Abstract
The study aimed to assess how the crystallization and ageing times in SBA-15 synthesis influence the reproducibility and particle size of mesoporous molecular sieves. X-ray diffraction showed that higher crystallization times provide greater reproducibility of mesoporous silica, due to the fact that there is no significant variation in the width and intensity of peaks, while the same is not true for shorter crystallization times. Ageing time does not seem to exercise a significant influence when higher crystallization times are used in the synthesis. Scanning electron microscopy observations revealed that shorter crystallization times led to larger crystals in addition to the formation of large agglomerates, whereas with higher crystallization times the trend is to obtain smaller and more uniform grains. It is proposed that hydrogen bonds may be responsible for the formation of smaller particles and it is also established that depending on the synthesis conditions the reproducibility of the process can become low. Keywords: reproducibility, SBA-15, crystallization time, ageing time.
Highlights
The mesoporous molecular sieve SBA-15 was synthesized for the first time using an organic surfactant of type Pluronic 123, a triblock copolymer of ethylene oxide (EO) and propylene oxide (PO) with the general formula EO20PO70EO20 [1]
The synthesis of molecular sieve SBA-15 was confirmed through the X-ray diffractograms shown in Figure 1, which are similar to those obtained in the literature
Samples prepared in a 3 h crystallization interval showed three well-defined peaks indexed to the planes (100), (110), and (200), which are indicative of the hexagonal symmetry of SBA-15
Summary
The mesoporous molecular sieve SBA-15 was synthesized for the first time using an organic surfactant of type Pluronic 123, a triblock copolymer of ethylene oxide (EO) and propylene oxide (PO) with the general formula EO20PO70EO20 [1]. Using block copolymers instead of low-molecular-weight surfactants, as generally occurs in MCM-41, has the advantage of giving more stable materials, as the silica walls are thicker and the pore diameters larger [2]
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