Isobutane dehydrogenation on zirconia-, alumina-, and zirconia/alumina-supported chromia catalysts

The performances of zirconia-, alumina-, and zirconia/alumina-supported chromia catalysts were investigated in the dehydrogenation of isobutane in order to elucidate the role of the support material in the dehydrogenation reaction. The dehydrogenation reaction was studied by activity measurements and by experiments using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and in situ Raman spectroscopy. Zirconia was deposited on alumina to clarify if it is possible to combine the beneficial properties of the industrially used chromia/alumina catalysts with those of the more active chromia/zirconia. Zirconia deposition on alumina decreased the Lewis acidity of the support and the coke formation rate during the dehydrogenation. The dehydrogenation activities of the supports were low. Deposition of chromium (1–2 atCr/nm2) increased the activity for all catalysts. The chromia/zirconia catalyst had the highest activity, whereas the use of zirconia/alumina support decreased the activity. The coke deposition rate increased with increasing dehydrogenation activity. The results suggested that the Lewis acidity alone is not important for the activity of the chromia-containing catalysts, but the phase of zirconia might have an influence.

The dehydrogenation activity of zirconia/alumina-, alumina-, and zirconia-supported chromia catalysts was compared. For the supports the deposition of zirconia decreased the acidity and the coke deposition, but had no effect on the cracking activity. Chromia/zirconia was the most active catalyst and chromia/zirconia/alumina the least. In contrast to the supports the coke deposition rate followed the activity for the chromia catalysts. Figure optionsDownload as PowerPoint slide