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Acidity and Catalytic Activity of Phosphoric Acid Modified Titanium Oxide Surface
Author(s) -
Cheng Soofin,
Lee JinChur
Publication year - 1988
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.198800028
Subject(s) - phosphoric acid , chemistry , anatase , titanium , inorganic chemistry , phosphate , titration , butylamine , titration curve , oxide , nuclear chemistry , catalysis , organic chemistry , photocatalysis , amine gas treating
By refluxing the anatase form of TiO 2 powder in phosphoric acid, the surface acidity was observed to increase. The amount of acid was determined by n‐butylamine titration in n‐heptane media, and was found to be proportional to the reflux period in phosphoric acid. XRD patterns and IR spectra revealed that the products contained a mixture of the anatase form of TiO 2 and titanium phosphate phases. Based on the calculated acid density on the surface, part of the titrant, n‐butylamine penetrated into the titanium phosphate layers. Further investigations using TGA, FT‐IR and TEM techniques along with surface area measurements indicated that the titanium phosphate phase was coated over the TiO 2 phase. The surface acidity of the phosphoric acid treated anatase increased due to the substitution of Ti‐OH groups by phosphate groups. Nevertheless, the chemical properties of the resultant surfaces were found to be influenced by the internal anatase phase. The kinetic data on the 2‐propanol dehydration reaction, where the activation energies were found to decrease gradually with an increase in phosphate content, also support these conclusion.