27Al NMR, FT-IR and Ethanol-18O TPD Characterization of Fluorided Alumina

Competitive hydrogenation of poly-aromatic hydrocarbons on sulfur-resistant bimetallic Pt-Pd catalysts

“…1a and b, the density of weaker sites, represented by the desorption peaks at lower temperatures, was about the same in both supports. However, the density of strong Brønsted acid sites was much higher on the fluorinated alumina than on the standard alumina, as previously reported [23,36].…”

Surface modification of fluorinated aluminas: Application of solid state NMR spectroscopy to the study of acidity and surface structure

“…Previous studies of fluorinated aluminas have employed fluorinating agents such as NH 4 F [9,11,12,14,17,18], HF [23], F 2 [21], and CHClF 2 [10,13,22]. Our work has, however, shown that the fluorination mechanism depends strongly on the fluorinating agent employed [13].…”

“…This is particularly evident when we consider the use of NH 4 F as a fluorinating agent. Here, several reports indicate NH 4 AlF 4 phase formation [9], which obviously has no role in the fluorination mechanism when halocarbons are used. Thus, in the subsequent discussion of the mechanism of fluorination, we pay particular attention to those studies using halocarbons.…”

“…In particular, the mechanism of fluorination of the surface of aluminas is dependent in part on the fluorinating agent and conditions used [2][3][4][5][6][7][8][9][10][11][12][13][14]. This is particularly evident when we consider the use of NH 4 F as a fluorinating agent.…”

“…Fluorination can significantly modify the acid properties of oxide catalysts and, for alumina, can lead to a strengthening of the acid sites [1][2][3][4][5][6][7]. Several techniques have been employed to study the effects of the fluorination of aluminum oxide, including NMR [9][10][11][12], XANES (X-ray absorption near-edge spectroscopy) [13], IR [14][15][16][17], and X-ray diffraction [9,10,[19][20][21]. There has been considerable discussion in the literature as to the basis of the modification of both Brønsted and Lewis acidity on the surface of alumina.…”