For the first time, the organic salt Na₂EDTA was used as a catalyst for an effective and facile preparation of spiro-4H-pyrans via single-pot three-component condensation of isatin/acenaphthoquinone/ninhydrin, malononitrile, and CH-acids through Knoevenagel–Michael–annulation sequence. This new protocol employing Na₂EDTA, which is a green, recyclable, and inexpensive catalyst, offers advantages such as solvent-free and highly efficient reaction conditions, short reaction times (10–15 min), easy work-up and high yields which make it more economic than other environmentally synthetic methods.     

Alum (KAl(SO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 12H<Subscript>2</Subscript>O) Catalyzed One-Pot Synthesis of Coumarins under Solvent-Free Conditions

Summary. Alum (KAl(SO₄)₂ · 12H₂O) is used as an efficient catalyst in the Pechmann condensation of phenol derivatives with β-keto esters leading to the formation of coumarins in excellent yields under solvent-free conditions. This methodology offers significant improvements for the synthesis of coumarins with regard to the yield of products, simplicity in operation, and green aspects by avoiding toxic catalysts and solvents.     

Oxidation of benzyl alcohol by K<Subscript>2</Subscript>FeO<Subscript>4</Subscript> to benzaldehyde over zeolites

A novel and green procedure for benzaldehyde synthesis by potassium ferrate oxidation of benzyl alcohol employing zeolite catalysts was studied. The prepared oxidant was characterized by SEM and XRD. The catalytic activity of various solid catalysts was studied using benzyl alcohol as a model compound. USY was found to be a very efficient catalyst for this particular oxidation process. Benzaldehyde yields up to 96.0% could be obtained at the following optimal conditions: 0.2 mL of benzyl alcohol, 4 mmol of K₂FeO₄, 0.5 g of USY zeolite; 20 mL of cyclohexene, 0.3 mL of acetic acid (36 wt %), 30°C temperature, 4 h reaction time.     

NH<Subscript>3</Subscript>(CH<Subscript>2</Subscript>)<Subscript>5</Subscript>NH<Subscript>3</Subscript>BiCl<Subscript>5</Subscript>: an efficient and recyclable catalyst for the synthesis of benzoxazole,benzimidazole and benzothiazole heterocycles

In this work, the condensation of aromatic aldehydes with different two-substituted aniline catalyzed by NH₃(CH₂)₅NH₃BiCl₅ as heterogeneous and recyclable catalyst was reported. It was demonstrated that NH₃(CH₂)₅NH₃BiCl₅ can act as an efficient and active catalyst and is reusable for six runs without a significant loss of their catalytic activity. Simple preparation of the catalyst, high catalytic activity and good reusability are noteworthy advantages of this catalytic system in the synthesis of benzoxazole, benzimidazole and benzothiazole heterocycles at room temperature under solvent-free conditions.     

Porous CeO<Subscript>2</Subscript> nanorod-catalyzed synthesis of poly-substituted imino-pyrrolidine-thiones

Porous CeO₂ nanorod has been used as efficient and recyclable heterogeneous catalyst for the synthesis of highly functionalized imino-pyrrolidine-thiones via the reaction of aromatic aldehyde (especially one bearing an electron-donating group), malononitrile, isocyanide and unactivated weakly acidic heterocyclic thiophenol. The high catalytic efficiency of porous CeO₂ nanorod in this reaction was discussed preliminarily based on their morphology and structure.     

Facile synthesis of Fe@Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> core-shell nanowires as O<Subscript>2</Subscript> electrode for high-energy Li-O<Subscript>2</Subscript> batteries

Fe@Fe₂O₃ core-shell nanowires were synthesized via the reduction of Fe³⁺ ions by sodium borohydride in an aqueous solution with a subsequent heat treatment to form Fe₂O₃ shell and employed as a cathode catalyst for non aqueous Li-air batteries. The synthesized core-shell nanowires with an average diameter of 50–100 nm manifest superior catalytic activity for oxygen evolution reaction (OER) in Li-O₂ batteries with the charge voltage plateau reduced to ～3.8 V. An outstanding performance of cycling stability was also achieved with a cutoff specific capacity of 1000 milliampere hour per gram over 40 cycles at a current density of 100 mA g^?1. The excellent electrochemical properties of Fe@Fe₂O₃ as an O₂ electrode are ascribed to the high surface area of the nanowires’ structure and high electron conductivity. This study indicates that the resulting iron-containing nanostructures are promising catalyst in Li-O₂ batteries.     

