the production of thymoquinone from thymol and carvacrol

7.1. Catalyst Characterization
CHAPTER 7
RESULTS AND DISCUSSIONS
Prepared catalysts were characterized by Inductively Coupled Plasma (ICP),
Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform
Infrared (FTIR) Spectroscopy, pore volume, surface area measurement techniques and
thermal gravimetric analyses (TGA).
7.1.1. Elemental Analysis by Inductively Coupled Plasma Analysis
Encapsulation of Cr(III), Fe(III), Bi(III), Ni(II) and Zn(II) complexes of H2 salpn
in NaY-zeolite was performed using flexible ligand method. In the literature, this
method was described and used by several researchers (Maurya et al. 2002; Chandra et
al. 1998, Balkus et al. 1995). The ligand molecule (H2 salpn), which was flexible
enough to diffuse through the zeolite channels, reacted with the previously ion
exchanged metal ions in the zeolite supercage to obtain the encapsulated metal
complexes. The final catalysts were purified from unreacted ligand and surface
complexes by extensive soxhlet-extraction with methanol. The remaining uncomplexed
free metal ions re-exchanged from the zeolite lattice by NaCl treatment. During the
purification process catalyst samples preserved their initial color, indicating that metal
complexes were formed in the zeolite cavities and the formed complexes were too large
to diffuse out of the channels of zeolite.
The color and metal content of various catalysts, which was estimated by ICP
technique, were presented in Table 7.1. The metal ion contents determined after
encapsulation were due to the presence of metal complexes in zeolite framework. Low
percentage of metal content was in good agreement with the results reported earlier in
the literature (Maurya et al. 2002).
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