Acid properties of titanium aluminophosphate molecular sieves

• Published in: Microporous and mesoporous materials Vol. 32; no. 3; pp. 251 - 255
• Main Authors: Zahedi-Niaki, M.Hassan, Zaidi, S.M.Javaid, Kaliaguine, Serge
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-12-1999; Elsevier
• Subjects: 1H MAS NMR; Acidic properties; Chemisorbed pyridine; Chemistry; Exact sciences and technology; General and physical chemistry; Ion-exchange; Other ion exchangers: preparations and properties; Surface physical chemistry; TAPO-35; TAPO-5; Titanium aluminophosphates; TAPO-35; TAPO-5; Acidic properties; Titanium aluminophosphates; 1H MAS NMR; Chemisorbed pyridine; Chemisorption; Fourier transformation; Acidic site; Cross polarization; NMR spectrometry; Surface analysis; Experimental study; Molecular sieve; Infrared spectrometry; Solid state; Brönsted acid; Pyridine; Hydrothermal treatment; Preparation; Titanium compound; Aluminium phosphate
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/S1387-1811(99)00111-0

Titanium aluminophosphate (TAPO) molecular sieves with AFI and ATS structure were synthesized hydrothermally and their acidic properties characterized by FTIR and proton NMR. These techniques confirmed the existence of Bronsted acid sites in TAPOs. Both
1H MAS NMR and FTIR of chemisorbed pyridine indicated that a new acidic OH appears upon insertion of titanium in the lattice of aluminophosphate molecular sieves AlPO-5 and AlPO-36. The bridging Ti
(OH)
Al species shows a Bronsted acidity only slightly less strong than the corresponding protons in SAPO-5. The appearance of Bronsted acid sites in the TAPOs support the isomorphous substitution of titanium for phosphorus in these solids.