H<Subscript>3</Subscript>PMo<Subscript>12</Subscript>O<Subscript>40</Subscript> immobilized chitosan/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> as a novel efficient,green and recyclable nanocatalyst in the synthesis of pyrano-pyrazole derivatives

A novel nanomagnetic composite heteropolyacid immobilized chitosan/Fe₃O₄ was prepared via a facile one-pot synthetic approach. This magnetically recoverable nanocatalyst, H₃PMo₁₂O₄₀/chitosan/Fe₃O₄ (PMo/chit/Fe₃O₄), was fully characterized by XRD, FTIR, SEM and EDX analysis methods. A rapid, efficient and the chemoselective synthesis of different pyrano-pyrazole derivatives was achieved in excellent yields via a one-pot four-component reaction in the presence of catalytic amount of PMo/Chit/Fe₃O₄.     

Hydrolysis of cellulose by the heteropoly acid H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript>

The potential of heteropoly acid H₃PW₁₂O₄₀ to catalyze the hydrolysis of cellulose to glucose under hydrothermal conditions was explored. This technology could contribute to sustainable societies in the future by using cellulose biomass. A study to optimize the reaction conditions, such as the amount of catalyst, reaction time, temperature, and the amount of cellulose used, was performed. A remarkably high yield of glucose (50.5%) and selectivity higher than 90% at 453 K for 2 h with a mass ratio of cellulose to H₃PW₁₂O₄₀ of 0.42 were achieved. This was attributed to the high hydrothermal stability and the excellent catalytic properties, such as the strong Brønsted acid sites. This homogeneous catalyst can be recycled for reuse by extraction with diethyl ether. The results illustrate that H₃PW₁₂O₄₀ is an environmentally benign acid catalyst for the hydrolysis of cellulose.     

Nano-TiO<Subscript>2</Subscript>: An eco-friendly and re-usable catalyst for the synthesis of 14-Aryl or alkyl-14<Emphasis Type="Italic">H</Emphasis>-dibenzo[<Emphasis Type="Italic">a,j</Emphasis>]xanthenes

Synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes using nano-TiO₂ as eco-friendly and efficient catalyst is reported. Short reaction times, high yields, a clean process, simple methodology, easy work-up and green conditions are advantages of this protocol.     

Development of RuO<Subscript>2</Subscript>/Rutile-TiO<Subscript>2</Subscript> Catalyst for Industrial HCl Oxidation Process

Sumitomo Chemical has developed a low energy consuming and green process for the catalytic oxidation of HCl to Cl₂, especially when compared with the electrolysis process. The RuO₂/rutile-TiO₂ catalyst has high catalytic activity and thermal stability due to ultra-fine RuO₂ crystallites that cover the surface of the TiO₂ primary particles with strong interaction. In addition, the silica modified RuO₂/rutile-TiO₂ catalyst shows higher thermal stability by preventing the RuO₂ sintering due to using dispersed SiO₂ particles. With these catalysts, high reaction rates required for industrial applications are achieved, even at low temperatures.     

Synthesis of N-2-aryl-substituted 1,2,3-triazoles mediated by magnetic and recoverable CuFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles

An efficient and economic system for the synthesis of N-2-aryl-substituted 1,2,3-triazoles in the presence of CuFe₂O₄ was developed. The corresponding products can be obtained in good to excellent yields. It is interesting to note that the catalyst could be reused for five consecutive trials without significant decreases in its activity.     

