SELECTIVE HYDROGENATION OF 1?BUTENE RICH CUTS: THE IMPACT OF INTRAPARTICLE DIFFUSION LIMATATIONS ON THE SELECTIVITY

S. P. BRESSA; J. A. ALVES; O. M. MARTINEZ; G. F.BARRETO

Simposio; 17 th INTERNATIONAL SYMPOSIUM ON CHEMICAL REACTION ENGINEERING, AGOSTO 2002, HONG KONG-CHINA. ISCRE17; 2002

In the production of polimerization-grade 1-butene from C4 olefin rich cuts, an attempt is made to promote the hydrogenation of 1-butyne and 1,3-butadiene present in the cut with the minimum loss of 1-butene. To this end, low-loaded Pd based catalysts of the eggshell type are used in industrial reactors. Despite the very thin active layer and low content of Pd, outstanding concentration gradients were experimentally proved. Thus, although Pd is the most selective agent, internal diffusion limitations severely impair the observed selectivity. In this paper, we evaluate the impact of intraparticle diffusion limitations on the selectivity of an industrial unit of selective hydrogenation. To perform this task we used a simple model of a trickle bed reactor. Operating conditions of an actual process were chosen. We adopted a kinetic model that parameters, which correspond to a commercial catalyst, were calculated from experiments done in conditions such as those of industrial operation. The complex diffusion-reaction phenomena occurring inside catalyst pellets placed at different depths of the reactor are comprehensively described. 1-Butene losses in the range 20?30%, which are usuall in commercial plants, were predicted. Some alternatives to enhance the selectivity are envisaged.