An X-ray absorption spectroscopic study on the local environment of copperin CuAPO-5

A copper-containing AlPO4-5 was synthesised using copper(II) oxide as the c opper source and tetraethylammonium hydroxide as the template. The local en vironment about copper in the as-synthesised, calcined and hydrogen-reduced materials has been studied using XANES and EXAFS. The results for the as-s ynthesised product show that copper is sited within the AlPO4-5 framework a nd that its local environment is a tetragonally distorted Cu(O)(6) octahedr on in which the axial bonds are possibly to hydroxy groups. On calcining at 550 degrees C the environment changes to a non-tetragonally distorted octa hedron for which the coordination to the framework is increased by two long bonds to framework oxygens. Copper(II) in CuAPO-5 is reduced by 5% H-2 in He to copper particles of dimensions > 40 Angstrom. The catalytic propertie s of two CuAPO-5 samples (derived from copper(II) oxide and, for comparison , from copper(II) acetate) in the selective catalytic reduction of NO in th e presence of NH3 and O-2 have been investigated, showing maximum conversio ns of 27% at 440 degrees C and 53% at 340 degrees C, respectively.