02412nas a2200217   4500008004100000022001400041245009800055210006900153260007300222300001200295490000800307520162800315653001801943653002201961653001401983653001201997653002202009100001802031700002002049856012502069       2008                        eng d  a1387-181100aThermal stability of mesoporous SBA-15 and Sn-SBA-15 molecular sieves: an in situ HTXRD study0 aThermal stability of mesoporous SBA15 and SnSBA15 molecular siev  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcSEP  a270-2800 v1143 a<p>Highly ordered SBA-15 and Sn-SBA-15 mesoporous molecular sieves with Si/Sn = 80, 60, 40 and 10 have been prepared through direct synthesis route under milder acidic conditions, which were used for the in situ high temperature X-ray diffraction (HTXRD) studies in the temperature range 298-1573 K for the first time in the literature. SBA-15 is found to be thermally stable up to 1473 K and appearance of alpha-cristobalite was observed at 1573 K also supported by the thermogravimetric (TG) data. A strong negative thermal expansion was observed on heating from 298 to 1573 K (alpha(a) = -4.3 x 10(-6) K-1). Sit containing samples (Si/Sn = 80 and 60) showed a positive thermal expansion (6.75 x 10(-6) K-1 and 9.04 x 10(-6) K-1, respectively). On the other hand, the samples with Si/Sn = 40 and 10 showed a strong negative thermal expansion (-4.12 x 10(-6) K-1 and -7.56 x 10(-6) K-1) similar to SBA-15. The linear thermal expansion coefficient varied in the order: Si/Sn = 60 &gt; 80 &gt; 40 &gt; 0 &gt; 10. Sn4+ ions exhibit both tetrahedral and octahedral coordination depending upon the location of these ions either on the walls of the silica (Si/Sn = 80 and 60) or in the corona region of the structure (Si/Sn = 40 and 10), respectively. The thermal decomposition of the samples (TG data) is correlated to the thermal expansion behavior (HTXRD data). The decomposition behavior of template ions located within the pores is strongly influenced by the presence of Sn in the framework and a `soft' interaction probably exists between the template ions and the Sn sites. (C) 2008 Elsevier Inc. All rights reserved.</p>10aHTXRD studies10aphase transitions10aSn-SBA-1510aTG data10aThermal expansion1 aShah, Pallavi1 aRamaswamy, Veda  uhttps://library.ncl.res.in/content/thermal-stability-mesoporous-sba-15-and-sn-sba-15-molecular-sieves-situ-htxrd-study-0