MS-1-P-1461 EFFECT OF SYNTHESIS PARAMETERS ON THE MESOPOROUS STRUCTURE OF SBA-15 AND SBA-16

SBA-15 and SBA-16 exhibiting arrangements of mesopores, have received particular attention for applications involving selective host-guest interactions or diffusion of large molecules.
SBA-15, prepared with the triblock copolymer PEO20PPO70PEO20 (Pluronic P123), consists of a mono-dimensional channel system distributed in a two-dimensional hexagonal structure. SBA-16 consists of two non-interpenetrating three dimensional
channel systems with spherical mesoporous cage-like cavities connected through windows.
A good understanding of how the synthesis conditions of these materials affect the meso- and macro-structure characteristics is important for their applications, since it allows to control  their properties.
In the present work the effect of variation of different synthesis conditions in the structure of both materials have been systematically investigated.
The synthesis was carried out in acidic medium from the triblock copolymers surfactants Pluronic F127 (EO106PO70EO106) and Pluronic P123 (PEO20PPO70PEO20) to obtain SBA16 and SBA 15, respectively  and TEOS was used as silica source. The synthesis parameters studied were temperature (70 to 110 ̊C), time (24 to 72 hours) and agitation. 
The synthesis carried out using Pluronic 123, resulted in an increase in pore diameter with temperature and time, from 5.6 nm at 70C, 24h to 8.3 nm at 110C, 72h and therefore  a decreases in mesoporous area and increase in  pore volume. It was observed that the microporosity was lost at high temperatures, and the mesoporous wall thickness decreases.
On the other hand, the synthesis carried out with Pluronic 127 showed a very small variation in  pore size with temperature and time. However, the mesoporous area increased, and the microporosity decreased with temperature showing some disorder on mesoporous arrangement at 100C, as it is observed by HRTEM.
Fig 1 shows HRTEM images of mesoporous materials SBA 15 synthesized at 90 °C, 48h and Fig 2 and 3 SBA 16 synthesized for 48h at 90 and 110 C, respectively, showing the disorder structure obtained at high temperatures.