Linear butenes from isobutene over H-Ferrierite: In situ studies using an oscillating balance reactor

H-Ferrierite is a particularly attractive catalyst for isomerization of linear butenes to isobutene. The behavior of H-Ferrierite during isobutene isomerization into linear butenes was studied using a packed-bed configured oscillating balance reactor, in situ diffuse reflectance FTIR spectroscopy, and MS. The zeolite surface was covered with oligomeric hydrocarbons within the first few minutes on stream. The kinetically controlled regimes of the isobutene isomerization reaction and the reverse (n-butene-to-isobutene) transformation were ~ 70 K apart. The difference in apparent activation energies for the two processes (ca. 11 kcal/mole) suggested that the two reactions were likely to proceed via different kinetic pathways. A higher degree of branching in the oligomeric species formed by acid-catalyzed polymerization of isobutene, relative to those from 1-butene, caused a smaller coke precursor critical uptake to effect the site-to-pore blockage transition. The ″aging″ (hydrogen loss and condensation leading to true coke) of such branched chains was slower than that of chains resulting from a 1-butene feed. The impact of intrazeolitic oligomeric hydrocarbons on the rate of formation of coke precursors and the isobutene isomerization process was presented.