The surface composition of two commercial ZSM-5 zeolites with and without PO 4 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 H 3 PO 4 followed by calcination, both zeolites showed surface enrichment of PO 4 . 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.

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The evolution of carbon (C) and nitrogen (N) in a spent (coked) fluid catalytic cracking (FCC) catalyst was investigated during regeneration. A commercial spent FCC catalyst from one refinery was submitted to calcination procedures with air, and samples were collected at different temperatures and times. These were analyzed by X-ray photoelectron spectroscopy (XPS) before and after milling to follow the variation of C and N contents in the surface. It was observed that both C and N are preferably located on the external FCC catalyst surface. For a total C amount of 1.3 wt %, the C content on the surface is about 18.3 wt %. The surface N present in coke is 1.4 wt %, so that the calculated amount of N in the spent catalyst is 176 ppmw. During thermal treatments a simultaneous removal of C and N from the spent catalyst was observed. However, N evolution was slightly slower and completed at a higher temperature than C.

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