Current Catalysis - Volume 4, Issue 1, 2015

A novel environmentally benign oxidation method for practical and highly selective production of various sulfoxides using n-Bu4NHSO5 catalyzed by simple tetradentate Schiff base Mn(III)-complexes in ethanol under mild conditions has been developed. The salen catalyst proved to be reusable for at least three times and the oxidant’s by-product (n- Bu4NHSO4) could also be recycled. The efficiency of the catalytic system was influenced by the nature of ligands so the best yields were achieved in the presence of Mn(Salphen)Cl as catalyst.

The anion exchange resin Amberlite IRA-900, in the chloride form, catalyzes the photolysis of carbon tetrachloride in methanol, ethanol, and n-propanol under visible and near-UV irradiation to produce the corresponding dialkyl carbonate and alkyl chloroformate, the latter readily converted to the carbonate with base. For diethyl carbonate, the rate of reaction increases with the partial pressure of oxygen and is relatively insensitive to either the amount of catalyst present or the fraction of CCl4 in ethanol above approximately 10 mg/mL and 5%, respectively. A yield of 15% could be achieved for diethyl carbonate under appropriate conditions, accompanied by acetaldehyde and chloroform as major side products. The reaction in methanol was slower and that in n-propanol somewhat faster than in ethanol.

Multiwalled carbon nanotubes (MWCNTs) synthesized earlier by catalytic chemical vapor deposition of acetylene, were used to develop heterogeneous supported acid catalysts by sonicating with 50% aqueous solutions of H2SO4, H3BO3 and H3PO4. The effect of acid treatment of MWCNTs, on their textural properties such as crystallinity, surface area, nature of the surface functional groups and elemental composition was investigated by appropriate instrumental methods of analysis such as BET surface area, Powder XRD, FT-IR, SEM-EDS, TEM and XPS. Acidity of the materials was estimated by n-butyl amine back titration method and the catalytic activity was evaluated in an acid catalyzed esterification reaction between benzyl alcohol and acetic acid. Further, the effect of duration and temperature of the reaction on the conversion of benzyl alcohol to benzyl acetate was studied. The product analysis was made by GC, LC-MS and 1HNMR techniques. The characterization techniques indicated that, the textural properties of the acid activated MWCNTs were distinctly different from those of the pristine MWCNTs inferring a possible incorporation of oxoacids into the mesoporous structure of MWCNTs. All the materials showed catalytic activity in the esterification of benzyl alcohol with acetic acid resulting benzyl acetate with 100% selectivity and 10-88% yield depending on the experimental conditions. Sulphuric acid activated MWCNTs exhibited highest surface acidity and catalytic activity. These catalysts were also found to be recyclable up to 5 times without any significant loss in its catalytic activity.

Hydrocracking catalysts consisting of metal and microporous molecular sieves play an essential role in petroleum industry. This review summarizes the compositions, preparation approaches and applications of hydrocracking catalysts based on molecular sieves. Specifically, this review includes: (i) a brief overview of selected methods of direct synthesis and the post-synthetic modification of molecular sieves; (ii) an introduction of the existing strategies to incorporate metals with microporous molecular sieves to prepare bifunctional catalysts, e.g., impregnation and ion exchange; and (iii) a summary of various hydrocracking catalysts for long chain paraffins and aromatics.

Novel Nickel(II) and Ruthenium(II) complexes of schiff base ligands were synthesized and studied using various spectral and thermoanalytical techniques. One of the metal complexes [NiII (L-2)2(CH3OH)2] has been structurally characterized on the basis of X-ray data and was found to adopt a helical structure stabilized by strong intermolecular H-bonding to form a dimeric structure. The complex crystallizes in the triclinic space group P-1 with unit cell dimensions a=11.1863(13) Å, b=12.0526(16) Å, c =12.5639(14) Å, α= 112.216°, β=95.065°, γ= 105.289° and Z=2. The coordination environment around the Ni(II) ion is in distorted octahedral geometry with four donor atoms (N2O2) coming from the two ligands providing four coordination sites (two by each ligand) through two azomethine nitrogen, N1 and N2 (Ni(1)–N(1) = 2.080(5) and Ni(1)–N(2) = 2.090(5)Å and two deprotonated hydroxyl oxygen, O1 and O2 (Ni(1)–O(1) = 2.008(3) and Ni(1)–O(2) = 1.998(3)Å. The remaining two coordination sites O3 and O4 are provided by two coordinated methanol molecules (Ni(1)–O(3) = 2.093(4) and Ni(1)–O(4) = 2.154(4)Å. Stability of the complexes was determined using TG-DTA.The fluorescence quantum yield of complexes was found to be lower than that of the (L-2) (Φ=0.032). [NiII (L-2)2(CH3OH)2] was used as a catalyst in hydrogenation.

As an extension of our earlier study, (E)-alkyl 3- (dialkoxyphosphoryl)-3-phenylacrylates were synthesized by the addition of dialkyl phosphites to the triple bond of alkyl phenylpropiolates under microwave irradiation. The (E)- diastereoselectivity of the monoadducts falls in the range of 84–90%. There was no need to use any catalyst.

A new, efficient and green methodology for obtaining quinolines based on the use of tungstophosphoric acid included in a polymeric matrix of polyacrylamide is proposed (APTPOL60). The methodology involves the formation of polysubstituted quinoline compounds using a variety of 2-aminoaryl ketones and β-dicarbonyl compounds, in absolute ethanol as reaction solvent, and a temperature of 78 ºC. The catalyst efficiency is not compromised after its successive use in reactions, and no leaching was observed. Seven examples of quinolone derivatives were obtained with excellent yields (89%–99%). This is the first report about the use of a heteropolyacid included in a polymeric matrix as recyclable catalyst in the Friedlander synthesis of quinoline derivatives (molecules with biological activity potential).