Novel promising modified clays adsorbents were synthesized by intercalating hydroxy-Al polymer associated with poly(ethyleneoxide) in the interlayer of montmorillonite. Two different PEOs of low molecular weight (600) and high molecular weight (100,000) were used. In both cases, the resulting materials are hydrolytically stable and display a slightly better crystallinity than the materials prepared in the absence of PEO. Thermal analysis and infrared spectroscopy indicate changes in the PEO molecular conformation after intercalation revealing interactions between the polycations and the organic molecules. The chain length of the polymer has a strong influence on the surface area of the pillared materials obtained after calcination at 500°C. The use of the high molecular weight polymer leads to products with a higher specific surface area (about 400 m2/g) whereas the lower molecular weight compound does not modify significantly the surface areas. This behavior can be explained by the different nature of the species intercalated in the interlayer. PEO(600) leads to isolated organometallic species whereas PEO(100,000) seems to lead to a network of complexed polycations linked by ethylene oxide units. In the case of the PEO(100,000), high amounts of polymer in the pillaring solution provoke a partial dissolution of the octahedral layer of the clay.

Ce/Al- and La/Al-pillared smectites were prepared by cation exchange of bentonite, saponite and laponite with hydrothermally treated (130–160 °C for 16–136 h) solutions containing mixtures of aluminumchlorohydrate (ACH) and Ce3+-/and La3+-salts. After calcination at 500 °C, the pillared products are characterized by basal spacings between 24.8 and 25.7 Å and surface areas of approximately 430 m2 g−1. The products are hydrothermally stable at 500 °C after 2 h in steam. The large basal spacings are due to the formation of a large Ce/La-bearing Al-polyoxocation, whose formation is favored by initially high Al concentrations ≥3.7 M and an OH/Al molar ratio of approximately 2.5. The Ce/Al or La/Al molar ratios can be as low as 1/30. 27Al nuclear magnetic resonance (NMR) spectroscopy has shown that the polyoxocation has a higher Altetrahedral/Aloctahedral ratio than the Keggin structure Al13, which may partly explain the higher stability compared to normal Al-pillared clays. Hydroconversion of n-heptane indicated that the activity of the Pt-loaded pillared products is higher than that of a conventional Pt-loaded amorphous silica-alumina catalyst. Selectivity is strongly dependent on the type of starting clay and its acidity. In industrial hydrocracking of normal feedstock, a Ni/W-loaded Ce/Al-pillared bentonite catalyst showed rapid deactivation due to coke-formation reducing the surface area and the pore volume. Additionally, coke-formation is facilitated by the relatively high iron content of the pillared bentonite (3.43 wt% Fe2O3).

The chemical, textural and structural transformations of Al13-intercalated montmorillonite, resulting from the depolymerization of the interlamellar Al13 polycations by Na salicylate solutions, were studied. Nitrogen gas adsorption shows a dramatic decrease in specific surface area from 493 to 39 m2g–1, due to the loss of microporosity. Modelling of small-angle X-ray scattering (SAXS) curves shows that the final product contains two phases: a Na-exchanged swelling phase accounting for 40% of the clay, and a fixed interlayer distance (20.8 Å ) phase accounting for 60% of the clay. The Al remaining in the clay galleries (45% of the initial Al) is composed of 13% Al13– and 87% hexacoordinated Al, probably Al(OH)03 and oligomeric Al-salicylate complexes, as shown by 27Al NMR. The instability of Al13-intercalated montmorillonite towards organic ligands is related to the hydration shell of the tridecamer, revealed by SAXS. These results focus on the necessity to take into account the presence of organic ligands in natural media when using materials such as Al13-intercalated clays.