Radial distribution model curves of electron density for aluminum oxides and hydroxides

Effect of structural defects in alumina supports on the formation and catalytic properties of the active component of reforming catalysts

“…A group of coordination peaks in the region of r = 3-3.5, 4.2-4.5, 4.85, 5.4, 5.9 Å belongs to Pt-Pt and Pt-O distances in the structure of platinum oxide PtO 2 . A peak in the region of r = 2.5 Å corresponding to the Pt-Cl bond within the PtCl 6 2-anion [29]. We assign this correlation to the Pt-Cl bond which is an expected to be interaction of the particles with the surface of the support.…”

“…Data collection covered a in the 2h angle range of 5-135°. PDF curves of the samples were calculated by a technique reported by Moroz et al [5,19,20] and then compared with the model curves for c-Al 2 O 3 presented in [6,19]. Considering the possible formation of oxide phases upon exposure of the catalysts to air, we plotted model curves for H 2 Pt(OH) 6 crystal phases and various platinum oxides using structural data from the ICSD/Retrieve database [21].…”

“…These phases may form upon contact with air of the reduced sample, which contains highly dispersed particles of metallic platinum. The H 2 Pt(OH) 6 phase corresponds to distances r = 2.15, 3.71, 4.15 and 5.17 Å (Pt-O and Pt-Pt distances in this phase). A group of coordination peaks in the region of r = 3-3.5, 4.2-4.5, 4.85, 5.4, 5.9 Å belongs to Pt-Pt and Pt-O distances in the structure of platinum oxide PtO 2 .…”

“…On the difference curve of (RH-1), the catalyst reduced at 500°C (Fig. 2), there are coordination peaks corresponding to PtO 2 and H 2 Pt(OH) 6 . These phases may form upon contact with air of the reduced sample, which contains highly dispersed particles of metallic platinum.…”

“…Structural defects typically emerge in c-Al 2 O 3 following the high-temperature calcination of aluminum hydroxide, which is the oxide precursor [4]. According to [5,6], alumina has a spinel-like structure, which is described by the more general formula, A Ã x1 A x2 ½B Ã y1 B y2 O 32Àz ðOHÞ z , where A*, B* and A, B are the nonspinel and spinel positions of cations in the oxide structure; x 1 , y 1 and x 2 , y 2 are their amounts.…”