Aluminum-Phosphate Binder Formation in Zeolites as Probed with X-ray Absorption Microscopy

Abstract

In this work, three industrially relevant zeolites with framework topologies of MOR, FAU and FER have been explored on their ability to form an AlPO4 phase by reaction of a phosphate precursor with expelled framework aluminum. A detailed study was performed on zeolite H-mordenite, using in situ STXM and soft X-ray absorption tomography, complemented with (27)Al and (31)P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, XRD, FT-IR spectroscopy, and N2 physisorption. Extraframework aluminum was extracted from steam-dealuminated H-mordenite and shown to dominantly consist of amorphous AlO(OH). It was found that phosphoric acid readily reacts with the AlO(OH) phase in dealuminated H-mordenite and forms an extraframework amorphous AlPO4 phase. It was found that while AlPO4 crystallizes outside of the zeolitic channel system forming AlPO4 islands, AlPO4 that remains inside tends to stay more amorphous. In the case of ultrastable zeolite Y the FAU framework collapsed during phosphatation, due to extraction of framework aluminum from the lattice. However, using milder phosphatation conditions an extraframework AlPO4 α-cristobalite/tridymite phase could also be produced within the FAU framework. Finally, in steamed zeolite ferrierite with FER topology the extraframework aluminum species were trapped and therefore not accessible for phosphoric acid; hence, no AlPO4 phase could be formed within the structure. Therefore, the parameters to be taken into account in AlPO4 synthesis are the framework Si/Al ratio, stability of framework aluminum, pore dimensionality and accessibility of extraframework aluminum species.

Visualizing Dealumination of a Single Zeolite Domain in a Real‐Life Catalytic Cracking Particle

“…[14,15] In order to understand zeolite activity in the context of FCC catalysis,w here matrix and binder materials play ak ey role,characterization techniques that possess both spatial and chemical information are required. [24][25][26][27][28] Here,wepresent afirst-of-its-kind study in which we used STXM to probe zeolite dealumination within real-life fresh and genuine,industrially deactivated FCC catalysts at the size regime of asingle zeolite domain. 10-30 nm) spatial resolution.…”

“…[16][17][18][19][20][21][22][23] One such technique,n amely soft X-ray scanning transmission Xray microscopy (STXM), has been successfully used to elucidate both spatial and chemical behavior of isolated steamed and dealuminated zeolites,b ut has never been extended to study multi-component and hierarchically structured zeolite-based catalysts. [24][25][26][27][28] Here,wepresent afirst-of-its-kind study in which we used STXM to probe zeolite dealumination within real-life fresh and genuine,industrially deactivated FCC catalysts at the size regime of asingle zeolite domain. Theexperimental approach of the study is illustrated in Figure 1.…”

Dual roles of f electrons in mixing Al 3p character into d -orbital conduction bands for lanthanide and actinide dialuminides

“…However, because many synchrotron beamlines are not optimized in the energy regime that includes the Al K-edge, measurements are often subject to reduced photon flux and require sample preparation methodologies that lead to significant self-absorption and saturation effects. To the best of our knowledge, Al K-edge XAS has not been used to characterize lanthanide or actinide electronic structure and is generally limited to, for example, studies of aluminum metal [35,36], oxides and minerals [37,38], zeolites [39][40][41], and a small number of synthetic materials [42][43][44].…”

Chemical and Morphological Inhomogeneity of Aluminum Metal and Oxides from Soft X-ray Spectromicroscopy

“…27,[87][88][89][90][91] In their detailed examination of aluminosilicate minerals, Li and coworkers developed assignments by comparing Al K-edge and Si K-edge spectra and using MO calculations of the AlO6 9-cluster.…”

“…26,27 Each also has unique advantages and limitations when compared with the electron-based analogs scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (STEM-EELS). 28 For example, modern STEM capabilities regularly achieve 0.1 nm spatial resolution and monochromated EELS can provide as fine as 0.2 eV energy resolution.…”