Evolution of strong acidity and high-alkane-cracking activity in ammonium-treated USY zeolites

Okumura, Kazu; Tomiyama, Takuya; Morishita, Nami; Sanada, Takashi; Kamiguchi, Kazuhiro; Katada, Naonobu; Niwa, Miki

doi:10.1016/j.apcata.2011.07.007

Cited by 24 publications

(18 citation statements)

References 31 publications

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“…The acid strength of Brønsted acid sites present in Ytype zeolites can be finely tuned by (a) the introduction of divalent cations such as Ca 2+ and (b) by dealumination in combination with posttreatment employing an aqueous solution of ammonium salts [16] Figure 5b shows XRD patterns of 3 wt% Au loaded on these supports. The samples were calcined at 773 K under a 6 % H 2 atmosphere.…”

Section: Resultsmentioning

confidence: 99%

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Formation of nanometer-sized Au particles on USY zeolites under hydrogen atmosphere

et al. 2012

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Gold was deposited on ultrastable Y (USY) zeolite using a newly developed method: just mixing an aqueous solution of HAuCl 4 and zeolite at 353 K in which the NH 4 + cation reacted with the Cl − in HAuCl 4 . Treatment of the Au-loaded USY zeolite in the atmosphere of hydrogen resulted in the formation of Au 0 nanoclusters with 1.8 nm diameter at 773 K. The size of Au particle was dependent on the type of zeolite support, composition of gas atmosphere, and temperature of calcination, which was correlated with catalytic performance. This study demonstrated the potential use of zeolites with strong Brønsted acid character as gold supports.

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Section: Resultsmentioning

confidence: 99%

“…In fact, metal clusters of Pd and Pt with high dispersion were obtained on zeolites having Brønsted acid sites [14,15]. Ultrastable Y (USY) zeolites contain strongly acid sites [16] (ca. 150 kJ mol −1 ) and also exhibit high thermal stability.…”

Section: Introductionmentioning

confidence: 99%

Formation of nanometer-sized Au particles on USY zeolites under hydrogen atmosphere

et al. 2012

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“…The IR-TPD of 1760 cm -1 -band had the broad peak temperature (450 to 500 K) higher than those of 1627 and 1760 cm -1 -bands, and similar to that of 1444 cm -1 -band. Figure 6 shows difference IR spectra between the spectra measured after pre-treatment and spectra measured after the ammonia adsorption and evacuation on MOR at 673 K. The MOR has strong Brønsted acid sites comparable to USY, and scarcely any Lewis acid sites [9,10]. The large band at 1430 cm -1 was assigned to the ν 4 vibration of NH 4 which was formed on the Brønsted acid site.…”

Section: Methodsmentioning

confidence: 99%

“…The employed metal oxides, and USY (ultrastable Y) and MOR (mordenite) zeolites are shown in Table 1. The preparation of TiO 2 was according to Cao et al [8], while the USY zeolite was prepared as described in our previous paper [9].…”

Section: Introductionmentioning

confidence: 99%

Assignments of Bending Vibrations of Ammonia Adsorbed on Surfaces of Metal Oxides

et al. 2015

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Bending vibrations in the infrared (IR) spectra of ammonia adsorbed on Lewis acidic metal oxides, i.e., Al 2 O 3 , ZrO 2 and TiO 2 , and zeolite were analyzed with an aid of density functional theory (DFT) calculations. The results by DFT methods reveal the wavenumbers of the vibration modes (ν 4 and ν 2) of NH 4 bonded to Brønsted acid site and the vibration modes (δ s and δ d) of NH 3 species coordinated to a Lewis acidic metal center (M = Al, Zr or Ti). The wavenumbers calculated based on DFT were reasonably in agreement with the experimentally observed values. The estimation of wavenumbers suggests that the δ s vibration of NH 3 hydrogen-bonded is invisible on a zeolite, because it is hidden by an intense absorption due to skeletal vibration. On the other hand, multiple bands of asymmetric bending modes (δ d and ν 2) observed on a zeolite were assigned. A quantification method of Brønsted and Lewis acid sites, and hydrogen-bonded NH 3 is provided based on the peak assignments.

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“…The USY zeolites were prepared by the steam treatment of NH 4 + -Y, followed by reaction with an ammonium nitrate solution. The resulting ammonium-treated USY zeolites had strong Brønsted acid sites [16]. First, we developed a new method for loading Au onto NH 4 + -USY zeolites using an aqueous solution of HAuCl 4 .…”

Section: Introductionmentioning

confidence: 99%

Fabrication and Catalytic Activity of Thermally Stable Gold Nanoparticles on Ultrastable Y (USY) Zeolites

et al. 2013

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Au was deposited on ultrastable Y (USY) zeolites using an ion-exchange method. Up to 5.5 wt% Au was introduced into the NH 4 -form of USY zeolites. In contrast, deposition of Au hardly took place on the H-and Na-forms of Y-type zeolites, NH 4 -forms of mordenite, and ZSM-5. Treatment of the Au-loaded USY zeolite in a H 2 atmosphere, afforded Au 0 nanoparticles. These particles were thermally stable even at 973 K, where their mean particle diameter was 3.7 nm. In contrast, highly aggregated Au particles were observed after thermal treatment at temperatures lower than 523 K, followed by storage in air for a month. The resulting particle sizes were in good correlation with the IR band intensity of the adsorbed CO and the catalytic activity of Au in the aerobic oxidation of benzyl alcohol. The Au nanoparticles showed highest activity when the Au/USY zeolite was thermally treated at 673-973 K. A negligible deactivation was observed after repeating the reaction at least 12 times. In the case of Au/TiO 2 catalyst prepared by the deposition-precipitation method, the highest activity was observed at 573 K, which was lower than the temperature used for the Au/USY zeolites. This study demonstrated the potential use of the NH 4 -form of USY zeolites for supporting Au. OPEN ACCESSCatalysts 2013, 3 600

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Evolution of strong acidity and high-alkane-cracking activity in ammonium-treated USY zeolites

Cited by 24 publications

References 31 publications

Formation of nanometer-sized Au particles on USY zeolites under hydrogen atmosphere

Formation of nanometer-sized Au particles on USY zeolites under hydrogen atmosphere

Assignments of Bending Vibrations of Ammonia Adsorbed on Surfaces of Metal Oxides

Fabrication and Catalytic Activity of Thermally Stable Gold Nanoparticles on Ultrastable Y (USY) Zeolites

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