the production of thymoquinone from thymol and carvacrol

ABSTRACT
In this thesis study, by using general flexible ligand method, Cr(III), Fe(III),
Bi(III), Ni(II) and Zn(II) complexes of N,N´-bis(salicylidene)propane-1,3-diamine
(H2salpn) encapsulated in NaY-zeolite were prepared. All catalyst were characterized
by Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and Scanning electron
microscopy (SEM) analyses to confirm the complex encapsulation.
Activities of all prepared catalysts for the decomposition of hydrogen peroxide
and oxidation of carvacrol were tested. Leaching test or heterogeneity test was also
performed. The performances of all catalysts were compared based on the leaching test
results and carvacrol conversion. Thymohydroquinone and benzoquinones were
observed as by-products at high conversions of carvacrol. No product was formed in the
absence of a catalyst. Fe(salpn)-NaY catalyst has shown the highest carvacrol
conversion of 27.6% with a yield of 22.0% which was followed by Cr(salpn)-NaY
catalyst with 23.5% carvacrol conversion with a yield of 17.6%. Other catalysts have
shown relatively lower performances in terms of carvacrol conversion and leaching. The
Cr(salpn)-NaY catalyst was found to be a more efficient catalyst than others based on
leaching and activity tests. Selected catalyst was extra characterized by Brunauer
Emmett and Teller (BET) and Thermal gravimetric (TGA) analyses. With selected
catalyst Cr (salpn)-NaY, temperature, catalyst amount, reactant carvacrol to hydrogen
peroxide molar ratio effects were investigated in carvacrol oxidation reactions.
Increasing the temperature from 40 to 60 ºC caused the increment of thymoquinone
yield from 6.2 to 16.0%. In addition to that the yield of thymoquinone was increased
from 7.4 to 20.7% by increasing catalyst amount from 0.05 to 0.2 g. And also
thymoquione yield was increased from 3.7 to 23.0% by decreasing carvacrol to
hydrogen peroxide molar ratio from 1 to 3. Moreover, Cr (salpn)-Y catalyst was also
tested in thymol and essential oil oxidation reactions.
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