An active phase transformation on surface of Ni-Au/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst during partial oxidation of methane to synthesis gas

It was studied the influence of gold addition on physico-chemical properties and catalytic activity of bimetallic Ni-Au/Al₂O₃ catalyst in partial oxidation of methane (POM). The reduction behavior in hydrogen, XRD crystal structure, XPS spectra and POM catalytic activity were investigated. The reduction of Ni-Au catalyst is a prerequisite condition to catalyze POM reaction. The formation of Ni-Au alloy during high temperature reduction in hydrogen and also in the conditions of POM reaction was experimentally proved. The addition of gold to Ni/Al₂O₃ system improves catalyst stability and activity in POM reaction.     

Initiation behaviour in hydrogenation of pyrolysis gasoline over presulphided Ni-Mo-Zn/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

A presulphided treatment was applied to the oxidic Ni-Mo-Zn/Al₂O₃ catalyst (nickel catalyst) in order to avoid thermal run-away during initiation of the hydrogenation of pyrolysis gasoline. The physico-chemical properties of the prepared oxidic nickel catalyst, the reduced and passivated (RP) nickel catalyst and the sulphided (RPS) nickel catalyst were characterised using N₂ adsorption-desorption, X-ray diffraction, temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The TPR results showed that the reducibility of the RP Ni-Mo-Zn/Al₂O₃ catalyst was improved over the oxidic nickel catalyst. The XPS spectra confirmed the binding energy of the RPS nickel catalyst to be higher than that of the oxidic nickel catalyst. The catalytic performance was evaluated on a fixed-bed reactor (reaction temperature between 30 °C and 70°C, at 2.8 MPa of total pressure and weight hourly space velocity of 2.0 h^?1, the volume of H₂/pyrogasoline = 200: 1). The rising temperature of the RPS nickel catalyst was almost 20°C lower than that of the oxidic nickel catalyst during the initial stage of the hydrogenation reaction. The results indicated that the RPS nickel catalyst exhibited better stability than the oxidic nickel catalyst during the start-up period, thereby providing a better selectivity in long-term operation.     

Performance and characterisation of CeO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript>-WO<Subscript>3</Subscript> catalysts for selective catalytic reduction of NO with NH<Subscript>3</Subscript>

Ce-Ti-W-O _x catalysts were prepared and applied to the NH₃-selective catalytic reduction (SCR) reaction. The experimental results showed that the Ce-Ti-W-O _x catalyst prepared by the hydrothermal method exhibited higher NO conversion than those synthesised via the sol-gel and impregnating methods, while the optimal content of WO₃ and molar ratio of Ce/Ti were 20 mass % and 4: 6, respectively. Under these conditions, the catalyst exhibited the highest level of catalytic activity (the NO conversion reached values higher than 90 %) across a wide temperature range of 225–450°C, with a range of gas hourly space velocity (GHSV) of 40000–140000 h^?1. The catalyst also exhibited good resistance to H₂O and SO₂. The influences of morphology, phase structure, and surface properties on the catalytic performance were investigated by N₂ adsorption-desorption measurement, XRD, XPS, H₂-TPR, and SEM. It was found that the high efficiency of NO removal was due to the large BET surface area, the amorphous surface species, the change to element valence states, and the strong interaction between Ce, Ti, and W.     

Hydrogen generation from H<Subscript>2</Subscript>O/H<Subscript>2</Subscript>O<Subscript>2</Subscript>/MnWO<Subscript>4</Subscript> system

Hydrogen gas as a clear energy resource was found to be largely bubbled from a H₂O/H₂O₂/MnWO₄ system. MnWO₄ powder was fabricated by an aqueous reaction method. The powder was characterized with X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectrometry (XPS). The efficiency of the hydrogen generation increases with an increase in initial pH in the appropriate range, H₂O₂ proportion, MnWO₄ proportion, and intensity of light resource. Calcining at 400 °C for 1 h can make the MnWO₄ powder synthesized by an aqueous reaction more effective for H₂ generation and more stable in higher initial pH. The MnWO₄ catalyst shows a long-term stability for photocatalytic H₂ generation. A mechanism was suggested for the hydrogen generation from the H₂O/H₂O₂/MnWO₄ system together with XPS analysis.