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Methanol ruthenium catalysis

G Braca, C. Sbrana, G. Valentmi, C- Andrich and G. Gregorio Carbonytation and Homologation of Methanol, Methyl Ethers and Esters in the presence of Ruthenium Catalysis (Fundamental Research in Homogeneous Catalysis v. 3. ed.. M. Tsutsui), pp. 221 238. Plenum Prevs (1979). [Pg.134]

Hilker et al. [59] studied the Novozym 435-catalyzed copolymerization of racemic a,a -dimethyl-l,4-benzenedimethanol with secondary hydroxyl groups with dimethyl adipate. Due to CALB enantioselectivity, hydroxyl groups at (R) stereocenters preferably reacted to form ester bonds with liberation of methanol. The reactivity ratio was estimated as (R)/(S) = 1 x 106. In situ racemization of monomer stereocenters from (S) to (R) by ruthenium catalysis allowed the polymerization to proceed and reach high functional group conversations. Readers should also refer to Chapter 11 for more information on chiral discriminations by lipases. [Pg.95]

Binary systems of ruthenium sulfide or selenide nanoparticles (RujcSy, RujcSey) are considered as the state-of-the-art ORR electrocatalysts in the class of non-Chevrel amorphous transition metal chalcogenides. Notably, in contrast to pyrite-type MS2 varieties (typically RUS2) utilized in industrial catalysis as effective cathodes for the molecular oxygen reduction in acid medium, these Ru-based cluster materials exhibit a fairly robust activity even in high methanol content environments of fuel cells. [Pg.314]

Waszczuk P, Lu GU, Wieckowski A, Lu C, Rice C, Masel MI. 2002. UHV and electrochemical studies of CO and methanol adsorbed at platinum/ruthenium surfaces, and reference to fuel cell catalysis. Electrochim Acta 47 3637-3652. [Pg.374]

Most of the catalysts employed in PEM and direct methanol fuel cells, DMFCs, are based on Pt, as discussed above. However, when used as cathode catalysts in DMFCs, Pt containing catalysts can become poisoned by methanol that crosses over from the anode. Thus, considerable effort has been invested in the search for both methanol resistant membranes and cathode catalysts that are tolerant to methanol. Two classes of catalysts have been shown to exhibit oxygen reduction catalysis and methanol resistance, ruthenium chalcogen based catalysts " " and metal macrocycle complexes, such as porphyrins or phthalocyanines. ... [Pg.393]

In the methanol synthesis, a fast hydrogenation of the adsorbed formaldehyde would overcome arguments invoking any thermodynamic limitation to its formation. Formaldehyde adsorbed through both the oxygen and the carbon ends has been characterized in homogeneous catalysis (43), on oxide surfaces (44) and more recently on ruthenium metal (45). [Pg.240]

Solutions of ruthenium carbonyl complexes in acetic acid solvent under 340 atm of 1 1 H2/CO are stable at temperatures up to about 265°C (166). Reactions at higher temperatures can lead to the precipitation of ruthenium metal and the formation of hydrocarbon products. Bradley has found that soluble ruthenium carbonyl complexes are unstable toward metallization at 271°C under 272 atm of 3 2 H2/CO [109 atm CO partial pressure (165)]. Solutions under these conditions form both methanol and alkanes, products of homogeneous and heterogeneous catalysis, respectively. Reactions followed with time exhibited an increasing rate of alkane formation corresponding to the decreasing concentration of soluble ruthenium and methanol formation rate. Nevertheless, solutions at temperatures as high as 290°C appear to be stable under 1300 atm of 3 2 H2/CO. [Pg.381]

The addition of increasing amounts of iodine promoters accelerates the hydrocarbonylation of methanol, but at the same time detioriates the hydrogenation ability of the cobalt catalysis. To obtain a high ethanol selectivity under these conditions, catalysts active for hydrogenation in the presence of iodine have to be added. Ruthenium compounds have been proved to be most suitable, as was mentioned earlier. Althou no detailed studies on the ruthenium intermediates involved are available, it is well known that aliphatic aldehydes... [Pg.126]

Transition metal surfaces enriched with S, Se and Te, have been considered as candidates for DAFC cathode catalysts [112-115], For example, ruthenium selenium (RuSe) is a weU-studied electro-catalyst for the ORR [116, 117]. The ORR catalysis on pure Ru surfaces depends on the formation of a Ru oxide-like phase [118]. Ru is also an active catalyst for methanol oxidation. On the other hand, the activity of the ORR on RuSe is found not be affected by methanol [116]. RuS, has also been reported insensitive to methanol [119-122], DPT studies of model transition metal surfaces have provided with atomistic insights into different classes of reactions relevant to fuel cells operation, such as the hydrogen evolution [123], the oxygen reduction [124], and the methanol oxidation [125] reaction. Tritsaris, et al. [126] recently used DPT calculatimis to study the ORR and methanol activation on selenium and sulfur-containing transition metal surfaces of Ru, Rh, Ir, Pd, Co and W (Fig. 8.9). With RuSe as a starting point, the authors studied the effect of the Se on... [Pg.284]

N. Alonso-Vante, P. Bogdanoff, H. Tributsch, On the origin of the selectivity of oxygen reduction of ruthenium-containing electrocatalysts in methanol-containing electrolyte , J. Catalysis 190 (2000) 240. ... [Pg.95]

However, the intermediate product during the oxidation of methanol makes the catalysis complicated, and the reaction rate for making CO out of methanol solution is slow. Moreover, a second metal such as Ruthenium (Ru) is required, which is explained by the bifunctional mechanism. In other words, activation of water or surface oxides at lower potentials makes the CO absorption bond weaker on the PtRu alloy catalyst. In the meantime, oxidative methanol dehydrogenation occurs on Pt by oxygen-like species on Ru, so that species on Pt-Ru pair sites enables the continuous oxidation of CO to CO. ... [Pg.310]


See other pages where Methanol ruthenium catalysis is mentioned: [Pg.41]    [Pg.42]    [Pg.157]    [Pg.113]    [Pg.147]    [Pg.218]    [Pg.234]    [Pg.204]    [Pg.226]    [Pg.375]    [Pg.397]    [Pg.397]    [Pg.399]    [Pg.358]    [Pg.129]    [Pg.33]    [Pg.115]    [Pg.153]    [Pg.177]    [Pg.277]    [Pg.117]    [Pg.282]    [Pg.32]    [Pg.572]    [Pg.142]    [Pg.609]    [Pg.831]    [Pg.275]    [Pg.536]    [Pg.32]    [Pg.520]    [Pg.56]    [Pg.250]   
See also in sourсe #XX -- [ Pg.375 , Pg.376 , Pg.384 , Pg.409 ]




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