ROLE OF H2S IN THE REDUCTION OF MOO3/AL2O3

MoO3/Al2O3 is reduced at least partly by sulfur which is formed from H2S in sulfidation with H2S/N2 mixture. SO2 formation during TPD of MoO3/Al2O3 with presorbed H2S provides evidence for the explanation.

Benzaldehyde derivatives from Eurotium rubrum, an endophytic fungus derived from the mangrove plant Hibiscus tiliaceus

Four new (1-4) and seven known (5-11) benzaldehyde derivatives were characterized from the liquid fermentation cultures of Eurotium rubrum, an endophytic fungus that was isolated from the inner tissue of stems of the mangrove plant Hibiscus tiliaceus. The structures of these compounds were determined by extensive analysis of their spectroscopic data. Among these metabolites, compound 1, which was named as eurotirumin, possesses a new carbon skeleton with a cyclopentabenzopyran ring system.

Chaetopyranin, a benzaldehyde derivative, and other related metabolites from Chaetomium globosum, an endophytic fungus derived from the marine red alga Polysiphonia urceolata

Cultivation of the endophytic fungus Chaetomium globosum, which was isolated from the inner tissue of the marine red alga Polysiphonia urceolata, resulted in the isolation of chaetopyranin (1), a new benzaldehyde secondary metabolite. Ten known compounds were also isolated, including two benzaldehyde congeners, 2-(2 ',3-epoxy-1 ',3 '-heptadienyl)-6-hydroxy- 5-(3-methyl-2-butenyl) benzaldehyde (2) and isotetrahydroauroglaucin (3), two anthraquinone derivatives, erythroglaucin (4) and parietin (5), five asperentin derivatives including asperentin ( 6, also known as cladosporin), 5 '-hydroxy-asperentin-8-methylether (7), asperentin-8-methyl ether (8), 4 '-hydroxyasperentin (9), and 5 '-hydroxyasperentin (10), and the prenylated diketopiperazine congener neoechinulin A (11). The structures of these compounds were determined on the basis of their spectroscopic data analysis (H-1, C-13, H-1-H-1 COSY, HMQC, and HMBC NMR, as well as low- and high-resolution mass experiments). To our knowledge, compound 1 represents the first example of a 2H-benzopyran derivative of marine algal-derived fungi as well as of the fungal genus Chaetomium. Each isolate was tested for its DPPH (1,1-diphenyl-2-picrylhydrazyl) radical-scavenging property. Compounds 1-4 were found to have moderate activity. Chaetopyranin (1) also exhibited moderate to weak cytotoxic activity toward several tumor cell lines.

Electrochemical impedance spectroscopy analysis for oxygen reduction reaction in 3.5% NaCl solution

The electrochemical impedance spectroscopy (EIS) at different potentials has been used to study the oxygen reduction reaction (ORR) in 3.5% NaCl solution on glassy carbon (GC) electrode in this work. Results show that ORR consists of three two-electron reaction steps and both superoxide ion (O-2(-)) and hydrogen peroxide (H2O2), which are produced by ORR, obstruct the diffusion of oxygen to the surface of the electrode and make the EIS results change into a transmissive finite diffusion process with the real part contraction and a reflective finite diffusion process from a semi-infinite diffusion process. The values of electron transfer resistance (R-t) and diffusion resistance (R-d) were calculated from EIS. O-2(-) influenced strongly on the Rt values and induced a maximum at -0.45 V.

Grey relational analysis on the relation between marine environmental factors and oxidation-reduction potential

The effects of marine environmental factors-temperature (T), dissolved oxygen (DO), salinity (S) and pH-on the oxidation-reduction potential (ORP) of natural seawater were studied in laboratory. The results show an indistinct relationship between these four factors and the ORP, but they did impact the ORP Common mathematical methods were not applicable for describing the relationship. Therefore, a grey relational analysis (GRA) method was developed. The degrees of correlation were calculated according to GRA and the values of T, pH, DO and S were 0.744, 0.710, 0.692 and 0.690, respectively. From these values, the relations of these factors to the ORP could be described and evaluated, and those of T and pH were relatively major. In general, ORP is influenced by the synergic effect of T, DO, pH and S, with no single factor having an outstanding role.

