Mesostructured zeolites: bridging the gap between zeolites and MCM-41

Surfactant-templating is one of the most versatile and useful techniques to implement mesoporous systems into solid materials. Various strategies based on various interactions between surfactants and solid precursors have been explored to produce new structures. Zeolites are invaluable as size- and shape-selective solid acid catalysts. Nevertheless, their micropores impose limitations on the mass transport of bulky feed and/or product molecules. Many studies have attempted to address this by utilizing surfactant-assisting technology to alleviate the diffusion constraints. However, most efforts have failed due to micro/mesopore phase separation. Recently, a new technique combining the uses of cationic surfactants and mild basic solutions was introduced to synthesise mesostructured zeolites. These materials sustain the unique characteristics of zeolites (i.e., strong acidity, crystallinity, microporosity, and hydrothermal stability), including tunable mesopore sizes and degrees of mesoporosity. The mesostructured zeolites are now commercially available through Rive Technology, and show superior performance in VGO cracking. This feature article provides an overview of recent explorations in the introduction of mesoporosity into zeolites using surfactant-templating techniques. Various porous materials, preparation methods, physical and catalytic properties of mesostructured zeolites will be discussed.

How can we enhance our security without damaging our liberty? For a Progressive and European Rehabilitation of Sovereignty. European Policy Brief No. 41, January 2016

How can we reinforce internal security without destroying basic freedoms? This dilemma will become increasingly topical in the context of rising terrorist threats and in view of some of the responses already put in place at the national level. Many observers have pointed out the threat that these measures pose to individual freedom. But few have highlighted their relative inefficiency. Indeed, if the right to security is one of the founding reasons for political government and one of its main sources of legitimacy, can states still guarantee this basic right? This article examines this dilemma and focuses more specifically on its implications for the notion and practice of sovereignty. It also sketches a strong, but nuanced, rescue of sovereignty at the European level in order to assure individual security while, at the same time, protecting our freedoms.