Showing papers in "The Open Catalysis Journal in 2011"

Non-Metal and Enzymatic Catalysts for Hydroperoxide Oxidation of Organic Compounds

Abstract: Oxidation of different groups of organic compounds, with hydroperoxides catalyzed by non-heavy metal containing low-molecular-weight compounds and enzymes is reviewed. This article is concentrated mainly on the hydrogen peroxide and tert-butyl hydroperoxide, however other less common hydroperoxides are also mentioned. Since hydroperoxides themselves are inactive toward most of the organic substrates, in situ activation of the oxidant is necessary. For this purpose various activators have been applied in stoichiometric or catalytic amounts. The carboxylic acids, nitriles, amides and urea are representative for the first category. The organocatalysts such as � -halo carbonyl compounds, ketones, imines, iminium salts, nitroxyl radicals and polyaminoacids, selenium compounds and enzymes are presented. They are involved in oxygen, and electron transfer processes whose mechanisms are briefly discussed, and their applications in laboratory and industrial synthesis are indicated.

Kinetics and Mechanism of Ruthenium(III) Catalyzed Oxidation of LProline by Hexacyanoferrate(III) in Aqueous Alkali

Abstract: Kinetics of ruthenium(III) catalyzed oxidation of L-proline by hexacyanoferrate(III)(HCF) in alkali was studied spectrophotometrically at 30 0 C. A reaction was found to be independent upon (L-proline). The reaction was occurred without intervening free radical. Since unit order each in (Ru(III)) and (HCF), the oxidation follows an outer-sphere mechanism. A suitable mechanism was proposed and rate law was derived as kobs = kK

Preparation of Nanostructured Pd-C-Ru Composite Electrodes for Alcohol Electrooxidations. Part-I: A Study of Ethanol Oxidation by Cyclic Voltammetry and Impedance Spectroscopy

Abstract: Ternary nanocomposites of Pd, Ru and nanocarbon (NC) have been prepared by the sodium borohydride reduction method and investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry techniques for their use as electrocatalysts for the methanol oxidation reaction (MOR). The study have shown that with addition of ruthenium from 1 to 50wt %, in the Pd-0.5wt %C composite, the rate of MOR initially increases, attains maximum and declines thereafter. Among ternary composites investigated, the Pd-0.5wt % C-20wt % Ru composite exhibited the greatest electrocatalytic activity. This electrode has approximately three times higher electrocatalytic activity than the base electrode (Pd-0.5wt % C). The electrochemical active surface area (� 133 m 2 /gPd) and the percentage utilization of Pd (30%) of the Pd-0.5wt % C-20wt % Ru electrode were also more than 5 times higher than that of the base electrode.

Amberlyst-15®: An Efficient, Cost-Effective and Recyclable Hetero Geneous Solid Acid Catalyst for the Synthesis of β-Enaminones and β- Enamino Esters

Abstract: The  -keto carbonyl compounds rapidly react with a variety of amines in the presence of Amberlyst-15  to produce  -enamino compounds in excellent yields. The reaction conditions are very mild and applicable to a wide range of substrates and the reactions are conveniently performed at ambient temperature. The catalyst is recovered by simple filtration and reused for further reactions.

Some Fused/Isolated Heterocyclic of Pyrimidine, β-Lactam, Thiazolidine and Triazine Derivatives

Abstract: Fused/isolated heterocyclic of pyrimidine  -lactam, thiazolidine and triazine derivatives incorporating benzpyrimidine derivatives have been synthesized by different method reactions (cycloaddition reaction, condensation reaction and cyclocondensation elimination reaction) of cinnamonitrile, aromatic aldehydes, chloroacetyl chloride, thioglycolic acid and nitroso compounds, respectively.

Stable Continuous Operation of a Biphasic Enantioselective Enzymatic Reduction

Abstract: Continuous operation of alcohol dehydrogenase (ADH) catalysed enantioselective reduction in a biphasic sytem showed gains in productivity and stability of the overall reaction system. The total turnover numbers obtained for the cofactor NADP + are high with up to 1.5� 10 4 . Productivity for (R)-2-butanol with Lactobacillus brevis ADH was up to 26 kmol (mol enzyme)  1 . Enantioselectivity was greater than 0.99 for (R)-phenylethanol and up to 0.99 for (R)-butanol.

Catalytic Asymmetric Addition of Diethylzinc to Benzaldehyde Using α- Pinene-Derived Ligands

Abstract: The amines obtained from � -pinene and containing a phenol or pyridine fragment can be used as ligands in the asymmetric addition of diethylzinc to aromatic aldehydes; the enantiomeric excess (ee) was up to 80%. The enantioselectivity of the reaction is not very sensitive to the nature of substituents in the aromatic ring of aldehydes.

A Study on Control of Microorganisms in Drinking Water Using Ag-Cu/C Catalysts

Abstract: Ag-Cu supported on activated carbon (Ag-Cu/C) catalysts with different compositions of Ag and Cu (total loading of Ag + Cu =1 weight %) were prepared by wet impregnation technique. These catalysts were characterized by BET surface area XRD, TPR, TEM and XPS. The catalytic activity of these catalysts was tested for control of microorganism in drinking water by nutrient agar coating method. Catalyst containing 0.5g each of Ag and Cu respectively exhibited superior catalytic activity compared to those of remaining compositions. The high catalytic activity possessed by this catalyst is attributed to the presence of smaller Ag particles and interaction between Ag and Cu as evidenced by XRD, TPR, XPS and TEM results respectively.

Catalytic Conversion of Isopropanol and CO Oxidation in Presence of NiO Supported on Modified Cordierite

Abstract: A commercial cordierite sample showed a small catalytic activity in isopropanol conversion carried out at 150- 350 oC and no measurable activity in CO oxidation by O2. On the other hand, supporting NiO on Al2O3-modified cordierite resulted in the formation of an active solid that having good catalytic activity in isopropanol conversion and CO oxidation by O2. These two reactions were carried out at 150-350 and 200 oC, respectively. The results revealed that the catalyst containing 5% (w/w) NiO showed the highest activity in the alcohol conversion and acted as selective dehydration catalyst. The catalyst sample containing 20% NiO (w/w) exhibited a good activity in CO oxidation by O2 which decreased progressively by increasing its calcination temperature within 350-600 oC. Al2O3-treated cordierite dissolved a portion of NiO in its lattice, increasing the calcination temperature within 350-600 oC increases the dissolution of NiO in the matrix of Al2O3-modified cordierite system.