the production of thymoquinone from thymol and carvacrol

shared oxygen atoms with various regular arrangements, to form hundreds of different
three-dimensional crystal frameworks (Kaduk et al. 1995).
The framework structure encloses cavities containing pores of molecular
dimensions. Their frameworks are made up of 4-connected networks of atoms. One way
of thinking about this is in terms of tetrahedra, with a silicon atom in the middle and
oxygen atoms at the corners. These tetrahedra can then link together by their corners as
seen in Figure 2.1. Zeolite Y has a faujasite type framework structure, with three
different cavities or cages which are the large supercage, the sodalite cage and the
double 6-ring.
The structural formula of a zeolite for a crystallographic unit cell is:
Mx/n((AlO2)x(SiO2)y).wH2O
Where M is the cation of valance of n, w is the number of water molecules. The
ratio y/x (Si/Al ratio) usually has values of 1-5 depending upon the structure. The sum
(x+y) is total number of tetrahedral in the unit cell (Breck 1974).
Figure 2.1. Framework structure of zeolite Y
(Source: Kaduk et al. 1995)
The replacement of SiO4 tetrahedra by the (AlO4) - tetrahedral in the zeolite
framework causes excess negative charge. Cations are needed to neutralize.
Compensation of negative charge by associated cations such as; H + , Na + , K + , Ca +2 ,
5