the production of thymoquinone from thymol and carvacrol

leaching of Cr (salpn) complexes from the catalyst. This was also confirmed by visible
gradual change in color of the catalyst surface for every cycle. Slow leaching of metal
was observed over reuse which can limit their application and needs further
investigation.
As seen in Figure 7.13, for second recycle carvacrol conversion did not change
significantly. This can be explained by checking Figure 7.11, after hot filtration of
catalysts carvacrol conversion did not increase significantly. For first recycle of catalyst,
no leaching of Cr metal ions was observed. So, deactivation or leaching of metal ions
was observed after the second recycle.
carvacrol conversion (wt.%)
16
14
12
10
8
6
4
2
0
1 2 3 4 5 6
no of recycle
Figure 7.13. Carvacrol conversion (wt. %) vs number of recycle
As a result of all of these studies, Cr (salpn)-NaY catalyst was found to be a
more efficient catalyst than other catalysts based on catalyst activity and leaching tests.
With this catalyst, some parameters effects on carvacrol oxidation reaction were
investigated.
7.3. Effect of Parameters for Carvacrol Oxidation Reactions with
Selected Cr (Salpn)-NaY Catalyst
In order to determine the effect of various reaction parameters such as catalyst
amount, temperature, reactant/H2O2 molar ratio on the catalytic performance, oxidation
of carvacrol was carried out using Cr (salpn)-NaY catalyst. The low, intermediate and
high values were presented in Table 7.7.
60