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

• 2,6-Lutidine adsorbed IR was used to study the acidic properties of CrO3–ZrO2.
• The presence of CrO3 resulted in several Brønsted and Lewis acid sites on ZrO2.
• The presence of Pt enhanced the activity of CrO3–ZrO2 in cumene hydrocracking.
• The Lewis acidic center at 1570 + 1560 cm−1 was involved in the formation of H+.
• CrO3–ZrO2 and Pt/CrO3–ZrO2 were not active in n-heptane hydroisomerization.

The properties of CrO3–ZrO2 and Pt/CrO3–ZrO2 were studied by IR and ESR spectroscopy to elucidate the active sites in n-heptane isomerization and cumene cracking. Surface analyses showed the presence of cubic, monoclinic and tetragonal phases of ZrO2 with a BET specific surface area of about 150 m2/g for both catalysts. 2,6-Lutidine adsorbed IR confirmed the presence of treble doublet bands at 1675 + 1660, 1650 + 1625 and 1640 + 1630 cm−1 corresponding to Brønsted acid sites and quartet doublet bands at 1604 + 1580, 1595 + 1580, 1590 + 1580 and 1570 + 1560 cm−1 corresponding to Lewis acid sites. The presence of Pt enhanced the activity of CrO3–ZrO2 in cumene hydrocracking, in which Pt facilitated the formation of protonic acid sites at 1675 + 1660 and 1650 + 1625 cm−1 through a hydrogen spillover mechanism. The IR study verified that the Lewis acidic center at 1570 + 1560 cm−1 was involved in the formation of protons by trapping electrons. Meanwhile, neither CrO3–ZrO2 nor Pt/CrO3–ZrO2 was active in n-heptane hydroisomerization.

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