Pillar interlayered clay minerals

The success of the HZSM-S catafyst is no doubt linked to the low coke forming tendency of this particular zeolite. Other acidic zeolites such as HY are initia% active but deactivate very r idly due to coke depo on. Bradley and Kydd [116] investigated the performance of seve pillar interlayered clay miner and although the Ga pillared montmorihonite was found to be the most effective it had a nnich lower activity than Ga/HZSM-5. 

Future EXAFS studies of the local structure of reactive sites in pillared clay derivatives and related hydroxy-interlayered clay minerals should help elucidate the reactivity of these materials as catalysts for synthetic organic chemical conversions, as well as for reactions occurring in the natural soil environment. 

Jie, G. J., M. E. Ze, and Y. Zhiquing. 1986. A class of pillared interlayered clay molecular sieve products with regularly interstratified mineral structure. Eur. Pat. Appl. 197012. 

Recent advances in this technology include the use of 2 1 clays converted to hydrophobic forms through the introduction of surfactants in the interlayer. For example, Boyd et al. (1991) introduced cationic chain surfactants into 2 1 clay minerals. Such clays were demonstrated to have high affinity for hydrophobic organic chemicals. Additionally, polyethylene oxides (PEOs) have been intercalated into aluminum-pillared montmorillonite (Montarges et al., 1995). Because PEOs have a... 

Bentonite, whose main ingredient is montmorillonite, is one kind of layer structure clay mineral. It is an ideal material for preparation of pillared clays. If metal cations with high catalytic activity were intercalated in the interlayers of montmorillonite, a new type of solid acid catalyst can be obtained. The catalytic activity of the catalyst is closely associated with its porosity, specific surface area and surface total acidity. One of the effective ways to enhance catalytic activity is to prepare catalyst with appropriate metal cations and structure. 

Zielk, R. C., and T. J. Pinnavaia. 1988. Modified clays for the adsorption of environmental toxicants binding of chlorophenols to pillared, delaminated, and hydroxy-interlayered smectites. Clays Clay Miner. 36(5) 403-8. 

In the early nineties, clays once more have come to the attention of researchers because thermally and hydrothermally stable expanded materials have been synthesized by interlayering 2 1 clay minerals with oligomeric molecules and colloidal particles derived from the hydrolysis of polyvalent cations. On heating, these inorganic polymers (or colloidal particles) form pillars that permanently prop open the clay layers generating high surface area solids enclosing cavities available to sorption and catalysis. 

Smectite clay catalysts are potential alternative adsorbents, although some modifications of the natural mineral are necessary. Interlayer sites in smectite dehydrate at temperatures above 200°C, collapsing to an illitic structure. Since the ion-exchange capacity of smectite centres on the interlayer site, collapse must be prevented if clay catalysts are to be used in thermal treatments of chemical organic toxins. The intercalation of thermally stable cations, which act as molecular props or pillars, is one... 

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