Action des substances humiques sur les propriétés de sorption des argiles : cas du césium

National audienc

Role of double-hydrophilic block copolymers in the synthesis of lanthanum-based nanoparticles

International audienc

Dialkylation of naphthalene with isopropanol over acidic zeolites - Influence of pore structure on selectivity

The liquid phase alkylation of naphthalene with isopropanol has been studied over various large pore zeolites with intermediate aluminum content. While H-Y zeolite exhibits the best activity. and shows a high selectivity in 2,6- and 2,7-diisopropylnaphthalenes, in agreement with previous studies, H-Beta displays a peculiar behavior under the same conditions. The latter produces little diisopropylnaphthalenes; instead, a series of unexpected compounds. consisting of (cyclopentyl)naphthalene derivatives (so-called cyclizates), are formed in high yields. H-Mordenite, which features low activity, also demonstrates such an unexpected behavior towards formation of multialkylated products. The results obtained over H-Beta are more particularly reported, and the identification of the cyclizates is confirmed. A mechanism is proposed to explain the formation of these compounds depending on the various catalytic materials used, and the impact of the pore structure on activity and product distribution is discussed. (C) 2001 Elsevier Science B.V. All rights reserved

Ethene adsorption and reaction on some zeolites and pillared clays

In the acidic solids used in this study, ethene undergoes a cationic polymerisation started by proton transfer. The larger the dimensions of the micropores, the higher is the degree of branching of the polymeric cationic species obtained. Such saturated polymeric cationic species evolve upon thermal treatment by loss of hydrogen to allylic carbocations (linear mono-, di- and trienic species as well as penta-cyclo and hexacyclo monoenic species), which are precursors to aromatics. All species have been characterised both in the infrared (IR) and ultraviolet (UV) regions. The overall chemistry is very close to that of propene on the same systems, though ethene appears less reactive

Highly stable metal hydrous oxide colloids by inorganic polycondensation in suspension

International audienc