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Characterization of the acid sites in dealuminated nanosized HZSM-5 zeolite with the probe molecule trimethylphosphine

“…So Uytterhoeven model is not accepted extensively so far. We and other authors [7,30] tend to accept the Jacobs model. In the 27 Al MAS NMR spectra, we find the increase of nonframework Al upon hydrothermal treatment.…”

“…A number of papers in the literature reported that dealumination of zeolite can enhance its activity in the acid-catalyzed reactions [1][2][3][4][5]. Most authors ascribed this to the existence of Lewis acid sites with the combination of Brönsted acid sites after dealumination of zeolite [6][7][8]. They employed a lot of methods to characterize the acidity in solid cata-lysts [9].…”

Hierarchically Nanoporous Zeolites and Their Heterogeneous Catalysis: Current Status and Future Perspectives

“…This post-synthetic route can be diversified into dealumination or desilication depending on the demetallated species such as Al or Si, respectively. In an old strategy, Al species can be leached out from the zeolite framework by steaming with water vapor at 500°C and subsequent washing with liquid acid, where mesopores are formed [16,17]. This is well known procedure for preparation of ultra-stable Y (USY) zeolites that can be used in fluid catalytic cracking (FCC) reaction [7].…”

Visualization of the Equilibrium FCC Catalyst Surface by AFM and SEM–EDS

“…Catalyst activity decreases as the production of coke and hydrogen increase at the expense of gasoline [1]. The presence of metal contaminants on the FCC (fluid catalytic cracking) catalyst has been widely studied by using microscopic and elemental imaging techniques such as scanning electron microscopy (SEM) [2,3] and secondary ion mass spectrometry (SIMS) [4,5]. These results have shown that vanadium is mobile and accumulates throughout the catalyst particles with a preference for rare earthexchanged Y-zeolite.…”