The authors look at the structure and stability of the bare and hydrogenated iridium tetramers involved in the process.
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Interaction of ethene and ethyne with bare and hydrogenated Ir4 clusters. A density functional study
Galina P. Petrova, Georgi N. Vayssilov and Notker Rösch
Catal. Sci. Technol., 2011, DOI: 10.1039/C1CY00114K
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The authors particularly look at the selective oxidation of benzene to phenol with hydrogen peroxide in acetic acid as the solvent.
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Nature of vanadium species on vanadium silicalite-1 zeolite and their stability in hydroxylation reaction of benzene to phenol
Bin Guo, Liangfang Zhu, Xiaoke Hu, Qian Zhang, Dongmei Tong, Guiying Li and Changwei Hu
Catal. Sci. Technol., 2011, DOI: 10.1039/C1CY00105A
The review focuses on gas to liquid processes, which are used in the conversion of natural gas to hydrocarbons (either to form a synthetic version of crude oil, or more specific higher molecular weight hydrocarbons)
The authors look at the gas to liquid process for making syngas, catalytic partial oxidation of methane, membrane reactors, Fischer-Tropsch synthesis and also the technological aspects of a GTL plant.
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The main catalytic challenges in GTL (gas-to-liquids) processes
Eduardo Falabella Sousa-Aguiar, Fabio Bellot Noronha and Arnaldo Faro, Jr.
Catal. Sci. Technol., 2011, DOI: 10.1039/C1CY00116G
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Glucans are an important part of a good diet as they help keep the immune system healthy and are important in glycemia control. Glucans are a type of polysaccharide, and include substances like cellulose.
Ferreira’s team wanted to obtain partially hydrolysed beta-glucan as this is more easily absorbed by the digestive system. Read the full article to find out how they did this…
A new method to obtain β-glucan from Saccharomyces cerevisiae cells
Tatiana Felix Ferreira, Leonardo Rodrigues de Andrade, Maria Alice Zarur Coelho and Maria Helena Miguez da Rocha-Leão
Catal. Sci. Technol., 2011, DOI: 10.1039/C0CY00057D
Tetsuya Shishido and co-workers from Kyoto University summarise recent progress in investigating the reaction mechanism to explain this important photocatalytic effect.
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A unique photo-activation mechanism by “in situ doping” for photo-assisted selective NO reduction with ammonia over TiO2 and photooxidation of alcohols over Nb2O5
Tetsuya Shishido, Kentaro Teramura and Tsunehiro Tanaka
Catal. Sci. Technol., 2011, DOI: 10.1039/C1CY00104C
Fructosyltransferase is extracted from Rhoduoturula, a strain of yeast found in flowers in the rainforests of Southern Brazil. It is used to catalyse the transformation of sucrose into fructooligosaccharides, which promote the growth of certain probiotics in the human digestive system.
In this paper the authors aim to describe a kinetic mathematical model for how the enzyme works, to help in the design of a fructooligosaccharide production bioreactor.
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Kinetic studies and modelling of the production of fructooligosaccharides by fructosyltransferase from Rhodotorula sp
Mónica B. Alvarado-Huallanco and Francisco Maugeri Filho
Catal. Sci. Technol., 2011, DOI: 10.1039/C0CY00059K
In this Catalysis Science & Technology Hot Article, Miguel José-Yacamán at the University of Texas, San Antonio and colleagues from Portugal and Mexico investigated the synthesis and catalytic activity of molybdenum disulfide nanoplates.
The authors found that the optimum synthesis and annealing temperatures for producing the most hexagonal nanoplates with no impurities were 700 and 1000 °C respectively and the optimum reaction time was 2.5 hours.
The catalytic activity of the nanoparticles in the hydrodesulfurization of dibenzothiophene was tested and the activity was found to be comparable to, or higher than, other molybdenum disulfide-based catalysts. The nanoplates, however, showed greater selectivity for the biphenyl (desulfurization) product rather than the direct hydrogenation products preferred by the other catalysts.
Theoretical studies revealed that the rotated state of the catalyst, with a tendency to more metallic behavior, is favored, which could explain the improved catalytic activity of the nanoplates.
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Structure and catalytic properties of hexagonal molybdenum disulfide nanoplates
Carlos Fernando Castro-Guerrero, Francis Leonard Deepak, Arturo Ponce, Juan Cruz-Reyes, Mario Del Valle-Granados, Sergio Fuentes-Moyado, D. H. Galván and Miguel José-Yacamán
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00055A, Paper
The formation of such bonds is important in organic chemistry, and various transition metal catalysed cross-coupling reactions have been investigated before, however this new method achieves excellent yields, is easily recyclable and easy to use.
This work is part of the authors research into organochalcogen derivatives for biological and asymmetric transformations.