Hydrogen ion reduction in the process of iron rusting

Since the acceptance of the electrochemical rusting mechanism, oxygen reduction has been considered the main cathodic process, while H+ reduction has been overlooked for the past four decades because oxygen can be readily renewed due to the thin layer Of Solution film formed during atmospheric corrosion. This study shows that measurable hydrogen call be detected at the surface opposite to the corroding side of the specimen during wet-dry cycles, and a clear correlation exists between the quantities of hydrogen permeated through iron sheet and weight loss. Results Suggest the intrinsic importance of H+ reduction that merits further investigation. (c) 2004 Elsevier Ltd. All rights reserved.

The electrochemical reduction reaction of dissolved oxygen on Q235 carbon steel in alkaline solution containing chloride ions

Cyclic voltammetry, electrochemical impedance spectroscopy, and rotating disk electrode voltammetry have been used to study the effect of chloride ions on the dissolved oxygen reduction reaction (ORR) on Q235 carbon steel electrode in a 0.02 M calcium hydroxide (Ca(OH)(2)) solutions imitating the liquid phase in concrete pores. The results indicate that the cathodic process on Q235 carbon steel electrode in oxygen-saturated 0.02 M Ca(OH)(2) with different concentrations of chloride ions contain three reactions except hydrogen evolution: dissolved oxygen reduction, the reduction of Fe(III) to Fe(II), and then the reduction of Fe(II) to Fe. The peak potential of ORR shifts to the positive direction as the chloride ion concentration increases. The oxygen molecule adsorption can be inhibited by the chloride ion adsorption, and the rate of ORR decreases as the concentration of chloride ions increases. The mechanism of ORR is changed from 2e(-) and 4e(-) reactions, occurring simultaneously, to quietly 4e(-) reaction with the increasing chloride ion concentration.

Microwave effects on the selective reduction of NO by CH4 over an In-Fe2O3/HZSM-5 catalyst

Microwave effects have been shown to promote the activation of NOx molecules in the process of selective reduction of NO by CH4 over an In-Fe2O3/HZSM-5 catalyst and to enhance the water tolerance of this catalyst for NO reduction.

Enhanced activity of an In-Fe2O3/H-ZSM-5 catalyst for NO reduction with methane

Selective reduction of NO by CH4 on an In-Fe2O3/H-ZSM-5 catalyst was investigated in the presence of excess oxygen. Compared with In/H-ZSM-5, the In-Fe2O3/H-ZSM-5 catalyst with high Fe2O3 contents showed higher activity in a wide range of reaction temperatures. It was found that the addition of Fe2O3 yielded a promotion effect on CH4 activation. The influence of water vapor on NO conversion was also investigated. The activity of the In/H-ZSM-5 catalyst has been found to be strongly inhibited by water vapor, while the In-Fe2O3/H-ZSM-5 catalyst remained fairly active in the presence of 3.3% steam. (C) 2000 Elsevier Science B.V. All rights reserved.

Catalytic reduction of NO over in situ synthesized Ir/ZSM-5 monoliths

The catalytic performance of Ir-based catalysts was investigated for the reduction of NO under lean-burn conditions over binderless Ir/ZSM-5 monoliths, which were prepared by a vapor phase transport (VPT) technique. The catalytic activity was found to be dependent not only on the Ir content, but also on the ZSM-5 loading of the monolith. With the decreasing of the Ir content or the increasing of the ZSM-5 loading of the monolith, NO conversion increased. When the ZSM-5 loading on the cordierite monolith was raised up to ca. 11% and the metal Ir content was about 5 g/l, the NO conversion reached its maximum value of 73% at 533 K and SV of 20 000 h(-1). Furthermore, both the presence of 10% water vapor in the feed gas and the variation of space velocity of the reaction gases have little effect on the NO conversion. A comparative test between Ir/ZSM-5 and Cu/ZSM-5, as well as the variation of the feed gas compositions, revealed that Ir/ZSM-5 is very active for the reduction of NO by CO under lean conditions, although it is a poor catalyst for the C3H8-SCR process. This unique property of Ir/ZSM-5 makes it superior to the traditional three-way catalyst (TWC) for NO reduction under lean conditions. (C) 2001 Elsevier Science B.V. All rights reserved.