One-pot synthesis of 1,3-thiazolidin-4-one using ammonium persulfate as catalyst

Ammonium persulfate can be used as a homogeneous catalyst for three-component one-pot synthesis of some 1,3-thiazolidin-4-one derivatives from aldehydes, amines and mercaptoacetic acid under solvent-free conditions with good yields. The characterization of products was generally achieved by IR and NMR techniques. Inexpensive catalyst, high yields, simple product isolation and high atom economy are the noteworthy aspects of the protocols.     

Amino Functionalized Nano Fe3O4@SiO2 as a Magnetically Green Catalyst for the One-Pot Synthesis of Spirooxindoles Under Mild Conditions

(3-Aminopropyl)-triethoxysilane attached to Fe₃O₄@SiO₂ nanoparticles has been characterized by powder X-ray diffraction, vibrating sample magnetometer, scanning electronic microscope, transmission electron microscope, energy dispersive X-ray, thermal gravimetric analysis, and Fourier transform infrared spectroscopy. The prepared nanoparticles employed as a heterogeneous catalyst in the synthesis of spirooxindoles derivatives in one-pot four-component reactions of isatin, methyl cyanoacetate or malononitrile, hydrazine hydrate, and ethyl acetoacetate. Amino-functionalized magnetic nanoparticles showed high catalytic activity in mild reaction conditions and excellent yields of products in short reaction times. Also, this nanocatalyst can be easily recovered by a magnet and reused for subsequent reactions for at least 5 times without noticeable loss in catalytic activity.     

Fe3O4@SiO2-SnCl4: An Efficient Catalyst for the Synthesis of Xanthene Derivatives under Ultrasonic Irradiation

Grafting of SnCl₄ on the Fe₃O₄@SiO₂ nanoparticles afforded Fe₃O₄@SiO₂-SnCl₄ as a novel inorganic heterogenous catalyst, which was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM), Field Emission Scanning Electron Microscopy (FE-SEM), and transmission electron microscopy (TEM). In this research, we report a convenient and efficient direct protocol for the preparation of xanthene derivatives via condensation of β-naphthol, dimedone, or mixture of β-naphthol and dimedone with various aromatic aldehydes in the presence of the catalytic amount of Fe₃O₄@SiO₂-SnCl₄ under ultrasonic irradiation. This procedure has a lot of advantages such as: very easy reaction conditions, absence of any tedious workup, or purification, and much milder method. The corresponding products have been obtained in excellent yields, high purity, and short reaction times.     

A facile and effective procedure for the synthesis of 4-thiazolidinone derivatives using Y(OTf)3 as catalyst

A one-pot three-component reaction for the synthesis of 4-thiazolidinone derivatives has been established by reacting readily available and inexpensive starting materials of amines, aldehydes and thioglycolic acid using Y(OTf)₃ (5?mol%) as catalyst in tetrahydrofuran. This method is very efficient due to low catalyst loading and mild reaction conditions and provides an efficient and promising synthetic strategy for the construction of the thiazolidinone skeleton.     

Pd nanoparticles supported on carbon-modified rutile TiO2 as a highly efficient catalyst for formic acid electrooxidation

In this article, Pd nanoparticles supported on carbon-modified rutile TiO₂ (CMRT) as a highly efficient catalyst for formic acid electrooxidation were investigated. Pd/CMRT catalyst was synthesized by using liquid phase reduction method in which Pd nanoparticles was loaded on the surface of CMRT obtained through a chemical vapor deposition (CVD) process. Pd/CMRT shows three times the catalytic activity of Pd/C, as well as better catalytic stability towards formic acid electrooxidation. The enhanced catalytic property of Pd/CMRT mainly arises from the improved electronic conductivity of carbon-modified rutile TiO₂, the dilated lattice constant of Pd nanoparticles, an increasing of surface steps and kinks in the microstructure of Pd nanoparticles and slightly better tolerance to the adsorption of poisonous intermediates.     

