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Effect of dealumination by acid treatment of a HMCM-22 zeolite on the acidity and activity of the pore systems

Paper ID Volume ID Publish Year Pages File Format Full-Text
42566 45931 2009 7 PDF Available
Title
Effect of dealumination by acid treatment of a HMCM-22 zeolite on the acidity and activity of the pore systems
Abstract

Acid leaching of a HMCM-22 zeolite (Si/Al = 14.5) was carried out at 100 °C for different times (3, 30, 60 and 480 min) with a 4 M nitric acid solution. The resulting samples were characterised by elemental analysis, X-ray diffraction, pyridine adsorption followed by infrared spectroscopy (FTIR) and nitrogen adsorption and their catalytic properties were established with methylcyclohexane transformation at 350 °C. The role played in this reaction by the three micropore systems was established by coupling selective deactivation of supercages by coking and poisoning of the outer cup acid sites with 2,4-dimethylquinoline. The change in the acid and catalytic properties with the time of acid treatment shows that dealumination is dominated by the accessibility of the framework Al atoms. Thus, the outer cup acid sites are highly sensitive to the acid treatment. The acidity and activity of the supercages are also strongly affected whereas those of the narrow sinusoidal channels are hardly affected.

Graphical abstractAcid leaching of a HMCM-22 zeolite (Si/Al = 14.5) was carried out at 100 °C with a 4 M nitric acid solution. The change with time in the acid and catalytic properties of the pore systems shows that the dealumination rate significantly increases with the accessibility of their Al atoms: outer cups > supercages ≫ sinusoidal channels.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Dealumination; Acid leaching; MCM-22 zeolite; Pore systems; Methylcyclohexane transformation
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Effect of dealumination by acid treatment of a HMCM-22 zeolite on the acidity and activity of the pore systems
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 365, Issue 2, 31 August 2009, Pages 207–213
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
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