- Hydrogenation on granular palladium-containing catalysts: I. Hydrogenation of tertiary acetylene alcohols
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Commercial granular palladium catalyst (0.5% of Pd on γ-Al 2O3) was modified by treating with zinc acetate (type 1) or successively with zinc acetate and ammonia (type 2). The treatment significantly increased the hydrogenation selectivity for a triple bond into a double bond: to 85.3-93.1% with the type 1 catalyst and to 96.3-97.8% with the type 2 catalyst. A construction of an autoclave with a fixed bed of the granular catalyst is described.
- Tolkacheva,Kislyi,Taits,Semenov
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p. 150 - 152
(2007/10/03)
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- KINETICS AND SELECTIVITY OF THE HYDROGENATION OF A C20 ACETYLENIC ALCOHOL (DEHYDROISOPHYTOL) ON SUPPORTED PALLADIUM CATALYSTS UNDER HYDROGEN PRESSURE IN A FLOW SYSTEM.
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The lack of a general mechanistic and kinetic analysis of the multistep reaction of dehydroisophytol in a tube reactor makes it difficult to choose a selective catalyst system or to determine the optimum conditions for the preparation of the desired products. For this reason the authors have carried out an investigation of the effect of various process parameters (PH//2, T, reactant feed rates, etc. ) on the kinetics and selectivity of the hydrogenation of dehydroisophytol in the presence of industrial supported palladium catalysts (0. 75% Pd on ShAS silica gel; 0. 5% Pd on ShN-2, P-5 silica gel) in a flow system by the 'streaming' method. The data reveal that the composition of the catalysate mixture for the hydrogenation of compound in 0. 5% Pd/ShN-2 changes appreciably in proportion to the rate of addition of excess hydrogen. For instance, as the rate of bubbling of hydrogen is increased from 60 to 100 cm**3/min, the concentration of the C//2//0 saturated alcohol increases from 20. 0-21. 0 to 39. 0-40. 0%, and the concentration of compound decreases from 49. 0-50. 0 to 42. 0-43. 0%. The amount of unreacted starting material is also reduced, from 30. 0-31. 0 to 18. 0-17. 0%. Based on experimental evidence it is concluded that the use of these catalysts under stationary (fixed-bed) conditions significantly increases the productivity of the process (20-30 times), although they are noticeably inferior to the industrially used catalysts with respect to selectivity. This work is pertinent to synthesis of vitamins.
- Omarkulov,Mukataev,Goncharova,L'dokova,Sokol'skii
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p. 1409 - 1412
(2007/10/02)
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- ORGANIC SYNTHESES WITH SULFONES (PART XXVIII) ;SYNTHESIS OF TERPENOID COMPOUNDS BY WAY OF MICHAEL ADDITION REACTIONS TO CONJUGATED DIENYL SULFONES.
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Michael additions of ethanol and ketones to allyl-dienyl sulfones yielded di-allylic sulfones which were transformed into isoprenoid compounds by either Ramberg-Baecklund reaction or thermolysis.
- Julia, M.,Lave, D.,Mulhauser, M.,Ramirez-Munoz, M.,Uguen, D.
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p. 1783 - 1786
(2007/10/02)
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- SEMIHYDROGENATION OF ACETYLENES; MODIFIED LINDLAR CATALYST
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The effect of doping Lindlar catalyst with different metal salts (shown in Table 1) on selectivity, during semihydrogenation of some acetylenes to the corresponding olefins, has been studied.Lindlar catalyst modified with MnCl2 has been found to be more selective and reproducible.
- Rajaram, J.,Narula, A. P. S.,Chawla, H. P. S.,Dev, Sukh
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p. 2315 - 2322
(2007/10/02)
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- HYDROGENATION OF ACETYLENIC COMPOUNDS IN THE PRESENCE OF A COMPLEX CATALYST BASED ON NICKEL STEARATE AND TRIETHYLALUMINUM
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Hydrogenation in the presence of a catalytic system based on nickel stearate and triethylaluminum was investigated for the following acetylenic compounds: Phenylacetylene; 1-hexyne; dimethylethynylcarbinol; dimethylvinylethynylcarbinol; 3,7,11,15-tetramethyl-1-hexadecyn-3-ol.The hydrogenation rate of the triple bond decreases in the order 1-hexyne > phenylacetylene > dimethylethynylcarbinol.The selectivity of the hydrogenation of the alcohols increases with increase in the molar ratio of the components of the Al(C2H5)3/Ni(C17H35COO)2.
- Izteleuova, M. B.,Noskova, N. F.,Sokol'skii, D. V.,Gafarova, N. A.,Nadirov, N. K.
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p. 975 - 978
(2007/10/02)
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