Green synthesis of thiiranes from epoxides catalyzed by magnetically separable CuFe2O4/Mg(OH)2 nanocomposite in water under benign conditions

The magnetically separable CuFe₂O₄/Mg(OH)₂ nanocomposite was prepared and characterized by FT-IR, XRD, SEM, EDS, and VSM techniques. The synthesized nanoparticles were used as a new and efficient heterogeneous catalyst for the conversion of various epoxides to the corresponding thiiranes with thiourea in water solvent at room temperature. The reactions were completed within 1–3.7?h to give thiiranes in 70–99% yields. The applied CuFe₂O₄/Mg(OH)₂ nanocomposite was separated easily using an external magnet and reused for several times without any considerable loss of activity.     

Functionalized magnetic core-shell Fe3O4@SiO2 nanoparticles as selectivity-enhanced chemosensor for Hg(II)

A colorimetric and ‘‘turn-on” fluorescent chemosensor Rho-Fe₃O₄@SiO₂ for Hg²⁺ in which N-(rhodamine-6G)lactam-ethylenediamine (Rho-en) is conjugated with the magnetic core-shell Fe₃O₄@SiO₂ NPs has been strategically designed and synthesized. The final product was characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and UV-visible absorption and fluorescence emission. Fluorescence and UV-visible spectra results showed that the resultant multifunctional nanoparticles Rho-Fe₃O₄@SiO₂ exhibited selective ‘turn-on’ type fluorescent enhancements and distinct color changes with Hg²⁺. The selectivity of the Rho-Fe₃O₄@SiO₂ for Hg(II) ion is better than that of the Rho-en in the same conditions. In addition, the presence of magnetic Fe₃O₄ nanoparticles in the sensor Rho-Fe₃O₄@SiO₂ NPs would also facilitate the magnetic separation of the Hg(II)-Rho-Fe₃O₄@SiO₂ from the solution.     

A green method for solvent-free conversion of epoxides to thiiranes using NH4SCN in the presence of NiFe2O4 and MgFe2O4 magnetic nanocatalysts

Nickel and magnesium ferrite magnetic nanoparticles were fabricated and applied as efficient and reusable catalysts in the solvent-free conversion of various epoxides to the corresponding thiiranes with ammonium thiocyanate under oil bath (60°C) conditions. NiFe₂O₄ and MgFe₂O₄ nanoparticles can catalyze the reactions at short times in high to excellent yields. The catalysts can also be recovered easily using an external magnetic field and be reused four times without any significant loss of activity.     

Activity and stability of Cu/ZnO/Al2O3 catalyst promoted with B2O3 for methanol synthesis

The addition of B₂O₃ to a Cu/ZnO/Al₂O₃ catalyst increased the activity of the catalyst for methanol synthesis after an induction period during the reaction. The stability of the B₂O₃-containing Cu/ZnO/Al₂O₃ catalyst was greatly improved by the addition of a small amount of colloidal silica to the catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Highly Flexible Green Synthesis of 3,4,5-Substituted Furan-2(5H)-ones Using Nano-CdZr4(PO4)6 as Catalyst under Microwave Irradiation

A concise and efficient method for the synthesis of 3,4,5-substituted furan-2 (5H)-ones was achieved through a three-component reaction of amines, dialkyl acetylene dicarboxylate, and aromatic aldehydes using nano-CdZr₄(PO₄)₆ as catalyst under microwave irradiation. This method has several advantages such as, high efficiency, short reaction times, simple workup, and recyclability of the catalyst up to seven runs without considerable loss of activity.     

