the production of thymoquinone from thymol and carvacrol

during the oxidation process and the carvacrol was monitored in the filtrate by HPLC.
This test was performed only for Cr(salpn)-NaY and Fe(salpn)-NaY catalysts which
showed good carvacrol oxidation performance. Times vs. conversion curves with
catalyst and after filtrating catalysts were presented in Figure 7.11.
carvacrol conversion(wt. %)
1 6
1 4
1 2
1 0
8
6
4
2
0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0 4 5 0 5 0 0
t i m e ( m i n . )
C r ( s a l p n ) - N a Y
H o t f i l t r a t i o n o f C r ( s a l p n ) - N a Y
F e ( s a l p n ) - N a Y
H o t f i l t r a t i o n o f F e ( s a l p n ) - N a Y
Figure 7.11. The percentage of carvacrol conversion (reaction conditions: carvacrol/
H2O2 molar ratio=3, 0.1 g catalyst, 60 ºC, hot filtration at 30 minutes)
No further reaction was noted after the catalyst removal for the Cr(salpn)-NaY
as seen in Figure 7.11. However, when Fe(salpn)-NaY catalyst was removed from the
reaction mixture the carvacrol conversion decreased but continued. It was clear that
heterogeneity of Cr-based catalyst was better than Fe-based catalyst.
Carvacrol/hydrogen peroxide molar ratios 1 and 3 were tested for leaching test at 60 ºC
with 0.1 g catalyst. No any significant differences were observed for Cr (salpn)-NaY
catalyst and Fe (salpn)-NaY catalyst. The chromium complex when immobilized
seemed to be more stable than the iron complex in the oxidizing medium
58