Glycerol Oxidation Reaction Research Articles

OXIDATION OF GLYCEROL USING TITANIA SUPPORTED Au–Pd BIMETALLIC CATALYSTS: EFFECT OF Au–Pd RATIOS ON CATALYTIC PERFORMANCE

Oxidation of glycerol to form various types of short chain oxygenated derivative compounds became an important reaction to support biodiesel industries. In this study, bimetallic Au–Pd catalysts supported on TiO2 with different Au/Pd atomic ratios have been successfully prepared by deposition-precipitation method with urea decomposition. The catalysts were tested in the glycerol oxidation reactions in order to examine the effect of Au–Pd ratio on the conversion and selectivity. Catalytic activity of all the catalysts were as follow: Au7Pd3/TiO2 > Au5Pd5/TiO2 > Au8Pd2/TiO2 > Au9Pd1/TiO2 > Au6Pd4/TiO2 . Analysis by XRD revealed the presence of metallic Au and gold-enriched Au–Pd alloy phase which were located between the [111] and [200] peaks of Au and Pd in the Au–Pd bimetallic catalysts. XPS analysis ascertained the formation of Au0 , Au3+ , Pd0 and PdO species together with Au–Pd alloy phase in the bimetallic Au–Pd catalysts. This shows that the catalytic activity of the catalysts was depended to the formation of mixture of active species namely Au0 , Au3+ , Pd0 dan PdO together with the presence of "synergisti" effect in the Au–Pd alloy. The reactions were performed at low and high temperatures (50°C and 100°C) and it was found that the selectivity to tartronic acid was enhanced at lower reaction temperature. The highest selectivity to tartronic acid (55% at 99% conversion) was obtained by using Au9Pd1/TiO2 at 50°C and after 8 h of reaction time.

Gold catalyzed liquid phase oxidation of alcohol: the issue of selectivity

Commercial carbon nanotubes (CNTs) and carbon nanofibers (CNFs) modified in various ways at the surface have been used as supports for gold nanoparticles (AuNPs) in order to study their influence on the activity/selectivity of catalysts in the aqueous oxidation of alcohol. Particularly oxidative treatment was used to introduce carboxylic functionalities, whereas subsequent treatment with NH3 at different temperatures (473 K, 673 K and 873 K) produced N-containing groups leading to an enhancement of basic properties as the NH3 treatment temperature was increased. The nature of the N-containing groups changed as the temperature increased, leading to an increase in the hydrophobicity of the support surface. Similar Au particle size and similar textural properties of the supports allowed the role of chemical surface groups in both the activity and the selectivity of the reaction of glycerol oxidation to be highlighted. An increase of basic functionalities produced a consistent increase in the activity of the catalyst, which was correlated to the promoting effect of the basic support in the alcoholate formation and the subsequent C-H bond cleavage. The selectivity towards primary oxidation products (C3 compounds) was the highest for the catalysts treated with NH3 at 873 K, which presented the most hydrophobic surface. The same trend in the catalyst activity has been obtained in the aqueous benzyl alcohol base-free oxidation. As in the case of glycerol, the increasing of basicity and/or hydrophobicity increased the consecutive reactions.

Magnetron sputtering of gold nanoparticles onto WO 3 and activated carbon

In this paper we describe the production and investigation of two supported gold catalyst systems prepared by magnetron sputtering: Au on WO 3 and Au on activated carbon. The magnetron sputtering technique entails using an argon plasma to sputter a high purity gold target producing a flux of gold atoms which are deposited onto a constantly tumbling support material. This technique offers a number of advantages over conventional chemical preparation methods. One advantage is the ability to create gold nanoparticles (diameters <3 nm) on unusual support materials, such as WO 3 and carbon, which are generally not accessible using the ubiquitous deposition-precipitation technique. We present data demonstrating the formation of catalytic gold nanoparticles with average diameters of 1.7 nm (Au/C) and 2.1 nm (Au/WO 3), as well as a substantial number of single atom species on the Au/C sample. Prototypical carbon monoxide oxidation (Au/WO 3) and glycerol oxidation (Au/C) reactions were performed in order to gauge the activity of these catalysts. The WO 3 supported catalyst exhibits substantial catalytic activity from room temperature to 135 °C (0.0018–0.082 mol CO/mol Au s) with an activation energy near 23 kJ/mol. The activity of the Au/C catalyst was compared to a Au/C catalyst prepared from a poly(vinyl alcohol) (PVA) sol. The smaller catalysts prepared by sputtering are more active than the large gold particles prepared using the PVA sol, however the larger gold nanoparticles are substantially more selective towards the production of intermediate products from the oxidation of glycerol.

