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

Abstract

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.

Double-bond isomerization of hexadecenes with solid acid catalysts

“…8). The importance of polar solvent swelling to AM-70 was noted previously both in alcohol condensation and oligomerization [31,45]. The extra -Cl groups change the swelling behavior of the resins to prefer more hydrophilic solvents.…”

“…5) and relative (Table 3) PS-DVBs K2620 and AM-35 have some acid sites that are close together on the same phenyl ring which provides more opportunity for the interaction of two acid sites. As the dimerization is generally considered to consist of a bimolecular rate-determining step in either a Langmuir-Hinshelwood or Eley-Rideal mechanism [5,31], such interaction would be expected to promote oligomerization, as observed here.…”

“…The narrowness suggests that the sites are more uniform in acid strength than in acidic zeolites; uniformity of acid strengths would be expected to promote reaction selectivity. Branching and oligomerization usually take place selectively at higher temperatures for these and other acid catalysts such as H-ZSM-5 and tungstated zirconia [31][32][33]. Therefore, the presence of these Brønsted sites in this particular temperature range suggests a correspondence between the location of this feature in the 1-PA TPDs and the catalysts' selectivity towards double-bond isomerization.…”

“…The crosslinking for each catalyst varied substantially (8% and 80%, respectively) from that of AM-35 (20%). For high crosslinking, the rigidity of the chains results in a more permanent microparticle structure [7,31,44] of high BET surface area (Table 2), in which there should be essentially no -SO 3 H interactions due to swelling. For low crosslinking the opposite should hold, if the catalyst is swollen.…”

“…This supposition can be deduced from the greatly decreasing rates of oligomerization in batch oligomerization reactions [31]. The TOFs in batch reactors at longer times are more than two orders of magnitude less (10 −4 -10 −3 s −1 at temperatures below 170 • C) than the initial rates [31,47,48]. Therefore it is difficult to establish quantitative relationships between site density and oligomerization rate, although a qualitative connection undoubtedly exists, as shown in Fig.…”