New Trends in Clay-Based Nanohybrid Applications: Essential Oil Encapsulation Strategies to Improve Their Biological Activity

Essential oils (EOs) are used in medicinal, pharmaceutical, cosmetic, agricultural, and food industries thanks to their key properties and multiple benefits. Several techniques and embedding materials are used to nanoencapsulate EOs, in order to keep them from environmental conditions and boost their bioefficiency by controlled release. In recent years, the interest for clay nanoparticles as nanoencapsulation materials for EOs is increasing owing to their abundance in nature, low cost, inertness, and special structure. Thus, this chapter focuses on highlighting data and contributions dealing with EOs incorporation into nanoclay particles, their current applications and nanohybrid formation benefits on the stability, bioavailability, and sustained release of EOs. An overview about nanoclays used for EOs nanoencapsulation is highlighted in the beginning of this chapter followed by a brief description of EOs’ chemical composition and properties

Preparation and characterization of new basic catalysts by nitridation of Y zeolites

In recent years, the base-catalyzed reactions play a more and more important role in modern fine chemicals, nonetheless reports about solid base catalysts are still far fewer than that of solid acid catalysts. Therefore, new solid base catalysts are imminently desirable to meet the need of the fine chemical industry. In the nineties, it was found that nitrogen incorporation is an effective way to synthesize new solids basic materials. Through treating various amorphous oxides with flowing ammonia at high temperatures "nitridation", a new family of heterogeneous basic catalysts was made. In the present work we demonstrated that the same "nitridation" approach can be also successfully applied for the incorporation of nitrogen into the framework of Y zeolites and therefore the preparation of porous basic catalysts. The nitrogen content of the nitride zeolites can be adjusted by varying both temperature and nitridation time. Furthermore, the nitridation temperature can influence also the nature of nitrogenous species into the zeolitic framework. The following species were identified by DRIFT spectroscopy and XPS: NH4+, NH3ads, -NH2, >NH and >N-. The presence of nitrogen into the zeolitic framework induced modifications in both aluminum and silicon environments. The evaluation of the catalytic properties of the nitrided zeolites in the Knoevenagel condensation reaction between benzaldehyde and malononitrile revealed that the activity of the zeolites is deeply improved by nitrogen incorporation as long as the zeolitic framework was maintained.Doctorat en sciences agronomiques et ingénierie biologique (AGRO 3)--UCL, 200

Effects of the Nitridation of Y and USY Zeolites on their Catalytic Activity for the Base Catalyzed Knoevenagel Condensation

This contribution reports on the preparation, physicochemical characterization and catalytic performances of nitrided zeolites in the Knoevenagel condensation reaction. These basic materials were prepared by subjecting one Y zeolite (Si/Al ratio of 2.6) and two ultrastable Y zeolites (Si/Al ratio of 13 and 37) to nitridation, i.e., treatment with ammonia at high temperature. Both the amount and the chemical nature of incorporated nitrogen species were controlled by the nitridation temperature. Namely, an increase of the temperature induces an increase of the nitrogen content and the appearance of nitrogenous species in the following order of increasing temperature: NH4 (+), adsorbed NH3, -NH2, > NH and > N-. The nitridation occurred practically in the same manner whatever the Si/Al ratio of the starting material. However, from a catalytic point of view different behavior was observed. No direct correlation was found with the nitrogen content of the samples. Nitrided zeolites were found to exhibit catalytic activity as long as the zeolitic framework was maintained

Nitrided Zeolites: A Spectroscopic Approach for the Identification and Quantification of Incorporated Nitrogen Species

The combination of X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) allowed a clear identification and quantification of nitrogenous species Incorporated Upon nitridation ill three different zeolites one Y zeolite (Si/Al ratio of 2.6) and two ultrastable Y zeolites (Si/Al ratios of 13 and 37). Both the amount and the chemical nature of incorporated nitrogen species were controlled by the nitridation temperature. Namely, ill increase of the temperature induces in increase of the nitrogen content and the appearance of nitrogenous species in the following order of increasing temperature: NH4+, adsorbed NH3, -NH2, > NH, and > N- Based on these spectroscopic results, a mechanism of nitridation in function of temperature was proposed, this mechanism being independent of the properties of the parent zeolite. We evidenced here that the replacement of hydroxyls groups located in the microposity of the zeolite by nitrogen species was effective which call be very motivating result for the application of these materials as shape selective catalysts

Nitrided ultrastable zeolite Y: Identification and quantification of incorporated nitrogen species and their influence on the basic catalytic activity

Novel microporous basic catalysts have been obtained by activation under ammonia flow of an ultrastable zeolite Y at temperatures in the range of 500-900 degrees C. The homogeneity of nitridation was confirmed by comparing the bulk (chemical analysis) and superficial (XPS) nitrogen content. DRIFTS experiments allow us to identify the nature and location of the nitrogen species, and to propose a mechanism of nitridation. The nitrided samples are active in the Knoevenagel condensation between benzaldehyde and malononitrile and their activity increases when the temperature of nitridation increases

Nitridation of ultrastable Y zeolite: influence of experimental parameters

Nitrided zeolites were prepared by thermal treatment of ultrastable zeolite Y (Si/Al ratio equal to 13) under ammonia flow for a prolonged time. The effects of the nitridation parameters on the extent of the nitrogen incorporation and on the structural and catalytic properties of the resulting zeolites were investigated. The amount of nitrogen incorporated in the zeolite increases with temperature and duration. Structural order and porous volume are preserved if the nitridation temperature and the nitridation time do not exceed 800°C and 72 h, respectively. Nitrided zeolites are base catalysts as revealed by the reaction of Knoevenagel condensation between benzaldehyde and malononitrile

X-ray photoelectron spectroscopy study of nitrided zeolites

X-ray photoelectron spectroscopy (XPS) was used to observe the changes in the nitrogen, silicon and aluminum local environments occurring upon nitridation of ultrastable Y zeolite (Si/Al = 13) at different temperatures. In the case of nitrogen an identification and quantification of incorporated species was possible. The substitution of oxygen by nitrogen in the immediate vicinity of both silicon and aluminum atoms was also demonstrated. The extent of this substitution was more important at high nitridation temperature