Hydrogenation of diene elastomers using palladium catalyst supported on carbon fiber

Abstract

Hydrogenation is one chemical modification methods to enhance the resistance of oxidative and thermal degradation of diene elastomers by reducing the amount of unsaturation in their structures. The purpose of this present work was to investigate the possibility to use palladium supported on carbon fiber (Pd/CF) as a catalyst for hydrogenation of diene elastomers such as butadiene rubber (BR), nitrile butadiene rubber (NBR) and natural rubber (NR). The effect of reaction parameters such as temperature, hydrogen pressure, rubber concentration and catalyst concentration on the level of hydrogenation of diene elastomers were studied. The palladium catalysts were characterized using X-ray diffractometer (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Degree of hydrogenation was calculated using proton nuclear magnetic resonance spectroscopy ([superscript 1] H-NMR). The kinetic results indicated that the hydrogenation of BR catalyzed by Pd/CF exhibited a first-order behavior. The apparent activation energy for BR hydrogenation catalyzed by Pd/CF was 4.83 kJ/mol. The experimental results indicated that the palladium (5.3% wt) supported onto the carbon fiber could promote the hydrogenation of BR, NBR and NR to achieve 70.4, 46.4 and 35.3% hydrogenation, respectively. For NR hydrogenation, it was found that two structures of rubber product were formed as the result of competitive reactions: hydrogenation and cis-trans isomerization.