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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7.3.2. Effect <strong>of</strong> Temperature<br />
Four different temperatures (25, 40, 50, 60 ºC) were used while keeping o<strong>the</strong>r<br />
parameters fixed (i.e. catalyst weight, <strong>carvacrol</strong> / (%30) H2O2 (molar ratio)). The results<br />
were presented in Table 7.8. At 60 ºC reaction temperature, high conversion (19.2 %)<br />
was observed. At low temperature value 25 ºC, no <strong>carvacrol</strong> conversion was observed.<br />
With <strong>the</strong> same catalyst, in phenol oxidation reactions at least 50 ºC was required<br />
temperature to obtain a conversion (Maurya et al. 2002, Maurya et al. 2003). At 50, 60<br />
ºC, 16, 15% TQ was observed with small amount <strong>of</strong> THQ <strong>and</strong> BQ derivatives. At low<br />
temperatures reactions were more selective for TQ formation compared to high<br />
temperatures. However, in <strong>the</strong>se reactions conversions were low (i.e. 6.2%).<br />
7.3.3. Effect <strong>of</strong> <strong>carvacrol</strong>/(%30) H2O2 (molar ratio)<br />
The effect <strong>of</strong> hydrogen peroxide concentration on percentage <strong>carvacrol</strong><br />
conversion as a function <strong>of</strong> reaction time has been also studied. The <strong>carvacrol</strong> / (%30)<br />
H2O2 (molar ratio) used were 1, 2, 3 while <strong>the</strong> amount <strong>of</strong> <strong>carvacrol</strong> was kept constant<br />
with o<strong>the</strong>r parameters. The percentage <strong>of</strong> <strong>carvacrol</strong> conversion has been found to<br />
increase with <strong>the</strong> decreasing <strong>carvacrol</strong>/(%30) H2O2 (molar ratio) in o<strong>the</strong>r words<br />
increasing H2O2 amount (Table 7.8). However by increasing <strong>the</strong> H2O2 amount <strong>the</strong><br />
system was attained a steady state after a certain time. This result showed good<br />
agreement with previously reported hydrogen peroxide effect on oxidation reactions<br />
(Maurya et al. 2002). When conversion increased by decreasing <strong>carvacrol</strong> / (%30) H2O2<br />
(molar ratio) in o<strong>the</strong>r words increasing H2O2 amount; higher TQ (23%) amount was<br />
observed with small amount <strong>of</strong> THQ <strong>and</strong> BQ derivatives. For lower conversions,<br />
reactions were more selective for TQ formation compared to higher conversions.<br />
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