ABSTRACT
Hydrotalcites can be used for different applications due to their chemical properties and to give rise to solids with high specific surface area, good thermal stability, high dispersion and basic character. These characteristics have led to the fact that these materials have received much attention and application in areas such as the removal of contaminants and the synthesis of catalysts. This study evaluated the effect of zinc substitution by nickel on zinc-aluminum hydrotalcites, which have shown activity for the catalytic depolymerization of poly(ethylene terephthalate). The hydrotalcite type structure was observed in all materials, noting that the increase of zinc leads to higher values of a parameter of the orthorhombic cells of the hydrotalcites. The decrease of the c parameter led to a greater interaction CO32-‧ ‧ ‧ OH in the interlaminar space. Solids with higher zinc content collapsed at lower temperatures, contrary to that induced by nickel. The calcined solids contain the ZnO, NiO y g-Al2O3 phases, whose presence depends on the metals present. The results suggest the presence of large particles with high crystallinity of the ZnO phase, whereas the broad peaks of NiO suggest the existence of small particles of this phase, whose crystallinity is affected by the presence of Zn2+ and Al3+ in the cubic lattice of NiO. Materials containing two metals presented isotherms characteristic of predominantly macroporous solids. In relation to the materials with three metals, the structures are mesoporous and with high specific surface area, observing that the solid Zn0,44Ni0,22Al0,33 contains slit-shaped pores, while the solids Zn0,33Ni0,33Al0,33 and Ni0,44Zn0,22Al0,33 presented typical isotherms of materials with narrow pores in the form of capillaries.
Keywords
Hydrotalcite; Zinc; Structure Collapse; Oxides Formation
