Q2. What is the effect of increasing Ti content on the structure of the template?
Ti content may obstruct the structure-directing action of the template by changing its ionic strength, hindering the formation of the tubular mesoporous structure.
Q3. What is the octahedral coordination of titanium?
According to the literature [32], the octahedral coordination may derive from conversion of tetracoordinated titanium located at the surface of the material to octahedrally coordinated titanium by reaction with H2O (g) in the atmosphere as well as to segregation of TiO2 species at the surface of the materials.
Q4. What is the widely studied member of the M41S family?
the member of the M41S family which possesses a hexagonal arrangement of uniformly sized mono-dimensional pores, has been the most widely studied.
Q5. What is the significance of secondary cavities?
The existence of such secondary cavities might have relevance for catalysis, as it would probably enhance the diffusion of reagents through the particles.
Q6. What is the effect of the use of DTMABr on the structure of the mes?
Considering that the use of DTMABr allows obtaining a better pore ordering, wehave chosen this surfactant as template in order to study the influence of other synthesis parameters on the mesostructures formed.
Q7. What is the reason for the weak regions in the samples?
Such weak regions can be attributed to the presence of cavities that permeate the entire bulk, giving rise to a secondary porosity [24].
Q8. What is the effect of increasing the XRD peak on the pores?
In addition, as the content of Ti is increased, the main XRD peak slightly shifts towards a lower diffraction angle and a slight increase in the parameter “a0” and the pores size is detected (Table 1).
Q9. What is the reason for the lower structural ordering of the sample?
Such Ti-O-Ti clustering, as result of a probably incipient polymerization of Ti species, could be contributing to the lower structural ordering and surface area observed for this sample.
Q10. Why is the importance of the inorganic materials with controlled pores growing?
The ever-growing importance of the inorganic materials with controlled poresize distribution is mainly due not barely to the deep theoretical interest on such compounds, but also to the wide number of applications in which they are used (not only in catalysis) [1].
Q11. What is the role of the Ti species in the synthesis of titanosilicates?
it becomes very crucial to control the synthesis parameters in order to obtain anatase-free titanosilicates with high structure quality, maximizing the presence of isolated framework Ti species.
Q12. What was the XRD pattern of the calcined samples?
Figure 1 presents the XRD patterns of calcined samples prepared usingDTMABr and CTMABr as templates with a Si/Ti molar ratio of 60 in the synthesis gel and 3 days of hydrothermal treatment.
Q13. What is the characterization of titanium in titanosilicates?
Although the characterization of titanium in titanosilicates by EPR is limited dueto the diamagnetic nature of the most common oxidation state of Ti (Ti+4) , this technique is a powerful tool to elucidate the local structure of catalytically active species such as the oxo-titanium radical ions.
Q14. What is the role of the Ti species in MCM-41 framework positions?
On the other hand, it is known that the Ti species in MCM-41 framework positions are the active sites for carrying out selective catalytic oxidations of hydrocarbons using peroxides as oxidants.
Q15. What was the spectra of the XPS?
EPR spectra were measured at 107, 220 and 295 K using a Bruker ESP 300 spectrometer operating at X band frequency and 9.5 GHz field modulation.
Q16. What is the spectra of the Ti-MCM-41?
Ti-MCM-41 type molecular sieves with various compositions have beensuccessfully prepared by hydrotermal synthesis at 373 K and compared to pure siliceousMCM-41.