微生物によるグリセリン代謝機構に関する研究

1. It was recognized that intact cells and dried cells of Saccharomyces saké could not oxidize glycerol. This seems to be resulted from the slow velocity of the following two reactions: glycerol → glycerophosphate and glycerophosphate → triose phosphate. 2. Hansenula anomala can oxidize glycerol, glycerophosphate and other poly alcohols. In the earlier stage of glycerol-oxidation, the rate was accelerated by inorganic phosphate and diphosphopyridine nucleotide. A cell-free enzyme solution from the autolyzed cells contained glycerokinase which transfers phosphate from ATP to glycerol and glycerophosphatase which splits phosphate from glycerophosphate. Therefore, the authors propose that the phosphorylation of glycerol as the first reaction of glycerol-oxidation couples in vivo with diphosphopyridine nucleotide, and that the first metabolite is glycerophosphate. 3. It was unsuccessful to extract enzymes which oxidize glycerol from H. anomala, but it was recognized that dried cells and homogenates prepared from them could oxidize glycero-phosphate. As the dried cells of S. saké can ferment glucose, it is apparent that they contain enzymes which metabolize triose phosphate. And the velocity of glycerophosphate-oxidation by H. anomala was accelerated by the addition of the minced matter of S. sake. 4. As metabolites resulting from glycerophosphate-oxidation by the extract of minced matter of intact cells of H. anomala, pyruvate' and a-ketoglutarate were found by the method of paper partition chromatography. And H. anomala could oxidize organic acids in the TCA-cycle; citrate, succinate, fumarate and malate. 5. From these findings, glycerol (via glycerophosphate and triose phosphate) may be oxidized to pyruvate and finally to CO2 through the TCA-cycle by H. anomala. In this case, the process via dihydroxyacetone rom glycerol may be unreasonable by the fact that little activity of glycerol dehydrogenase and negligible oxidation of dihydroxyacetone are recognized.

微生物によるグリセリン代謝機構に関する研究

1. It was recognized that intact cells and dried cells of Saccharomyces sake could not oxidize glycerol. This seems to be resulted from the slow velocity of the following two reactions: glycerol → glycerophosphate and glycerophosphate → triose phosphate. 2. Hansenula anomala can oxidize glycerol, glycerophosphate and other poly alcohols. In the earlier stage of glycerol-oxidation, the rate was accelerated by inorganic phosphate and diphosphopyridine nucleotide. A cell-free enzyme solution from the autolyzed cells contained glycerokinase which transfers phosphate from ATP to glycerol and glycerophosphatase which splits phosphate from glycerophosphate. Therefore, the authors propose that the phosphorylation of glycerol as the first reaction of glycerol-oxidation couples in vivo with diphosphopyridine nucleotide, and that the first metabolite is glycerophosphate. 3. It was unsuccessful to extract enzymes which oxidize glycerol from H. anomala, but it was recognized that dried cells and homogenates prepared from them could oxidize glycero-phosphate. As the dried cells of S. sake can ferment glucose, it is apparent that they contain enzymes which metabolize triose phosphate. And the velocity of glycerophosphate-oxidation by H. anomala was accelerated by the addition of the minced matter of S. sake. 4. As metabolites resulting from glycerophosphate-oxidation by the extract of minced matter of intact cells of H. anomala, pyruvate' and a-ketoglutarate were found by the method of paper partition chromatography. And H. anomala could oxidize organic acids in the TCA-cycle; citrate, succinate, fumarate and malate. 5. From these findings, glycerol (via glycerophosphate and triose phosphate) may be oxidized to pyruvate and finally to CO2 through the TCA-cycle by H. anomala. In this case, the process via dihydroxyacetone rom glycerol may be unreasonable by the fact that little activity of glycerol dehydrogenase and negligible oxidation of dihydroxyacetone are recognized.