Atomic layer deposition of iridium(III) acetylacetonate on alumina, silica–alumina, and silica supports

Supported iridium catalysts prepared by atomic layer deposition: effect of reduction and calcination on activity in toluene hydrogenation

“…Until now, TPD or TG analyses have not been reported for supported Ir(acac) 3 . The following results have been obtained for chromium(III) acetylacetonate, Cr(acac) 3 , a compound proposed to behave similarly to Ir(acac) 3 in ALD reactions [3], and for acetylacetonate (2,4-pentanedione), H-acac. The main thermal desorption products for silica-supported Cr(acac) 3 and alumina-supported H-acac were acetone (at 250-400°C) and CO 2 (at 300-450°C) [7,8].…”

“…M(acac) 3 ). Until now, TPD or TG analyses have not been reported for supported Ir(acac) 3 . The following results have been obtained for chromium(III) acetylacetonate, Cr(acac) 3 , a compound proposed to behave similarly to Ir(acac) 3 in ALD reactions [3], and for acetylacetonate (2,4-pentanedione), H-acac.…”

“…Acetone is formed in the reaction of M-acac x (M = Cr or Al) species with OH groups on the surface or with water released from the support upon heating. The mass loss in thermogravimetric analysis of silica-supported Cr(acac) 3 samples with a maximum at 290-310°C has been attributed to the decomposition of hydrogen bonded acac ligands in associatively adsorbed Cr(acac) 3 [7,[9][10][11]. The stability of surface Cr complexes increases when there is no hydrogen bond between acac ligands and the silica surface and when acac ligands decompose to acetate.…”

“…We have described the deposition of iridium from iridium(III) acetylacetonate, Ir(acac) 3 , on alumina, silica, and silicaalumina supports [3]. After deposition of the metal compound, the catalyst is commonly activated through removal of the ligands in treatments with hydrogen (reduction) or oxygen (calcination).…”

TPD‐MS and IR Studies of Cr(acac)3 Binding Upon CVD at Silica and Alumina Surfaces

“…[11,15,17,22,24,25] We have not succeeded in IR identification of H-bonding of Cr(acac) 3 with hydroxyl groups of silica and alumina because of the possible presence of water adsorbed from the atmosphere. Furthermore, the role of surface hydroxyls of alumina in the reaction mechanism is always difficult to assess due to the heterogeneity of its surface and the complexity of the hydroxyl-stretching region in the IR spectrum of alumina.…”