**3. The Ti-SBA-15 – titanium silicate mesoporous material, its synthesis and characteristic**

One of the newer titanium silicate catalysts is Ti-SBA-15. It is a mesoporous material, which is much more durable than Ti-MCM-41 catalyst [20, 21]. Greater durability of this catalyst is likely due to its construction – a honeycomb structure, wherein unlike Ti-MCM-41, in Ti-SBA-15 the main cylindrical channels are connected together by transverse channels which introduces additional porosity and, at the same time, strengthens the structure. Furthermore, Ti-SBA-15 is characterized by thicker pore walls, and its synthesis is carried out in the presence of a biodegradable template – Pluronic P123, as opposed to Ti-MCM-41 whose synthesis is carried out in the presence of an ammonium compound (hexadecyltrimethylammonium bromide) and is uncomfortable to the environment due to formation of amines during calcination of this catalyst [22–31]. Our studies on the epoxidation of allylic alcohols over the Ti-SBA-15 catalyst showed that this catalyst is very active in this process and these compounds can be effectively converted to epoxides [18]. This is the main reason why this catalyst has been chosen to conduct the epoxidation of AGE.

Ti-SBA-15 was obtained by the method of Berube et al. [30] and the following raw materials were used in its synthesis: Pluronic P123 (Aldrich, MW = 5800) as structure-directing agent, tetraethylortosilicalite (TEOS 98%, Aldrich) as a silicon source, and tetraisopropyl orthotita‐ nate (TiPOT >98%, Merck) as a titanium precursor. The characterization of Ti-SBA-15 was performed with the following instrumental methods: XRD (X'Pert PRO Philips diffractometer, Co Kα radiation), IR (Shimadzu FTIR-8100 spectrometer, KBr pellet technique), UV-vis (SPECORD M40 type V-530 with the attachment for solid materials measurements), X-ray microanalysis (Oxford X-ray analyzer ISIS 300), SEM (JOEL JSM-6100 instrument), and porosimetric analysis (porosimetry analyzer ASAP Micromeritics).

The XRD pattern of the obtained Ti-SBA-15 catalyst was similar to the literature data [28, 32– 33]. For the SBA-15 material are typical: one characteristic very intensive diffraction peak at 2 Theta angle of 1.01° and two weak peaks at 2 Theta angle of 1.75° and 2.05°, corresponding to the (100), (110), and (200) Bragg reflections. These reflections confirm the 2-d hexagonal symmetry (P6mm) of the SBA-15. The IR spectrum of the obtained Ti-SBA-15 was also similar to the literature data [23, 34–35]. To the main bands characterized, this kind of materials belong to: the band at 800 cm–1 which is assigned to symmetric stretching vibrations of Si-O-Si in SiO4 units the same as the band at 1, 000–1, 300 cm–1, the band at 1625-1650 cm-1 which is assigned to adsorbed water molecules, the band at 3, 000–3, 700 cm–1 which is characteristic for surface Si-OH groups and adsorbed water molecules, and the band 957 cm–1 which is associated with Ti=O or Si-O-Ti vibrations. The UV-VIS spectrum of the obtained Ti-SBA-15 catalyst showed an intense absorption band at 211 nm, associated with ligand-to-metal charge transfer from oxygen to Ti of an isolated tetrahedral Ti species. This band is direct evidence for titanium atoms incorporated into the framework of the silica [36]. In this spectrum also a shoulder with a maximum around of 290 nm was present. This band is connected with the presence of Ti atoms in fivefold and sixfold coordination. This fivefold and sixfold coordination is generated through hydration by one or two water molecules of the tetrahedral titanium ion in the first coordination sphere [36]. Moreover, in the spectra was visible a weak band at 340 nm, which is assigned to the presence of anatase in the sample. The obtained UV-VIS spectrum is similar to the literature data [32, 36].

