The paper presents a detailed 27Al, 29Si, and 31P n.m.r. and i.r. study of the interaction of zeolites with PCl3. The faujasite framework collapses upon the PCl3 treatment, whereas the mordenite framework is more stable. Phosphorus can be incorporated into zeolites as surface phosphite or phosphate groups but cannot be introduced in a tetrahedral framework position. HM-MOR was dealuminated with PCl3 in one step, whereas the HY-FAU was first dealuminated with SiCl4 followed by a COCl2 treatment, and finally dealumination was completed with PCl3. The HM-MOR sample is only partially dealuminated, as confirmed by 29Si and 27Al n.m.r. data. The dealumination of HY-FAU zeolite is quasi-complete, although a high amount of amorphous aluminosilicate is also formed during the dealumination steps. 31P n.m.r. data show the presence of dihydrogenophosphate SiOP=O(OH)2 and phosphite (SiO)2P=O(H) groups attached to the surface of both zeolites. Infrared data reveal the presence of the phosphite group. Part of the phosphorus is found in a crystalline aluminophosphate phase in the HM-MOR sample, but the aluminophosphate phase of the Y zeolite sample proved to be amorphous with the P/Al molar ratio much lower than unity. Keywords: Zeolite Y; mordenite; dealumination; PCl3, i.r.; MAS n.m.r.
ASJC Scopus subject areas
- Environmental Science(all)