HIGH-PRESSURE HYDROGENATION OF NITRILE RUBBER - THERMODYNAMICS AND KINETICS

Homogeneous catalytic hydrogenation of nitrile rubber (NBR) having various acrylonitrile contents was carried out with tris(triphenylphosphine)chlororhodium(I) under high pressure. Thermodynamic parameters of hydrogenation reaction show that the reaction is thermodynamically feasible. Optimum reaction conditions were developed by varying the reaction parameters-temperature, time, pressure, catalyst concentration, and solvent. Reaction of NBR at a catalyst concentration of 0.02 mmol, under 5.6-MPa hydrogen pressure at 373 K in chlorobenzene for 11 h, was found to be optimum for complete hydrogenation. The activation energy of the reaction was 22 kJ/mol. Carboxylated nitrile rubber and polybutadiene rubber were also used. The hydrogenated product was characterized by IR and NMR spectroscopies, iodine value, molecular weight, glass transition temperature (T(g)), and stress-strain behavior.