Jm. Dominguez et al., STUDY OF PILLAR PRECURSORS [GA(III)-AL(III), LN(III)-AL(III), ZR(IV)]FOR HYDROTHERMALLY STABLE PILLARED CLAYS, Catalysis today, 43(1-2), 1998, pp. 69-77
The hydrolysis of mixed solutions of AI(III), Ga(III), Al(III), Ln(III
) and Zr(IV) was studied by potenbometric, spectrophotometric and Al-2
7- and Ga-71-NMR techniques. For the AI-Ga system formation of GaAl12(
OH)(28)(11+) species seems more probable into the pH range 4 less than
or equal to pH less than or equal to 5. Afterwards, the Al-13(OH)(32)
(7+) species predominate in agreement with thermodynamic data obtained
by SUPERQUAD program. Both tetrahedral Ga-IV and Al-IV may coexist in
solution, the interval being defined by potentiometric methods. For t
he Ln(III)-Al(III) systems Al-27-and La-139-NMR does not confirm the c
hemical interaction between the two species in solution, but the physi
cochemical properties of the La-Al/PILCS were different than Al/PILCS,
suggesting a strong interaction in the solid state. Ce(III) and Ce(IV
) ions do interact with AI(III) in solution, into the pH range 2.78<pH
<3.99, according with the spectrophotometric behavior. Finally, the Zr
(IV) hydrolysis was followed by UV in the pH range greater than 2.0, s
howing the formation of Zr-4(OH)(8)(8+) species, which was verified by
calculations using SQUAD program, but the precipitation occurs at pH>
3.0. (C) 1998 Elsevier Science B.V. All rights reserved.