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C–S cross-coupling of thiols with aryl iodides under ligand-free conditions using nano copper oxide as a recyclable catalyst in ionic liquid
Ricardo S. Schwab, Devender Singh, Eduardo E. Alberto, Paulo Piquini, Oscar E. D. Rodrigues and Antonio L. Braga
Catal. Sci. Technol., 2011, DOI: 10.1039/C1CY00091H
The population of Earth is rising day by day, forcing agriculture to boost its production through the use of GM crops, the exploitment of new plant species for human consumption and, more traditionally, by employing increasingly large amounts of fertilizers (see the EFMA EU trend here).
Most of the commonly used fertilizers are sources of phosphate and nitrate ions that if used constantly can percolate through soil and contaminate groundwater and eventually affect the quality of drinking water.
Following the WHO guidelines reviewed in 2003, the maximum limit of nitrate in drinking water is set at 5omg/Litre and a maximum of 3mg/L for nitrite for short term exposure. The main consequences of exposure to higher doses of nitrate and nitrite are methaemoglobinaemia (conversion of hameoglobulin into methaemoglobulin, unable to carry oxygen) and morphological changes in the adrenal glands, lungs and heart (in animal models).
Ion exchange and chlorination, two common water denitrification processes are unable to efficiently remove nitrite due to its solubility and other processes produce a number of undesired toxic products like nitrite and ammonia.
Mishra et al., in a study presented in Catalysis Science and Technology proposed a preliminary but encouraging process to photocatalitically convert nitrate in nitrogen gas with minimal production of side-products.
In the first application in this field, tungsten and nitrogen doped titania was used in association with formic acid (a hole scavenger that increase the rate of reduction) for the reduction of nitrate with visible light produced by a high pressure Hg vapour lamp. After several studies on the ideal combination of doping agents and manufacturing conditions, the group found that a 2% of tungsten yielded the most active form of the catalyst (although larger percentages of the metal increased the absorption in the visible region).
Testing of the material for activity unveiled a selectivity for nitrogen gas of around 95% in contrast with just 50% obtained when tungsten wasn`t incorporated into the catalyst. To mimic potential real-life application, the tests were performed in air and also in the presence of chloride anions, the effect of which appeared to be overall beneficial to the reaction.
A discussion of the factors determining the activity of the system pointed out the importance of the exact combination of doping, hole scavenger, morphology of the material, mesoporosity and the presence of hydroxyl groups on the surface.
The characteristics of the material could make it a good candidate for a solar light-powered version of the process.
Mesoporous WN co-doped titania nanomaterial with enhanced photocatalytic aqueous nitrate removal activity under visible light
T. Mishra, M. Mahato, Noor Aman, J. N. Patel and R. K. Sahu
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00042J, Paper
Nitrogen oxides are among the most harmful pollutants produced by the combustion of fossil fuels, cause of euthropication of waters and soil contamination.
The reduction of the release of these nitrogen oxides from industrial flue gases and diesel engines into the atmosphere is more than ever a hot topic, as testified by the increasing amount of scientific publications on NOx storage and disposal; some of which appeared in Catalysis Science and Technology last month (here and here, also reviewed in this blog).
One of the main strategies to convert these oxides into harmless product is the Selective Catalytic Reduction (SCR) that takes place on supported catalysts like those found in exhausts pipes of modern cars. Due to the presence of alkaline metals in biomass derived and fossil fuels that can poison and deactivate them , though, the activity of these catalysts decreases with time; metals like potassium and barium affect the Brønsted acid sites of the catalysts and prevent the ammonia adsorbtion process, essential in the functioning of the system.
A new study by the Danish research group lead by Rasmus Fehrmann addresses this weakness and proposes a possible improvement to the process; the group postulated that in the presence of a super-acidic support for the catalyst, the alkali would preferentially react with the support, leaving the catalytic species untouched.
The super-acid of choice was a member of the heteropoly acids family, a class of solid acids composed of clusters of hydrogen, oxigen and transition metals coordinated around elements of the p-block like silicon, phosphorus or arsenic.
The chosen heteropoly acids, among which the 12-tungstophoshporic acid (TPA), were added to the titanium oxide support in conjunction with V2O6 as the active catalyst and tested in the NH3 promoted SCR. Traditional V2O6/TiO2 and mixed V2O6-WO3/TiO2 catalysts were used as a reference during the activity tests.
After doping with a source of potassium, the catalysts were tested against their pristine counterparts to measure the difference in activity, resulting in a superior performance of the super-acid supports which retained up to 88% of the original activity compared to 33% of the untreated ones.
Find out about these promising catalysts here.
Heteropoly acid promoted V2O5/TiO2 catalysts for NO abatement with ammonia in alkali containing flue gases
Siva Sankar Reddy Putluru, Anker Degn Jensen, Anders Riisager and Rasmus Fehrmann
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00081K, Paper
