Catalytic hydrogenation of styrene-g-natural rubber (ST-g-NR) in the presence of OsHCl(CO)(O2)(PCy3)2

OsHCl(CO)(O₂)(PCy₃)₂, was used as a catalyst for hydrogenation of styrene-g-natural rubber copolymer (ST-g-NR). Univariate experiments were conducted to explore the effect of variables on the rate of hydrogenation by measuring the hydrogen consumption as a function of time using a gas-uptake apparatus. From the kinetic results, the hydrogenation of ST-g-NR was observed to exhibit a first-order dependence on CC]. The rate of hydrogenation showed a first-order dependence on the catalyst concentration and a first-order shift to zero-order dependence on hydrogen pressure with increasing hydrogen pressure. The rate of hydrogenation was also found to decrease with an increase in rubber concentration. The addition of a small amount of acid provided a beneficial effect on the hydrogenation rate of the grafted natural rubber. The hydrogenation rate of ST-g-NR was dependent on the reaction temperature and the apparent activation energy over the range of 120-160 °C was found to be 83.3 kJ/mol.