Pillared Interlayer Clays PILC

PILC are so wide and important a subject that they require a full paper, thus discussion here is limited to a survey of the main aspects for more detailed information, reference should be made to the original literature [e. g. 2,8,9,11,19,20, 26-28,66-71]. 

Many of the different pillaring agents reported in the literature (organic compounds, metal trischelates, organometallic complexes, metal cluster cations, metal oxide sols, polyoxocations, etc.) have drawbacks such as low reactivity or lack of thermal stability, and polyoxocations are by far the most widely employed. Many different polyoxocations (Al, Ni, Zr, Fe, Cr, Mg, Si, Bi, Be, B, Nb, Ta, Mo, Ti, and, more recently, Cu, Ga, and Ce) have been reported in the open and patent literature and clays with multielement or doped pillars also have been claimed [2,8,9,19,20,68-70,73-75]. However, the chemical composition, structure and charge are at present well defined only for the Al-polyoxocation, in which the Keggin ion [Al,304(0H)24(H20)i2] is identified. 

PILC are prepared by controlled hydrolysis reactions which can be carried out in solution or in the interlamellar space of the clay (the former allows better control of the nature of the polyoxocations). In addition to the different parameters already mentioned, the calcination process also plays a key role. Three general cases may occur (i) the polyoxocations exit from the clay (no pillaring), (ii) they degrade in situ giving rise to layers of aluminum hydroxide (thick ca. 

From the viewpoint of making catalysts at a competitive price, three important criteria need to be met (i) use the whole clay material, after minimal refining (i. e., low cost), (ii) pillar the Ca or (Ca, Na) forms, not only the Na forms (i. e., no preexchange), and (iii) be able to use clay-polyoxocation concentrations ( 15 % wtw solids) that can be economically and effectively spray-dried to give a usable particle size distribution (40-200 pm) [8]. Non-purified clays as starting materials 

PILC have also been investigated in the acylation of mesitylene with acetyl chloride [62], showing in comparison with the starting clays (i) higher activities related to the presence of additional Lewis acid sites in the pillars 

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New Adsorbent Materials. SihcaUte and other hydrophobic molecular sieves, the new family of AlPO molecular sieves, and steadily increasing families of other new molecular sieves (including stmctures with much larger pores than those now commercially available), as well as new carbon molecular sieves and pillared interlayer clays (PILCS), will become more available for commercial appHcations, including adsorption. Adsorbents with enhanced performance, both highly selective physical adsorbents and easily regenerated, weak chemisorbents will be developed, as will new rate-selective adsorbents. 

The hydroamination of alkenes has been performed in the presence of heterogeneous acidic catalysts such as zeolites, amorphous aluminosilicates, phosphates, mesoporous oxides, pillared interlayered clays (PILCs), amorphous oxides, acid-treated sheet silicates or NafioN-H resins. They can be used either under batch conditions or in continuous operation at high temperature (above 200°C) under high pressure (above 100 bar). 

Pillared interlayer clays (PILCs), 1 655 Pill-box cell, 13 417-419 Pilling, reduced, 11 211 Pillow cases, number produced from one bale of cotton, 8 133t Pilot plant(s), 19 457-471... 

Pillared interlayered clays (PILCs), nanostructured adsorbents, 120 Platinum, dendrimers, 14-15 Polarizability... 

Pillared interlayered clays (PILC) can be regarded as nanocomposites, in which oxide particles of nano- and subnanometer scales are incorporated into the interlayer space of two-dimensional aluminosilicates [1]. In recent years, much attention has been focused on this new type of materials with large heights of pillars, because they provide larger pores in comparison to conventional zeolites. Smectites pillared with transition metal oxides (e.g. Cr, Fe, Ti) are of particular interest because the incorporated phases have themselves catalytic properties. Such solids are claimed to possess a remarkable activity in a notable number of reactions [2,3]. 

Since the first commercial announcements of Pillared Interlayered Clays (PILC) in 1979 (11. much interest has focused on these materials as potential sources of new materials in sorption, separations and catalysis. In this review I will attempt to summarise some of the recent developments that continue to make PILCs an exciting and opportunistic research area for the petroleum oriented industries. These developments can conveniently be divided into the following areas ... 

Since 1973, pillared interlayered clays (PILCS) have been extensively studied because they can be attractive as potential catalysts for the conversion of heavy fuels as shown by several reviews on the subject (1-4). 

To avoid this problem, researchers found a way to prop open the clay layers by the introduction of stable pillars in the interlayer region. By doing so, a high pore volume is created. The pillared interlayered clay (PILC) maintains its porosity during the hydration or dehydration process. The idea is schematically represented in Fig. 1. 

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