Hydrogenation of nitrile groups in HNBR with a rhodium catalyst

Functional polymer materials show a variety of functional properties, such as chemical reactivity, photosensitivity, conductivity, catalysis, biocompatibility and so on. The polymer containing amine group can be used in many fields such as organic polymer catalyst carrier, sewage adsorption treatment, medicine and pharmacy, biological engineering, etc. We note that the amination of small nitrile groups has formed a relatively mature system, but similar reactions for macromolecular raw materials have not been reported. Based on this, the catalytic hydrogenation of nitrile groups on macromolecules was achieved for the first time, the nitrile group was successfully reduced to an amino group, and an efficient and stable hydrogenation catalytic system of HNBR was successfully developed. The reactivity of the catalytic system was studied, considering the catalyst/polymer ratio, reaction temperature, and hydrogen pressure. The optimal experimental conditions were obtained. The study successfully established a corresponding catalytic system to produce HNBR with a controlled amount of ACN. Within a reaction time of 5 hours at 60°C and 500 psig H₂, the nitrile content in HNBR systems could be reduced from 40% to less than 10%, without the formation of side products like secondary amines. This reduction process involved the conversion of nitrile groups into primary amines, and a possible mechanism for this transformation was proposed for the first time. The formation of gel during nitrile reduction was also investigated, and a potential mechanism was suggested. Various additives were tested, and it was found that some of them effectively slowed down or prevented gel formation. Among these additives, triphenylphosphine (TPP) was identified as the most effective one.