NH3 TPD study and thermal behaviour of vanadium-exchanged titanium phosphates as catalysts

The ion exchange technique was employed for the preparation of VO²⁺ modified titanium phosphates as catalysts for the selective reduction of NO with NH₃. The samples were prepared by contacting with a vanadyl sulphate solution different precursor materials, amorphous, crystalline or sodium half exchanged titanium phosphate. The vanadium contents of modified phosphates were in the range 0.08–2.3 wt%. XRD and thermal analysis TG/DTA showed that vanadium loading does not cause structural modification in hydrogen titanium phosphate. A vanadyl containing phase was obtained when half sodium titanium phosphate was employed. The NH₃ TPD measurements indicated the presence of a wide distribution of NH₃ adsorbing sites with medium-high strength. Catalytic activity measurements were performed under dilute conditions. It was found that the presence of vanadium even in low amounts strongly promote the catalytic activity.