New methods have been developed in recent years that are now being successfully applied in the preparation of pillared interlayered clays (PILCs). Variations in the procedures concern different parameters involved in the synthesis, such as the starting clay, the intercalating solution, the intercalation process, and the drying and calcination steps of the pillared solids, among others. In the present article, the latest results obtained when introducing modifications in the chemical aspects of PILC synthesis are reviewed. These include (1) pillaring with mixed solutions containing two or more cations, (2) using coordination or organometallic compounds, (3) using polymers and surfactants, (4) pillaring of acid-activated clays, and (5) enhancement of PILC acidity. A separate section is devoted to the specific features of preparing these solids in amounts large enough to make their manufacture on an industrial scale economically feasible. Recent developments in the catalytic applications of PILCs are also re...

Recent Advances in the Synthesis and Catalytic Applications of Pillared Clays

This paper reviews the synthesis of smectites and porous pillared clay catalysts. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si, and other pillared clays as well as mixed Fe/Al, Ga/Al, Si/Al, Zr/Al and other mixed metal/Al pillared clays. The use of these pillared clays in some catalytic reactions is also briefly reviewed.

Synthesis of Smectites and Porous Pillared Clay Catalysts: A Review

Several methods have been developed and applied in recent years in the characterization of the structure of microporous materials, in general, and of pillared clays, in particular. In the present article, the latest results obtained in the control of the microstructure developed in alumina‐pillared clays and various approaches used to the evaluation of the porosity of these materials are reviewed. These include the control of the microstructure developed in pillared clays by adjusting the several parameters involved in the synthesis process, and the evaluation of the porosity of pillared clays. Emphasis is given to the methods to evaluate the pore size and pore size distribution (PSD) of these materials. Two separate sections are devoted to review mathematical modeling studies and 129Xe NMR spectroscopy of physisorbed Xe to investigate the microporous structural properties of these materials.

Recent Advances in the Control and Characterization of the Porous Structure of Pillared Clay Catalysts

There have been significant developments in the pillaring of lamellar ionic materials, and the resulting zeolite-like pillared derivatives have built a large family of microporous materials. This review focuses on the host−guest reactions involved in the preparative procedures. Furthermore, approaches to the modification of the low-dimensional porous network structure are discussed.

Preparation and Properties of Two-Dimensional Microporous Pillared Interlayered Solids

TiO2 pillared clay was applied for the adsorption-photocatalytic degradation of the endocrine disruptors with various hydrophobicities (di-n-butyl phthalate, diethyl phthalate, dimethyl phthalate and bisphenol-A). The hydrothermal treatment developed the crystallinity of the TiO2 pillar and the size of the TiO2 crystallites, and enhanced the photocatalytic degradation rate. However, the hydrothermal treatment in hard condition made the specific photocatalytic activity decrease since the size of crystallites increased. The surface hydrophobicity of the pillared clay was not affected so much, but reduced slightly, by the hydrothermal treatment. Higher hydrophobic endocrine disruptor was more adsorbed and enriched on the TiO2 pillared clay. Enrichment of the reactant enhanced the rate of photocatalytic degradation on the pillared clay.

Adsorptive and photocatalytic performance of TiO2 pillared montmorillonite in degradation of endocrine disruptors having different hydrophobicity

The silicate layers of montmorillonite clay were pillared with SiO2–TiO2 sol particles. Although only the SiO2 sols were negatively charged, the SiO2–TiO2 mixed oxide sols were positively charged and could be ion-exchanged with the interlayer cations of montmorillonite. The resulting pillared clays had a basal spacing expanded to more than 40 A; the spacing was maintained during calcination up to 773 K. The adsorption properties of the calcined samples were studied for nitrogen as well as organic vapors. A structural model for the arrangement of the intercalated sol particles is proposed in which small SiO2–TiO2 sol particles are packed between the silicate layers. Micropores with a slit width of 10–12 A are formed in the interstices between the sol particles and the silicate layers.

Preparation and Properties of Clays Pillared with SiO2-TiO2 Sol Particles.

PURPOSE: To produce the titled derivative having large layer-to-layer spacing and specific surface and which is extremely stable and useful to pigments, adsorbents, catalysts (carrier), heat insulators, etc., by allowing a Ti salt soluble in water and acids and/or a titania sol to react with swelling phyllosilicate. CONSTITUTION: A Ti salt soluble in water and acids and/or a titania sol (e.g., TiCl 4 , TiOSO 4 , etc., and their salts) are allowed to react with swelling phyllosilicate (e.g., smectite, vermiculite, synthetic mica, etc.) to produce a clay derivative having porous structure. Since the clay derivative thus produced has large layer-to-layer spacing of 25W63Å and a large specific surface of 300W470m 2 /g and is highly stable, the derivative can be extensively used as pigments, encapsulating agents, adsorbents, catalysts, catalyst carriers, and heat insulators. COPYRIGHT: (C)1987,JPO&Japio

Fumio Okumura

Papers

Preparation and Properties of Clays Pillared with SiO2-TiO2 Sol Particles.

Production of clay derivative having porous structure

Preparation and Properties of Clays Pillared with SiO2‐TiO2 Sol Particles.

Manufacture of adsorbents

Production of slow releasing preparation of 55fluorouracil