Direct synthesis of titanium-substituted mesostructured materials using non-ionic surfactants and titanocene dichloride

One-step synthesis of chromium and aluminium containing SBA-15 materialsNew phillips catalysts for ethylene polymerization

“…The incorporation of transition metals into the framework of mesostructured SBA-15 material by direct synthesis has become a very attractive subject for many researchers because the heteroatom incorporation into the silica structure is carried out in only one step and more stable and dispersed metal species are obtained [9]. So, Yue et al reported a successful direct method to prepare aluminium-containing SBA-15 with Si/Al ratios equal to 10 and 20 by a hydrothermal procedure at pH 1.5 using aluminium tri-tert-butoxide as a precursor [10]; Melero et al prepared titanium-substituted SBA-15 catalysts in one step under strong acidic conditions starting from titanocene dichloride with Si/Ti ratios in the range 13-40 [9]; Newalkar et al synthesized Ti-SBA-15 (Si/Ti = 5-40) [11] and Zr-SBA-15 (Si/Zr = 20-80) [12] mesoporous materials by means of a direct method under micro-wave-hydrothermal conditions; Wei et al developed a direct synthesis method for in situ coating SBA-15 with MgO by adding magnesium acetate salt into the initial mixture [13]; Wang et al used a sol-gel method to obtain directly Fe-SBA-15 materials (Si/Fe = 16 and 33) using Fe(NO 3 ) 3 as metal precursor and adjusting the pH to 7 with ammonia [14]; besides, a new approach to the direct synthesis of Cu-SBA-15 materials using H 3 PO 4 as acid source and Al(NO 3 ) 3 as concomitant salt has been reported [15].…”

Enhanced formaldehyde selectivity in catalytic methane oxidation by vanadia on Ti-doped SBA-15

“…It was derived that with decreasing electronegativity of support cations the catalytic activity increases. In the recent years, many reports on heteroatom substituted mesoporous silicas were published; for the integration of Ti into mesoporous silicas several concepts were developed [21][22][23][24][25]. During oxidative dehydrogenation (ODH) of propane, VO x on Ti-MCM-41 showed different redox behaviour compared to VO x on pure MCM-41.…”

“…For comparison, pure SBA-15 was synthesized as described by Zhao et al [26] and Ti-SBA-15 with 0.2 wt% Ti was prepared according to a synthesis protocol of Melero et al [21] (see Experimental section, ESI †). Vanadia species were obtained by incipient wetness impregnation of these supports with a nominal value of 2.8 wt% V metal using NH 4 VO 3 as precursor followed by calcination at 650 °C in air.…”

Designing Porous Inorganic Architectures

“…Other authors have also introduced metals into SBA-15, not by increasing the pH but by choosing an adequate metal precursor and/or by the proper control of the hydrothermal aging step. In this sense, Melero et al [97] prepared titanium-substituted SBA-15 catalysts in one step under strong acidic conditions starting from titanocene dichloride with Si/Ti ratios in the range 13-40; the same authors have used recently this methodology to incorporate Zr into SBA-15 with high accessibility [98]. The efficiency of the direct synthesis method described previously is not always enough to reach the necessary metal content and, sometimes, if high enough, only a small portion of the heteroatom loaded into the initial gel is readily accessible through the mesopores, as most of it is located inside the walls.…”