Catalysis selective hydrogenation

Supported iron catalysts are notoriously difficult to reduce [6-8] and thus a substantial fraction of the iron can be expected to remain inactive for the catalysis of hydrogenation. Particular attention has therefore been paid to the preparation of Fe/MgO catalysts by several different methods and examination of their effectiveness in producing metallic iron of adequate specific surface area after reduction in hydrogen. The activity and selectivity for primary amine formation have been determined for the hydrogenation of ethanenitrile (acetonitrile) and propanenitrile. 

B.W. Hoffer, E. Crezee, P.R.M. Mooijman, A.D. van Langeveld, F. Kapteijn and J.A. Mouhjn, Carbon supported Ru catalysts as promising alternative for Raney-type Ni in the selective hydrogenation of D-glucose, Catalysis Today 79-80 (2003) 35. 

It is possible to extract the nanocolloids from aqueous solution into an organic phase or to support them onto inorganic supports by what is called the precursor method (described in Section 3.5) to generate heterogeneous catalysts. Such catalysts find application in chemical catalysis, e.g., in selective hydrogenation of fatty acids. 

Tessonnier JP, Pesant L, Ehret G, Ledoux MJ, Pham-Huu C (2005) Pd nanoparticles introduced inside multi-walled carbon nanotubes for selective hydrogenation of cinnamaldehyde into hydiocinnamaldehyde. Applied Catalysis A General 288 203-210. 

One of the systems was found to be very efficient catalyzing enantioface-selective hydrogen transfer reactions to aromatic and in particular to aliphatic ketones with up to 95% ee. Regarding the latter reaction these are unprecedented ee values. The reaction mechanism of these transformations is best described as a metal-ligand bifunctional catalysis passing through a pericyclic-like transition state. 

Gryaznov, V. M. and Smirnov. 1977. Selective hydrogenation on membrane catalysts. Kinetics and Catalysis 3 485-87. 

The investigations done by Claus and coworkers as part of the project Smart Solvents/Smart Ligands focussed on the selective hydrogenation of Q ,/3-unsaturated carbonyl compounds and showed the potential of aqueous multiphasic catalysis for the production of chemicals for fine chemistry, e.g., fragrance materials. 

Enantioselective hydrogenation of a-ketoesters on cinchona alkaloid-modified Pt/Al203 is an interesting system in heterogeneous catalysis [143-146], The key feature is that on cinchonidine-modified platinum, ethyl pyruvate is selectively hydrogenated to R-ethyl lactate, whereas on einchonine-modified platinum, S-ethyl pyruvate is the dominant product (Figure 16) [143]. 

Another example is butene dimerization catalyzed by nickel complexes in acidic chloroaluminates 14). This reaction has been performed on a continuous basis on the pilot scale by IFF (Difasol process). Relative to the industrial process involving homogeneous catalysis (Dimersol process), the overall yield in dimers is increased. Similarly, selective hydrogenation of diene can be performed in ionic liquids, because the solubility of dienes is higher than that of monoene, which is higher than that of paraffins. In the case of the Difasol process, a reduction of the volume of the reaction section by a factor of up to 40 can be achieved. This new Difasol technology enables lower dimer (e.g., octenes) production costs 14). 

The three themes of the symposium selective hydrogenation, selective oxidation and acid-base catalysis were introduced by four plenary lectures and two invited communications. A panel concerned with the future of zeolites and other shape-selective materials for fine chemical synthesis was conducted by specialists in the field D. Barthomeuf (University of Paris 6), E. Derouane (University of Namur), L. Forni (University of Milan), M. Gubelmann (Rhone-Poulenc, St Fons), W. Hoelderich (BASF, Ludwigshafen) and G. Perot (University of Poitiers). An exhibition of equipment was held during the symposium on October 3 and 4. Over 20 firms exhibited equipment, chemicals and catalysts which were of interest to researchers involved with the synthesis of functional compounds by heterogeneous catalysis. 

For certain metal systems, the chemical properties of bimetallic DENs include selective extraction from the dendrimer interior into organic solvents. Catalytic properties include homogeneous hydrogenation catalysis heterogeneous hydrogenation and oxidation catalysis have also been examined. Homogeneous hydrogenation studies indicate that... 

A final example of shape selective catalysis is the selective hydrogenation of alkynes, alkenes and other hydrocarbons over Pd complexes anchored to montmorillonite clay supports.29 In these studies, phosphines and amine ligands were first reacted with montmorillonite and then reacted with palladium (II) salts to form anchored Pd(II) complexes in the interlamellar spacings of the montmorillonite clay. 

In addition to performing acid/base catalysis, zeolite structures can serve as hosts for small metal particles. Transition metal ions, e.g., platinum, rhodium, can be ion exchanged into zeolites and then reduced to their zero valent state to yield zeolite encapsulated metal particles. Inside the zeolite structure, these particles can perform shape selective catalysis. Joh et al. (16) reported the shape selective hydrogenation of olefins by rhodium encapsulated in zeolite Y (specifically, cyclohexene and cyclododecene). Although both molecules can be hydrogenated by rhodium supported on nonmicroporous carbon, only cyclohexene can be hydrogenated by rhodium encapsulated in zeolite Y since cyclododecene is too large to adsorb into the pores of zeolite Y. 

Scire, S., Minico, S., and Crisafulli, C., Selective hydrogenation of phenol to cyclohexanone over supported Pd and Pd-Ca catalysts an investigation on the influence of different supports and Pd precursors. Appl Catalysis A-General 2002, 235 (1-2), 21-31. 

Application Increase the value of steam cracker C4 cuts via low-temperature selective hydrogenation and hydroisomerization catalysis. Several options exist removal of ethyl and vinyl acetylenes to facilitate butadiene extraction processing downstream conversion of 1, 3 butadiene to maximize 1-butene or 2-butene production production of high-purity isobutylene from crude C4 cuts total C4 cut hydrogenation and total hydrogenation of combined C3/C4 and C4C5 cuts for recycle to cracking furnaces or LPG production. 

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