The surface composition of two commercial ZSM-5 zeolites with and without PO4 modification was examined by X-ray photoelectron spectroscopy. Both zeolites were slightly enriched in aluminum on the surface. The surface silica/alumina ratio (SAR) was about half of that of the bulk. Calcination at 600∘C decreased slightly this enrichment. After drying with H3PO4 followed by calcination, both zeolites showed surface enrichment of PO4. The surface of the zeolite with large crystal was more enriched. Steaming resulted in enrichment of aluminum on the surface, in agreement with migration of extra-framework alumina. Increasing phosphate content decreased this enrichment.
Keywordssynthesis techniques characterization of structure properties measurement methods
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