FT-IR solid-state NMR investigation of surface hydroxyl groups on dealuminated ZSM-S

Aila Maijanen (Corresponding Author), Eric Derouane, Janos Nagy

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

H-ZSM-5 (Si/Al = 14.6) was progressively dealuminated by steaming at 350°C (1–72 h) and then characterized by transmission infra-red and solid-state NMR spectroscopies (29Si, 27Al, and 1H). The structural hydroxyl groups on the activated zeolite surface were examined by FT-IR before and after pyridine adsorption in the range 400–4000 cm-1. The number of Brönsted acid sites decreases as the steaming time increases and Brönsted sites of varying acid strength are shown to be present on the surface. Moderately steamed (25–50 h at 350°C) ZSM-5 contains three distinct types of hydroxyl groups, namely, bridged Si-OH-Al species of strong Brönsted acidity, non-acidic terminal SiOH groups, and weakly acidic hydroxylated aluminum species, which was also shown by 1H NMR. Two distinct types of Lewis acid sites were observed. The number of Si-OH defects estimated by 29Si and 27Al NMR is at maximum in a sample steamed for 25 h and then decreases due to the healing of hydroxyl nests during further dealumination.
Original languageEnglish
Pages (from-to)204-212
Number of pages9
JournalApplied Surface Science
Volume75
Issue number1-4
DOIs
Publication statusPublished - 1994
MoE publication typeA1 Journal article-refereed
Event2nd International Symposium on Atomically Controlled Surfaces and Iterfaces, ACSI-2, Univ. of Joensuu. Joensuu, 16 - 18 June 1993 -
Duration: 1 Jan 1994 → …

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Hydroxyl Radical
Nuclear magnetic resonance
Acids
Zeolites
Lewis Acids
Aluminum
Acidity
Pyridine
Nuclear magnetic resonance spectroscopy
Infrared radiation
Adsorption
Defects
pyridine
hydroxide ion

Cite this

Maijanen, Aila ; Derouane, Eric ; Nagy, Janos. / FT-IR solid-state NMR investigation of surface hydroxyl groups on dealuminated ZSM-S. In: Applied Surface Science. 1994 ; Vol. 75, No. 1-4. pp. 204-212.
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title = "FT-IR solid-state NMR investigation of surface hydroxyl groups on dealuminated ZSM-S",
abstract = "H-ZSM-5 (Si/Al = 14.6) was progressively dealuminated by steaming at 350°C (1–72 h) and then characterized by transmission infra-red and solid-state NMR spectroscopies (29Si, 27Al, and 1H). The structural hydroxyl groups on the activated zeolite surface were examined by FT-IR before and after pyridine adsorption in the range 400–4000 cm-1. The number of Br{\"o}nsted acid sites decreases as the steaming time increases and Br{\"o}nsted sites of varying acid strength are shown to be present on the surface. Moderately steamed (25–50 h at 350°C) ZSM-5 contains three distinct types of hydroxyl groups, namely, bridged Si-OH-Al species of strong Br{\"o}nsted acidity, non-acidic terminal SiOH groups, and weakly acidic hydroxylated aluminum species, which was also shown by 1H NMR. Two distinct types of Lewis acid sites were observed. The number of Si-OH defects estimated by 29Si and 27Al NMR is at maximum in a sample steamed for 25 h and then decreases due to the healing of hydroxyl nests during further dealumination.",
author = "Aila Maijanen and Eric Derouane and Janos Nagy",
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journal = "Applied Surface Science",
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FT-IR solid-state NMR investigation of surface hydroxyl groups on dealuminated ZSM-S. / Maijanen, Aila (Corresponding Author); Derouane, Eric; Nagy, Janos.

In: Applied Surface Science, Vol. 75, No. 1-4, 1994, p. 204-212.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - FT-IR solid-state NMR investigation of surface hydroxyl groups on dealuminated ZSM-S

AU - Maijanen, Aila

AU - Derouane, Eric

AU - Nagy, Janos

N1 - Project code: KEM1019

PY - 1994

Y1 - 1994

N2 - H-ZSM-5 (Si/Al = 14.6) was progressively dealuminated by steaming at 350°C (1–72 h) and then characterized by transmission infra-red and solid-state NMR spectroscopies (29Si, 27Al, and 1H). The structural hydroxyl groups on the activated zeolite surface were examined by FT-IR before and after pyridine adsorption in the range 400–4000 cm-1. The number of Brönsted acid sites decreases as the steaming time increases and Brönsted sites of varying acid strength are shown to be present on the surface. Moderately steamed (25–50 h at 350°C) ZSM-5 contains three distinct types of hydroxyl groups, namely, bridged Si-OH-Al species of strong Brönsted acidity, non-acidic terminal SiOH groups, and weakly acidic hydroxylated aluminum species, which was also shown by 1H NMR. Two distinct types of Lewis acid sites were observed. The number of Si-OH defects estimated by 29Si and 27Al NMR is at maximum in a sample steamed for 25 h and then decreases due to the healing of hydroxyl nests during further dealumination.

AB - H-ZSM-5 (Si/Al = 14.6) was progressively dealuminated by steaming at 350°C (1–72 h) and then characterized by transmission infra-red and solid-state NMR spectroscopies (29Si, 27Al, and 1H). The structural hydroxyl groups on the activated zeolite surface were examined by FT-IR before and after pyridine adsorption in the range 400–4000 cm-1. The number of Brönsted acid sites decreases as the steaming time increases and Brönsted sites of varying acid strength are shown to be present on the surface. Moderately steamed (25–50 h at 350°C) ZSM-5 contains three distinct types of hydroxyl groups, namely, bridged Si-OH-Al species of strong Brönsted acidity, non-acidic terminal SiOH groups, and weakly acidic hydroxylated aluminum species, which was also shown by 1H NMR. Two distinct types of Lewis acid sites were observed. The number of Si-OH defects estimated by 29Si and 27Al NMR is at maximum in a sample steamed for 25 h and then decreases due to the healing of hydroxyl nests during further dealumination.

U2 - 10.1016/0169-4332(94)90160-0

DO - 10.1016/0169-4332(94)90160-0

M3 - Article

VL - 75

SP - 204

EP - 212

JO - Applied Surface Science

JF - Applied Surface Science

SN - 0169-4332

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