Interaction of La3+- and Ce3+-exchanged hectorites with oligomeric hydroxy-Al cations results in the formation of cross-linked hectorites possessing moderately high surface areas (~ 220–280 m2/g) and high thermal stability. The basal spacings of these products were generally in the range 17.0–18.0 A, the exact d(001) value depending on the age of the hydroxy-Al oligomeric solution and on the pH of the starting hectorite dispersion. Interaction of Li- or Ce-fluorhectorite with hydroxy-Al oligocations produced the corresponding cross-linked fluorhectorites, which showed markedly higher basal spacings (18.2–20.0 Å for air-dried samples), surface areas (~300–380 m2/g), and thermal stability, as compared with those of the cross-linked hectorites. The cross-linking agent applied in the synthesis of the hydroxy-Al hectorite and fluorhectorite products consisted of a solution of hydroxy-Al oligomers aged for periods of 7 to 27 days. A constant ratio of 2.0 mmole Al/g of smectite was used in all preparations. The high basal spacings and porosity of the newly synthesized products are consistent with a structure similar to that previously proposed for cross-linked hydroxy-Al montmorillonite.

Pillared bentonites were found to be efficient catalysts for the O-methyl bond cleavage of anisoles (e.g., m-methylanisole, guaiacol, and creosol) under very mild, static conditions (150°C, a few hours, inert atmosphere). The O-methyl bond cleavage led to phenolic products. Gas chromatographymass spectrometry and solid-state 13C nuclear magnetic resonance (NMR) techniques used to probe 13C-labeled anisoles revealed that dealkylation and transalkylation reactions occurred to a large extent, and that conversion was efficient at >95% after two days. Ortho- and para-isomers were observed exclusively, without any evidence of meta-substitution. Volatile products were determined by mass spectrometry to be 13CH3OH and (13CH3)2O. Magic-angle spinning 13C NMR experiments showed that the molecules were fairly mobile in the clay micropores prior to catalysis. After catalysis, cross-polarization NMR showed that molecular motion had decreased markedly. Ultraviolet-visible spectroscopy of the colored complexes suggested some quinone formation. The trend of clay reactivity was found to be: pillared bentonite ≫ acid-washed montmorillonite > untreated bentonite > pillared fluorhectorite ≃ untreated fluorhectorite.

Fourier-transform infrared (FTIR) spectroscopic studies were carried out on 1,6-hexanediamine hydrochloride (HDA)-treated synthetic fluorhectorite to determine the orientation of functional groups within the structure. Oriented crystal layers were prepared by flocculating the smectite slurry with glass fibers to obtain a 100-µm-thick paper. Orientations were determined by measuring integrated IR band intensities at various incident beam angles (≤60°), inasmuch as absorption occurred only if the oscillating dipole of the functional group interacted with the electric vector of the incident radiation. The H-N-H plane in amine groups was aligned parallel to the lamellar plane. The H-O-H plane of the small amount of sorbed water was inclined 45° or more to the interlamellar layer, and the OH groups were inclined 45° to this layer.

Even with the incorporation of HDA in the interlamellar structure, at high humidity, additional water sorbed. The sorbed water competed with and displaced amine groups from the surface, resulting in randomly oriented amine groups. Many of the amine groups were ionized, whereas the additional sorbed water showed little orientation.

This study demonstrated that the orientation of intercalated amines in fluorhectorite can be determined by following the intensity changes in infrared-active bands as a function of the incident beam angle. With intercalated HDA, the orientations were influenced by the presence of interlayer water.

Solutions containing hydroxy-SiAl (HSA) oligocations were prepared by two procedures: (1) treatment of a mixture of orthosilicic acid and AlCl3 with aqueous NaOH, followed by aging of the product; and (2) preliminary preparation and aging of hydroxy-Al13 oligocations followed by reaction of the latter with orthosilicic acid. Ion exchange of Na,Ca-montmorillonite with HSA oligocations yielded pillared, cross-linked montmorillonites (designated as HSA-CLM) showing a maximum d(001) value of 19.5 Å for air-dried samples, and maximum surface areas of ~500 m2/g after outgassing at 250°C/10−3 torr. Corresponding ion exchange of Li-fluorhectorite yielded HSA fluorhectorites (HSA-CLFH) showing a maximum d(001) value of 19.0 Å and a surface area of 355 m2/g. Calculated structural formulae for the HSA-CLM and HSA-CLFH products, based on elemental analysis, showed a gradual increase in the Si/Al ratio in the intercalated HSA oligocations with increasing Si/Al ratio in the pillaring solution. Optimum d(001) values and surface areas of HSA-CLM and HSA-CLFH products were obtained using method 2 and applying a ratio of 1.6–2.5 mmole (Si)Al/g smectite.

The thermal stabilities of HSA-CLM and HSA-CLFH products were determined by heat treatment between 250° and 700°C and subsequent measurement of the d(001) values and surface areas. HSA-CLFH products showed the unusual behavior of increase of d(001) with increase in temperature from 400° to 500°C, and essential constancy of d(001) from 500° to 600°C. The HSA-CLM products showed a gradual decrease in surface area, whereas the HSA-CLFH products prepared with a Si/Al ratio of 1.04–2.18 in the pillaring solution showed constant surface areas with increasing temperature from 250° to 600°C. HSA-CLM and HSA-CLFH show sharply higher acidities compared with those of reference Al-CLM and Al-CLFH samples obtained by pillaring with hydroxy-Al13 oligocations. This increased acidity is probably due to the presence of acidic, surface silanol groups in the HSA oligocations.