THE EFFECT OF BUTADIENE AND REACTION CONDITIONS ON THE DIMERIZATION OF 1-BUTENE OVER NIY ZEOLITE

Oligomerization could effectively upgrade the n-butenes in Raffinate I I to more valuable octenes. In order to use this feedstock, however, o ne must consider the effects of butadiene and isobutylene on the catal yst. Experiments were conducted with industrially supplied Raffinate I I, and with pure l-butene, to study the influence of these compounds a nd reaction conditions on the activity of NiY zeolite catalyst. Result s show that isobutylene increases the activity of the catalyst, but th at butadiene strongly deactivates the catalyst even at low levels. Evi dence suggests that deactivation is caused by butadiene irreversibly c omplexing with active nickel sites, and by pore blockage. We propose t hat the oligomers blocking the zeolitic pores are formed via the Diels -Alder reaction. Catalyst deactivation is so severe that Raffinate II cannot be used with Ni catalysts unless steps are taken to remove all traces of butadiene from the feed.