Preparation and properties of zirconia-pillared zirconium phosphate and phenylphosphonate

Zirconium-pillared layered phosphates were prepared from a-zirconium phosphate and zirconium phosphate phenylphosphonate by colloid manipulation method. The pillared a-zirconium phosphates are less thermally stable than the pillared phosphate phenylphosphonates. The latter can hold their layered structure intact until 500 degrees C, because the phenyl groups in the interlayer region inhibit the strong interaction between the oxide pillars and the sheets. Infrared and P-31 MAS-NMR spectroscopic studies show that P-O-Zr linkages are formed after calcination as a result of this strong interaction. The surface areas of the pillared materials may reach 153-183 m(2)/g, and their pore size distributions are narrow and centered ca. 2 nm. Surface acidity and basicity of the pillared materials were measured by infrared spectroscopy of pyridine adsorption and temperature-programmed desorption methods. They are weakly acidic, but almost non-basic. In comparison with ZrO2, they have more and stronger acid sites. The pillared materials, in particular the zirconium-pillared phosphate phenylphosphonate, are more catalytically active than ZrO2 for reactions such as dehydration of isopropanol, esterification of acetic acid with ethanol and reduction of benzaldehyde. (C) 1999 Elsevier Science B.V. All rights reserved.