Isoamylene Trimerization in Liquid-Phase over Ion Exchange Resins and Zeolites

Liquid-phase trimerization of 2-methyl-1-butene and 2-methyl-2-butene mixtures over solid acid catalysts was carried out in a batch-stirred tank reactor in the temperature range 333−373 K. Diisoamylenes and triisoamylenes were the main products. Cracking products among C6−C9 and C11−C14 were also obtained under the assayed conditions. The catalityc performance of five different acidic ion exchange resins (Amberlyst 15, Amberlyst 35, Amberlyst 70, Purolite CT-252, Purolite CT-276) and four zeolites (H-BEA-25, H-FAU-30, H-FAU-6 and H-MOR-20) was assessed. Experimental results showed that Amberlyst 15 and H-FAU-30 were the best catalysts for isoamylene trimerization, with selectivities above 40% at 373 K. The most influencing physical properties of the catalysts on the selectivity toward dimers and trimers were acid capacity, acid strength, and specific surface area for resins, and microporous surface area for zeolites. Isoamylene trimerization extent was larger at higher temperature. The most probable mechanism of formation of these compounds involves the reaction between one molecule of dimer with one molecule of isoamylenes, although trimers could also be formed directly from three molecules of isoamylenes.