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The homogeneous catalytic hydrogenation of nitrile-butadiene rubber (NBR) has been extensively studied during the past three decades. Many transition metal complexes, generally containing a group VIII transition metal, were used as homogeneous catalysts for this process.  Particularly for the hydrogenation of olefins, the Wilkinson catalyst, RhCl (PPh₃)₃, was the most popular catalyst employed for this process. Due to the fact that it is a highly active catalyst ability of providing an excellent hydrogenation degree and without reduction of nitrile group. But separating catalyst from substrates has being the major obstacles in the industrialization.

Recently, a new concept, metal-organic complexes catalysis, which can hydrogenate in organic phase at higher temperature, has been proposed. Especially the metal-organic complex can be separated from substrates by adding water at lower temperature. This catalyst was named themoregulated phase transfer catalyst. This kind of catalyst has been successfully applied to hydroformylation of olefins. However few papers mentioned about hydrogenation for unsaturated polymer.

In this study, a new complex RhCl[PPh[(OCH₂CH₂)_5≤n≤6CH₃]₂]₃ (Rh/AEOPP) with thermoregulated phase transfer property was synthesized with a good yield, which was further used as catalyst to selectively hydrogenated Nitrile-Butadiene Rubber (NBR). This is the first time that Rh/AEOPP complex was synthesized and applied in NBR hydrogenation. The result shows that hydrogenation degree of product (HNBR) can be extended to 90%, when the condition is [Cat] = 3% (based the weight of NBR), L₂ : Cat (Weight Ratio) = 2, [NBR] = 5% (based on the weight of xylene solution), P (H₂) = 1.5MPa, T = 155°C, t = 8 hrs. Also, by adjusting temperature the catalyst could be easily separated from products with 89% catalyst complex recovery. In addition, ¹H-NMR and Infrared (IR) spectra showed that C=C double bonds in NBR was successfully hydrogenated without causing reduction of the CN group.

Keywords: Hydrogenation; Nitrile-Butadiene rubber; Thermal properties; Metal-organic catalysts