Catalytic behaviors of Co-Mn/TiO2 catalysts for Fischer-Tropsch synthesis

The 15%(Co-Mn)/TiO₂,(Co/Mn=1/6) catalyst was prepared using fusion procedure and studied for the conversion of synthesis gas to C_2~4 olefins. The effects of calcination conditions and operation conditions such as the H₂/CO molar feed ratio at different temperatures, gas hourly space velocity (GHSV) and total reaction pressure on the catalytic performance of catalyst were investigated. The stability of the catalyst during 150 h at optimal operation conditions (t=250 ℃ H₂/CO=2/1, GHSV=1 500 h^-1 and p=0.3 MPa) has been investigated. It is found that this catalyst is high stable for production C_2~4 olefins. Characterizations of both precursors and calcined catalysts by powder X-ray diffraction, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area measurement and thermal analysis methods such as thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) show that the different preparation method influences the catalyst precursor structure and morphology.     

Tubularenes

We report the synthesis and characterization of conjugated, conformationally rigid, and electroactive carbon-based nanotubes that we term tubularenes. These structures are constructed from a resorcin[n_b]arene base. Cyclization of the conjugated aromatic nanotube is achieved in one-pot eight-fold C–C bond formation via Suzuki–Miyaura cross-coupling. DFT calculations indicate a buildup of strain energy in excess of 90 kcal mol⁻¹. The resulting architectures contain large internal void spaces >260 ų, are fluorescent, and able to accept up to 4 electrons. This represents the first scaffolding approach that provides conjugated nanotube architectures.

First scaffolding approach to obtain tubular-shaped contorted aromatic architectures.     

An inorganic–organic hybrid material based on a Keggin-type polyoxometalate@Dysprosium as an effective and green catalyst in the synthesis of 2-amino-4H-chromenes via multicomponent reactions

A novel inorganic–organic hybrid, [Dy₄(PDA)₄(H₂O)₁₁(SiMo₁₂O₄₀)]·7H₂O denoted as (POM@Dy-PDA), based on a lanthanide cluster, a Keggin-type polyoxomolybdate, and PDA (1,10-phenanthroline-2,9-dicarboxylic acid) was prepared and fully characterized by elemental analysis, Fourier-transform infrared and UV–Vis spectroscopies, thermogravimetric analysis, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. The structural analysis study showed that the [SiMo₁₂O₄₀]⁴⁻ ions reside in the interspace between two cationic layers as discrete counterions and are not coordinated to the rare-earth ions. Significantly, this hybrid catalyst is a rare case of an inorganic–organic hybrid polyoxometalate (POM) with a PDA ligand based on CSD search (CSD version 5.40/November2018). The hybrid catalyst was further characterized via powder X-ray diffraction (PXRD) pattern at room temperature which indicated the good phase purity of the catalyst. BET and Langmuir surface area analysis indicate surface area of POM@Dy-PDA 6.6 and 51.3 m2g-1, respectively. The catalytic activity of the hybrid catalyst was successfully examined in the synthesis of 2-amino-4H-chromene derivatives through a multicomponent reaction. A three-component, one-pot reaction involving differently substituted benzaldehydes, resorcinol/α-naphthol/β-naphthol/4-hydroxycoumarin/3-methyl-4H-pyrazole-5(4H)-one, and malononitrile or ethyl cyanoacetate in the presence of a catalytic quantity of the aforementioned hybrid catalyst in EtOH/H₂O under reflux condition gave the corresponding highly functionalized 2-amino-4H-chromenes in satisfactory yields. The catalyst can be reused several times without appreciable loss in its catalytic activity.     

A one-pot synthesis of piperidinium spirooxindoline-pyridineolates and indole-substituted pyridones in aqueous or ethanol medium

Molecular Diversity - Piperidinium spirooxindoline-pyridineolate has been prepared via one-pot multicomponent reaction of isatin, malononitrile, cyanoacetohydrazide, and piperidine in water or...     

Green oxidations. The use of potassium permanganate supported on manganese dioxide

Permanganate supported on active manganese dioxide can be used effectively for the oxidation of organic compounds under heterogeneous or solvent-free conditions. The residue that remains after extraction of the organic products, manganese dioxide, can be recycled, making the process infinitely sustainable, in theory. The use of this approach for the oxidation of arenes, alcohols and sulfides is described.     

Modified Glaser Reaction of Terminal Alkynes on KF/Alumina

Summary. A variety of 1,3-diyne compounds are prepared in a solvent-free reaction on KF/alumina in the presence of catalytic amounts of Cu(OAc)₂·H₂O with up to 96% yields at room temperature.     

Rapid Microwave Induced Palladium Catalyzed Amination of Aryl Bromides

Summary.  The palladium-catalyzed coupling reaction of aryl bromides with various amines under microwave irradiation was studied using PdCl₂ [P(o-tolyl)₃]₂ which gave various aryl amines in good yields. The reactions were carried out under normal atmospheric conditions. Received September 3, 2001. Accepted October 10, 2001