Selective hydrogenation of 1,3-butadiene: Improvement of selectivity by using additives

Abstract

The objective of this work is to evaluate the behavior of isoprene as an additive to improve selectivity in the selective hydrogenation of 1,3-butadiene from 1-butene-rich cuts. To this end, the liquid-phase hydrogenation of 1,3-butadiene, 1-butene and isoprene on a commercial Pd/Al2O3 catalyst of the eggshell type at 313 K was studied in a batch system. It was found that the adsorption strength of isoprene is between those of 1,3-butadiene and 1-butene. Thus, in the presence of isoprene, 1-butene concentration remains practically constant even when the liquid is almost depleted from 1,3-butadiene. The improvement of the selectivity of an industrial reactor for 1-butene purification by adding isoprene was evaluated. To this end, a kinetic model was fitted to the experimental results and a simplified model of an industrial unit was adopted. It was found that adding 1% of isoprene can reduce 1-butene losses by a factor between 1.3 and 10 for H2 partial pressures ranging 100-500 kPa, respectively.