JMCA 377-2013-162

Relating cumene hydrocracking activity to the acidic center of CrO3–ZrO2

The properties of CrO3–ZrO2and Pt/CrO3–ZrO2were studied by IR and ESR spectroscopy to elucidate theactive sites in n-heptane isomerization and cumene cracking. Surface analyses showed the presence ofcubic, monoclinic and tetragonal phases of ZrO2with a BET specific surface area of about 150 m2/g forboth catalysts. 2,6-Lutidine adsorbed IR confirmed the presence of treble doublet bands at 1675 + 1660,1650 + 1625 and 1640 + 1630 cm−1corresponding to Brønsted acid sites and quartet doublet bands at1604 + 1580, 1595 + 1580, 1590 + 1580 and 1570 + 1560 cm−1corresponding to Lewis acid sites. The pres-ence of Pt enhanced the activity of CrO3–ZrO2in cumene hydrocracking, in which Pt facilitated theformation of protonic acid sites at 1675 + 1660 and 1650 + 1625 cm−1through a hydrogen spillovermechanism. The IR study verified that the Lewis acidic center at 1570 + 1560 cm−1was involved in theformation of protons by trapping electrons. Meanwhile, neither CrO3–ZrO2nor Pt/CrO3–ZrO2was activein n-heptane hydroisomerization.