Influence of Mg and Ce addition to ruthenium based catalysts used in the selective hydrogenation of α,β-unsaturated aldehydes (original) (raw)
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Applied Catalysis A: General, 2000
The gas-phase hydrogenation of crotonaldehyde has been performed over platinum and ruthenium catalysts supported over graphites with a tailored content in surface oxygen groups and prepared with different metal precursors. It is found that the selectivity to the unsaturated alcohol is independent of the amount of oxygen groups on the surface of the graphite supports. Notwithstanding this, their presence has an effect when a metal chloride precursor is used in the catalyst preparation since they act as anchoring sites of the chloride ions and the latter in residual amounts promote the hydrogenation of the carbonyl group. The addition of tin to platinum enhances also the selectivity to crotyl alcohol.
Selective hydrogenation of α,β-unsaturated carbonyl compounds on supported Ru-Sn catalysts
Research on Chemical Intermediates, 2005
Selective catalytic hydrogenation of unsaturated carbonylic compounds to unsaturated alcohols on bi-metallic Ru-Sn catalysts/support was studied. The catalysts were prepared by the solgel method and the method of co-impregnation with the objective to evaluate selected parameters of preparation, i.e., the amount of modifying tin and the support (TiO 2 , SiO 2 , Al 2 O 3), on their catalytic activity and selectivity. A significant modifying effect of tin was proved, especially its positive effect on the selectivity. Concerning the selectivity as well as the activity, Al 2 O 3 was found to be the optimal support. Furthermore, the effect of a substrate was studied with results proving suitability of this catalytic system for hydrogenation of unsaturated aldehydes; however, the utilization for selective hydrogenation of unsaturated ketones was found inadequate.
Catalysis Today, 1998
The effect of pH on the formation and equilibrium distribution of the water soluble ruthenium hydrides [HRuCl(TPPMS) 2 ] 2 , [HRuCl(TPPMS) 3 ] and [H 2 Ru(TPPMS) 4 ] (TPPMS(3-sulfonatophenyl)diphenylphosphine sodium salt) was studied in aqueous solution by pH-potentiometric and 1 H and 31 P NMR methods. Depending on the pH, [RuCl 2 (TPPMS) 2 ] 2 and its hydrido-derivatives hydrolyse extensively, giving rise to formation of hydroxo-ruthenium complexes. It was established that at pH 3.3 the dominant ruthenium(II) species was [HRuCl(TPPMS) 3 ], while at pH!7 it was [H 2 Ru(TPPMS) 4 ]. While [HRuCl(TPPMS) 3 ] catalyzed the slow, selective hydrogenation of the C=C bond in trans-cinnamaldehyde, [H 2 Ru(TPPMS) 4 ] was found an active and selective catalyst for C=O reduction. Consequently, the selectivity of the hydrogenation of transcinnamaldehyde could be completely inverted by minor changes in the solution pH, shifting the equilibrium between [HRuCl(TPPMS) 3 ] and [H 2 Ru(TPPMS) 4 ]. # 1998 Elsevier Science B.V. All rights reserved. Catalysis Today 42 (1998) 441±448 *Corresponding author.
Homogeneous hydrogenation of α,β-unsaturated aldehydes catalyzed by ruthenium and osmium complexes
Journal of Molecular Catalysis, 1984
Although a variety of stoichiometric reagents for the regioselective reduction of o&unsaturated aldehydes have been developed [l], few homogeneous catalytic systems are known, and these have been mainly based on cobalt or rhodium . Apart from a few notable exceptions [ 3 -51, most of the complexes produce the fully reduced product or show selectivity for the hydrogenation of the C=C bond. Furthermore, in the case of rhodium, competing decarbonylation of the aldehyde has been observed
Applied Catalysis, 1990
The influence of the ruthenium compound used as precursor to prepare ruthenium catalysts, and of the carrier, have been investigated using the hydrogenolysis of n-hexane, 2-methylpentane and 2,2,3,3_tetramethylbutane as model reactions. Similar activities and selectivities are reproduced for catalysts obtained from Ru(NH,),Cl, or Ru(acac), and a highly crystalline alumina. When RuCl,(NH,), is used as precursor, the catalytic properties are shifted towards those of large particles. At similar dispersions, the catalysts obtained by deposition of Ru(acac), on AlaOa, MgO or TiOa (reduced at 573 K) present similar properties. By high-temperature reduction of the Ru/ TiO, sample, the hydrogen chemisorption decreases, but the specific activity of surface ruthenium atoms is not changed, activation energies for hydrogenolysis decrease and selectivities are shifted towards those of smaller particles. The SMSI effect on Ru/TiOz cannot be reduced to a simple dilution of the ruthenium surface by titanium species.
Organometallics, 2006
Density functional theory has been applied to identify possible reaction intermediates for the catalytic CdC hydrogenation of cinnamaldehyde, which occurs in acidic aqueous solutions in the presence of water-soluble ruthenium phosphine complexes. On the basis of ONIOM calculations, two different active species and, hence, two pathways were proposed. The CdC bond hydrogenation takes place through the insertion of the terminal carbon atom into the Ru-H bond and subsequent protonation of the other carbon by hydroxonium ions present in the solution. We find that water is directly involved in several steps of the reaction, either as a protonating/deprotonating agent or as a coordinating ligand. Selectivity against CdO hydrogenation is due to the much higher barrier of either C insertion or O insertion into the Ru-H bond as compared to that of the C insertion in the case of the CdC functionality.
Support effect over bimetallic ruthenium–promoter catalysts in hydrogenation reactions
Chemical Engineering Journal, 2010
The present work evaluates the influence of RuSn catalyst supported on La 2 O 3 , TiO 2 , SiO 2 and Nb 2 O 5 in dimethyl adipate (DMA) hydrogenation to obtain 1,6-hexanodiol. The catalysts were prepared by impregnation method, calcined and reduced at 673 K. The reactions were carried out in liquid phase in a Parr high pressure reactor at 528 K and 50 bar. The catalysts supported on SiO 2 and Nb 2 O 5 show higher selectivity to diol, 59% and 50% and conversion of 57% and 28%, respectively, indicating that the new active phases formed in the metal-support interface are able to hydrogenate the DMA ester group. The presence of positively charged tin species acting as Lewis acid sites could be considered as responsible for the carbonyl activation. It is also verified that a synergic effect between promoter and support is extremely important for the formation of 1,6-hexanediol.
Catalytic hydrogenation of aromatic aldehydes and ketones over ruthenium catalysts
Research on Chemical Intermediates, 1996
Ruthenium catalysts show some specific features in hydrogenation reactions [ 1-4], which raise interest in their thorough recognition and practical utilization. Using them it is possible to hydrogenate aromatic rings under very mild conditions. In some of the cases it is even possible to ...