Abstract

PICASSO, Gino  and  SUN KOU, María del Rosario. Technological applications of modified clays. Rev. Soc. Quím. Perú [online]. 2008, vol.74, n.1, pp.57-74. ISSN 1810-634X.

Clay-type smectites are an important group of minerals, composed from different crystal compounds, mainly filosilicats whose physicochemical properties are depending from their structure and their very thin grain size (less than 2 µm). An important property of these structures is the ability to exchange the silicon atom (Si) positioned in the center of tetrad by aluminum (Al³⁺) or in analogy the replacement of Al in the octaedric positions by lower charge elements as Mg²⁺, Mn²⁺, Fe²⁺, causing a positive charge lack or a negative charge excess from one of oxygens in the octahedron which is compensated by attraction of interchange cations of the structure as Na⁺, K⁺, Ca²⁺ or polar molecules, water for instance, which provide surface properties as acidity and ion exchange. Mainly, these features are claimed to be responsible of catalytic properties of clays. The process of pillaring of clay, particularly the bentonite, consists in the chargecompensation cation in the interlamellar space of the parent clay with bulky inorganic polyoxocations formed by hydrolysis of some metal salts. Upon calcination these polyoxocations undergo limited structural transformations and are converted to metal oxyhydroxide clusters, named pillars that keep the clay layers apart thus preventing their collapse. These modified clays are named PILC's (pillared interlayer clays). The purpose of this work is to compile the main scientific contributions in the last years and show the main technological applications of modified clays (adsorption and catalysis) in the literature. This paper shows the multisided applications of modified clays in heterogeneous catalysis particularly in the reactions of hydrogenations and catalytic, combustion. Their specific lamellar structure and the possibility of introduce some hydroxications between the layers allow to develop catalysts with high stable active phase and high contact specific surface. Particularly, the bentonites are material of interest in Peru for their easy reachness and abundance.

Keywords : modified clays; pillared clays; PILC's.