Preparation and characterization of W/γ-Al2O3 and Pd-W/γ-Al2O3 catalysts from organometallic precursors.: The catalytic activity for NO decomposition

The photochemical reaction of W(CO)(6) with triphenylphosphine (PPh3) in the presence of gamma-Al2O3 and Pd/gamma-Al2O3 has been used to prepare W/gamma-Al2O3 and Pd-W/gamma-Al2O3 catalysts. Adsorbed mono- and disubstituted W species have been identified by FTIR. spectroscopy. There is evidence of the adsorption of W(CO)(6-x) L-x species on both the alumina and the Pd surface. After thermal decomposition and reduction at 573 K the catalysts have been characterized by FTLR spectroscopy of adsorbed NH3, CO and NO. The retention of W and P suppresses the Lewis acidity of the alumina support. On Pd-W/gamma-Al2O3, the W is present in a partially reduced state in close association with Pd. This interaction modifies the chemisorptive properties of NO relative to those of the monometallic Pd and W catalysts. In line with these observations the Pd-W/gamma-Al2O3 catalyst presents an enhanced activity for NO decomposition at 473 K. (C) 1999 Elsevier Science B.V. All rights reserved.