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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Table 7.1. Metal content <strong>of</strong> encapsulated catalysts.<br />
Catalyst Metal content (wt. %) Color<br />
Cr(salpn)-NaY 1.74 Pale blue-green<br />
Fe(salpn)-NaY 1.36 Pale brown<br />
Bi(salpn)-NaY 1.04 White<br />
Ni(salpn)-NaY 0.15 Off white<br />
Zn(salpn)-NaY 0.51 Off white<br />
The prepared catalysts were fur<strong>the</strong>r characterized by using SEM, XRD <strong>and</strong> FTIR<br />
techniques to confirm <strong>the</strong> encapsulation <strong>of</strong> metal complexes inside <strong>the</strong> zeolite<br />
supercage.<br />
7.1.2. Scanning Electron Microscopy (SEM) Analysis<br />
SEM micrograph can be used to observe changes in <strong>the</strong> morphology <strong>of</strong> zeolite<br />
after encapsulation <strong>of</strong> <strong>the</strong> metal complexes. It was also possible to observe <strong>the</strong> excess<br />
complexes, if any, located on <strong>the</strong> external surface <strong>of</strong> zeolite.<br />
The SEM images <strong>of</strong> M(salpn)-NaY were similar to those observed for NaY,<br />
indicating that <strong>the</strong>y possessed <strong>the</strong> same morphology, i.e., <strong>the</strong> framework around <strong>the</strong><br />
guest molecule M(salpn) was faujasite-Y (Figure 7.1). The Si/Al ratio <strong>of</strong> <strong>the</strong> catalyst<br />
samples was 2.5±0.1, ascertained by EDS. It was observed that <strong>the</strong> Si/Al ratio (2.5±0.1)<br />
<strong>of</strong> <strong>the</strong> catalyst samples did not change comparing with <strong>the</strong> Si/Al ratio (2.5±0.1) <strong>of</strong> NaY<br />
zeolite. This result confirmed that <strong>the</strong>re was no dealumination <strong>of</strong> <strong>the</strong> zeolite during<br />
catalyst preparation. SEM micrographs <strong>of</strong> NaY <strong>and</strong> Cr(salpn)-NaY Ni(salpn)-NaY,<br />
Fe(salpn)-NaY, Zn(salpn)NaY <strong>and</strong> Bi(salpn)-NaY were shown in Figure 7.1. In <strong>the</strong><br />
SEM <strong>of</strong> catalyst samples, no surface complexes were seen <strong>and</strong> <strong>the</strong> particle boundaries<br />
on <strong>the</strong> external surface <strong>of</strong> zeolite were clearly distinguishable. These micrographs<br />
revealed <strong>the</strong> efficiency <strong>of</strong> purification with soxhlet-extraction for complete removal <strong>of</strong><br />
extraneous complexes, leading to well-defined encapsulation in <strong>the</strong> cavity only (Skrobot<br />
et al. 2003, Varkey et al. 1998, Xavier et al. 2004, Maurya et al. 2003).<br />
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