THE OLIGOMERIZATION OF BUTENES WITH PARTIALLY ALKALI EXCHANGED NINAY ZEOLITE CATALYSTS

A number of catalysts were prepared by exchanging NaY zeolite with var ious amounts of nickel (NiNaY) as well as partially exchanging NaY zeo lite with alkali and alkaline-earth cations (M) followed by nickel pro motion (NiMNaY). These catalysts were used to oligomerize butenes in t he liquid phase. For the NiMNaY catalysts prepared from similar concen trations of nickel chloride, the nickel loading decreased with increas e in the cationic size of M. The acidity of catalysts was measured usi ng temperature programmed desorption of ammonia. The NiNaY catalysts s howed an increase in acid concentration with nickel loading. For the N iMNaY catalysts, a linear correlation between the acid concentration a nd the Sanderson electronegativity of M was found. The oligomerization activity of NiNaY and NiMNaY catalysts increased with nickel loading and acidity. It was observed that the increase in activity also led to an increase in the deactivation rate. This is attributed to the incre ased adsorption of olefins on the more acidic catalysts leading to the formation of long chain oligomers that foul the catalysts. For the ca talysts with similar activities, the dimer selectivity was found to in crease with cationic size of M, but decreased with increase in Sanders on's electronegativity of M. This improvement in catalyst stability im parted by M is probably due to the partial blocking of windows for the hexagonal prisms and/or sodalite cages of the nickel exchanged cataly sts. The NiCsNaY catalyst was found to be an almost exclusive dimer se lective catalyst and has the lowest deactivation rate.