Volume 69, Issue 9

Copper or iron supported on commercially available oxides, such as γ-Al 2 O 3 , TiO 2 (anatase) and monoclinic tetragonal ZrO 2 (mt-ZrO 2 ) were tested as catalysts for selective catalytic oxidation of ammonia into nitrogen and water vapour (NH 3 -SCO) in the low temperature range. Different commercial oxides were used in this study to determine the influence of the specific surface area, acidic nature of the support and crystalline phases as well as of the type of species and aggregation state of transition metals on the catalytic performance in selective ammonia oxidation. Copper modified oxide supports were found to be more active and selective to nitrogen than catalysts impregnated with iron. Activities of both transition metal modified samples decreased in the following order: mt-ZrO 2 , TiO 2 (anatase), γ-Al 2 O 3 . Quantitative total ammonia conversion was achieved with the Cu/ZrO 2 catalytic system at 400°C. Characterisation techniques, e.g. H 2 -temperature programmed reduction, UV-VIS-diffuse reflectance spectroscopy, suggest that easily reducible copper oxide species are important in achieving high catalytic performances at low temperatures

A novel environmentally-friendly catalytic system for the carbonylation of cyclohexene with molecular oxygen under conditions of mild temperature, and under an atmospheric oxygen pressure is presented. In this system, a series of readily-prepared cobalt complexes of 2-aminophenol and its derivatives immobilised onto montmorillonite were used as catalysts. The catalysts were characterised by FT-IR, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, diffuse reflectance ultraviolet visible spectra, scanning electron microscopic measurements, transmission electron microscopic measurements and the Brunauer-Emmett-Teller method. The effects of various reaction conditions such as catalyst dosage, temperature and time were optimised, obtaining an 88.7 % conversion with 72.0 % selectivity of 2-cyclohexene-1-one in 6 h. The results show that the catalytic activity of the cobalt complexes encapsulated in montmorillonite is higher than those of the free complexes. In addition, the heterogeneous catalysts were stable and can be recycled up to five times without any noticeable change in the catalytic activity.

Olivine is abundant in the Earth’s upper mantle; it has applications in catalysts to enhance their stability in structures. The olivine-type catalysts were prepared by co-precipitation and hydrothermal synthesis and tested in the auto-thermal reforming (ATR) of acetic acid (AC), a model compound from bio-oil, for hydrogen production. In the meantime, the natural olivine impregnated with Ni was also tested. Characterisations of XRD, nitrogen physisorption, temperature-programmed reduction, and SEM-EDX were used to find the structure-reactivity relationship. The results indicate that the natural olivine produced a low H 2 yield close to 0.17 mole of H 2 per 1 mole of AC, while the olivine impregnated with Ni produced a H 2 yield of from 2.19 mole to 2.73 mole of H 2 per mole of AC. The olivine catalyst prepared by hydrothermal synthesis performed better in both activity and stability: the H 2 yield achieved 3.06 mole of H 2 per mole of AC and remained stable, which could be attributed to the higher surface area and stability with Ni inserted in the skeleton of olivine.

A new type of bulk liquid membrane system, which represents the first example of a bulk liquid membrane oscillator characterised by the presence of two coupled oscillators, is described. When the benzyldimethyltetradecylammonium chloride surfactant undergoes an oscillatory mass transfer through a nitromethane liquid membrane, a new liquid layer (phase X) appears between the membrane and the acceptor phase. Kinetic analysis provides evidence that the whole system is composed of two coupled oscillators with diffusion-mediated physical coupling. The first component oscillator (based on nitromethane) of lower frequency delivers the driving material to the second one (phase X-based oscillator) leading to additional higher frequency oscillations. A new molecular mechanism is proposed for interpreting the experimental observations. The results might enhance understanding of intercellular communication in biology, where periodic signalling is more efficient than any other type of signalling mode.

The dissolution of malachite particles in ammonium carbamate (AC) solutions was investigated in a batch reactor, using the parameters of temperature, AC concentration, particle size, and stirring speed. The shrinking core model was evaluated for the dissolution rate increased by decreasing particle size and increasing the temperature and AC concentration. No important effect was observed for variations in stirring speed. Dissolution curves were evaluated in order to test shrinking core models for fluid-solid systems. The dissolution rate was determined as being controlled by surface chemical reaction. The activation energy of the leaching process was determined as 46.04 kJ mol -1 .

