Catalytic and acidic properties of silica-alumina prepared by chemical vapour deposition

Characterization of SiO2 Deposited by CVD on MoxOy/Al2O3 using NMR and TOF‐SIMS

“…[6] In addition, on the atomic scale, the uniformity of the deposition is uncertain and may depend to a varying extent on the type of carrier gas [9][10][11] and operating conditions. [5,12] In this work, the thickness and uniformity of SiO 2 deposited on Mo x O y /Al 2 O 3 using FBCVD has been studied using various techniques including N 2 physisorption, ICP, 29 Si NMR and TOF-SIMS.…”

“…In particular, solidstate NMR has been very useful for the characterization of silicates and aluminosilicates. [9][10][11][13][14][15][16][17] Maciel and Sindorf [14] used 29 Si NMR to investigate the structure of silica gel, and their analysis revealed the interactions between Si-OSi bonds and Si-OH bonds on the molecular level. Similar studies have been performed by Magi et al [18] for silicates, and Fyfe et al [15] for silicalites and zeolites.…”

“…Similar studies have been performed by Magi et al [18] for silicates, and Fyfe et al [15] for silicalites and zeolites. The 29 Si NMR technique has been used by other investigators, including Sato et al, [11] Sheng et al, [10] and Katada and Niwa, [9] to investigate the structure of SiO 2 deposition on Al 2 O 3 . SiO 2 deposited by CVD typically bonds strongly to Al 2 O 3 [1,[9][10][11] but the deposition may be random with multilayer formation.…”

“…[10] Cross-polarization magic angle spinning (CPMAS, a polarization transfer technique) in NMR can be used to indirectly detect the presence of hydrogen on the surface of a substance. [19] For 29 Si NMR, CPMAS enables the detection of hydroxyl groups attached to the Si atoms. Knowledge of the 29 Si chemical shifts allows the determination of the relative location of the 29 Si atoms within the structure, as well as the various atomic species bonded to those 29 Si atoms, [15,20] such as Mo in Hbeta, [17] or HZSM-5 [21] zeolites.…”

“…The resulting deposit is characterized using N 2 physisorption, inductively coupled plasma (ICP) spectrometry, 29 Si nuclear magnetic resonance (NMR) and time of flight-secondary ion mass spectrometry (TOF-SIMS). The ICP and physisorption results show that the amount deposited on the surface reaches a plateau value after 30-60 min.…”