the production of thymoquinone from thymol and carvacrol

stoichiometric and structural integrity of the salens is preserved on encapsulation in the
zeolites.
4.2. Ligand Synthesis (LS) Method
In this method, ligand is synthesized inside the pores of zeolite. The synthesized
complex becomes too large and rigid to escape out of the cages. This method is used in
which the ligand itself is constructed inside the zeolite matrix. A metal exchanged
zeolite is evacuated to a pressure of 10 -5 torr. The molecules that constitute the ligand
species (ligand precursors) are then adsorbed into the zeolite matrix in an inert
atmosphere. The molecules form the ligands of interest and then make complexes with
the metals, which present in the zeolite. The excess ligand precursors, the ligand present
on the external surface and the complex present on the external surface are removed by
soxhlet extraction (Nakagaki et al. 2000, Armengol et al. 1999).
Metal complexes which were prepared by ligand synthesis method were used for
some oxidation reactions such as hydrocarbon and cyclohexane oxidation as shown in
Table 4.1.
For hydrocarbon oxidation reactions, synthesis of, metalloporphyrins of Fe(III)
and Cu(II) (zeolite-encapsulated metalloporphyrins) were prepared inside the large
pores of the zeolite NaY (Nakagaki et al. 2000). For oxidation of cyclohexane, a series
of Cu +2 -phthalocyanine and Co +2 -perfluorophthalocyanine has been prepared inside the
pores of MCM-41 (MPcMCM-41) by ligand synthesis method. MCM-41 and zeolite Y
was tested for oxidation of cyclohexane.
The void dimension of the porous host can play an important role in the catalytic
activity and selectivity of MPc as oxidation catalysts because of differences between the
planar and distorted conformation of the encaged MPc. The highest activity and
selectivity of the CuPc complex is observed when incorporated inside Y zeolite
according to MCM-41 for cyclohexane oxidation reaction (Armengol et al. 1999).
4.3. Zeolite Synthesis (ZS) Method
In the zeolite synthesis method, transition metal complexes, which are stable
under the conditions of zeolite synthesis (high pH and elevated temperature etc.), are
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