Waterborne polyurethane-silanized CoFe2O4-acrylate magnetic pressure-sensitive adhesive

A novel waterborne polyurethane-silanized CoFe₂O-acrylate magnetic pressure-sensitive adhesive was prepared. With the increase of PU content, gel content, swelling capability, and SAFT increased, and fracture energy increased first, then decreased. The T-peeling strength increased from 8.93 to 19.07 N · m^?1, tack force increased from No.3 to No.10, while shear resistance increased from 35 to 72 h, and then they decreased. Two empirical models: W_A = 90.46 + 125.04[PU]-319.96[PU]² and T = 9.09 + 96.07[PU]-235.11[PU]², were obtained. With the increase of CoFe₂O₄ content, the saturation magnetization increased from 5.5 to 14.2 emu · g^?1, and remanence increased from 1.7 to 3.7 emu · g^?1, while coercivity decreased from 875 to 763 Oe.     

A Novel Catalyst Pt/CoAl2O4/Al2O3 for Combination CO2 Reforming and Partial Oxidation of CH4

Pt/CoAl₂O₄/Al₂O₃, Pt/CoO_x/Al₂O₃, CoAl₂O₄/Al₂O₃ and CoO_x/Al₂O₃ catalysts were studied for combination CO₂ reforming and partial oxidation of CH₄. The results indicate that Pt/CoAl₂O₄/Al₂O₃ is the most effective, and XRD results indicate that Pt species are well dispersed over the Pt/CoAl₂O₄/Al₂O₃. High dispersion is related to the presence of CoAl₂O₄, formed during calcining at high temperature before Pt addition. In the presence of Pt, CoAl₂O₄ in the catalyst could be reduced partially at 973 K. Based on these results, it appears that zerovalent platinum with high dispersion and zerovalent cobalt resulting from CoAl₂O₄ reduction are responsible for high activity in the Pt/CoAl₂O₄/Al₂O₃ catalyst.     

Magnetoelectricity in CoFe2O4 nanocrystal-P(VDF-HFP) thin films

Transition metal ferrites such as CoFe₂O₄, possessing a large magnetostriction coefficient and high Curie temperature (T_c > 600 K), are excellent candidates for creating magnetic order at the nanoscale and provide a pathway to the fabrication of uniform particle-matrix films with optimized potential for magnetoelectric coupling. Here, a series of 0–3 type nanocomposite thin films composed of ferrimagnetic cobalt ferrite nanocrystals (8 to 18 nm) and a ferroelectric/piezoelectric polymer poly(vinylidene fluoride-co-hexafluoropropene), P(VDF-HFP), were prepared by multiple spin coating and cast coating over a thickness range of 200 nm to 1.6 μm. We describe the synthesis and structural characterization of the nanocrystals and composite films by XRD, TEM, HRTEM, STEM, and SEM, as well as dielectric and magnetic properties, in order to identify evidence of cooperative interactions between the two phases. The CoFe₂O₄ polymer nanocomposite thin films exhibit composition-dependent effective permittivity, loss tangent, and specific saturation magnetization (M_s). An enhancement of the effective permittivity and saturation magnetization of the CoFe₂O₄-P(VDF-HFP) films was observed and directly compared with CoFe₂O₄-polyvinylpyrrolidone, a non-ferroelectric polymer-based nanocomposite prepared by the same method. The comparison provided evidence for the observation of a magnetoelectric effect in the case of CoFe₂O₄-P(VDF-HFP), attributed to a magnetostrictive/piezoelectric interaction. An enhancement of M_s up to +20.7% was observed at room temperature in the case of the 10 wt.% CoFe₂O₄-P(VDF-HFP) sample.     

ZnO/Cr2O3 catalyst for reverse-water-gas-shift reaction of CAMERE process

The stability and the activity of Fe₂O₃/Cr₂O₃ and ZnO/Cr₂O₃ catalysts were examined for a reverse-watergas-shift reaction (RWReaction). The initial activities of those catalysts were quite high so that the conversion reached close to equilibrium. The activity of Fe₂O₃/Cr₂O₃ catalyst decreased from 33.5 to 29.8% during the RWReaction for 75 h at 873 K with GHSV (ml/gcat · h) of 100,000. Moreover, the coke formation on the Fe₂O₃/Cr₂O₃ catalyst caused clogging in the RWReactor of the CAMERE process. On the other hand, the ZnO/Cr₂O₃ catalyst showed no coke formation and no deactivation for the RWReaction at 873 K with GHSV (ml/gcat · h) of 150,000. The ZnO/Cr₂O₃ was a good catalyst for the RWReaction of the CAMERE process.     

