Hydrogenation of Polybutadiene at High Pressure

The problem of low reaction rate due to poor mass transfer in the two-fluid-phase conventional hydrogenation of unsaturated polymers can be overcome by using dimethyl ether/n-pentane as a light solvent mixture as the medium to carry out the reaction. In this work, a series of polybutadiene (PB) batch hydrogenation reactions were performed at high-pressure using Wilkinson/triphenylphosphine as a homogeneous catalyst/cocatalyst. Hydrogenated PBs with 86%-100% of saturation degree were obtained by changing processing variables: overall density, temperature, stirring frequency, initial hydrogen (H-2)/double bonds ratio, global concentration of catalyst/cocatalyst, and reaction time. The variables that most affect the process are temperature, H-2 excess, stirring frequency, and reaction time. By increasing these variables, the larger the saturation degree will be. The use of Wilkinson's catalyst gives place to totally hydrogenated PB four times faster than conventional hydrogenation based on homogeneous catalysis (e.g., RhCl(PPh3)(3), RhCl(P(C6H4-m-SO3Na))(3), RhCl(PPh2(C6H4-m-SO3Na))) but giving place to some scission and cross-linking reactions.