8/10/2019 kel7

1/8

J. Phys. Chem.

1990,

94, 165-112 765

high Si/AI ratio^.^^,^^

In

our case, this observation could indicate

that , a t the first stages of

P,

zeolite formation, the Si and

AI

availabilities are similar, as a consequence of the dissolution of

phases with Si/AI = ratio, but late r the increase of Si polym-

erized species in th e solution favors the incorporation of a higher

am oun t of silicon in this zeolite. However, durin g the synthesis

of P, zeolite from

980

O heated kaolinite, the fast increase of

Si

polymerized species in the liquid phase ensures that the P, eolite

formed is more siliceous and homogeneous than those obtained

in the previous cases. Th e observed differences show the im-

portance that the control of the degree of polymerization of silica

has during the synthesis of a given zeolite.

Conclusions

NM R study (27Aland

%i

signals) of t he solid and liquid phases

corresponding to the alkali treatm ent of kaolinites heated pre-

viously at different temperatures (400