Mechanochemical synthesis of kaolin-KH2PO4 and kaolin-NH4H2PO4 complexes for application as slow release fertilizer

A milling process to reduce kaolin to amorphous phase in the presence of KH₂PO₄ or NH₄H₂PO₄ and allow mechanochemical (MC) reaction for incorporation of KH₂PO₄ and NH₄H₂PO₄ into the kaolin structure was investigated in this work. Mixtures of kaolin and KH₂PO₄ and NH₄H₂PO₄ in separate systems were prepared by milling in a planetary ball mill. Tests with kaolin contents ranging from 25 to 75 wt.% and mill rotational speeds from 200 to 700 rpm were performed to evaluate incorporation of KH₂PO₄ and NH₄H₂PO₄ and release of K⁺, NH₄⁺ and PO₄³⁻ ions into solution. Analyses by XRD, DTA and ion chromatography indicated that the MC process was successfully applied to incorporate both KH₂PO₄ and NH₄H₂PO₄ into the amorphous kaolin structure. Release of K⁺ and PO₄³⁻ ions from the system (kaolin-KH₂PO₄) when dispersed in water for 24 h reached only up to 10%. Under similar conditions for the system (kaolin-NH₄H₂PO₄), release of NH₄⁺ and PO₄³⁻ ions reached between 25 and 40%. These results indicated that the MC process can be developed to allow amorphous kaolin to act as a carrier of K⁺, NH₄⁺ and PO₄³⁻ nutrients to be released slowly for use as fertilizer.     

A highly efficient Cu/ZnO/Al2O3 catalyst via gel-coprecipitation of oxalate precursors for low-temperature steam reforming of methanol

The impact of preparation methods on the structure and catalytic behavior of Cu/ZnO/Al₂O₃ catalysts for H₂ production from steam reforming of methanol (SRM) has been reported. The results show that the nanostructured Cu/ZnO/Al₂O₃ catalyst obtained by a novel gel-coprecipitation of oxalate precursors has a high specific surface area and high component dispersion, exhibiting much higher activity in the SRM reaction as compared to the catalysts prepared by conventional coprecipitation techniques. It is suggested that the superior catalytic performance of the oxalate gel-coprecipitation-derived Cu/ZnO/Al₂O₃ catalyst could be attributed to the generation of “catalytically active” copper material with a much higher metallic copper specific surface as well as a stronger Cu–Zn interaction due to an easier incorporation of zinc species into CuC₂O₄ · x H₂O precursors as a consequence of isomorphous substitution between copper and zinc in the oxalate gel-precursors.     

Spinel CuFe2O4: a precursor for copper catalyst with high thermal stability and activity

Spinel CuFe₂O₄ has been studied as a precursor for copper catalyst. The spinel CuFe₂O₄ was effectively formed on the SiO₂ by calcination in air at 800 °C with the atomic ratio of Fe/Cu = 2. The spinel CuFe₂O₄ on the SiO₂ was reduced to fine dispersion of Cu and Fe₃O₄ particles by the H₂ reduction at 240 °C. After H₂ reduction at 600 °C, sintering of Cu particles over the CuFe₂O₄/SiO₂ (Fe/Cu = 2) was inhibited significantly, while fatal sintering of Cu particles over the Cu/SiO₂ (Fe/Cu = 0) occurred. The CuFe₂O₄/SiO₂ catalyst exhibited much higher activity and thermal stability for steam reforming of methanol (SRM), compared with the Cu/SiO₂ catalyst. The spinel CuFe₂O₄ on the SiO₂ can be regenerated after an intentional sintering treatment by calcination in air at 800 °C where the activity is also restored completely. Based on these findings, we propose that spinel CuFe₂O₄ is an effective precursor for a high performance copper catalyst in which the immiscible interaction between Cu and Fe (or Fe oxide) plays an important role in the stabilization of Cu particles.     

