the production of thymoquinone from thymol and carvacrol

Metal ions can be isomorphously substituted in framework positions of
moleculer sieves such as zeolites, silicalites, aluminaphosphates (APOs), silica-
aluminaphosphates (SAPOs), via hydrothermal or post synthesis modification.
Amorphous mixed oxides can be prepared by grafting of metal compound on the
surface of, e.g. silica. Metal complexes can be tethered to the surface of solid, e.g. silica
with ligand. The major disadvantages of substitution, grafting and tethering is the
mobility of the metal ion. The final approach is to encapsulate transition metal
complexes in a solid inorganic matrix (ship in a bottle concept). It involves the
entrapment of complex in zeolite supercages (Arends et al. 2001). Transition metals
react with a variety of molecules or groups, called ligands to form metal complexes.
These transition metal complexes act as catalyst (Solomons 1988).
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