Kinetic evidence for two different active sites on dry Amberlyst® 15 catalyst in the alkylation between 1-dodecene and p-xylene

Not all acid sites are created equal: Alkene isomerization and dimerization occur on separate sites on Amberlyst®15 catalyst

“…Scheme 1 shows a simple model for heterogeneous isomerization of 1‐alkene to 2‐alkene. [ 2,3 ] Adsorption and desorption are assumed to be rapid. This model is appropriate for short reaction times, before much 2‐alkene has isomerized to 3‐alkene, etc.…”

“…For example, direct esterification of linear 1‐alkenes on Amberlyst®15 catalyst appears to occur via rapidly isomerizing carbenium ion intermediates adsorbed onto the esterification sites, [ 3 ] and reaction between linear 1‐alkenes and p ‐xylene on Amberlyst®15 catalyst appears to occur via rapidly isomerizing π‐complexes. [ 2 ] Both these reactions yield product mixtures with much more structural diversity than a simple reaction of one alkene would produce. Rapidly isomerizing carbenium ions are likely involved in alkene dimerization on Amberlyst®15 catalyst, just as they are involved in direct esterification of alkenes.…”

“…Kinetic investigations have shown that two different types of acidic sites likely exist on the surface of dry Amberlyst®15 catalyst. [ 1–3 ] For example, during addition of p ‐xylene to 1‐dodecene to make dodecyl p ‐xylenes, double bond isomerization of 1‐dodecene appears to occur on a site that is different than the site where the addition reaction occurs. [ 2 ] Similarly, for addition of heptanoic or nonanoic acid to 1‐tetradecene to make secondary esters, the esterification reaction occurs on a different site than the double bond isomerization.…”