Textural,Structural and Catalytic Properties of ZnCr 2 O 4 –A1 2 O 3 Ternary Solid Catalysts

Abstract

Two series of ternary solid catalysts containing Al, Cr and Zn but with different ZN₂+ or Cr3+ ion contents were prepared by impregnation methods. All systems were calcined by heating within the temperature range 773–1073 K. Structural characterization of the systems was effected by X-ray diffraction (XRD) methods and by differential thermal analysis (DTA). The textural properties of the precalcined products were measured from adsorption/desorption studies of nitrogen at 77 K. The surface acidities of the precalcined products were also studied using a poisoning method employing pyridine as the probe base. The adsorption and disproportionation of NO at 298 K was followed via in-situ FT-IR spectroscopic methods, while the catalytic activities of the prepared samples towards the dehydration (DHD)/dehydrogenation (DHG) of propan-2-ol were studied using a pulse microcatalytic technique.

XRD and DTA analyses showed the presence of γ-A1₂O₃ and ZnCr₂O₄ in the prepared samples but did not provide any evidence for other detectable species in the ternary solid materials. The disproportionation of NO, as well as the catalytic conversion of propan-2-ol, was apparently strongly influenced by the structural properties of these materials but to a lesser extent by their textural properties.