Selective hydrogenation reactions

In contrast, 1,5-cyclo-octadiene remains coordinated during the catalytic cycle of hydrogenation of phenylacetylene to styrene, catalyzed by the related iridium complex [Ir(C0D)( Pr2PCH2CH20Me)]BF4. This complex, which contains an ether-phosphine-chelated ligand, catalyzes the selective hydrogenation reaction via a dihydrido-cyclo-octadiene intermediate. The reaction is first order in each of catalyst, phenylacetylene and hydrogen [11] the proposed catalytic cycle is shown in Scheme 2.3. 

Different mixed carbonyl cluster precursors of Ru and Pt having phenyl-containing tin Hgands have recently been proposed for the preparation of Ru PtySnz nanoparticles on mesoporous sihca support These systems show high performance for the production of cyclododecene and 1,4-cyclohexanedimethanol by selective hydrogenation reactions [117]. 

In addition to this we have several examples of which the polymer conformation of the polymeric complex leads the asymmetrical selectivity Hydrogenation reactions of 1-methylcinnamic acid and 1-acetamidocinnamic acid by several poly(L-amino acid)-Pd complexes are observed (142-144). Poly(L-valine) (/3-form) and poly(/3-benzyl-L-aspartate) (a-helix, sinistral) give dextrorotative products, and poly(L-leucine) and poly( 3-benzyl-L-aspartate) (a-helix, dextral) do levo-rotatory products. Also, optical active poly-/3-hydroxyl esters-Raney Ni catalyst (145) and Ion-exchange resin modified by optical active amino acid-metal complex (146,147) are observed in asymmetrically selective hydrogenations. 

The performance of the acicular monolith for the selective hydrogenation reaction represented in Figure 39 was determined experimentally. A comparison of the rates per unit volume of catalyst coating ry, siOj arid the maximum yield Ymax (mean values were taken over several runs) is... 

Lange C, Storck S, Tesche B, and Maier WF. Selective hydrogenation reactions with a microporous membrane catalyst, prepared by sol-gel dip coating. J. Catal. 1998 175(2) 280-293. 

Desai and Neurock [81] use period DFT calculations along with ab initio (DFT) MD simulations in order to establish the effects of protic solvents on the hydrogenation of formaldehyde to methoxy and hydroxy methyl intermediates over Pd(lll). Although this work was carried out in order to gain insight into solvent effects for selective hydrogenation reactions, it also has direct relevance to the oxidation of methanol since these two steps are simply the microscopic reverse reactions for the decomposition of hydroxy methyl and methoxy. 

In spite of the initial enthusiasm and the large amount of work that has been carried out in the meantime, any important practical application of an immobilized metal complex catalyst is not known so far. Promising and really satisfying results could only be obtained to a small extent in selective hydrogenation reactions in the synthesis of chemical specialities and pharmaceutical products and in polymerization reactions with immobilized metallocene catalysts [21]. The situation for the latter type of reactions, however, is different. 

Activity, Selectivity and Coking of Bimetallic Ni-Co-Spinel Catalysts in Selective Hydrogenation Reactions. 

Partly because gold catalysts are active under mild conditions, they have been investigated for other selective oxidation and for selective hydrogenation reactions. Details are given in Sect. 6.2.4. 

The great potential of CNF as catalyst support material is demonstrated by several researchers. Metals like Pt [2], Pd [3,4] and Ni [58] are applied on CNF and tested in various reactions, a.o., selective hydrogenations. Selective hydrogenation reactions are important for the fine chemical industry. Ruthenium is one of the active metals for this reaction. Its performance is sensitive to subtle changes in dispersion and nature of the support. In this study we have applied ruthenium on a CNF support. For CNF supported ruthenium catalysts much higher selectivities (up to 92%) to cinnamylalcohol were found... 

CAMP was prepared by a selective hydrogenation reaction of 10 (Fig. 13) using a heterogeneous rhodium-on-carbon catalyst. It was important to monitor the reaction... 

Modeling of Kinetically Coupled Selective Hydrogenation Reactions Kinetic Rationalization of Pressure Effects on Enantioselectivity... 

This concept might be considered in other selective hydrogenation reactions, for example the case of unsaturated aldehydes where parallel pathways for C=C and C=0 bond hydrogenation exist. 

A number of rhodium catalysts supported on FibreCat (the 2000 series, see Figure 5) have been developed for the catalysis of selective hydrogenation reactions... 

During our studies on the use of supported copper catalysts in selective hydrogenation reactions, we found that these systems can be effectively applied to the chemoselective hydrogenation of a,P-unsaturated ketones giving quantitative yields in the corresponding saturated ketone also when another olefinic bond is present in the molecule [3]. 

An activated carbon was functionalized using nitric acid and the surface acidity was evaluated by Boehm s titrations and XPS. Chosen Pd and Ru complexes were then grafted onto the unmodified and the modified carhon supports. After thermal activation, the obtained Pd-Ru/C catalysts were tested in a selective hydrogenation reaction. The amount of metal grafted in the final catalysts was measured by ICP and seemed to be correlated to the surface acidity. Results from catalytic testing in the hydrogenation of... 

Despite the extended studies on supported Sn-Ru catalysts used in different selective hydrogenation reactions and hydrogenolysis of esters there is a need to further investigate the effect of catalyst preparation and pretreatment parameters on the performance of this bimetallic system. 

C., and Rooney, D.W. (2004) Heterogeneously catalysed selective hydrogenation reactions in ionic liquids. Green Chem., 5, 448-453. 

---