An X-ray microanalysis showed that the amount of Ti in the sample after calcination was 2.9 wt%. According to the porosimetric analysis, the specific surface area of the obtained catalyst amounted to 620 m2 /g, the size of the pores achieved was 5.0 nm, and the pore volume was 0.6 cm3 /g. The SEM analyses showed that the Ti-SBA-15 catalyst consisted of large and long, branched, pipe-like structures with diameter of about 4 μm. These structures consisted of smaller particles with diameter of about 0.3–0.6 μm and length about 1–2 μm. This morphology is typical for structures such as SBA-15 [28, 37].

is characterized by thicker pore walls, and its synthesis is carried out in the presence of a biodegradable template – Pluronic P123, as opposed to Ti-MCM-41 whose synthesis is carried out in the presence of an ammonium compound (hexadecyltrimethylammonium bromide) and is uncomfortable to the environment due to formation of amines during calcination of this catalyst [22–31]. Our studies on the epoxidation of allylic alcohols over the Ti-SBA-15 catalyst showed that this catalyst is very active in this process and these compounds can be effectively converted to epoxides [18]. This is the main reason why this catalyst has been chosen to conduct

Ti-SBA-15 was obtained by the method of Berube et al. [30] and the following raw materials were used in its synthesis: Pluronic P123 (Aldrich, MW = 5800) as structure-directing agent, tetraethylortosilicalite (TEOS 98%, Aldrich) as a silicon source, and tetraisopropyl orthotita‐ nate (TiPOT >98%, Merck) as a titanium precursor. The characterization of Ti-SBA-15 was performed with the following instrumental methods: XRD (X'Pert PRO Philips diffractometer, Co Kα radiation), IR (Shimadzu FTIR-8100 spectrometer, KBr pellet technique), UV-vis (SPECORD M40 type V-530 with the attachment for solid materials measurements), X-ray microanalysis (Oxford X-ray analyzer ISIS 300), SEM (JOEL JSM-6100 instrument), and

The XRD pattern of the obtained Ti-SBA-15 catalyst was similar to the literature data [28, 32– 33]. For the SBA-15 material are typical: one characteristic very intensive diffraction peak at 2 Theta angle of 1.01° and two weak peaks at 2 Theta angle of 1.75° and 2.05°, corresponding to the (100), (110), and (200) Bragg reflections. These reflections confirm the 2-d hexagonal symmetry (P6mm) of the SBA-15. The IR spectrum of the obtained Ti-SBA-15 was also similar to the literature data [23, 34–35]. To the main bands characterized, this kind of materials belong to: the band at 800 cm–1 which is assigned to symmetric stretching vibrations of Si-O-Si in SiO4 units the same as the band at 1, 000–1, 300 cm–1, the band at 1625-1650 cm-1 which is assigned to adsorbed water molecules, the band at 3, 000–3, 700 cm–1 which is characteristic for surface Si-OH groups and adsorbed water molecules, and the band 957 cm–1 which is associated with Ti=O or Si-O-Ti vibrations. The UV-VIS spectrum of the obtained Ti-SBA-15 catalyst showed an intense absorption band at 211 nm, associated with ligand-to-metal charge transfer from oxygen to Ti of an isolated tetrahedral Ti species. This band is direct evidence for titanium atoms incorporated into the framework of the silica [36]. In this spectrum also a shoulder with a maximum around of 290 nm was present. This band is connected with the presence of Ti atoms in fivefold and sixfold coordination. This fivefold and sixfold coordination is generated through hydration by one or two water molecules of the tetrahedral titanium ion in the first coordination sphere [36]. Moreover, in the spectra was visible a weak band at 340 nm, which is assigned to the presence of anatase in the sample. The obtained UV-VIS spectrum is similar

An X-ray microanalysis showed that the amount of Ti in the sample after calcination was 2.9 wt%. According to the porosimetric analysis, the specific surface area of the obtained catalyst

/g. The SEM analyses showed that the Ti-SBA-15 catalyst consisted of large and long, branched, pipe-like structures with diameter of about 4 μm. These structures consisted of

/g, the size of the pores achieved was 5.0 nm, and the pore volume was 0.6

porosimetric analysis (porosimetry analyzer ASAP Micromeritics).

the epoxidation of AGE.

126 Advanced Catalytic Materials - Photocatalysis and Other Current Trends

to the literature data [32, 36].

amounted to 620 m2

cm3
