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

Abstract

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 in 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, 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−. 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 can be very motivating result for the application of these materials as shape selective catalysts.

Probing zeolites by vibrational spectroscopies

“…Therefore, the charge on oxygen increases with the amount of Al in the framework (S Al = 2.22 vs. S Si = 2.84) or when the electronegativity of the extraframework counter-cations is low (for instance, for alkali metal-exchanged zeolites, the charge on oxygen increases from Li-to Cs-exchanged zeolites: S Li = 0.74, S Cs = 0.28). 571,572 Thus, the general approach to the characterization of zeolite basicity involves the use of acidic probe molecules that ideally would react with the basic centers according to reactions (8) or (9) mentioned above. 569 The characterization of the basicity of a zeolite involves determining the number and strength of these basic centers.…”

Gas phase nitridation of silicate fiber glass materials with ammonia:Three case studies

“…In nitridated REM-Si glass new absorption bands at 3282, 3373, 3424 and 3500 cm − 1 appeared in the spectra. The first two bands correspond to stretching vibrations of the hydrogen-bonded Si-NH 2 groups, whereas the low-intensive bands 3424 and 3500 cm − 1 are typical of isolated Si-NH 2 groups [22,23,35]. As seen from Fig.…”

“…Among these materials are zeolites [18][19][20][21][22][23], amorphous silica [24,25] and various mesoporous crystalline silicas [26][27][28][29]. The substitution of O for N results in acquisition of new properties like pronounced basicity of nitridated silicate materials which makes them as potential solid base catalysts.…”

Enhancement of Alkene Epoxidation Activity of Titanosilicates by Gas‐Phase Ammonia Modification

“…The treatment introduces the nitrogen atoms into the framework by substituting lattice oxygen. Thereafter, various nitrogen incorporated zeolites or mesoporous silica have been synthesized by nitridation, such as zeolite Y, [17] ZSM-5, [18,19] SAPO-11, [20] BEA, [21] MCM-48, [22] and SBA-15. [23] The structures of the parent materials are well preserved and their acid-base properties can be tailored by adjusting the content and chemical configurations of nitrogen [24][25][26] ( In this study, we used Ti-MWW as the precursor to prepare ammonia-treated catalysts at a relatively low temperature by using a similar strategy.…”