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Modification of zsm-5 zeolite with trimethyl phosphite part 1. structure and acidity

✍ Scribed by Pekka Tynjälä; Tuula T. Pakkanen

Book ID
104431372
Publisher
Elsevier Science
Year
1998
Tongue
English
Weight
557 KB
Volume
20
Category
Article
ISSN
1387-1811

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✦ Synopsis

In the present work we have studied the structure and the acidic properties of HZSM-5 zeolite modified with trimethyl phosphite. The modifications were carried out by using a chemical vapour deposition method as well as impregnation from n-octane solution. Both modification techniques resulted in materials with similar acidic properties.

Trimethyl phosphite reacted with both Br(insted acid sites and terminal SiOH groups. The modifications resulted in the total elimination of strong Br(insted acid sites accompanied by the formation of new Briinsted type sites with decreased acid strength. However, the total acidity of the modified zeolites stayed relatively high. A possible structural transformation resulting from the phosphite modifications was proposed to be an insertion of phosphorus species between the structural aluminium-and silicon--oxygen tetrahedra. However. on the basis of 3'P MAS NMR studies no evidence of the isomorphous substitution of structural T-atoms by phosphorus was found.

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