Landfill represents the least environmentally-friendly method of waste disposal because of possible pollution to the environment. Dangerous wastes pose the greatest problems and are often disposed of by combustion. This process reduces their volume but entails the formation of new types of dangerous waste. The present study focuses on the possibilities of the removal of the hazardous properties of waste originating from hazardous waste incinerators (three types of bottom ash and charcoal from flue gas cleaning) by bioleaching. Toxic pollutants originating from waste could be removed by bioleaching with Acidithiobacillus ferrooxidans. The effectiveness of bioleaching was evaluated on the basis of the pollutant content in the aqueous leachates. For studying the relation between the efficiency of bioleaching and the binding of pollutants in the waste, Tessier’s sequential extraction was used. A comparison of bioleaching efficiency and the results of sequential extraction shows that bioleaching can be used to remove elements which are in an exchangeable form or are bound to carbonates, meaning that they are bound in bio-available forms. Bacterial activity was also shown to change the bonds of pollutants in wastes, leading to increased solubility of the pollutant.

Potential protective effects of elderberry (Sambucus nigra) extracts against oxidative degradation of hyaluronan (HA) were detected in vitro. To induce free-radical-mediated HA degradation, Weissberger’s biogenic oxidative system, which mimics the situation of acute inflammation, was applied. Time- and dose-dependent changes of dynamic viscosity of the HA solutions in the presence and absence of two elderberry extracts produced in 2006 and 2012 were recorded by rotational viscometry (RV). Radical scavenging capacity of both extracts was investigated by the spectrocolorimetric ABTS [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt] assay and the “inverted” ABTS assay. Oxygen consumption of the system oxidizing HA either in the absence or presence of the elderberry extracts was determined. The results of RV revealed that an addition of the newer extract (2012) promoted the inhibition of HA degradation more markedly compared to the older extract (2006). The same effect of both extracts on ABTS .+ scavenging was observed. Inverted ABTS assay demonstrated that colorful substances were not responsible for the radicalscavenging activity. Results of oximetry demonstrated that the effect of the extract from 2006 was more significant than that of the extract from 2012.

A novel polymeric ionic liquid (PIL), bearing high C-N and N-N content, potentially suitable for new safe energetic materials and catalyst supports was introduced. The PIL was prepared by way of radical co-polymerisation of 1-vinyl-3-p-nitrobenzylimidazolium bromide and 1-vinylimidazole at 80◦C using azobisisobutyronitrile (AIBN) as an initiator. The PIL thus produced was successfully transformed into NO 3 @PIL and N 3 @PIL for potential application as safe energetic materials and/or catalyst supports. The polymers were obtained in quantitative yields and were characterised by NMR, FTIR, DSC and TGA data. This study reveals the adequate thermal stability of novel salt-based nitrogen-rich polymeric ionic liquids for application as safe energetic materials and/or supports in heterogeneous catalysis.

Electro-membrane generation of Ag(II) in nitric acid was experimentally explored in a threeelectrode laboratory cell with respect to various operating parameters. DSA-O 2 , titanium plate and saturated Ag/AgCl were employed as the anode, cathode and reference electrode, respectively. The considered process parameters included anolyte temperature and Ag(I) initial concentration, electrolysis time, current density and supporting electrolyte concentration. Parameter effect on the Ag(II) concentration, current density and energy consumption were determined by the Taguchi and ANOVA methods for test design and data analysis, respectively. The results revealed that current density, AgNO 3 concentration and temperature had noticeable effect on the generation of Ag(II). On the other hand, AgNO 3 concentration and current density showed the most dominant effect on the Ag(II) current efficiency: 48.5 % and 30.3 %, respectively. AgNO 3 concentration and current density were also found to have the highest effect on the energy consumption: 72.4 % and 15.9 %, respectively. Validity of the Taguchi method was also assessed by collecting the actual data.

The present study on tetrazole compounds, which have a wide area of application, proposes a new, simple and highly effective method. A series of 5-substituted 1H-tetrazoles were synthesised in DMF via the [3 + 2] cycloaddition reaction, in which different aryl nitriles with sodium azide were used and copper(I) chloride served as a catalyst. Short reaction times, high yields and simple procedures rendered this method attractive and useful for the organic synthesis of 5-substituted 1H-tetrazoles. A further advantage was the use of an environmentally friendly catalyst.

