APCATA 475-2014-487

Cumene cracking over chromium oxide zirconia: Effect ofchromium(VI) oxide precursors

Two types of ZrO2supported with chromium nitrate (CN) and ammonium chromate (AC) for cumenecatalytic cracking were studied. The physical properties of the catalysts were characterized with XRD,nitrogen physisorption, IR and TGA–SDTA. The acidic properties of the catalysts were determined by 2,6-lutidine and CO adsorbed IR spectroscopy. The XRD and nitrogen physisorption analyses confirmed highertetragonal phase of ZrO2and specific surface area for Cr2O3–ZrO2(AC) showing the ammonium chromateperformed better interaction with Zr(OH)4than chromium nitrate. Besides, some of the chromium nitratedid not interact with Zr(OH)4and formed bulk crystalline Cr2O3during the calcination. 2,6-lutidine andCO adsorbed IR spectroscopies distinguished that Cr2O3–ZrO2(CN) possessed a stronger Lewis acid sites,while Cr2O3–ZrO2(AC) possessed a stronger Brønsted acid sites. In situ IR spectroscopy demonstratedthat Cr2O3–ZrO2(CN) showed better interaction with a molecular hydrogen than Cr2O3–ZrO2(AC) in thetemperature range of 263–473 K. In addition, the bulk crystalline Cr2O3interacted with a molecularhydrogen to form hydrogen bonded OH groups. At 523 K, the cumene hydrocracking indicated that theactivity of Cr2O3–ZrO2(CN) was about 1.7-fold higher than that of Cr2O3–ZrO2(AC) with the main productsof propylene and benzene. The high activity and stability of Cr2O3–ZrO2(CN) were due to the betterinteraction with hydrogen molecules which generating high number of active protonic acid sites duringthe reaction. The activity of Cr2O3–ZrO2(CN) is comparable with SO42−–ZrO2in the temperature range of323–573 K.