Selective hydrogenation of 1, 3-butadiene. Effect of the operating conditions

A three-phase fixed-bed reactor for selective hydrogenation of butadiene in liquid phase with toluene as solvent is modeled using published kinetics. Thermodynamic and transport properties are estimated from models and correlations available in the literature. The model incorporates momentum and energy balances and mass transfer resistances. The results show that use of toluene increases the yield of cis-butane and trans-butane isomers by comparison with a previous study by Bressa et al. where a solvent was not included. The effects of temperature, pressure, hydrogen/butadiene ratio and toluene/feed ratio on the reactor performance are studied. A temperature rise of 37.8 K and a pressure drop of 100 kPa are predicted for a reactor 1 m in length and 0.58 m in diameter using a typical feed composition. Greater reactor lengths result in complete vaporization of the reacting mixture. This vaporization effect can be controlled by increasing the inlet pressure and toluene/feed ratio, and by decreasing the inlet temperature and hydrogen/butadiene ratio. The effect of inlet hydrogen/butadiene ratio is found to be negligible, whereas a rise in inlet temperature rise has a significant effect on the conversions and yields for the same reactor length. Finally, it was found that the yield of 1-butene increases with increasing inlet solvent/feed ratio and pressure.