TY - JOUR

T1 - Influence of hot liquid flowing water on Zeolite Y stability

AU - Latschka, Markus

AU - Wellscheid, B.

AU - Rameshan, Raffael

AU - Schöberl, Tobias Rahphael

AU - Essmeister, Johannes

AU - Pacholik, Gernot

AU - Valentini, F.

AU - Balta, L.

AU - Limbeck, Andreas

AU - Rameshan, Christoph

AU - Kählig, Hanspeter

AU - Föttinger, Karin

N1 - Publisher Copyright: © 2023

PY - 2023/4/15

Y1 - 2023/4/15

N2 - Zeolite Y is used in a wide field of catalysis because of its high surface area and strong acidity. Since flowing water is present in many catalytic liquid phase reactions, its impact was investigated. For that, the zeolite Y was treated with water at 200 °C and 42 bar in a flow reactor. The resulting characterization showed strong structural changes at high water flows. The typical zeolite structure was almost completely lost, but an amorphous phase similar to the faujasite framework was formed. Due to this, the characteristic micropores were destroyed (d = 0.7 nm, volume was reduced from 0.18 to 0.01 cm3/g) and small mesopores were created (d = 2–3 nm, volume was increased from 0.25 to 0.51 cm3/g). As a result, the specific surface area was not greatly reduced and was still at around 250 m2/g. In addition, the amount of octahedrally coordinated EFAl increased from 54 to 70% and a γ-Al2O3 as well as a kaolinite phase was observed. The formed tetrahedrally coordinated EFAl is responsible for EFAl-OH groups, which are strong Brønsted acid sites. In general, the total acid sites of the zeolite Y were not strongly reduced and the ratio of Lewis to Brønsted acid sites slightly increased from 70:30% to 80:20%. For all Al species, the oxygen coordination was strongly distorted. After water treatment, on Si a large number of coordinated OSi and OAl groups were substituted with OH groups. The ratio of Si to Al decreased from 1 to 0.7, because Si was dissolved out of the zeolite by the water. On the surface, it was vice versa, there the Si accumulated (the Si/Al ratio increased from 0.2 to 0.8), presumably as silica gel.

AB - Zeolite Y is used in a wide field of catalysis because of its high surface area and strong acidity. Since flowing water is present in many catalytic liquid phase reactions, its impact was investigated. For that, the zeolite Y was treated with water at 200 °C and 42 bar in a flow reactor. The resulting characterization showed strong structural changes at high water flows. The typical zeolite structure was almost completely lost, but an amorphous phase similar to the faujasite framework was formed. Due to this, the characteristic micropores were destroyed (d = 0.7 nm, volume was reduced from 0.18 to 0.01 cm3/g) and small mesopores were created (d = 2–3 nm, volume was increased from 0.25 to 0.51 cm3/g). As a result, the specific surface area was not greatly reduced and was still at around 250 m2/g. In addition, the amount of octahedrally coordinated EFAl increased from 54 to 70% and a γ-Al2O3 as well as a kaolinite phase was observed. The formed tetrahedrally coordinated EFAl is responsible for EFAl-OH groups, which are strong Brønsted acid sites. In general, the total acid sites of the zeolite Y were not strongly reduced and the ratio of Lewis to Brønsted acid sites slightly increased from 70:30% to 80:20%. For all Al species, the oxygen coordination was strongly distorted. After water treatment, on Si a large number of coordinated OSi and OAl groups were substituted with OH groups. The ratio of Si to Al decreased from 1 to 0.7, because Si was dissolved out of the zeolite by the water. On the surface, it was vice versa, there the Si accumulated (the Si/Al ratio increased from 0.2 to 0.8), presumably as silica gel.

KW - Aqueous phase reactions

KW - Phase modification

KW - Si and Al coordination

KW - Stability

KW - Structure changes

KW - Zeolite

UR - http://www.scopus.com/inward/record.url?scp=85151012734&partnerID=8YFLogxK

U2 - 10.1016/j.micromeso.2023.112557

DO - 10.1016/j.micromeso.2023.112557

M3 - Article

AN - SCOPUS:85151012734

VL - 354.2023

JO - Microporous and Mesoporous Materials

JF - Microporous and Mesoporous Materials

SN - 1387-1811

IS - 15 April

M1 - 112557

ER -