Preparation of hydrogenated nitrile-butadiene rubber (H-NBR) with controllable molecular weight with heterogeneous catalytic hydrogenation after degradation via olefin cross metathesis

Liquid hydrogenated nitrile-butadiene rubber (LH-NBR), hydrogenated nitrile-butadiene rubber (H-NBR) with number-averaged molecular weight of < 10,000, shows potential application owing to its integrated advantages. In the present work, a two-step strategy was established for the production of H-NBR with controllable molecular weight via the heterogeneous catalytic hydrogenation of commercial NBR product, after degradation via olefin cross metathesis. The effects of the olefin cross metathesis conditions (solvent, NBR concentration, reaction temperature and time, and catalyst amount) on the molecular weight of the degraded products have been investigated in detail. Then the selectively catalytic hydrogenation of the CC groups instead of the CN ones in the liquid nitrile-butadiene rubber (L-NBR) with narrow molecular weight distribution was conducted with palladium nanoparticles supported on macroporous hollow silica microspheres (Pd/MHS) catalyst, with the hydrogenation degree (HD%) > 95% for the 5th reuse.