the production of thymoquinone from thymol and carvacrol
the production of thymoquinone from thymol and carvacrol
the production of thymoquinone from thymol and carvacrol
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7.1.4. FTIR Spectroscopy Analysis<br />
IR spectra <strong>of</strong> NaY zeolite <strong>and</strong> metal-exchanged zeolites showed strong zeolite<br />
lattice b<strong>and</strong>s in <strong>the</strong> range 450-1200 1/cm as shown in Figure 7.3. The strong <strong>and</strong> broad<br />
b<strong>and</strong> at <strong>the</strong> region 1000 1/cm could be attributed to <strong>the</strong> asymmetric stretching vibrations<br />
<strong>of</strong> (Si/Al)O4 units. The broad b<strong>and</strong>s at <strong>the</strong> region 1650 <strong>and</strong> 3500 1/cm were due to<br />
lattice water molecules <strong>and</strong> surface hydroxylic groups. No shift <strong>of</strong> zeolite lattice b<strong>and</strong>s<br />
was observed in <strong>the</strong> spectra <strong>of</strong> encapsulated complexes given in Figure 7.4, which<br />
fur<strong>the</strong>r implies that <strong>the</strong> zeolite framework has remained unchanged upon <strong>the</strong><br />
encapsulation <strong>of</strong> complexes.<br />
Figure 7.3. IR spectra <strong>of</strong> zeolite NaY, CrNaY, ZnNaY, FeNaY, NiNaY, BiNaY<br />
A partial list <strong>of</strong> <strong>the</strong> IR spectra results <strong>of</strong> lig<strong>and</strong> (Figure 7.5), encapsulated<br />
complexes <strong>and</strong> free complexes (Figure 7.4) were given in Table 7.2. The IR spectra <strong>of</strong><br />
lig<strong>and</strong> exhibited a broad b<strong>and</strong> between 2400-2700 1/cm region due to hydrogen bonding<br />
between phenolic hydrogen <strong>and</strong> azomethine nitrogen atoms. The multiple b<strong>and</strong>s around<br />
2900 1/cm in IR spectrum <strong>of</strong> lig<strong>and</strong> were due to <strong>the</strong> presence <strong>of</strong> -CH2- group. Absence<br />
<strong>of</strong> <strong>the</strong> b<strong>and</strong> was due to hydrogen bonding <strong>and</strong> coordination <strong>of</strong> oxygen to <strong>the</strong> metal after<br />
proton removal. In IR spectra <strong>of</strong> encapsulated complexes <strong>the</strong> zeolite b<strong>and</strong>s were<br />
dominant. Only weak b<strong>and</strong>s were observed for zeolite-encapsulated complexes due to<br />
lower complex concentration. The coordination in <strong>the</strong> pores could be identified <strong>from</strong> <strong>the</strong><br />
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