A new, practical and cost-effective route for scalable synthesis of 2-[(4-dodecyloxyphenyl)sulfonyl] butanoic acid, a key intermediate of a new cyan dye-forming coupler containing a sulfone group, was developed by adopting phenol as the starting material. The synthesis was accomplished in five steps with etherification, chlorosulfonation, reduction, nucleophilic reaction by C-S coupling and hydrolyzation. An important objective of the new synthetic route was the synthesis of 2-[4- (dodecyloxyphenyl)sulfonyl]butanoate. Overall yield obtained at optimized conditions increased to 66 %. The synthetic strategy was proven to be a process enabling rapid delivery of the target product with high purity.

One-pot anti-Mannich reaction of vanillin, aniline and cyclohexanone was successfully catalyzed by ionic liquid triethanolammonium chloroacetate, at room temperature. Yield of the obtained Mannich base was very good and excellent diastereoselectivity was achieved. Mechanism of the reaction was investigated using the density functional theory. The reaction started with a nucleophilic attack of aniline nitrogen at the carbonyl group of vanillin. The intermediate α-amino alcohol formed in this way was further subjected to protonation by the triethanolammonium ion yielding the imminium ion. Theoretically, the obtained imminium ion and the enol form of cyclohexanone can build the protonated Mannich base via the anti and syn pathways. The chloroacetic anion spontaneously abstracts the proton yielding the final product of the reaction anti 2-[1-(N-phenylamino)-1-(4-hydroxy- 3-methoxyphenyl)]methylcyclohexanone (MB-H). The syn pathway requires lower activation energy but the anti pathway yields a thermodynamically more stable product, which implies that the examined Mannich reaction is thermodynamically controlled

3-Phosphoinositide-dependent kinase-1 (PDK1) plays a key role in the regulation of physiological processes and its catalytic activity is tightly regulated by allosteric modulators which bind to the PDK1 Interacting Fragment (PIF) pocket. However, details on the allosteric modulators regulation of the PDK1 catalytic activity remain elusive. Here, molecular docking and molecular dynamics (MD) simulations were performed to investigate the allosteric regulation of PDK1 induced by one of the benzoazepin-2-ones, the most potent compound 17 (BAZ2O). Molecular docking and MD simulation revealed that BAZ2O was located in the PIF pocket formed by residues from β4 and β5 sheets and helices αB and αC. BAZ2O formed a hydrogen bond with Arg131 and participated in hydrophobic interactions with Ile119, Thr148, Gln150, Leu155 and Phe157. Further comparative analyses of PDK1 in its apo and BAZ2O-bound states unveiled that BAZ2O promoted the structural coupling between the important catalytic domains of PDK1, including the activation loop and the helices αB and αC, thereby stabilizing the PDK1 conformation for catalysis. Understanding the allosteric interaction of PDK1 with small molecules provides a potentially valuable possibility of designing more potent allosteric modulators with therapeutic implications for lung cancer.

Amyloid-beta (Aβ) peptide readily forms aggregates that are associated with Alzheimer’s disease. Transition metals play a key role in this process. Recently, it has been shown that curcumin (CUA), a polyphenolic phytochemical, inhibits the aggregation of Aβ peptide. However, interactions of Aβ peptide with metal ions or CUA are not entirely clear. In this work, molecular dynamics (MD) simulations were carried out to clear the nature of interactions between the 42-residue Aβ peptide (Aβ-42) and Cu 2+ ions and CUA. Altogether nine different models were investigated, and more than 2 μs of the simulation data were analyzed. The models represent the possible modes of arrangement between Aβ-42 and Cu 2+ ions and CUA, respectively, and were used to shed light on the Aβ-42 conformational behavior in the presence of Cu 2+ ions and CUA molecules. Obtained data clearly showed that the presence of a CUA molecule or a higher concentration of copper ions significantly affect the conformational behavior of Aβ-42. Calculations showed that the change of the His13 protonation state (Aβ(H13δ)-Cu 2+ , Aβ(H13δ)-Cu 2+ -CUA models) leads to higher occurrence of the Asp23-Lys28 salt bridge. Analyzes of trajectories revealed that C-terminal β-sheet structures occurred significantly less frequently, and CUA promoted the stabilization of the α-helical structure. Further, calculations of the Aβ-42 complex with CUA and Cu 2+ ions showed that CUA can chelate the Cu 2+ ion and directly interact with Aβ, which may explain why CUA acts as an inhibitor of Aβ aggregation.