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    STUDIA CHEMIA - Issue no. 1-2 / 2002  
         
  Article:   ADSORPTION OF AMMONIA AND PYRIDINE ON COAPO-5 SINGLE CRYSTALS STUDIED BY IN SITU FT-IR MICRO-SPECTROSCOPY.

Authors:  J. BÓDIS, G. MÜLLER, J. KORNATOWSKI, J.A. LERCHER.
 
       
         
  Abstract:  Direct spectroscopic evidence for the existence of Brnsted acid sites in CoAPO-5 single crystal molecular sieves is reported. Compared with unsubstituted AlPO4-5 single crystals, the cobalt substituted samples exhibit well developed bands of isolated bridging hydroxyl groups and a broad absorption band indicating the existence of hydrogen bonded OH groups. Ammonia and pyridine interact with the bridging OH groups. This seems to involve simultaneous interactions with Lewis and Brnsted acid sites. Upon adsorption of pyridine new hydroxyl groups (νOH = 3682 and 3590 cm-1) were observed in parallel to pyridine bonding to Lewis acid sites. This suggests opening framework metal-oxygen bonds during sorption of pyridine.  
         
     
         
         
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