Elias Haddad

Continuous flow hyperpolarized 129Xe-MAS NMR studies of microporous materials

A magic angle spinning (MAS) NMR probe has been developed to allow in situ measurements of NMR spectra. Two applications are targeted with this device: i) in situ and operando MAS NMR spectroscopy of working catalysts and ii) the hyperpolarized (HP) 129Xe spectroscopy of porous materials under MAS and continuous flow conditions. The construction of the MAS probe is described and the usefulness of this system is demonstrated by studying the adsorption of hyperpolarized xenon on AlPO-41 and ITQ-6 zeolites. The high stability of the HP xenon flow allowed us to perform two-dimensional exchange experiments under MAS conditions, in a short time and with very good resolution.

Application of continuously circulating flow of hyperpolarized (HP)129Xe-NMR on mesoporous materials

The continuously circulating flow of hyperpolarized (HP) 129Xe NMR technique has been used to study the porous structure of ordered purely siliceous and Al-containing MCM-41 and SBA-15 mesoporous materials. In this paper, we report 129Xe chemical shift measurements of xenon adsorbed on mesoporous materials having different porosities and surface composition. The use of hyperpolarized xenon allows us to measure spectra at very low xenon concentration where xenon reflects mainly the interaction between the adsorbed xenon atoms and the surface. The effect of compression on the mesopore structure has also been studied by HP 129Xe NMR. The obtained NMR spectra are interpreted in terms of an exchange between adsorbed xenon in the pores and gazeous Xe atoms in the interparticle spaces. Variable temperature measurments allowed us to obtain information on the heat of adsorption of xenon on the surface and to evaluate the chemical shift of xenon in interaction with the surface.

X-ray diffraction analysis of mesostructured materials by continuous density function technique

Abstract A continuous density function technique has been developed for X-ray diffraction (XRD) structural investigations of mesostructured materials. The technique is designed for the analysis of the density distribution in materials exhibiting nanoscale (2-50 nm) ordering of structural elements without atomic long-range order. The results of structure investigations of a series of silicate, metallosilicate and carbon mesostructured materials with hexagonal and cubic symmetry are presented.

Spectroscopic evidence of SBA-15 mesoporous solids functionalization

Abstract In order to enhance the acid properties of mesoporous materials, the functionalization of the SBA-15 silica surface with arene-sulfonic acid groups has been adopted via a one-step synthesis procedure. The structures of the sulfonic acid surface-functionalized mesoporous silica were studied and identified by using nitrogen adsorption, X-ray diffraction (XRD), FT-IR, TEM, CP/MAS 29 Si and 13 C NMR, and hyperpolarized 129 Xe NMR techniques. The number of acid groups was determined by ammonia adsorption and catalytic properties were also studied in liquid phase. The structure of the obtained materials showed hexagonal mesoscopic order, possessed large surface areas with a heterogeneous distribution of sulfonic functions within the pore of the mesoporous solid. The anchoring of acid groups has been proved by 29 Si, 13 C CP-MAS-NMR measurements and using the recent technique of hyperpolarized 129 Xe NMR. The number of acid groups is directly proportional to the functionalization ratio. Moreover, these acidified solids display interesting catalytic properties for the esterification of acetic acid with ethanol.

The first direct probing of porosity on supported mesoporous silica thin films through hyperpolarised 129Xe NMRElectronic supplementary information (ESI) available: materials, NMR measurements, modification of silica surface. See http://www.rsc.org/suppdata/cc/b2/b207127d/

The continuous flow hyperpolarised (HP) 129Xe NMR technique has been used for the first time on mesoporous silica thin films. This study demonstrates the possibility of recording information about the porosity of a very small quantity of materials and the high sensitivity of the NMR response to pore size and pore functionality.

08-P-14-Comparative study of the wall properties in highly-ordered silicate and aluminosilicate mesostructured materials of the MCM-41 and SBA-15 types

Publisher Summary This chapter discusses a comparative study of the wall properties in highly ordered silicate and aluminosilicate mesostructured materials of the MCM-41 and SBA-15 types. X-ray diffraction (XRD) structural modeling based on a continuous electron density representation and textural analyses by the combined XRD-adsorption method is applied to quantify distinctions in the wall structure of the MCM-41 and SBA-15 types of mesostructured materials.