Selective Isomerization of p-Diisopropylbenzene to m-Diisopropylbenzene Over Metal Modified Hβ Zeolites
Mahesh S. Edake and Shriniwas D. Samant
Affiliation: Organic Chemistry Research Laboratory, Department of Chemistry, Institute of Chemical Technology, N.M. Parekh Road, Matunga, Mumbai 400 019, India.
Keywords: Diisopropylbenzene, heterogeneous catalysis, isomerization, metal modified zeolite Hβ, rearrangement of dialkylbenzenes.
Isomerization of p-diisopropylbenzene (p-DIPB) to m-diisopropylbenzene (m-DIPB) was carried out using
metal modified Hβ zeolites at high temperature and in the absence of a solvent. The metal cations used for the modification
of Hβ were typical Lewis acidic cations Fe3+, Al3+, Ti4+, Sn4+ and Sb3+. The modified zeolite catalysts were heated at
120oC, and calcined at 280oC, and 550oC. They were characterized by XRD, FE-SEM, HR-TEM, FT-IR, N2-desorption
(BET), NH3-TPD, Pyridine-IR and TGA techniques for structural, morphological, acidity and stability investigation. Particle
size of the crystallites was determined by HR-TEM analysis and the size was in the range of 15-35 nm. At 250oC, Al-
Hβ, Fe-Hβ and Ti-Hβ showed 68-75% conversion of p-DIPB and 42-54% selectivity towards m-DIPB. The calcination
temperature had no effect on the activity. Isomerization increases with increased acidity. Thus, metal modified Hβ catalysts
are excellent, efficient, and alternative heterogeneous catalysts for the isomerization of p-diisopropylbenzene (p-
DIPB) to m-diisopropylbenzene (m-DIPB). This process is a greener alternative for the classical AlCl3 process as discussed
in the article along with the relevant patents.
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