Study of different states of nonframework aluminum in hydrothermally dealuminated HZSM-5 zeolites using diffuse reflectance i.r. spectroscopy

Loeffler, E.; Lohse, U.; Peuker, Ch.; Oehlmann, G.; Кustov, Leonid М.; Zholobenko, Vladimir L.; Kazansky, V.B.

doi:10.1016/0144-2449(94)90138-4

Cited by 150 publications

(56 citation statements)

References 7 publications

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“…Based on literature we attribute these species to tetrahedrally coordinated aluminium that is connected with only two bonds to the framework (TFAl dis ). 48 Two terminal Al-OH groups are formed and one proton compensates for the negative charge on the framework, as can be seen in Fig. 11c.…”

Section: Formation Of Partially Dislodged Tfal Speciesmentioning

confidence: 94%

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Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Bij

Weckhuysen

2014

Phys. Chem. Chem. Phys.

127

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In order to elucidate phosphorus-zeolite H-ZSM-5 interactions, a variety of phosphorus-modified zeolite H-ZSM-5 materials were studied in a multi-spectroscopic manner. By deploying single pulse 27 Al, 31 P MAS NMR, 2D heteronuclear 27 Al-31 P correlation (HETCOR), 27 Al MQ MAS NMR spectroscopy, TPD of pyridine monitored by FT-IR spectroscopy, and Scanning Transmission X-ray Microscopy (STXM) the interplay and influence of acidity, thermal treatment and phosphorus on the structure and acidity of H-ZSM-5 were established. It was found that while acid treatment did not affect the zeolite structure, thermal treatment leads to the breaking of Si-OH-Al bonds, a decrease in the strong acid site number and the formation of terminal Al-OH groups. No extra-framework aluminium species was observed. Phosphorus precursors interact with the zeolitic framework through hydrogen bonds and physical coordination, as phosphorus species can be simply washed out with hot water. After phosphatation and thermal treatment two effects occur simultaneously, namely (i) phosphorus species transform into water insoluble condensed poly-phosphoric acid and (ii) phosphoric acid binds irreversibly to the terminal Al-OH groups of partially dislodged four-coordinated framework aluminium, forming local silico-aluminophosphate interfaces.These interfaces are potentially the promoters of hydrothermal stability in phosphated zeolite H-ZSM-5.

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Section: Formation Of Partially Dislodged Tfal Speciesmentioning

confidence: 94%

“…Acid leaching does not remove these species, excluding that they are extra-framework. 48 The decrease in the number of TFAl species leads to a decrease in the number of strong Brønsted acid sites with about 45%.…”

Section: Formation Of Partially Dislodged Tfal Speciesmentioning

confidence: 99%

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

Bij

Weckhuysen

2014

Phys. Chem. Chem. Phys.

127

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“…It showed bands at 3745 cm-1 (fundamental stretch of silanol groups, v [Si~H)), at 4540 cm-1 (combination of stretching and bending, v+ 6 [SiOH]) and at 7325 cm-1 (overtone, v(0-2) [SiOH]). With the help of the silica spectrum and the well-established assignment of the fundamental stretching bands ofH-ZSM-5 [60][61][62] and hydrogen mordenite [56][57][58] , Kazansky et al [93] were able to assign the bands of, e.g., H-ZSM-5 ( Fig. 4.17 …”

Section: Fundamental Stretching Bandsmentioning

confidence: 98%

“…In other cases such as mordenite [56,57], clinoptilolite [58,59], H-ZSM-5 (compare [60] and [61]), only one band due to acidic hydroxyls was observed. In several IR studies hydroxyl groups attached to (framework or non-framework) aluminum, both acidic and non-acidic were also identified [62]. The data reported until 1976 have been reviewed in articles by Ward [5] and Foerster [6] and in a book by Jacobs [63].…”

Section: Fundamental Stretching Bandsmentioning

confidence: 99%

Characterization of Zeolites — Infrared and Nuclear Magnetic Resonance Spectroscopy and X-Ray Diffraction

Karge¹,

Hunger²,

Beyer³

1999

Catalysis and Zeolites

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“…An interesting alternative to studying zeolite-sorbate interaction consists of following the high-temperature behaviour of bridged hydroxyl groups in zeolites with 1H NMR [12]. In IR spectroscopy the principle of following the response of hydroxyl groups to their interaction with adsorbed weak bases to determine the acidic strength is already well established by Kazansky [13,14] and applied by other groups [15].…”

Section: Introductionmentioning

confidence: 99%