the production of thymoquinone from thymol and carvacrol

CHAPTER 8
CONCLUSION
NaY zeolite-encapsulated Ni (II), Zn(II), Bi(III), Fe(III) and Cr(III) complexes
of H2salpn ligand have been prepared using flexible ligand method. The characterization
results obtained by XRD, SEM and FTIR, BET, TGA confirmed the encapsulation of
metal complexes in the supercages of NaY zeolite. The all of the NaY zeolite-
encapsulated complexes were active catalysts for the decomposition of hydrogen
peroxide and for the oxidation of carvacrol.
Thymoquinone, is a compound with a commercial value considerably higher
than its precursors (thymol and carvacrol). Thymol and carvacrol found in thyme
essential oil. Thymoquinone can be easily obtained by catalytic oxidation of these
precursors using environmentally cheap oxidizing agent, hydrogen peroxide and zeolite-
encapsulated metal(salpn) complexes as heterogeneous catalysts.
Leaching tests revealed the heterogeneity of the catalysts. However, Cr(salpn)-
NaY and Fe(salpn)-NaY catalysts have shown good activity. So heterogeneity test was
performed for two catalysts. Cr(salpn)-NaY showed a good performance in terms of
activity towards carvacrol oxidation reaction and heterogeneity. With this catalyst,
catalyst amount, temperature and carvacrol to hydrogen peroxide molar ratio effects on
carvacrol oxidation reaction were investigated. All parameters were found as effective
parameters. Increasing the temperature, catalysts amount, hydrogen peroxide amount
caused the increasing the yield of thymoquinone and carvacrol conversion.
Thymol and thyme essential oil were oxidized with Cr-(salpn)-NaY catalyst.
Thymoquinone yield in carvacrol and thymol oxidation reactions were found to be very
close to each other due to the similarities in their chemical structures. After the essential
oil oxidation reaction, thymoquinone amount was increased in oil.
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