Synthesis and characterization of porous chromia-pillared layered titanoniobate

Oligomeric chromium(III)-intercalated titanoniobate has been prepared by the intercalation of propylamine into KTiNbO5 followed by substitution of propylammonium for tetramethylammonium and finally refluxing with an aqueous solution of Cr(O(2)CMe)(3). The first chromia-pillared layered titanoniobate was then obtained by calcination of oligomeric chromium(III)-intercalated titanoniobate at 400 degrees C in a flow of N-2. Characterization of chromia-pillared titanoniobate revealed that the material has the porous layered structure with a Brunauer-Emmett-Teller surface area of 122.4 m(2) g(-1) and an interlayer distance of 13.4 Angstrom as well as a narrow pore-size distribution in the range 30-46 Angstrom. The layered structure can be retained up to 500 degrees C. However, calcination of the oligomeric chromium(III)-intercalated titanoniobate in air at the same temperature led to a product with a low Surface area and a small interlayer space. X-Ray photoelectron studies indicate the existence of different states of chromia in the products obtained in the different atmospheres. The IR spectra of the pyridine-adsorbed material and the ammonia temperature-programmed desorption profile demonstrate the presence of a large amount of acid sites with medium strength on the surface of the new chromia-pillared material. Isopropyl alcohol decomposition confirms the existence of only acid sites in the sample.