Novel Synthesis of Microporous and Mesoporous Materials and their Applications for Hydrocarbon Transformation and Chiral Recognition »

ABSTRACT i i ABSTRACTi i ABSTRACT In the present work, the elaboration, characterisation and applications of different porous materials have been studied. Porous materials are divided into three categories depending on the porous cavity size, namely microporous materials (pore diameter < 2 nm), mesoporous materials (2 nm < pore diameter < 50 nm) and macroporous materials (pore diameter > 50 nm). The thesis work is organized in three major parts: the synthesis of hierarchical micro/mesoporous zeolites and their potential application for the petrochemical industry, the theoretical study of reaction mechanisms on microporous zeolite and the design of mesoporous metals with intrinsic chirality at their inner surface. The hierarchical micro/mesoporous zeolite, composed of microporous and mesoporous features, has been prepared using carbon-silica (C/SiO2) composites derived from a pyrolysis of hydrocarbon gas on silica gel. Our findings demonstrate that not only the presence of a high surface area and porosity, but also an improved efficiency of these materials for many petrochemical processes such as n-butene isomerization, nhexadecane catalytic cracking and hydrocracking. The novel synthetic method is expected to be generalized for other types of zeolites, and is considered to be a promising method for creating hierarchical micro/mesoporous zeolites for potential catalytic applications, especially in the petrochemical industry. In addition to the study of practical catalytic aspects, a theoretical approach has been used to investigate potential reaction mechanisms such as the selective isomerization of 1-butene into isobutene. More specifically, the monomolecular skeletal isomerization of 1-butene into isobutene on H-FER zeolite was theoretically studied by using the ONIOM approach. This process was found to involve the transformation of adsorbed 1butene through 2-butoxide, isobutoxide, and tert-butyl cation intermediates. The ratedetermining step is the conversion of isobutoxide into isobutene, in which the reaction has to proceed through the primary isobutyl cation transition state. The shape selectivity due to the “nano-confinement” effect of the zeolite framework strongly affects the te l-0 09 12 33 9, v er si on 1 2 D ec 2 01 3