FeVO4 as a highly active heterogeneous Fenton-like catalyst towards the degradation of Orange II

The iron vanadate, FeVO₄, was prepared and characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). It was found that FeVO₄ could effectively catalyze H₂O₂ to generate active hydroxyl radical OH, which was confirmed with electron spin resonance (ESR) spin-trapping technique. Therefore, it was employed as a heterogeneous Fenton-like catalyst in the present contribution, and its catalytic activity was mainly evaluated in terms of the degradation efficiency of Orange II. Compared with the conventional heterogeneous Fenton-like catalysts, α-Fe₂O₃, Fe₃O₄ and γ-FeOOH, FeVO₄ possessed a much higher catalytic activity. The high catalytic activity possibly involved in a special two-way Fenton-like mechanism, that is, the activation of H₂O₂ by both Fe(III) and V(V) in FeVO₄. Moreover, FeVO₄ possessed a wide applicable pH range and its catalytic activity was slightly affected by the solution pH values in the range of 3–8.     

Nb2O5 as efficient and recyclable photocatalyst for indigo carmine degradation

Heterogeneous photocatalysis is a significant green technology for application in water purification. The application of Nb₂O₅ catalyst for the photodegradation of contaminants is few reported in the literature. Thus, the Nb₂O₅ catalyst was characterized by SEM, FTIR, surface area and charge surface density. This catalyst was applied to degrade indigo carmine dye, which was compared with degradation catalyzed by TiO₂ and ZnO. Almost 100% of dye degradation occurred at 20, 45 and 90 min for TiO₂, ZnO and Nb₂O₅, respectively. The effect of Nb₂O₅ catalyst concentration, pH and ionic strength (μ) was investigated. The Nb₂O₅ activity increased at 0.7 g/L and for higher catalyst concentrations the degradation was kept constant. Degradation of indigo carmine dye catalyzed by Nb₂O₅ was improved at pH < 4.0 and μ = 0.05 mol/L. TiO₂, ZnO and Nb₂O₅ were recovered and re-applied in other nine reaction cycles. While TiO₂ and ZnO have an abrupt loss of their catalytic activity, Nb₂O₅ maintained 85% of catalytic activity after 10 reaction cycles.     

Catalytic Activities of Al2O3-promoted NiSO4/TiO2 for Acid Catalysis

A series of catalysts, NiSO₄/Al₂O₃–TiO₂, for acid catalysis was prepared by the impregnation method, where support, Al₂O₃–TiO₂ was prepared by the coprecipitation method using a mixed aqueous solution of titanium tetrachloride and aluminum nitrate solution followed by adding an aqueous ammonia solution. The addition of nickel sulfate (or Al₂O₃) to TiO₂ shifted the phase transition of TiO₂ from amorphous to anatase to higher temperature because of the interaction between nickel sulfate (or Al₂O₃) and TiO₂. 15-NiSO₄/5-Al₂O₃–TiO₂ containing 15 wt% NiSO₄ and 5 mol% Al₂O₃, and calcined at 400°C exhibited maximum catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation. The catalytic activities for both reactions were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The charge transfer from Ti atoms to the neighboring Al atoms strengthens the Al–O bond between Al and the surface sulfate species. The addition of Al₂O₃ up to 5 mol% enhanced the acidity, thermal property, and catalytic activities of NiSO₄/Al₂O₃–TiO₂ gradually due to the interaction between Al₂O₃ and TiO₂ and consequent formation of Al–O–Ti bond.