Hydrogenation of alkenes catalyzed by supported Ziegler catalysts

Svoboda, P.; Hetflejš, J.; Schulz, Wolfgang; Pracejus, H.

doi:10.1007/bf02063447

Cited by 4 publications

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…refs. 22–25) led us to test these systems in the above reaction with the following aims: (1) to compare quantitatively the catalytic efficiency of different Ni catalysts; (2) to evaluate the effect of solvents and type of polymer OH end groups on the rate of hydrogenation; (3) to determine kinetics and activation parameters of the reaction; (4) to evaluate changes in the microstructure and OH functionality of the polybutadienes; and finally (5) to find conditions under which the hydrogenation affords the saturated polymers with retained OH functionality and minimum residual CC unsaturation. …”

Section: Introductionmentioning

confidence: 99%

Hydrogenation of low molar mass OH‐telechelic polybutadienes catalyzed by homogeneous Ziegler nickel catalysts

Šabata

Hetflejš

2002

J of Applied Polymer Sci

View full text Add to dashboard Cite

Two types of low molar mass, medium vinylic polybutadienes containing 2-hydroxypropyl and 2-hydroxyethyl end groups were hydrogenated in the presence of several homogeneous Ziegler Ni catalysts prepared by using Ni(acac) 2 and Ni(2-ethylhexanoate) 2 as metal precursors and BuLi, Li adduct to a diene and Et 3 Al as activators. The catalytic efficiency of these systems determined by rate measurements showed that the best results can be achieved with the Ni(2-hexanoate) 2 ϩ Li-diene (Ni : Li mol ratio ϭ l : 8 -10) catalyst in the solvents commonly used in the synthesis of these polyalkadienes by anionic polymerization of 1,3-butadiene. As found by the kinetic study, the hydrogenation carried out under mild reaction conditions (temperatures of 10 -35°C, hydrogen pressure of 72-178 kPa, Ni concentration of 2.1-10.0 mmol/dm Ϫ3 ) was the first order in the OH-polybutadiene and hydrogen and, over narrow range of catalyst concentrations (4.3-10.0 mmol Ni/dm Ϫ3 ), also in the catalyst. The activation energy of the hydrogenation estimated from the Arrhenius plot was 42 kJ/mol. Changes in the relative proportion of 1,2-, cis-1,4-, and trans-1,4-CAC units of the polymer during hydrogenation indicate the selectivity of the catalyst to the 1,2-hydrogenation. The ease of the addition of hydrogen to the internal CAC unsaturation was found to be opposite to that usually observed (trans Ͼ cis). The present low-pressure hydrogenation of both types of telechelic OH-polybutadienes proceeds with full retention of the average OH functionality and affords the saturated polymers, the residual CAC unsaturation of which (Ͻ1%) has so far been usually achieved by high-pressure hydrogenations.

show abstract